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1
da Rocha Lindner, Gabriela, Najeh Maissar Khalil, and Rubiana Mara Mainardes. "Resveratrol-Loaded Polymeric Nanoparticles: Validation of an HPLC-PDA Method to Determine the Drug Entrapment and Evaluation of Its Antioxidant Activity." Scientific World Journal 2013 (2013): 1–9. http://dx.doi.org/10.1155/2013/506083.
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Poly(lactic acid) (PLA) and PLA-poly(ethylene glycol) (PLA-PEG) nanoparticles containing resveratrol (RVT) were developed, and their antioxidant activity was evaluated. An analytical method using high performance liquid chromatography (HPLC)/photodiode array (PDA) detection was also developed and validated for RVT determination in nanoparticles. The mobile phase consisted of methanol : water (51 : 49, v/v) flowed at 0.9 mL/min, and the PDA detector was set at wavelength of 306 nm. The mean diameter of the nanoparticles varied between 180 and 220 nm, and the encapsulation efficiency of RVT ranged from 60% to 88%. The nanoparticles containing RVT were evaluated for their ability to scavenge the radical (2,2-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt) (ABTS•+). The profile obtained from the PLA nanoparticles containing RVT demonstrated that after 24 h, there was almost no increase in antioxidant activity, which was lower than that of the free RVT and RVT-loaded PLA-PEG nanoparticles. For PLA-PEG nanoparticles, the radical-scavenging activity of RVT was shown to increase with time, and after 48 h, it was similar to that observed with free RVT.
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Dunaj, Paweł, Stefan Berczyński, Karol Miądlicki, Izabela Irska, and Beata Niesterowicz. "Increasing Damping of Thin-Walled Structures Using Additively Manufactured Vibration Eliminators." Materials 13, no. 9 (May 3, 2020): 2125. http://dx.doi.org/10.3390/ma13092125.
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The paper presents a new way to conduct passive elimination of vibrations consisting of covering elements of structures with low dynamic stiffness with polylactide (PLA). The PLA cover was created in 3D printing technology. The PLA cover was connected with the structure by means of a press connection. Appropriate arrangement of the PLA cover allows us to significantly increase the dissipation properties of the structure. The paper presents parametric analyses of the influence of the thickness of the cover and its distribution on the increase of the dissipation properties of the structure. Both analyses were carried out using finite element models (FEM). The effectiveness of the proposed method of increasing damping and the accuracy of the developed FEM models was verified by experimental studies. As a result, it has been proven that the developed FEM model of a free-free steel beam covered with polylactide enables the mapping of resonance frequencies at a level not exceeding 0.6% of relative error. Therefore, on its basis, it is possible to determine the parameters of the PLA cover. Comparing a free-free steel beam without cover with its PLA-covered counterpart, a reduction in the amplitude levels of the receptance function was achieved by up to 90%. The solution was validated for a steel frame for which a 37% decrease in the amplitude of the receptance function was obtained.
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Li, Fenfen, Caili Zhang, Yunxuan Weng, Xiaoqian Diao, Yingxin Zhou, and Xinyu Song. "Enhancement of Gas Barrier Properties of Graphene Oxide/Poly (Lactic Acid) Films Using a Solvent-free Method." Materials 13, no. 13 (July 6, 2020): 3024. http://dx.doi.org/10.3390/ma13133024.
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Graphene oxide(GO)/polylactic acid (PLA) nanocomposite, prepared using a solvent-free melt mixing processing, is investigated as a potential oxygen barrier packaging film in this work. In order to disperse GO homogeneously in PLA matrix, hydrophobic silane coupling agent, i.e., γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560), is used to modify the graphene oxide sheets. The modified GO is able to be well bonded to the PLA due to the formation of covalent bonds between the epoxy groups of KH560 and the carboxyl and hydroxyl terminal groups of PLA. Furthermore, the thermal stability of GO is enhanced due to the long alkyl side chain of KH560, which could also increase the crystallinity of PLA. As a result, the crystallinity of PLA is significantly improved because of the linear KH560 chains, which can act as nucleating agents to improve the crystallization. The KH560-GO helps to reduce the O2 permeability of KH560-GO/PLA composite films via a dual-action mechanism: (1) providing physical barrier due to their native barrier properties, and (2) by resulting in higher degree of crystallinity. The as-prepared KH560-GO0.75/PLA is able to exhibit ca. 33% and ca. 13% decrease in the PO2 than the neat PLA and GO0.75/PLA film, respectively. Finally, the mechanical properties and impact fractured surfaces indicate that the increase in the tensile strength and elongation at break value of KH560-GO/PLA are due to the strong interfacial adhesion and the strong bonding between the epoxy group of KH560-GO and hydroxyl and carboxyl acid terminal groups of PLA matrix.
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Mohammad, Nor Nisa Balqis, Agus Arsad, Abdul Razak Rahmat, Mohammad Shukor Talib, and Mohd Shaiful Zaidi Mat Desa. "Influence of Compatibilizer on Mechanical Properties of Polylactic Acid/Natural Rubber Blends." Applied Mechanics and Materials 554 (June 2014): 81–85. http://dx.doi.org/10.4028/www.scientific.net/amm.554.81.
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Derived from renewable resources, Poly (lactic) acid (PLA) exhibits good mechanical properties comparable with conventional polyolefins. However, major obstacle in PLA which may limit its application is due to brittleness. Thus, PLA requires toughening to overcome the weakness. In this study, PLA was blended with different ratio of natural rubber (0 to 20 wt.%) through melt blending in a twin screw extruder. The results of tensile strength and Young’s modulus of PLA/NR blends were decreased. In order to enhance the blend performance, PLA grafted maleic anhydride (PLA-g-MA) was used as compatibilizer. The preparation of PLA-g-MA was carried out using internal mixer by free radical melt grafting reaction followed by Fourier Transform Infrared Spectroscopy (FTIR) analysis to confirm the grafting reaction. To investigate the compatibilization effect on the mechanical properties of PLA/NR blends, PLA-g-MA was added to the blends at various compositions (1 – 10 phr). Mechanical properties increased markedly compared to the virgin PLA/NR blends and FTIR result confirmed grafting reaction occurred between MA and PLA.
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Chitrattha, Sasiprapa, and Thawatchai Phaechamud. "Modifying Poly(L-Lactic Acid) Matrix Film Properties with High Loaded Poly(Ethylene Glycol)." Key Engineering Materials 545 (March 2013): 57–62. http://dx.doi.org/10.4028/www.scientific.net/kem.545.57.
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Poly(L-lactic acid) (PLA) is a biodegradable and bioabsorbable polymer which has many potential uses. However, PLA shows the poor toughness, slow degradation rate and relatively hydrophobic.Poly(ethylene glycol) (PEG) is widely used as a plasticizer and of great interest because it presents outstanding properties, e.g. solubility in water and also in some organic solvents, lack of toxicity and absence of antigenicity and immunogenicity, which are essential for biomedical applications. The aim of this study was to investigate the ability of high amount PEG 400 to improve the characteristics of PLA matrix film. PLA matrix films were prepared using a solvent casting method and their various properties were investigated. Mechanical properties were determined with texture analyzer. Contact angle and surface free energy were measured using the goniometer. From the mechanical properties evaluated (tensile strength (TS) and elongation at break (E)), all plasticized PLA films exhibited the softer behavior and the plasticized PLA films with150 % PEG 400 indicated the higher % elongation at break than pure PLA, significantly. The contact angle and surface free energy values indicated that PEG 400 could improve the wettability of solventsand also increase % water sorption and % weight loss with as dose dependent.Surprisingly, SEM photographs revealed more porous structure as the higher amount PEG 400 was incorporated in PLA film. This porous structure and density of developed plasticized PLA film could be modified with temperature change technique. Parameters affecting the 3-D porous plasticized PLA matrix were revealed in this study. The optimum condition for producing the continuous 3-D porous plasticized PLA matrix was obtained. This porous topography in PLA matrix film will be applied further as material in tissue engineering and drug delivery systems.
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Chitrattha, Sasiprapa, and Thawatchai Phaechamud. "Film Properties of Poly(lactic Acid) Comprising N-Methyl-2-Pyrrolidone." Advanced Materials Research 528 (June 2012): 140–43. http://dx.doi.org/10.4028/www.scientific.net/amr.528.140.
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Poly (lactic acid) (PLA) has many potential uses, for example as packaging, textiles, biomedical fields, including suture, bone fixation material, drug delivery microsphere, and tissue engineering. However, PLA shows the poor toughness, slow degradation rate and relatively hydrophobic. The aim of this study was to investigate the ability of N-methyl-2-pyrrolidone (NMP) to improve the characteristics of PLA film. PLA films were prepared using a solvent casting method and their various properties were investigated. From tensile strength (TS), elongation at break (E) and young’s modulus (ε) determinations, the incorporated PLA films exhibited the softer behavior than plain PLA film. On the other hand, from the contact angle and surface free energy values, the PLA films incorporated with NMP could improve the wettability of solvents and also increased % water sorption (WS) and % weight loss (WL) than PLA films with NMP dose dependent. However SEM photographs revealed the more rather rough and cracked surface as the higher amount of NMP was incorporated in PLA film.
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Tateishi, Ikki, Mai Furukawa, Hideyuki Katsumata, and Satoshi Kaneco. "Development of Heavy Metal-Free Photocatalytic RhB Decomposition System Using a Biodegradable Plastic Substrate." ChemEngineering 5, no. 1 (March 3, 2021): 11. http://dx.doi.org/10.3390/chemengineering5010011.
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The heavy-metal-free photocatalytic system, in which carbon nitride is coated on polylactic acid (PLA) as biodegradable plastic through a simple dip coating method, was used for dye decomposition under visible light irradiation. Solvent selection, solvent concentration, and the number of coatings for dip coating were investigated to optimize the conditions for loading carbon nitride on PLA. Carbon nitride cannot be coated on PLA in water, but it can be strongly coated by decomposing the surface of PLA with ethanol or chlorobenzene to promote physical adsorption and activate surface. The number of dip coatings also affected the photocatalytic decomposition ability. The photocatalytic system was able to decompose the dye continuously in the flow method, and dye (rhodamine B) was decomposed by about 50% at a residence time of 12 min (flow rate 0.350 mL/min) for 30 h.
