Littérature scientifique sur le sujet « Gum arabic nanoparticles »

Gold nanoparticles (AuNP) are potentially developed as nanomedicine because AuNP is easily synthesized, functionalized, and biocompatible. With gum arabic as a stabilizer, vincristine was conjugated with gold nanoparticles. As a reducing agent, it used 0.02 M Natrium Boro Hidrat (NaBH4) solution. Gold nanoparticles (AuNP) coated with conjugated gum Arabic (GA) and vincristine (VCR) were successfully synthesized and characterized. The conjugation of GA-VCR and AuNP displayed a narrow hydrodynamic particle size distribution with average size < 100 nm by TEM and PSA (particle size analyzer). We investigated the cytotoxic activity of conjugated vincristine-gum arabic-gold nanoparticle by tetrazolium salt assay (MTT) using cancer cell line CCR-CEM. Cytotoxic activity of conjugated VCR-GA-AuNP before and after purification by Size Exclusion Chromatography (SEC), against leukemia cell line CCRF-CEM, was described by IC50 value. All formulation had a cytotoxic of activity with IC50 <20 μg/ml. The IC50 of samples against CCRF cell line were 1,026 μg/mL and 2,607 ug/mL, respectively.

In this study, iron oxide nanoparticles (NPs) had been prepared by co-precipitation method. In order to reduce their toxicity and increase stability, prepared iron oxide was coated with gum Arabic. Gum Arabic is preferred over synthetic materials due to their non-toxicity, low cost and availability. Characterization of coated and non-coated iron oxide NPs had been performed by spectrophotometer, Fourier transfer infra-red spectrophotometer (FTIR), Zeta potential, X-ray diffraction (XRD) and field emission scanning electron microscopic (FE-SEM). The fabricated nanoparticles appeared purity and crystalline nature by XRD, with diameter average of 27.01 nm and 55.12 nm for iron oxide NPs and iron oxide NPs coated with gum Arabic, respectively. On the other hand, four biological activities of coated and non-coated iron oxide had been investigated. High removal of methylene blue pollutant dye (46%) was observed with iron oxide NPs, while removal percentage was 22.6 performed by iron oxide NPs coated with gum Arabic within 72 h. Iron oxide NPs revealed high inhibition zones of 27.5 nm and 30 mm, at 1000 [Formula: see text]g/ml, against S. aureus and E. coli, respectively, while coated iron oxide NPs with gum Arabic revealed low antibacterial activity against both examined bacteria even when used at 1000 [Formula: see text]g/ml. The hemolytic activity of prepared NPs had been determined. The hemolytic percentage was increased whenever concentrations of nanoparticles increased. Lower hemolytic percentages were 69.76 and 50.98 for iron oxide NPs and iron oxide NPs coated with gum Arabic were observed at a concentration of 250 [Formula: see text]g/ml. Finally, cytotoxic activity was estimated against MCF-7 cell line and normal cell line WRL68 by MTT assay. A decrease in MCF-7 viability to 65.1% was observed when 400 [Formula: see text]g/ml of iron oxide NPs was used, while WRL68 viability was 75.03%. Iron oxide NPs coated with gum Arabic revealed significant reduction in MCF-7 and WRL68 viability to 69.90% and 80.05%, respectively, when 400 [Formula: see text]g/ml of nanoparticles was applied.

Noble gold nanoparticles (AuNps) are generally nontoxic due to their inert nature. The gold nanoparticles are easily tagged with various proteins and biomolecules rich in aminoacid leading to important biomedical applications including targeted drug delivery, cellular imaging, and biosensing. In this study, three cytotoxicity detection assays 3-(4,5-dimethylthiozol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT), neutral red cell, and lactate dehydrogenase (LDH) on gold nanoparticles stabilized with citrate, starch, and gum arabic are used. The assays used are based on different mode of detection like LDH release, MTT metabolism, and neutral red uptake. We found that the AuNps stabilized with citrate are very sensitive to the change of concentration and time assay compared to starch and gum arabic stabilized gold nanoparticles.