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Miao, Junming, Feng Lin, Ning Huang, and Yan Teng. "Improving Anti-Inflammatory Effect of Luteolin with Nano-Micelles in the Bacteria-Induced Lung Infection." Journal of Biomedical Nanotechnology 17, no. 6 (June 1, 2021): 1229–41. http://dx.doi.org/10.1166/jbn.2021.3101.
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The effective therapy for lung infectious diseases became more and more difficult since the severe antibiotic resistance of pathogenic microorganisms, it is urgent to develop new antimicrobial agents. Luteolin has been reported to play a crucial part in host immune responses. However, the clinical use of luteolin is impeded due to its hydrophobicity and low oral bioavailability. In this study, we formulated luteolin-loaded Methoxy poly(ethylene glycol)-poly(lactide) micelles (luteolin/MPEG-PLA), to improve the bioavailability of luteolin in lung infectious diseases. The results showed that luteolin/MPEG-PLA treatment could reduce the adhesion of Klebsiella pneumoniae (K. pneumoniae) to lung epithelial cells and enhance the germicidal ability of macrophages against K. pneumoniae compared to untreated group. Meanwhile, luteolin/MPEG-PLA showed stronger adhesion resistance of epithelial cells and germicidal ability of macrophages compared with free luteolin. In vivo study, luteolin/MPEG-PLA administration significantly promoted the clearance of bacteria and reduced inflammatory infiltration of lung tissue in K. pneumoniae induced lung infectious mice model. Further studies showed that treatment with luteolin/MPEG-PLA reduced the mRNA expression of LPS-induced inflammatory cytokines and chemokines in macrophages significantly. In general, luteolin/MPEG-PLA can enhance the anti-bacterial ability of lung epithelial cells and macrophages, and has a stronger therapeutic effect than free luteolin in bacterial-induced lung infection. Luteolin/MPEG-PLA may be an excellent potential drug for bacterial-induced lung infectious diseases treatment.
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Vadas, Dániel, Dávid Kmetykó, György Marosi, and Katalin Bocz. "Application of Melt-Blown Poly(lactic acid) Fibres in Self-Reinforced Composites." Polymers 10, no. 7 (July 12, 2018): 766. http://dx.doi.org/10.3390/polym10070766.
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The aim of our research was to produce poly(lactic acid) (PLA) fibres with diameters in the micrometer size range, serving as the reinforcing phase in self-reinforced (SR) PLA composites. Nonwoven PLA mats were manufactured by solvent-free melt-blowing technology. Three types of PLA differing in d-lactide content were processed with a productivity as high as 36 g/h. The crystallinity of the PLA microfibres was enhanced by thermal annealing. A 2–3-fold increase in the degree of crystallinity was obtained, as measured by differential scanning calorimetry (DSC). Fibre diameters between 2–14 µm were revealed by scanning electron microscopy (SEM). Static tensile tests were performed on the nonwoven mats, showing the reduced moduli of the annealed fibres due the amorphous relaxation. The PLA mats were processed via the hot compaction technique and formed into SR–PLA composites. The morphological and mechanical properties of the obtained microstructural composites were comprehensively studied. Composites prepared from annealed, thermally more stable PLA nonwoven mats showed superior mechanical properties; the tensile strength improved by 47% due to the higher residual fibre content.
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Chang, Jing, Zhe Yang, Junfeng Li, Yufen Jin, Yihang Gao, Yanwen Sun, Hainan Li, and Ting Yu. "Preparation and In Vitro and In Vivo Antitumor Effects of VEGF Targeting Micelles." Technology in Cancer Research & Treatment 19 (January 1, 2020): 153303382095702. http://dx.doi.org/10.1177/1533033820957022.
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Background: Doxorubicin (DOX) has antitumor effects mediated by cell viability inhibition and by inducing cellular apoptosis. However, it has limited use in clinical applications due to various factors such as hydrophobicity, dose-dependent toxicity effects on normal tissues, short cycle retention time, and low targeting ability. This study aims at enhancing hydrophilicity of DOX to restrict its toxic effects to within or around the tumor sites and also to improve its targeting ability to enhance antitumor efficiency. Methods: Micelles composed of biodegradable poly (ethylene glycol)-poly (lactic acid) copolymers (PEG-PLA) were employed to deliver DOX via a self-assembly method and were coupled to VEGF antibodies. The morphology, size, and physical stability of PEG-PLA-DOX targeting VEGF micelles (VEGF-PEG-PLA-DOX micelles) were assessed. Then, the release ability of DOX from these micelles was monitored, and their drug loading capacity was calculated. MTT assay revealed the in vitro antitumor effect of VEGF-PEG-PLA-DOX micelles. Moreover, ROS release was measured to evaluate apoptotic effects of these nanoparticle micelles. In vivo therapeutic efficiencies of VEGF-PEG-PLA-DOX micelles on a lung cancer nude mouse model was evaluated. Results: DOX-loaded micelles were obtained with a drug loading capacity of 12.2% and were monodisperse with 220 nm average diameter and a controlled in vitro DOX release for extended periods. In addition, VEGF-PEG-PLA-DOX micelles displayed a larger cell viability inhibitory effect as measured via MTT assays and greater cell apoptosis induction through in vitro ROS levels compared with PEG-PLA-DOX micelles or free DOX. Furthermore, VEGF-PEG-PLA-DOX micelles could improve in vivo antitumor effects of DOX by reducing tumor volume and weight. Conclusions: VEGF-PEG-PLA-DOX micelles displayed a larger anti-tumor effect both in in vitro A549 cells and in an in vivo lung cancer nude mouse model compared with PEG-PLA-DOX micelles or free DOX, and hence they have potential clinical applications in human lung cancer therapy.
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Cicogna, Francesca, Guido Giachi, Luca Rosi, Elisa Passaglia, Serena Coiai, Roberto Spiniello, Federico Prescimone, and Marco Frediani. "Macromolecular Dyes by Chromophore-Initiated Ring Opening Polymerization of L-Lactide." Polymers 12, no. 9 (August 31, 2020): 1979. http://dx.doi.org/10.3390/polym12091979.
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End functionalized polylactides are prepared by ring opening polymerization of L-lactide in the presence of stannous octoate (Sn(Oct)2). Three chromophores, 9H-carbazol-ethanol (CA), 9-fluorenyl-methanol (FM), and 2-(4-(2-chloro-4-nitrophenylazo)-N-ethylphenylamino)ethanol (Disperse Red 13, DR), are for the first time used as co-initiators in the polymerization process. The polymerization reaction is initiated by conventional thermal treatment, but in the case of FM, microwave-assisted polymerization is also carried out. CA and FM absorb and emit in the UV portion of the electromagnetic spectrum, whereas DR absorbs in the visible part. The obtained end-capped polylactides derivatives show the same photophysical properties as the initiator, so they are “macromolecular dyes” (MDs) that can be used “as synthesized” or can be blended with commercial poly(lactic acid) (PLA). The blends of PLA with MDs have ultraviolet-visible (UV-Vis) absorption and fluorescence emission features similar to that of MDs and thermal properties typical of PLA. Finally, migration tests, carried out onto the blends of PLA with MDs and PLA with free chromophores, show that MDs are less released than free chromophores both in solution and in the solid phase.
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Torres, Elena, Aide Gaona, Nadia García-Bosch, Miguel Muñoz, Vicent Fombuena, Rosana Moriana, and Ana Vallés-Lluch. "Improved Mechanical, Thermal, and Hydrophobic Properties of PLA Modified with Alkoxysilanes by Reactive Extrusion Process." Polymers 13, no. 15 (July 27, 2021): 2475. http://dx.doi.org/10.3390/polym13152475.
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An eco-friendly strategy for the modification of polylactic acid (PLA) surface properties, using a solvent-free process, is reported. Reactive extrusion (REX) allowed the formation of new covalent bonds between functional molecules and the PLA polymeric matrix, enhancing its mechanical properties and modifying surface hydrophobicity. To this end, the PLA backbone was modified using two alkoxysilanes, phenyltriethoxysilane and N-octyltriethoxysilane. The reactive extrusion process was carried out under mild conditions, using melting temperatures between 150 and 180 °C, 300 rpm as screw speed, and a feeding rate of 3 kg·h−1. To complete the study, flat tapes of neat and functionalized PLA were obtained through monofilament melt extrusion to quantify the enhancement of mechanical properties and hydrophobicity. The results verified that PLA modified with 3 wt% of N-octyltriethoxysilane improves mechanical and thermal properties, reaching Young’s modulus values of 4.8 GPa, and PLA hydrophobic behavior, with values of water contact angle shifting from 68.6° to 82.2°.
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Chakraborty, Proshant, Nayreen Daruwalla, Apoorwa Deepak Gupta, Unnati Machchhar, Bhaskar Kakad, Shilpa Adelkar, and David Osrin. "Using Participatory Learning and Action in a Community-Based Intervention to Prevent Violence Against Women and Girls in Mumbai’s Informal Settlements." International Journal of Qualitative Methods 19 (January 1, 2020): 160940692097223. http://dx.doi.org/10.1177/1609406920972234.
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For over 3 decades, participatory learning and action (PLA) techniques have been prominent in formative and evaluative studies in community-based development programs in the Global South. In this paper, we describe and discuss the use of PLA approaches at the beginning of a community-based program for prevention of violence against women and girls in Mumbai’s urban informal settlements. We adapted six PLA techniques as part of a formative community mobilization and rapid needs assessment exercise, addressing perceptions of violence prevalence, sources of household conflict, experiences of safety and mobility, access to services, preferences for service and support, and visualization of an ideal community free from violence. We describe the collaborative process of developing and implementing PLA techniques and discuss its relevance in generating contextual and grounded understandings of violence as well as in identifying factors which can potentially enable and constrain interventions.
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Pušnik Črešnar, Klementina, Alexandra Aulova, Dimitrios N. Bikiaris, Dimitra Lambropoulou, Katja Kuzmič, and Lidija Fras Zemljič. "Incorporation of Metal-Based Nanoadditives into the PLA Matrix: Effect of Surface Properties on Antibacterial Activity and Mechanical Performance of PLA Nanoadditive Films." Molecules 26, no. 14 (July 8, 2021): 4161. http://dx.doi.org/10.3390/molecules26144161.
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In this work, the modification process of poly(lactic acid) (PLA) with metal-based nanoparticle (NPs) additives (Ag, ZnO, TiO2) at different loading (0.5, 1.0, and 2.5 wt%) and by melt-mix extrusion method followed by film formation as one of the advantageous techniques for industrial application have been investigated. PLA nanoparticle composite films (PLA-NPs) of PLA-Ag, PLA-ZnO, PLA-TiO2 were fabricated, allowing convenient dispersion of NPs within the PLA matrix to further pursue the challenge of investigating the surface properties of PLA-NPs reinforced plastics (as films) for the final functional properties, such as antimicrobial activity and surface mechanical properties. The main objective was to clarify how the addition of NPs to the PLA during the melt extrusion process affects the chemistry, morphology, and wettability of the surface and its further influence on the antibacterial efficiency and mechanical properties of the PLA-NPs. Therefore, the effect of Ag, ZnO, and TiO2 NPs incorporation on the morphology (SEM), elemental mapping analysis (SEM-EDX), roughness, surface free energy (SFE) of PLA-NPs measured by goniometry and calculated by OWRK (Owens, Wendt, Rabel, and Kaelble) model was evaluated and correlated with the final functional properties such as antimicrobial activity and surface mechanical properties. The developed PLA-metal-based nanocomposites, with improved mechanical and antimicrobial surface properties, could be used as sustainable and biodegradable materials, offering desirable multifunctionalities not only for food packaging but also for cosmetics and hygiene products, as well as for broader plastic products where antimicrobial activity is desirable.
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Mohammad, N. N. B., A. Arsad, A. R. Rahmat, and N. S. Abdullah Sani. "Effects of Maleated Natural Rubber on Mechanical Properties of Polylactic Acid/Natural Rubber Blends." Materials Science Forum 819 (June 2015): 284–89. http://dx.doi.org/10.4028/www.scientific.net/msf.819.284.
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Brittle Polylactic acid (PLA) was toughened by introducing 5-20 wt. % of Natural Rubber (NR) through melt blending in a twin screw extruder. The results of tensile strength and Young’s modulus of PLA/NR blends were dramatically decreased. Maleic anhydride grafted natural rubber (NR-g-MA) was prepared and used to enhance the blends performance. The preparation of NR-g-MA was carried out using internal mixer by free radical melt grafting reaction followed by Fourier transform infrared spectroscopy (FTIR) to analyze the incorporation of MA on the NR. The compatibilization effect on the mechanical properties of PLA/NR blends was investigated with addition of 3 phr NR-g-MA. Comparison between PLA/NR/Compatibilizer and virgin PLA/NR blends significantly improved on the mechanical properties. FTIR result confirmed grafting reaction occurred between MA and NR.
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Miller, Sharon L., Carl M. Maresh, Lawrence E. Armstrong, Cara B. Ebbeling, Shannon Lennon, and Nancy R. Rodriguez. "Metabolic Response to Provision of Mixed Protein-Carbohydrate Supplementation during Endurance Exercise." International Journal of Sport Nutrition and Exercise Metabolism 12, no. 4 (December 2002): 384–97. http://dx.doi.org/10.1123/ijsnem.12.4.384.
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The interaction of substrates and hormones in response to ingestion of intact proteins during endurance exercise is unknown. This study characterized substrate and hormone responses to supplementation during endurance exercise. Nine male runners participated in 3 trials in which a non-fat (MILK), carbohydrate (CHO), or placebo (PLA) drink was consumed during a 2-hour treadmill >· run at 65% V̇O2max. Circulating levels of insulin, glucagon, epinephrine, norepi-nephrine, growth hormone, testosterone, and cortisol were measured. Plasma substrates included glucose, lactate, free fatty acids, and select amino acids. Except for insulin and cortisol, hormones increased with exercise. While post-exercise insulin concentrations declined similarly in all 3 trials, the glucagon increase was greatest following MILK consumption. CHO blunted the post-exercise increase in growth hormone compared to levels in MILK. Free fatty acids and plasma amino acids also were responsive to nutritional supplementation with both CHO and MILK attenuating the rise in free fatty acids compared to the increase observed in PLA. Correspondingly, respiratory exchange ratio increased during CHO. Essential amino acids increased significantly only after MILK and were either unchanged or decreased in CHO. PLA was characterized by a decrease in branched-chain amino acid concentrations. Modest nutritional supplementation in this study altered the endocrine response as well as substrate availability and utilization following and during an endurance run, respectively.
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Mamiński, Mariusz Ł., Igor Novák, Matej Mičušík, Artur Małolepszy, and Renata Toczyłowska-Mamińska. "Discharge Plasma Treatment as an Efficient Tool for Improved Poly(lactide) Adhesive–Wood Interactions." Materials 14, no. 13 (June 30, 2021): 3672. http://dx.doi.org/10.3390/ma14133672.
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Poly(lactide) (PLA) films obtained by thermoforming or solution-casting were modified by diffuse coplanar surface barrier discharge plasma (300 W and 60 s). PLA films were used as hot-melt adhesive in joints in oak wood. It was demonstrated that lap shear strength increased from 3.4 to 8.2 MPa, respectively, for the untreated and plasma-treated series. Pull-off tests performed on particleboard for the untreated and treated PLA films showed 100% cohesive failure. Pull-off strength tests on solid oak demonstrated adhesion enhancement from 3.3 MPa with the adhesion failure mode to 6.6 MPa with the cohesion failure mode for untreated and treated PLA. XPS revealed that carbonyl oxygen content increased by two-to-three-fold, which was confirmed in the Fourier-transform infrared spectroscopy experiments of the treated PLA. The water contact angle decreased from 66.4° for the pristine PLA to 49.8° after treatment. Subsequently, the surface free energy increased from 47.9 to 61.05 mJ/m2. Thus, it was clearly proven that discharge air plasma can be an efficient tool to change surface properties and to strengthen adhesive interactions between PLA and woody substrates.
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Yang, Li, and Weijun Zhen. "Synthesis of Graphene Oxide-Polystyrene Graft Polymer Based on Reversible Addition Fragmentation Chain Transfer and Its Effect on Properties, Crystallization, and Rheological Behavior of Poly (Lactic Acid)." Advances in Polymer Technology 2020 (July 29, 2020): 1–16. http://dx.doi.org/10.1155/2020/9364657.
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Graphene oxide-polystyrene graft polymer (SGO-PS) was prepared by reversible addition-fragmentation chain transfer radical polymerization method. Orthogonal experiments indicated that the optimum synthesis reaction conditions for SGO-PS were as follows: the millimole ratio of chain transfer agent to initiator was 0.15 : 0.3, and the amount of styrene was 8 mL at 80°C for 12 hours. The products were characterized by Fourier transform infrared spectroscopy and thermal weightlessness analysis, and the highest grafting rate of SGO-PS was 62.46%. Then, PLA/SGO-PS nanocomposites were prepared using SGO-PS as fillers by melt intercalation method, and its crystallinity, mechanical properties, and thermal stability were significantly improved. Compared with pure PLA, the crystallinity of PLA/SGO-PS (0.3 wt%) nanocomposites was increased by 5 times. Multiple melting behavior tests showed that the introduction of SGO-PS caused the PLA molecular chain to be discharged into the unit cell in time, and the melting temperature shifted to a higher temperature, which ultimately made the grain structure of PLA composites more complete and stable than pure PLA. The rheological performance test showed that the uniform dispersion of SGO-PS in the PLA matrix inhibited the free movement of the PLA molecular chain and caused higher flow resistance, resulting in an increase in the complex viscosity, storage modulus, and loss modulus of PLA/SGO-PS.
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Jian, Rong-Kun, Long Xia, Yuan-Fang Ai, and De-Yi Wang. "Novel Dihydroxy-Containing Ammonium Phosphate Based Poly(Lactic Acid): Synthesis, Characterization and Flame Retardancy." Polymers 10, no. 8 (August 5, 2018): 871. http://dx.doi.org/10.3390/polym10080871.
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The aim of this work is to prepare flame-retardant biobased poly(lactic acid) materials through incorporating a novel flame retardant dihydroxy-containing ammonium phosphate (DAP) derived from 2-chloro-5,5-dimethyl-1,3,2-dioxaphosphinane-2-oxide (DOP) and 2-amino-2-methyl-1,3-propanediol (AMPD). Interestingly, PLA modified with only 0.5% DAP passed UL-94 V-0 rating, and possessed a limiting oxygen index (LOI) value of 24.6%, which would further increase with the increasing loading of DAP. PLA/DAP did not exhibit obviously improved results in terms of heat release rate (HRR), as the loading of DAP was relatively low. It was found that DAP showed little effect on the thermal stability of PLA and the onset decomposition temperatures of PLA and PLA/DAP blends were very close. Besides, the degree of crystallization increased because of the plasticized effect of DAP. Based on the analyses of flame-retardant mechanism of DAP, it disclosed that DAP decomposed to generate incombustible compounds, such as water and ammonia, to dilute the concentration of oxygen and fuels, and then release some phosphorus-containing fragments that could produce phosphorus-containing free radicals to interrupt free-radical reactions, and finally noncombustible melt dripping was produced so as to bring away large amount of heat and stop the feedback of heat to the matrix.
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Izuchukwu, Sandra C. P., Casparus J. R. Verbeek, and James Micheal Bier. "Decoloured Novatein® and PLA Blends Compatibilized with Itaconic Anhydride." Applied Mechanics and Materials 884 (August 2018): 3–13. http://dx.doi.org/10.4028/www.scientific.net/amm.884.3.
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Poly (lactic acid) (PLA) was modified through free radical grafting of itaconic anhydride to create reactive side-chain groups. Modified PLA was blended with Decoloured Novatein®(DNTP), a thermoplastic protein material using reactive extrusion to produce a degradable material with improved properties compared to neat Decoloured Novatein®. Varying ratios of blends were prepared. Blending DNTP with PLA was found to increase tensile strength between 22% to 538% and modulus between 201 GPa to 3193 GPa, whereas the strain at break decreased between 80% to 94% depending on the blend ratio. The glass transition temperature of the blends which was measured as the tan δ peak, also revealed an increase when compared to neat DNTP. Scanning electron microscope revealed an enhanced interfacial adhesion between the two phases in the blends with PLA-g-IA suggesting a more homogenous microstructure. The results show the possibility and feasibility of blending DNTP with PLA for use in agricultural and packaging applications.