Dissertação apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para obtenção do grau de Mestre em Biotecnologia
The aims of this work were the functionalization of magnetic nanoparticles (MNPs)with Gum Arabic (GA) and the study of the effect of these modified particles on the growth and survival of mammalian cell cultures. MNPs consisting of Fe3O4 were synthesized by the Massart Method and further functionalized with GA by adsorption and covalent coupling via GA amino or carboxylic acid groups. The GA adsorption and binding isotherms displayed a Langmuir type. The maximum of GA coated on MNPs followed the order MNP_GAAPTS < MNP_GA_GAADS < MNP_GAADS < MNP_GAEDC,where MNPs coated with GA via EDC activation gave the best result for coupling (2,80g GA bound/g MNP for 2,62 mg/ml GA (eq.)). The particles were characterized by FTIR, BET, TEM and DLS, showing the greater dispersion and colloidal stability of particles in aqueous solution when GA is present. Cultures of mammalian cell lines(HEK293, CHO and TE671) were grown in the presence of uncoated and GA coated MNPs. Cellular viability was assessed for different incubation periods by means of the Trypan Blue exclusion test and by comparing cellular density with that of cells grown in the absence of particles. Different MNPs need different incubation periods to deposit at cellular surface, and the results vary with the cell type tested. With HEK293 cells, MNP_GAAPTS attach to the cell surface after only 30 minutes, while bare magnetite and MNP_GAEDC have a greater effect on compromising cellular viability. On the other hand, MNP_GAADS needed longer incubation periods to attach to the cell surface and caused less cellular damage for identical incubation times with the other particles tested.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Os artrópodes tem sido uma das principais causas de perdas agrícolas em todo o mundo. Só no Brasil essas perdas podem chegar a 7,7 % ao ano. A utilização extensiva de pesticidas sintéticos tem sido a principal forma de controle deste tipo de praga, no entanto, os efeitos adversos destes compostos tanto para o meio ambiente quanto para a saúde humana tem motivado a busca por alternativas menos impactantes. Neste contexto, diversos mecanismos estão sendo estudados a fim de minimizar estes danos, como por exemplo, o desenvolvimento de sistemas de liberação modificada, utilizando polímeros biodegradáveis e proteínas. Aliado a isto, a utilização de pesticidas botânicos também tem demostrado potencialidade para o combate a essas pragas, devido aos menores impactos causados por esses produtos de origem natural. Portanto, o presente trabalho apresenta o desenvolvimento (preparo e caracterização) de sistemas nanocarreadores produzidos a partir dos polímeros quitosana e goma arábica e da proteína zeína para os compostos botânicos (geraniol, citronelal, eugenol e cinamaldeído), bem como, os potenciais efeitos cito e fitotóxicos destes sistemas. Ademais foram também realizados ensaios de atividade biológica destes sistemas em pragas agrícolas (mosca-branca, ácaro-rajado e lagarta falsamedideira). Os compostos botânicos apresentaram elevada eficiência de encapsulação em ambos os sistemas carreadores, sendo que os sistemas foram capazes de proteger os compostos contra uma degradação prematura e também contra a radiação ultravioleta. Os resultados de fito e citotoxicidade mostraram que a encapsulação diminuiu o efeito tóxico dos ativos. Os sistemas também apresentaram atividade biológica contra as pragas agrícolas testadas. As nanopartículas de zeína contendo os compostos botânicos mostraram efeito repelente contra o ácaro-rajado (Tetranychus urticae) em condições laboratoriais e de semi-campo, além de efeito subletal em largarta falsa-medideira (Chrysodeixis includes). Já as nanopartículas de quitosana/goma arábica contendo geraniol mostraram efeito atrativo para mosca-branca, sendo promissora para aplicações em sistemas de armadilha. A importância desta tese reside na dimensão que o setor agrícola representa para a economia brasileira e mundial, aliado a isto o mercado de defensivos agrícolas cresce anualmente, sendo o Brasil um dos líderes no consumo destes produtos. Desta forma, o desenvolvimento de tecnologia com elevado valor agregado à área de controle de pragas em agricultura é promissora uma vez que podem ser produzidos sistemas mais eficientes no controle de pragas, menos impactantes ao ambiente e consequentemente à saúde humana.
Arthropods have been a major cause of agricultural losses worldwide. Only in Brazil can these losses reach 7.7% per year. The extensive use of synthetic pesticides has been the main form of control of this type of pest, however, the adverse effects of these compounds for both the environment and human health have motivated the search for less impactful alternatives. In this context, several mechanisms are being studied in order to minimize these damages, such as the development of modified release systems using biodegradable polymers and proteins. In addition to this, the use of botanical pesticides has also shown potential for combating these pests, due to the lower impacts caused by these products of natural origin. Therefore, the present work showed the development (preparation and characterization) of nanocarrier systems produced from chitosan and gum arabic polymers and zein protein for the botanical compounds (geraniol, citronellal, eugenol and cinnamaldehyde), as well as the potential effects and phytotoxic systems. In addition, tests of the biological activity of these systems on agricultural pests (whitefly, two-spotted spider mite and soybean looper) were also carried out. The botanical compounds showed high encapsulation efficiency in both carrier systems, and the systems were able to protect the compounds against premature degradation and also against ultraviolet radiation. The phyto and cytotoxicity results showed that encapsulation decreased the toxic effect of the active compounds. The systems also showed biological activity against the agricultural pests tested. The zein nanoparticles containing the botanicals showed a repellent effect against the brindle two-spotted spider mite (Tetranychus urticae) under laboratory and semi-field conditions, as well as a sublethal effect on soybean looper (Chrysodeixis includes). The chitosan/gum arabic nanoparticles containing geraniol showed attractive effect for whitefly, being promising for applications in trap systems. The importance of this thesis lies in the dimension that the agricultural sector represents for the Brazilian and world economy, in addition to that the market for agricultural pesticides grows annually, in special as Brazil is one of the leaders in the consumption of these products. In this way, the development of new technologies to pest control in agriculture is promising since more efficient pest control systems can be produced, less impacting the environment and consequently to human health.
FAPESP: 2014/20286-9