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Abdallah, A., and N. Benrekaa. "Study of the free volume fraction in polylactic acid (PLA) by thermal analysis." International Journal of Modern Physics B 29, no. 31 (December 2015): 1550226. http://dx.doi.org/10.1142/s0217979215502264.
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The poly (lactic acid) or polylactide (PLA) is a biodegradable polymer with high modulus, strength and thermoplastic properties. In this work, the evolution of various properties of PLA is studied, such as glass transition temperature, mechanical modules and elongation percentage with the aim of investigating the free volume fraction. To do so, two thermal techniques have been used: the dynamic mechanical analysis (DMA) and dilatometry. The results obtained by these techniques are combined to go back to the structural properties of the studied material.
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Xu, Daifang, Kejing Yu, Kun Qian, and Chul B. Park. "Foaming behavior of microcellular poly(lactic acid)/TPU composites in supercritical CO2." Journal of Thermoplastic Composite Materials 31, no. 1 (February 2, 2017): 61–78. http://dx.doi.org/10.1177/0892705716679480.
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This article presents the effects of thermoplastic polyurethane (TPU) on the crystallization and melt strength of poly(lactic acid) (PLA) and on the enhancement of cell nucleation and expansion ratio to manufacture microcellular thermoplastic PLA foams in supercritical carbon dioxide. Addition of TPU increased the crystallinity and decreased the crystallite size as observed by differential scanning calorimetry and polarized optical microscope. The formed crystal domains worked as cross-linking points to increase the melt strength of a polymer that potentially affected the cell growth. Scanning electron microscope confirmed the immiscibility between PLA and TPU, and TPU was dispersed as islands in the PLA matrix. This phase morphology further influenced the cell structure of the PLA/TPU foams. TPU acted as a nucleating agent to enhance heterogeneous cell nucleation that is caused by the decrease in free energy barrier. Tensile stress that generated around the TPU and in some local regions surrounding the crystals and crystallization was dominant to induce cell nucleation.
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Song, Yan, Xu Zong, Nan Wang, Ning Yan, Xueying Shan, and Jinchun Li. "Preparation of γ-Divinyl-3-Aminopropyltriethoxysilane Modified Lignin and Its Application in Flame Retardant Poly(lactic acid)." Materials 11, no. 9 (August 22, 2018): 1505. http://dx.doi.org/10.3390/ma11091505.
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Lignin can be a candidate as a charring agent applied in halogen-free flame retardant polymers, and incorporation of silicon and nitrogen elements in lignin can benefit to enhancing its thermal stability and charring ability. In the present work, wheat straw alkali lignin (Lig) was modified to incorporate silicon and nitrogen elements by γ-divinyl-3-aminopropyltriethoxysilane, and the modified lignin (CLig) was combined with ammonium polyphosphate (APP) as intumescent flame retardant to be applied in poly(Lactic acid) (PLA). The flame retardancy, combustion behavior and thermal stability of PLA composites were studied by the limited oxygen index (LOI), vertical burning testing (UL-94), cone calorimetry testing (CCT) and thermogravimetric analysis (TGA), respectively. The results showed a significant synergistic effect between CLig and APP in flame retarded PLA (PLA/APP/CLig) occured, and the PLA/APP/CLig had better flame retardancy. CCT data analysis revealed that CLig and APP largely reduced the peak heat release rate (PHRR) and total heat release rate (THR) of PLA, indicating their effectiveness in decreasing the combustion of PLA. TGA results exhibited that APP and CLig improved the thermal stability of PLA at high temperature. The analysis of morphology and structure of residual char indicated that a continuous, compact and intumescent char layer on the material surface formed during firing, and had higher graphitization degree. Mechanical properties data showed that PLA/APP/CLig had higher tensile strength as well as elongation at break.
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Von Minckwitz, Gunter, Marion Jennifer Procter, Evandro De Azambuja, Dimitrios Zardavas, Adam Knott, Giuseppe Viale, Thomas M. Suter, et al. "APHINITY trial (BIG 4-11): A randomized comparison of chemotherapy (C) plus trastuzumab (T) plus placebo (Pla) versus chemotherapy plus trastuzumab (T) plus pertuzumab (P) as adjuvant therapy in patients (pts) with HER2-positive early breast cancer (EBC)." Journal of Clinical Oncology 35, no. 18_suppl (June 20, 2017): LBA500. http://dx.doi.org/10.1200/jco.2017.35.18_suppl.lba500.
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LBA500 Background: In previous trials P significantly prolonged progression free and overall survival and increased pCR rates when added to T+C in pts with HER2-positive breast cancer (BC). The APHINITY trial was designed to test whether the addition of P to adjuvant T+C improves pt outcomes. Methods: Pts with adequately excised HER2-positive, pT1-3 EBC were randomly assigned to receive standard adjuvant C plus one year of either T + P or T + Pla. Eligible pts had either node-positive disease, or node-negative disease (pN0) and a tumor size of > 1.0 cm. Pts with pN0, T1b tumors with high risk features were initially eligible. The primary efficacy endpoint was invasive disease-free survival (IDFS); we assumed a 3-year IDFS of 91.8% with P and 89,.2% with Pla. Results: 4805 pts were randomized to C and T plus either P (n = 2400) or Pla (n = 2405). Baseline demographics and tumor characteristics between the arms were well balanced, with 63% and 36% of pts having node-positive and hormone receptor negative EBC respectively. P and Pla treatments were completed in 84.5% and 87.4% of patients, respectively. IDFS events occurred in 171 (7.1%) P pts and 210 (8.7%) Pla pts (hazard ratio (HR) 0.81 (95% CI 0.68-1.00), P = 0.045). Estimates of IDFS at 3 years were 94.1% and 93.2% in the P and Pla arms, respectively. The node-positive cohort had a 3-year IDFS rate of 92.0% for P compared with 90.2% for Pla (HR 0.77 (95% CI 0.62-0.96), P = 0.019). The pN0 cohort had a 3-year IDFS rate of 97.5% for P and 98.4% for Pla; HR = 1.13 (95% CI 0.68-1.86). The safety profile of P was consistent with previous trials. For the primary cardiac endpoint (heart failure or cardiac death) and secondary cardiac endpoint (asymptomatic or mildly symptomatic LVEF decline) rates were low, 0.7% vs 0.3% and 2.7% vs 2.8%, in the P and Pla arms, respectively. Diarrhea grade ≥3 was more frequent with P (9.9% vs 3.7%). Conclusions: The APHINITY trial met its primary endpoint: P significantly improved IDFS in patients with HER2-positive EBC when added to T+C. No new safety signals were identified. Clinical trial information: NCT01358877.
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Abdullah Sani, Nur Syazana, Agus Arsad, and Abdul Razak Rahmat. "Synthesis of a Compatibilizer and the Effects of Monomer Concentrations." Applied Mechanics and Materials 554 (June 2014): 96–100. http://dx.doi.org/10.4028/www.scientific.net/amm.554.96.
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The aim of this research was to modify Poly (lactic acid) (PLA) and Natural Rubber (NR) using maleic anhydride (MA). The preparation was carried out using internal mixer by free radical melt grafting reaction to produce PLA-g-MA and NR-g-MA as a compatibilizer. The effects of concentrations of MA (3-12 phr) were studied in details. The samples structure of copolymers were then characterized using 1H nuclear magnetic resonance (1H-NMR) and Fourier transforms infrared spectrometer (FTIR). Quantities of grafted MA (% grafting) were characterized by titration analysis and when increasing the monomer used, the quantities of the grafted MA on PLA and NR molecules also increased. The optimum grafting degree for PLA-g-MA and NR-g-MA was at 9 phr of MA with value of 1.63% and 5.02%, respectively.
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Brüster, Berit, Yann-Olivier Adjoua, Reiner Dieden, Patrick Grysan, Carlos Eloy Federico, Vincent Berthé, and Frédéric Addiego. "Plasticization of Polylactide with Myrcene and Limonene as Bio-Based Plasticizers: Conventional vs. Reactive Extrusion." Polymers 11, no. 8 (August 18, 2019): 1363. http://dx.doi.org/10.3390/polym11081363.
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Polylactide (PLA) was blended by conventional and reactive extrusion with limonene (LM) or myrcene (My) as bio-based plasticizers. As-processed blends were carefully analyzed by a multiscale and multidisciplinary approach to tentatively determine their chemical structure, microstructure, thermal properties, tensile and impact behaviors, and hydrothermal stability. The main results indicated that LM and My were efficient plasticizers for PLA, since compared to neat PLA, the glass transition temperature was reduced, the ultimate tensile strain was increased, and the impact strength was increased, independently of the type of extrusion. The addition of a free radical initiator during the extrusion of PLA/LM was beneficial for the mechanical properties. Indeed, the probable formation of local branched/crosslinked regions in the PLA matrix enhanced the matrix crystallinity, the tensile yield stress, and the tensile ultimate stress compared to the non-reactive blend PLA/LM, while the other properties were retained. For PLA/My blends, reactive extrusion was detrimental for the mechanical properties since My polymerization was accelerated resulting in a drop of the tensile ultimate strain and impact strength, and an increase of the glass transition temperature. Indeed, large inclusions of polymerized My were formed, decreasing the available content of My for the plasticization and enhancing cavitation from inclusion-matrix debonding.
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Jalili, Roxana, Joe Horecka, James R. Swartz, Ronald W. Davis, and Henrik H. J. Persson. "Streamlined circular proximity ligation assay provides high stringency and compatibility with low-affinity antibodies." Proceedings of the National Academy of Sciences 115, no. 5 (January 16, 2018): E925—E933. http://dx.doi.org/10.1073/pnas.1718283115.
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Proximity ligation assay (PLA) is a powerful tool for quantitative detection of protein biomarkers in biological fluids and tissues. Here, we present the circular proximity ligation assay (c-PLA), a highly specific protein detection method that outperforms traditional PLA in stringency, ease of use, and compatibility with low-affinity reagents. In c-PLA, two proximity probes bind to an analyte, providing a scaffolding that positions two free oligonucleotides such that they can be ligated into a circular DNA molecule. This assay format stabilizes antigen proximity probe complexes and enhances stringency by reducing the probability of random background ligation events. Circle formation also increases selectivity, since the uncircularized DNA can be removed enzymatically. We compare this method with traditional PLA on several biomarkers and show that the higher stringency for c-PLA improves reproducibility and enhances sensitivity in both buffer and human plasma. The limit of detection ranges from femtomolar to nanomolar concentrations for both methods. Kinetic analyses using surface plasmon resonance (SPR) and biolayer interferometry (BLI) reveal that the variation in limit of detection is due to the variation in antibody affinity and that c-PLA outperforms traditional PLA for low-affinity antibodies. The lower background signal can be used to increase proximity probe concentration while maintaining a high signal-to-noise ratio, thereby enabling the use of low-affinity reagents in a homogeneous assay format. We anticipate that the advantages of c-PLA will be useful in a variety of clinical protein detection applications where high-affinity reagents are lacking.
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Min, Qing, Jiaoyan Liu, Jing Li, Ying Wan, and Jiliang Wu. "Chitosan-Polylactide/Hyaluronic Acid Complex Microspheres as Carriers for Controlled Release of Bioactive Transforming Growth Factor-β1." Pharmaceutics 10, no. 4 (November 17, 2018): 239. http://dx.doi.org/10.3390/pharmaceutics10040239.
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Chitosan(CH)-polylactide(PLA) copolymers containing varied PLA percentages were synthesized using a group-protection method and one of them with solubility in water-based solvents was used to prepare CH-PLA/hyaluronic acid (HA) complex microspheres for the delivery of transforming growth factor-β1 (TGF-β1). An emulsification processing method was developed for producing TGF-β1-loaded CH-PLA/HA microspheres using sodium tripolyphosphate (TPP) as ionic crosslinker and the size of the microspheres was devised to the micron level in order to achieve high encapsulating efficiency. The encapsulating efficiency, swelling property and release administration of the microspheres could be synergistically regulated by PLA component, the applied TPP dose and the incorporated HA amount. In comparison to CH/HA microspheres, the CH-PLA/HA microspheres had greatly reduced TGF-β1 release rates and were able to administrate the TGF-β1 release at controlled rates over a significant longer period of time. The released TGF-β1 was detected to be bioactive when compared to the free TGF-β1. These results suggest that the presently developed CH-PLA/HA complex microspheres have promising potential in delivering TGF-β1 for cartilage repair applications where the applied TGF-β1 amount in the early stage needs to be low whilst the sustained TGF-β1 release at an appropriate dose in the later stage has to be maintained
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Li, Jingyan, and Cristina Sabliov. "PLA/PLGA nanoparticles for delivery of drugs across the blood-brain barrier." Nanotechnology Reviews 2, no. 3 (June 1, 2013): 241–57. http://dx.doi.org/10.1515/ntrev-2012-0084.
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AbstractThe blood-brain barrier (BBB), which protects the central nervous system (CNS) from unnecessary substances, is a challenging obstacle in the treatment of CNS disease. Many therapeutic agents such as hydrophilic and macromolecular drugs cannot overcome the BBB. One promising solution is the employment of polymeric nanoparticles (NPs) such as poly (lactic-co-glycolic acid) (PLGA) NPs as drug carrier. Over the past few years, significant breakthroughs have been made in developing suitable PLGA and poly (lactic acid) (PLA) NPs for drug delivery across the BBB. Recent advances on PLGA/PLA NPs enhanced neural delivery of drugs are reviewed in this paper. Both in vitro and in vivo studies are included. In these papers, enhanced cellular uptake and therapeutic efficacy of drugs delivered with modified PLGA/PLA NPs compared with free drugs or drugs delivered by unmodified PLGA/PLA NPs were shown; no significant in vitro cytotoxicity was observed for PLGA/PLA NPs. Surface modification of PLGA/PLA NPs by coating with surfactants/polymers or covalently conjugating the NPs with targeting ligands has been confirmed to enhance drug delivery across the BBB. Most unmodified PLGA NPs showed low brain uptake (<1%), which indirectly confirms the safety of PLGA/PLA NPs used for other purposes than treating CNS diseases.
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Paris, Hunter L., Timothy J. Fulton, Robert F. Chapman, Alyce D. Fly, David M. Koceja, and Timothy D. Mickleborough. "Effect of carbohydrate ingestion on central fatigue during prolonged running exercise in moderate hypoxia." Journal of Applied Physiology 126, no. 1 (January 1, 2019): 141–51. http://dx.doi.org/10.1152/japplphysiol.00684.2018.
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To determine whether acute exposure to moderate hypoxia alters central and peripheral fatigue and to test whether carbohydrate ingestion impacts fatigue characteristics, 12 trained runners completed three running trials lasting 1 h each at 65% of normoxic maximum oxygen uptake. The first trial was performed in normoxia [inspired O2 fraction ([Formula: see text]) = 0.21], and the last two trials were completed in hypoxia ([Formula: see text] = 0.15). Participants ingested a placebo drink in normoxia (NORM-PLA), a placebo drink in hypoxia (HYP-PLA), or a carbohydrate solution in hypoxia (HYP-CHO). HYP conditions were randomized. Peripheral [change in potentiated quadriceps twitch force (ΔQtw,pot)] and central [change in voluntary activation (ΔVA)] fatigue were assessed via preexercise-to-postexercise changes in magnetically evoked quadriceps twitch. In HYP, blood was drawn to determine the ratio of free-tryptophan (f-TRP) to branched-chain amino acids (BCAA). After exercise, peripheral fatigue was reduced to a similar degree in normoxia and hypoxia (ΔQtw,pot = −4.5 ± 1.3% and −4.0 ± 1.5% in NORM-PLA and HYP-PLA, respectively; P = 0.61). Central fatigue was present after normoxic and hypoxic exercise but to a greater degree in HYP-PLA compared with NORM-PLA (ΔVA: −4.7 ± 0.9% vs. −1.9 ± 0.7%; P < 0.01). Carbohydrate ingestion did not influence central fatigue (ΔVA in HYP-CHO: −5.7 ± 1.2%; P = 0.51 vs. HYP-PLA). After exercise, no differences were observed in the ratio of f-TRP to BCAA between HYP-PLA and HYP-CHO ( P = 0.67). Central fatigue increased during prolonged running exercise in moderate hypoxia although the ratio of f-TRP to BCAA remained unchanged. Ingesting carbohydrates while running in hypoxia did not influence fatigue development. NEW & NOTEWORTHY Hypoxic exposure influences the origin of exercise-induced fatigue and the rate of fatigue development depending on the severity of hypoxia. Our data suggest that moderate hypoxia increases central, but not peripheral, fatigue in trained runners exercising at 65% of normoxic maximum oxygen uptake. The increase in central fatigue was unaffected by carbohydrate intake and occurred although the ratio of free tryptophan to branched-chain amino acids remained unchanged.
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Lesage, Flore, Sabiniano Roman, Savitree Pranpanus, Simona Ospitalieri, Silvia Zia, Julio Jimenez, Sheila MacNeil, Jaan Toelen, and Jan Deprest. "Modulation of the Early Host Response to Electrospun Polylactic Acid Matrices by Mesenchymal Stem Cells from the Amniotic Fluid." European Journal of Pediatric Surgery 28, no. 03 (May 31, 2017): 285–92. http://dx.doi.org/10.1055/s-0037-1603522.
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Purpose The reconstruction of congenital diaphragmatic hernia or other congenital soft tissue defects often requires implants. These can be either degradable or permanent, each having their advantages. Whatever type is being used, the host response induced by implants plays a crucial role to determine the outcome. Macrophages are pivotal during implant remodeling; they are plastic and acquire in response to environmental stimuli either an inflammatory status and mediate subsequent fibrosis or a regulatory status and facilitate functional remodeling. Matrices engineered with mesenchymal stem cells (MSCs) have the capacity to modulate the host immune reaction. MSCs are believed to promote constructive remodeling of the implant through a regulatory macrophage response among others. Herein, we evaluate this potential of MSC derived from the amniotic fluid (AF-MSC), an interesting MSC type for neonatal reconstruction, on electrospun polylactic acid (PLA) scaffolds. Methods We seeded AF-MSC at a density of 1.105/cm2 on electrospun PLA matrices and determined cell viability. In vivo, we used cell-seeded or cell-free PLA matrices for subcutaneous implantation in immune competent rats. The host immune response was evaluated by histomorphometry at 14 days postoperatively. Results The PLA matrix supported adherence and proliferation of AF-MSC. Fourteen days after implantation, PLA matrices were well penetrated by inflammatory cells, new blood vessels, and collagen fibers. AF-MSC–seeded scaffolds were associated with a similar response yet with a decreased number of eosinophils, increased matrix degradation and collagen fiber deposition compared with controls. The amount of total macrophages and of M2-subtype was similar for all animals. Conclusion Electrospun PLA matrices are a suitable substrate for short-term culture of AF-MSC. In rats, addition of AF-MSC to PLA matrices modulates the host response after subcutaneous implantation, yet without a difference in macrophage profile compared with control.
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Cloughesy, Timothy, Gaetano Finocchiaro, Cristóbal Belda-Iniesta, Lawrence Recht, Alba A. Brandes, Estela Pineda, Tom Mikkelsen, et al. "Randomized, Double-Blind, Placebo-Controlled, Multicenter Phase II Study of Onartuzumab Plus Bevacizumab Versus Placebo Plus Bevacizumab in Patients With Recurrent Glioblastoma: Efficacy, Safety, and Hepatocyte Growth Factor and O6-Methylguanine–DNA Methyltransferase Biomarker Analyses." Journal of Clinical Oncology 35, no. 3 (January 20, 2017): 343–51. http://dx.doi.org/10.1200/jco.2015.64.7685.