This project aimed to engineer new T2 MRI contrast agents for cell labeling based on formulations containing monodisperse iron oxide magnetic nanoparticles (MNP) coated with natural and synthetic polymers. Monodisperse MNP capped with hydrophobic ligands were synthesized by a thermal decomposition method, and further stabilized in aqueous media with citric acid or meso-2,3-dimercaptosuccinic acid (DMSA) through a ligand exchange reaction. Hydrophilic MNP-DMSA, with optimal hydrodynamic size distribution, colloidal stability and magnetic properties, were used for further functionalization with different coating materials. A covalent coupling strategy was devised to bind the biopolymer gum Arabic (GA) onto MNPDMSA and produce an efficient contrast agent, which enhanced cellular uptake in human colorectal carcinoma cells (HCT116 cell line) compared to uncoated MNP-DMSA. A similar protocol was employed to coat MNP-DMSA with a novel biopolymer produced by a biotechnological process, the exopolysaccharide (EPS) Fucopol. Similar to MNP-DMSA-GA, MNP-DMSA-EPS improved cellular uptake in HCT116 cells compared to MNP-DMSA. However, MNP-DMSA-EPS were particularly efficient towards the neural stem/progenitor cell line ReNcell VM, for which a better iron dose-dependent MRI contrast enhancement was obtained at low iron concentrations and short incubation times. A combination of synthetic and biological coating materials was also explored in this project, to design a dynamic tumortargeting nanoprobe activated by the acidic pH of tumors. The pH-dependent affinity pair neutravidin/iminobiotin, was combined in a multilayer architecture with the synthetic polymers poy-L-lysine and poly(ethylene glycol) and yielded an efficient MRI nanoprobe with ability to distinguish cells cultured in acidic pH conditions form cells cultured in physiological pH conditions.

Literature review of molten salt nanofluids is performed in this study with focus on the thermo-fluidic properties and performance in thermal management applications. The colloidal mixture of nanoparticles in a base liquid phase is called nanofluid. Molten salts such as alkali nitrate eutectics, alkali carbonate eutectics and alkali chloride eutectics have high melting temperatures. These materials are suitable for various high temperature applications, including as Heat Transfer Fluid (HTF), Thermal Energy Storage (TES), Concentrated Solar Power (CSP) plants, nuclear power, etc. The major drawback of molten salt materials is their low thermal conductivity and specific heat capacity. Enhancing the thermo-physical properties of molten salt materials can lower the cost of power production involving these materials (e.g., as HTF and/ or TES in CSP or nuclear power plants. Mixing molten alt eutectics with nanoparticles (e.g., molten salt nanofluids) can provide a cost-effective technique for enhancing the specific heat capacity and thermal conductivity which in turn can enable the reduction in the cost of power production. In this review - the following topics involving molten salt nanofluids were explored: thermo-physical property measurements, numerical modeling (e.g., Molecular Dynamics/ MD simulations), materials characterization (e.g., using electron microscopy techniques — such as SEM and TEM). For example, SEM studies in conjunction with MD simulation results confirm the formation of a dense layer of fluid molecules on the surface of nanoparticles that can enhance the specific heat capacity of these molten salt nanomaterials. Subsequently the concepts of nanofins was explored (which involves the study of interfacial thermal impedance, such as resistance, capacitance and diodicity). The contribution of these interfacial thermal impedances to the enhancement of specific heat capacity and thermal conductivity are also explored. Specific heat enhancement as high as 100% has been observed for various molten salt eutectics when doped with 1.5% (weight) silica nanoparticles. Various synthesis protocols such as one-step, two-step and three-step methods as well as conventional experimental methods used for specific heat capacity measurement are compared and examined. A review of the effects of concentration, nanoparticle size, temperature, base fluid, and nanofluid chemical properties is also performed. Other topics of interest are the anomalous enhancement of thermal conductivity in molten salt nanofluids which contradict typical predictions obtained from using the effective medium theory. The available data in literature shows enhancement in thermal conductivity by as much as 35–45% for carbonate eutectics doped with silica nanoparticles at 1% mass fraction. The possible mechanisms suggested for this improvement are briefly discussed and compared with experimental observations (e.g., using SEM). In addition, nanofluids often display non-Newtonian rheological behavior. This necessitates a rigorous study, since the applications of nanofluids will impact the required pumping power. Studies show that the rheological properties of molten salt nanofluids are a function of base salt composition, shape of nanoparticles selected, chemical formula of nanoparticles, concentration of nanoparticles, size of nanoparticles, temperature, shear rate and synthesis protocol of the nanofluid. Several models are introduced to predict the viscosity variation along with their advantageous and disadvantages. SEM results show agglomeration of nanoparticles can be reduced by doping the nanofluids with very small values of mass fractions of additives such as Gum Arabic.