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Purpose Bevacizumab regimens are approved for the treatment of recurrent glioblastoma in many countries. Aberrant mesenchymal-epithelial transition factor (MET) expression has been reported in glioblastoma and may contribute to bevacizumab resistance. The phase II study GO27819 investigated the monovalent MET inhibitor onartuzumab plus bevacizumab (Ona + Bev) versus placebo plus bevacizumab (Pla + Bev) in recurrent glioblastoma. Methods At first recurrence after chemoradiation, bevacizumab-naïve patients with glioblastoma were randomly assigned 1:1 to receive Ona (15 mg/kg, once every 3 weeks) + Bev (15 mg/kg, once every 3 weeks) or Pla + Bev until disease progression. The primary end point was progression-free survival by response assessment in neuro-oncology criteria. Secondary end points were overall survival, objective response rate, duration of response, and safety. Exploratory biomarker analyses correlated efficacy with expression levels of MET ligand hepatocyte growth factor, O6-methylguanine–DNA methyltransferase promoter methylation, and glioblastoma subtype. Results Among 129 patients enrolled (Ona + Bev, n = 64; Pla + Bev, n = 65), baseline characteristics were balanced. The median progression-free survival was 3.9 months for Ona + Bev versus 2.9 months for Pla + Bev (hazard ratio, 1.06; 95% CI, 0.72 to 1.56; P = .7444). The median overall survival was 8.8 months for Ona + Bev and 12.6 months for Pla + Bev (hazard ratio, 1.45; 95% CI, 0.88 to 2.37; P = .1389). Grade ≥ 3 adverse events were reported in 38.5% of patients who received Ona + Bev and 35.9% of patients who received Pla + Bev. Exploratory biomarker analyses suggested that patients with high expression of hepatocyte growth factor or unmethylated O6-methylguanine–DNA methyltransferase may benefit from Ona + Bev. Conclusion There was no evidence of further clinical benefit with the addition of onartuzumab to bevacizumab compared with bevacizumab plus placebo in unselected patients with recurrent glioblastoma in this phase II study; however, further investigation into biomarker subgroups is warranted.
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Redl, H., G. Schlag, A. Schiesser, and J. Davies. "Tumor necrosis factor is a mediator of phospholipase release during bacteremia in baboons." American Journal of Physiology-Heart and Circulatory Physiology 264, no. 6 (June 1, 1993): H2119—H2123. http://dx.doi.org/10.1152/ajpheart.1993.264.6.h2119.
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Phospholipase A (PLA) activity is elevated in plasma after polytrauma and in sepsis. During both situations, tumor necrosis factor (TNF) and free fatty acids (FFAs) are also increased. To determine whether there is a relationship between the changes in PLA and in TNF that occur during sepsis, we used a primate model of bacteremia. Live Escherichia coli (5 x 10(8) colony-forming units/kg) was injected into anesthetized baboons (n = 10). Four of these animals were pretreated with an anti-TNF antibody (anti-TNF Ab, 15 mg/kg). After the administration of bacteria (2 h), the plasma TNF was 10.2 +/- 3.2 ng/ml. PLA and FFA reached their maximum values of 191 +/- 14 U/l and 1.5 +/- 0.3 mM at 10 and 24 h after the injection of bacteria, respectively. In the animals treated with anti-TNF Ab, plasma TNF was undetectable; the highest values recorded for PLA and FFA were 71 +/- 23 U/l and 0.7 +/- 0.3 mM, respectively. Thus TNF appears to be an important mediator of PLA release during sepsis.
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Zhu, Hai Yan, Ying Chen Zhang, Jing Zou, Hong Yan Wu, and Y. P. Qiu. "The Microstructural Deformation of the Montmorillonite Particles/Polypropylene/Polylactic Acid Nanocomposite Filaments Infused with Plasma Treated Montmorillonite." Materials Science Forum 620-622 (April 2009): 469–72. http://dx.doi.org/10.4028/www.scientific.net/msf.620-622.469.
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The purpose of the present work is to investigate the microstructural deformation of the montmorillonite (MMT) particles/polypropylene (PP)/polylactic acid (PLA) nanocomposite filaments infused with plasma treated MMT. The activation volumes of the MMT/PP/PLA nanocomposite filaments ranging from 31.4572 to 151.2100 (nm)3 estimated by the Eyring’s equation quantitatively revealed that the plasma treated MMT acted as obstacles to dislocation motion during microstructural plastic deformation mechanisms. DSC analysis showed marked increases in glass transition temperature (Tg), indicating the plasma treated MMT could effectively help resist the free crankshaft movement of the macromolecular chain in the nanocomposite filaments. In addition, the MMT/PP/PLA nanocomposite filaments developed intercalated structures which had been examined by SEM.
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Rockwell, Michelle S., Madlyn I. Frisard, Janet W. Rankin, Jennifer S. Zabinsky, Ryan P. Mcmillan, Wen You, Kevin P. Davy, and Matthew W. Hulver. "Effects of Seasonal Vitamin D3 Supplementation on Strength, Power, and Body Composition in College Swimmers." International Journal of Sport Nutrition and Exercise Metabolism 30, no. 2 (March 1, 2020): 165–73. http://dx.doi.org/10.1123/ijsnem.2019-0250.
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The purpose of this study was to evaluate the impact of fall season vitamin D3 supplementation on strength/power, body composition, and anabolic hormones in swimmers with optimal vitamin D status at summer’s end. Male and female National Collegiate Athletic Association Division I swimmers (N = 19) with optimal 25-hydroxyvitamin D [25(OH)D] randomly received 5,000 IU of vitamin D3 (VITD) or placebo (PLA) daily for 12 weeks while participating in swimming and strength and conditioning training (August–November). Before and after the intervention, the participants underwent blood sampling for analysis of serum 25(OH)D, parathyroid hormone, total testosterone, free testosterone, sex hormone-binding globulin, and insulin-like growth factor 1, dual-energy X-ray absorptiometry, and strength/power testing (bench press, squat, dead lift, standing broad jump, vertical jump, and dips and pull-ups). Sex was used as a covariate for analyses. The 25(OH)D was decreased by 44% in PLA (p < .05) and increased by 8% in VITD over the 12 weeks. Fat-free mass increased in VITD (56.4–59.1 kg; p < .05), but not PLA (59.4–59.7 kg; p < .01). Significant Group × Time interaction effects were observed for dead lift (F = 21.577, p < .01) and vertical jump (F = 11.219, p < .01), but no other strength/power tests. Total testosterone decreased similarly in both groups, but free testosterone decreased and sex hormone-binding globulin increased only in PLA (p < .01). There were no group differences or changes in insulin-like growth factor 1 with the intervention. The findings suggest that vitamin D supplementation is an efficacious strategy to maintain 25(OH)D during the fall season training and to enhance some aspects of strength/power and fat-free mass in swimmers. Further research on the relationship between vitamin D and anabolic hormones is needed.
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Chisholm, Malcolm H. "Concerning the ring-opening polymerization of lactide and cyclic esters by coordination metal catalysts." Pure and Applied Chemistry 82, no. 8 (June 19, 2010): 1647–62. http://dx.doi.org/10.1351/pac-con-09-09-24.
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A summary of the reactions involved in the ring-opening polymerization (ROP) of lactide (LA) to give polylactides (PLAs) is presented along with competing reactions. Particular attention is given to the stereoselective polymerization of rac-LA to give heterotactic PLA and meso-LA to give syndiotactic PLA by aluminum Schiff-based catalysts and to the development of highly active group 2 metal single-site catalysts. Melt or solvent-free polymerization is also described along with reactions that lead exclusively to cyclic-polylactides.
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Park, S. G., A. Abdal-Hay, and J. K. Lim. "Biodegradable Poly(Lactic Acid)/Multiwalled Carbon Nanotube Nanocomposite Fabrication Using Casting And Hot Press Techniques." Archives of Metallurgy and Materials 60, no. 2 (June 1, 2015): 1557–59. http://dx.doi.org/10.1515/amm-2015-0172.
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Abstract Biodegradable advanced polymer composites have recently received a large amount of attention. The present study aimed to design poly(lactic acid) multiwalled carbon nanotube nanocomposites (PLA/MWCNTs) using a simple fabrication technique. A PLA sheet was first dissolved in dichloromethane, and MWCNTs were subsequently added at various concentrations (0.5, 1.5 and 5%) while applying shear strain stirring to achieve dispersion of carbon nanotubes (CNTs). These solutions were then molded and a hot press was used to generate sheets free of voids with entrapped solvent. The prepared samples were characterized using field emission scanning electron microscopy (FE-SEM), x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). Our data showed composite samples free of defects and voids, indicating that the hot press is capable of generating sufficiently compact polymer matrices. Additionally, TGA and FTIR showed significant bonding interactions between the PLA matrix and the nano-fillers. Collectively, our results suggest that incorporation of CNTs as nano-fillers into biodegradable polymers may have multiple applications in many different sectors.
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Liu, Mingxing, Jing Dong, Yajiang Yang, Xiangliang Yang, and Huibi Xu. "Effect of Poly(D, L-lactic acid) Nanoparticles as Triptolide Carrier on Abating Rats Renal Toxicity by NMR-Based Metabolic Analysis." Journal of Nanoscience and Nanotechnology 8, no. 7 (July 1, 2008): 3493–99. http://dx.doi.org/10.1166/jnn.2008.136.
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The aim of this study is to investigate the effect of poly(D, L-lactic acid) (PLA) nanoparticles as triptolide carrier on abating renal toxicity for Sprague Dawley rats after oral administration. Triptolide has severe toxicities on digestive, urogenital and blood circulatory system. High-resolution 600-MHz 1H-nuclear magnetic resonance (1H-NMR)-based metabolic analysis was performed on urine samples obtained from five groups of Sprague Dawley rats administrated with free triptolide and triptolide-loaded PLA nanoparticles at day 5, 10 and 15. The relative concentrations of biomarkers for renal lesion caused by triptolide were determined by 1H-NMR. The disorder of metabolism was characterized by the exceptional changes of the relative concentrations of succinate, 2-oxoglutarate and citrate. Similarly, the renal lesion was characterized by an increase of the relative concentrations of trimethylamine N-oxide and dimethylglycine, and a decrease of that of urea and allantoin. These results revealed that triptolide-loaded PLA nanoparticles might abate the renal toxicity of triptolide in comparison with identical doses of the free drug. The higher the dose (0.6 mg/kg), the more pronounced was this trend during long-term application. These results were further confirmed by histopathological changes. These results indicated that PLA nanoparticles provided a promising new formulation to abate the renal toxicity caused by triptolide.
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Yaguchi, Yuta, Kenji Takeuchi, Tadashi Waragai, and Toshitake Tateno. "Durability Evaluation of an Additive Manufactured Biodegradable Composite with Continuous Natural Fiber in Various Conditions Reproducing Usage Environment." International Journal of Automation Technology 14, no. 6 (November 5, 2020): 959–65. http://dx.doi.org/10.20965/ijat.2020.p0959.
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Recently, biodegradable plastic materials that can be decomposed by living organisms have attracted significant attention because of the great demand for the safe disposal of plastics. Recycling has failed to provide a practical solution for plastic waste disposal (60% of all plastics produced are discarded). It is difficult to achieve both durability and biodegradability in biodegradable plastics. In additive manufacturing processes, polylactic acid (PLA), one of the biodegradable plastics, is typically used, but it presents strength and durability problems. We developed novel additive manufactured biodegradable composite plastics by inserting continuous natural fibers (cotton, hemp, jute, etc.) into fabricated layers of PLA. The composite had a greater strength than normal additive manufactured PLA materials and could be used like a normal PLA filament in fused deposition modeling to create free-form three-dimensional objects. In this study, we performed experiments to evaluate the durability and biodegradability of the composite (PLA as matrix and hemp fibers as reinforcement). Specimens made from the composite were exposed to a normal indoor environment and to severe environments that products might encounter during use (presence of water and UV light (300–400 nm)). The decrease in strength over time was compared with that of PLA, and the durability was evaluated. The results indicated that the strength of the manufactured composite material exceeded that of PLA under all conditions. Whereas the stiffness of PLA exposed to UV light reduced significantly, that of the composite material remained constant, suggesting the significant effect of fiber reinforcement. In addition, test specimens were buried in a simulated soil environment, and their biodegradability was evaluated. The strength of the composite material decreased rapidly, and the biodegradability was confirmed to be at an acceptable level.
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Dai, Shulin, Yucheng Feng, Shuyi Li, Yuxiao Chen, Meiqing Liu, Chao Zhang, Wei Zhang, and Yihua Yin. "Stereocomplexation Assisted Assembly of Poly(γ-glutamic Acid)-graft-polylactide Nano-micelles and Their Efficacy as Anticancer Drug Carrier." Anti-Cancer Agents in Medicinal Chemistry 18, no. 2 (April 19, 2018): 302–11. http://dx.doi.org/10.2174/1871520617666170911170104.
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Background: Micelles as drug carriers are characterized by their inherent instability due to the weak physical interactions that facilitate the self-assembly of amphiphilic block copolymers. As one of the strong physical interactions, the stereocomplexation between the equal molar of enantiomeric polylactides, i.e., the poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA), may be harnessed to obtain micelles with enhanced stability and drug loading capacity and consequent sustained release. </P><P> Aims/Methods: In this paper, stereocomplexed micelles gama-PGA-g-PLA micelles) were fabricated from the stereocomplexation between poly(gama-glutamic acid)-graft-PLLA gama-PGA-g-PLA) and poly(gamaglutamic acid)-graft-PDLA gama-PGA-g-PLA). These stereocomplexed micelles exhibited a lower CMC than the corresponding enantiomeric micelles. Result: Furthermore, they showed higher drug loading content and drug loading efficiency in addition to more sustained drug release profile in vitro. In vivo imaging confirmed that the DiR-encapsulated stereocomplexed gama-PGA-g-PLA micelles can deliver anti-cancer drug to tumors with enhanced tissue penetration. Overall, gama-PGA-g-PLA micelles exhibited greater anti-cancer effects as compared with the free drug and the stereocomplexation may be a promising strategy for fabrication of anti-cancer drug carriers with significantly enhanced efficacy.
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Török, Jozef, Monika Törökova, Darina Duplakova, Zuzana Murcinkova, Jan Duplak, Jakub Kascak, and Monika Karkova. "Advanced Configuration Parameters of Post Processor Influencing Tensile Testing PLA and Add-Mixtures in Polymer Matrix in the Process of FDM Technology." Applied Sciences 11, no. 13 (July 5, 2021): 6212. http://dx.doi.org/10.3390/app11136212.
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The present paper focuses on the configuration possibilities of post -processor influencing mechanical properties of a given test sample produced by the FDM printer from different materials. The research consists of assessing the composite material configurations through a static tensile test conducted on 80 samples produced. The samples were produced based on ISO 527-2 standard, type 1A, with a horizontal position and a layer height of 0.2 mm. The individual samples consisted of four basic groups of materials—the pure Polylactic acid (PLA) plastic (reference sample), and three composite samples with admixtures—PLA matrix with a copper admixture, PLA matrix with an iron admixture, and PLA matrix with a steel admixture. The static tensile test was conducted at a test speed of 5 mm/min. During the research, reference samples (pure PLA) were assessed in five orientations. Samples made of the PLA composite materials with admixtures were manufactured, tested, and evaluated only in the 0° orientation. The paper concludes by comparing the results of measurement with the original material, free from additives, and with the researched influence of the orientation of the prints on the resulting mechanical properties of shear samples and their surface structure. In the conducted experiments, the lowest tensile strength has been demonstrated in test samples the orbital transitions and the upper surface layers of which were parallel to the infill.
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Mincheva, Rosica, Satya Narayana Murthy Chilla, Richard Todd, Brieuc Guillerm, Julien De Winter, Pascal Gerbaux, Olivier Coulembier, Philippe Dubois, and Jean-Marie Raquez. "Reactive Extrusion and Magnesium (II) N-Heterocyclic Carbene Catalyst in Continuous PLA Production." Polymers 11, no. 12 (December 2, 2019): 1987. http://dx.doi.org/10.3390/polym11121987.
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Reactive extrusion and magnesium (II) N-heterocyclic carbene catalyst are successfully employed in continuous polylactide synthesis. The possibility of using six-membered N-heterocyclic carbene adducts to act as efficient catalysts towards the sustainable synthesis of poly(l-lactide) through ring-opening polymerization of l-lactide (LA) is first investigated in bulk batch reactions. Under optimized solvent-free conditions, polylactide (PLA) of moderate to high molecular weights and excellent optical activities are successfully achieved. These promising results are further applied in the continuous production of PLA in an extruder.
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Zhou, Yu Yan, Gui Yu Li, Hong Xia Wang, Lei Tao, and Jian Ping Liang. "Preparation and Properties of PLA Microspheres Containing ENRO by an S/O/W Emulsion Technique." Advanced Materials Research 335-336 (September 2011): 1439–42. http://dx.doi.org/10.4028/www.scientific.net/amr.335-336.1439.
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In the present paper, monodisperse poly(lactic acid) (PLA) microspheres (MS) containing the enrofloxacin (ENRO), were manufactured by using a modified solid in oil in water (S/O/W) emulsion solvent evaporation method. In order to prepare PLA microspheres with a higher drug loading efficiency by this modified technique, the test of stability and productivity of the primary emulsion was preliminary examined by change species or concentration of the oil-soluble surfactant and the ratio of water and organic solvent. Firstly, enrofloxacin polylactic acid microspheres (ENRO-PLA-MS) were producted, then the morphology and particle size distribution were estimated by scanning electron microscopy (SEM), its encapsulation efficiency and drug loading efficiency were assessed by High performance liquid chromatography (HPLC). In vivo conditions were simulated by an stable release buffer to obtain a detailed release and polymer degradation profile. Consequently, the ENRO-PLA-MS had a denser structure with a smooth, pore-free surface, the preparation of microspheres was simple, the prepared microspheres had excellent controlled drug release characteristics in vitro.
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Branquinho, Renata Tupinambá, Vanessa Carla Furtado Mosqueira, Jaquelline Carla Valamiel de Oliveira-Silva, Marianne Rocha Simões-Silva, Dênia Antunes Saúde-Guimarães, and Marta de Lana. "Sesquiterpene Lactone in Nanostructured Parenteral Dosage Form Is Efficacious in Experimental Chagas Disease." Antimicrobial Agents and Chemotherapy 58, no. 4 (January 21, 2014): 2067–75. http://dx.doi.org/10.1128/aac.00617-13.
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ABSTRACTThe drugs available for Chagas disease treatment are toxic and ineffective. We studied thein vivoactivity of a new drug, lychnopholide (LYC). LYC was loaded in nanocapsules (NC), and its effects were compared to free LYC and benznidazole againstTrypanosoma cruzi. Infected mice were treated in the acute phase at 2.0 mg/kg/day with free LYC, LYC-poly-ε-caprolactone NC (LYC-PCL), and LYC-poly(lactic acid)-co-polyethylene glycol NC (LYC-PLA-PEG) or at 50 mg/kg/day with benznidazole solution by the intravenous route. Animals infected with the CL strain, treated 24 h after infection for 10 days, evaluated by hemoculture, PCR, and enzyme-linked immunosorbent assay exhibited a 50% parasitological cure when treated with LYC-PCL NC and 100% cure when treated with benznidazole, but 100% of the animals treated during the prepatent period for 20 days with these formulations or LYC-PLA-PEG NC were cured. In animals with the Y strain treated 24 h after infection for 10 days, only mice treated by LYC-PCL NC were cured, but animals treated in the prepatent period for 20 days exhibited 100, 75, and 62.5% cure when treated with LYC-PLA-PEG NC, benznidazole, and LYC-PCL NC, respectively. Free LYC reduced the parasitemia and improved mice survival, but no mice were cured. LYC-loaded NC showed higher cure rates, reduced parasitemia, and increased survival when used in doses 2five times lower than those used for benznidazole. This study confirms that LYC is a potential new treatment for Chagas disease. Furthermore, the long-circulating property of PLA-PEG NC and its ability to improve LYC efficacy showed that this formulation is more effective in reaching the parasitein vivo.
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Touny, Ahmed H., Joseph G. Lawrence, Andrew D. Jones, and Sarit B. Bhaduri. "Effect of electrospinning parameters on the characterization of PLA/HNT nanocomposite fibers." Journal of Materials Research 25, no. 5 (May 2010): 857–65. http://dx.doi.org/10.1557/jmr.2010.0122.
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Halloysite nanotubes (HNT) reinforced polylactic acid (PLA) nanocomposite fibers were produced using an electrospinning approach for biomedical applications. The PLA/HNT nanocomposite fibers were characterized using x-ray diffraction (XRD) and scanning electron microscopy (SEM). The various factors such as type of solvent, solution concentration, HNT loading and feed rate, affecting the electrospinning process, and the morphology of the nanofibers were investigated, and the optimum values for these parameters are suggested. The results indicated that the addition of dimethylformamide (DMF) to chloroform facilitated the electrospinning process because of the improvement in electrical conductivity and viscosity of the solution. Nanometer-sized fibers were obtained by the addition of HNT to PLA. HNT loadings had a significant effect on the morphology of the nanofibers. Bead-free fibers were produced at feed rates between 1 and 4 mL/h.
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Maqsood, Langensiepen, and Seide. "The Efficiency of Biobased Carbonization Agent and Intumescent Flame Retardant on Flame Retardancy of Biopolymer Composites and Investigation of their Melt-Spinnability." Molecules 24, no. 8 (April 17, 2019): 1513. http://dx.doi.org/10.3390/molecules24081513.
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The objective of this study is to assess the efficiency of biobased carbonization agent in intumescent formulations (IFRs) to examine the flame retardant properties of polylactic acid (PLA) composites and to investigate their melt-spinnability. We used phosphorous-based halogen free flame retardant (FR) and kraft lignin (KL) as bio-based carbonization agent. After melt compounding and molding into sheets by hot pressing various fire related characteristics of IFR composites were inspected and were characterized by different characterization methods. It was fascinating to discover that the introduction of 5−20 wt% FR increased the limiting oxygen index (LOI) of PLA composites from 20.1% to 23.2−33.5%. The addition of KL with content of 3−5 wt% further increased the LOI up to 36.6−37.8% and also endowed PLA/FR/KL composites with improved anti-dripping properties. Cone calorimetry revealed a 50% reduction in the peak heat release rate of the IFR composites in comparison to 100% PLA and confirmed the development of an intumescent char structure containing residue up to 40%. For comparative study, IFR composites containing pentaerythritol (PER) as a carbonization agent were also prepared and their FR properties were compared. IFR composites were melt spun and mechanical properties of multifilament yarns were tested. The analysis of char residues by energy dispersive X-ray spectrometry (EDS) and SEM images confirmed that PLA/FR/KL composites developed a thicker and more homogeneous char layer with better flame retardant properties confirming that the fire properties of PLA can be enhanced by using KL as a carbonization agent.
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Maqsood, Muhammad, and Gunnar Seide. "Improved Thermal Processing of Polylactic Acid/Oxidized Starch Composites and Flame-Retardant Behavior of Intumescent Non-Wovens." Coatings 10, no. 3 (March 20, 2020): 291. http://dx.doi.org/10.3390/coatings10030291.
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Thermoplastic processing and spinning of native starch is very challenging due to (a) the linear and branched polymers (amylose and amylopectin) present in its structure and (b) the presence of inter-and-intramolecular hydrogen bond linkages in its macromolecules that restrict the molecular chain mobility. Therefore, in this study, oxidized starch (OS) (obtained after oxidation of native starch with sodium perborate) was melt-blended with polylactic acid (PLA) polymer to prepare PLA/OS blends that were then mixed together with ammonium polyphosphate (APP), a halogen-free flame retardant (FR) used as acid donor in intumescent formulations on twin-screw extruder to prepare PLA/OS/APP composites. OS with different concentrations also served as bio-based carbonic source in intumescent formulations. PLA/OS/APP composites were melt spun to multifilament fibers on pilot scale melt-spinning machine and their crystallinity and mechanical properties were optimized by varying spinning parameters. The crystallinity of the fibers was studied by differential scanning calorimetry and thermal stabilities were analyzed by thermogravimetric analysis. Scanning electron microscopy was used to investigate the surface morphology and dispersion of the additives in the fibers. Needle-punched non-woven fabrics from as prepared melt-spun PLA/OS/APP fibers were developed and their fire properties such as heat release rate, total heat release, time to ignition, residual mass % etc. by cone calorimetry test were measured. It was found that PLA/OS/APP composites can be melt spun to multifilament fibers and non-woven flame-retardant fabrics produced thereof can be used in industrial FR applications.
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Buckinx, Fanny, Vincent Marcangeli, Lívia Pinheiro Carvalho, Maude Dulac, Guy Hajj Boutros, Gilles Gouspillou, Pierrette Gaudreau, José Morais, Philippe Noirez, and Mylène Aubertin-Leheudre. "Initial Dietary Protein Intake Influence Muscle Function Adaptations in Older Men and Women Following High-Intensity Interval Training Combined with Citrulline." Nutrients 11, no. 7 (July 22, 2019): 1685. http://dx.doi.org/10.3390/nu11071685.
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Background: This study evaluates whether the initial amount of dietary protein intake could influence the combined effect of high-intensity interval training (HIIT) and citrulline (CIT), or HIIT alone, on body composition, muscle strength, and functional capacities in obese older adults. Methods: Seventy-three sedentary obese older men and women who completed a 12-week elliptical HIIT program with double-blinded randomized supplementation of CIT or placebo (PLA) were divided into four groups according to their initial protein intake (CIT–PROT+: n = 21; CIT–PROT−: n = 19; PLA–PROT+: n = 19; PLA–PROT−: n = 14). Body composition (fat and fat-free masses), handgrip (HSr) strength, knee extensor (KESr) strength, muscle power, and functional capacities were measured pre-intervention and post-intervention. Results: Following the intervention, the four groups improved significantly regarding all the parameters measured. For the same initial amount of protein intake, the CIT–PROT− group decreased more gynoid fat mass (p = 0.04) than the PLA–PROT− group. The CIT–PROT+ group increased more KESr (p = 0.04) than the PLA–PROT+ group. In addition, the CIT–PROT− group decreased more gynoid FM (p = 0.02) and improved more leg FFM (p = 0.02) and HSr (p = 0.02) than the CIT–PROT+ group. Conclusion: HIIT combined with CIT induced greater positive changes than in the PLA groups. The combination seems more beneficial in participants consuming less than 1 g/kg/d of protein, since greater improvements on body composition and muscle strength were observed.
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Perez-Nakai, Aina, Alejandro Lerma-Canto, Ivan Domingez-Candela, Daniel Garcia-Garcia, Jose Miguel Ferri, and Vicent Fombuena. "Comparative Study of the Properties of Plasticized Polylactic Acid with Maleinized Hemp Seed Oil and a Novel Maleinized Brazil Nut Seed Oil." Polymers 13, no. 14 (July 20, 2021): 2376. http://dx.doi.org/10.3390/polym13142376.
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In this study, for the first time, Brazil nut seed oil was chemically modified with maleic anhydride to obtain maleinized Brazil nut seed oil (MBNO). The same process was developed to obtain maleinized hemp seed oil (MHO). The use of MBNO and MHO was studied as bio-based plasticizers by incorporating them with different contents ranging from 0 to 10 phr in a polylactic acid (PLA) matrix. By means of mechanical, thermal and thermomechanical characterization techniques, the properties of the different formulations were studied to evaluate the plasticizing effect of the MBNO and MHO. With the addition of both plasticizers, a significant increase in ductile properties was observed, reaching an increase in elongation at break of 643% with 7.5 phr MBNO and 771% with 10 phr MHO compared to neat PLA. In addition, it has been observed that the mechanical resistant properties do not decrease, since the oils enhance the crystallization of PLA by increasing the free volume between its chains and counteracting the effect. Finally, a disintegration test was carried out under thermophilic conditions at 58 °C for 27 days, demonstrating that the incorporation of MHO and MBNO does not significantly affect the biodegradability of neat PLA.
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Chinevere, Troy D., Robert D. Sawyer, Andrew R. Creer, Robert K. Conlee, and Allen C. Parcell. "Effects of l-tyrosine and carbohydrate ingestion on endurance exercise performance." Journal of Applied Physiology 93, no. 5 (November 1, 2002): 1590–97. http://dx.doi.org/10.1152/japplphysiol.00625.2001.
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To test the effects of tyrosine ingestion with or without carbohydrate supplementation on endurance performance, nine competitive cyclists cycled at 70% peak oxygen uptake for 90 min under four different feeding conditions followed immediately by a time trial. At 30-min intervals, beginning 60 min before exercise, each subject consumed either 5 ml/kg body wt of water sweetened with aspartame [placebo (Pla)], polydextrose (70 g/l) (CHO), l-tyrosine (25 mg/kg body wt) (Tyr), or polydextrose (70 g/l) and l-tyrosine (25 mg/kg body wt) (CHO+Tyr). The experimental trials were given in random order and were carried out by using a counterbalanced double-blind design. No differences were found between treatments for oxygen uptake, heart rate, or rating of perceived exertion at any time during the 90-min ride. Plasma tyrosine rose significantly from 60 min before exercise to test termination (TT) in Tyr (means ± SE) (480 ± 26 μmol) and CHO+Tyr (463 ± 34 μmol) and was significantly higher in these groups from 30 min before exercise to TT vs. CHO (90 ± 3 μmol) and Pla (111 ± 7 μmol) ( P < 0.05). Plasma free tryptophan was higher after 90 min of exercise, 15 min into the endurance time trial, and at TT in Tyr (10.1 ± 0.9, 10.4 ± 0.8, and 12.0 ± 0.9 μmol, respectively) and Pla (9.7 ± 0.5, 10.0 ± 0.3, and 11.7 ± 0.5 μmol, respectively) vs. CHO (7.8 ± 0.5, 8.6 ± 0.5, and 9.3 ± 0.6 μmol, respectively) and CHO+Tyr (7.8 ± 0.5, 8.5 ± 0.5, 9.4 ± 0.5 μmol, respectively) ( P < 0.05). The plasma tyrosine-to-free tryptophan ratio was significantly higher in Tyr and CHO+Tyr vs. CHO and Pla from 30 min before exercise to TT ( P < 0.05). CHO (27.1 ± 0.9 min) and CHO+Tyr (26.1 ± 1.1 min) treatments resulted in a reduced time to complete the endurance time trial compared with Pla (34.4 ± 2.9 min) and Tyr (32.6 ± 3.0 min) ( P < 0.05). These findings demonstrate that tyrosine ingestion did not enhance performance during a cycling time trial after 90 min of steady-state exercise.