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1
Corkhill, P. H. "Novel hydrogel polymers." Thesis, Aston University, 1988. http://publications.aston.ac.uk/9725/.
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Hydrogels may be conveniently described as hydrophilic polymers that are swollen by, but do not dissolve in water. In this work a series of copolymer hydrogels and semi-interpenetrating polymer networks based on the monomers 2-hydroxyethyl methacrylate, N-vinyl pyrrolidone and N'N' dimethyl acrylamide, together with some less hydrophilic hydroxyalkyl acrylates and methacrylates have been synthesised. Variations in structure and composition have been correlated both with the total equilibrium water content of the resultant hydrogel and with the more detailed water binding behaviour, as revealed by differential scanning calorimetry studies. The water binding characteristics of the hydrogels were found to be primarily a function of the water structuring groups present in gel. The water binding abilities of these groups were, however, modified by steric effects. The mechanical properties of the hydrogels were also investigated. These were found to be dependent on both the polymer composition and the amount and nature of the water present in the gels. In biological systems, composite formation provides a means of producing strong, high water content materials. As an analogy with these systems hydrogel composites were prepared. In an initial study of these materials the water binding and mechanical properties of semi-interpenetrating polymer networks of N'N'dimethyl acrylamide with cellulosic type materials, with polyurethanes and with ester containing polymers were examined. A preliminary investigation of surface properties of both the copolymers and semi-interpenetrating polymer networks has been completed, using both contact angle measurements and anchorage dependent fibroblast cells. Measurable differences in surface properties attributable to structural variations in the polymers were detected by droplet techniques in the dehydrated state. However, in the hydrated state these differences were masked by the water in the gels. The use of cells enabled the underlying differences to be probed and the nature of the water structuring group was again found to be the dominant factor.
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Ma, James J. "Novel hydrogel polymers." Thesis, Aston University, 1995. http://publications.aston.ac.uk/9661/.
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Hydrogels are a unique class of polymers which swell, but do not dissolve in water. A range of 2-hydroxyethyl methacrylate based copolymer hydrogels have been synthesised and are described in this thesis. Initially, hydrogels were synthesised containing acryloylmorpholine, N,N-dimethyl acrylamide and N-vinyl pyrrolidone. Variations in structure and composition have been correlated with the sequence distribution, equilibrium water content (EWC) , mechanical and surface properties of the hydrogels. The sequence distribution was found to be dependant on the structure and reactivity of the monomers. The Ewe was found to be dependant on the water structuring groups present in the hydrogel, although the water binding abili ties were modified by steric effects. The mechanical properties were also investigated and were found to be dependant on the monomer structure, sequence distribution and the amount and nature of water in the hydrogel. The macroscopic surface properties of the hydrogels were probed using surface energy determinations and were found to be a function of the water content and the hydrogel composition. At a molecular level, surface properties were investigated using an in vitro ocular spoilation model and single protein adhesion studies. The results indicate that the sequence distribution and the polarity of the surface affect the adhesion of biological species. Finally, a range of 2-hydroxyethyl methacrylate based copolymer hydrogels containing both charged monomer groups and linear polyethers have been synthesised and described. Although variations in the Ewe are observed with the structure of the monomers, it was observed that the Ewe increased due to the polar character of the charged monomers and the chain length and hydrophilicity of the polyethers. Investigation of these hydrogel surfaces revealed subtle changes. The molecular surface properties indicate the significance of the effect of charge and molecular mobility of the groups expressed at the hydrogel surface
3
Kim, Jongseong. "Stimuli-Responsive Hydrogel Microlenses." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14496.
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This dissertation is aimed towards using stimuli-responsive pNIPAm-co-AAc microgels synthesized via free-radical precipitation polymerization to prepare stimuli-responsive hydrogel microlenses. Chapter 1 gives a detailed background of hydrogels, and their applications using responsive hydrogels. Chapter 2 describes the use of colloidal hydrogel microparticles as microlens elements and the fabrication method to form the hydrogel microlens arrays via Coulombic interactions. Chapter 3 shows the demonstration of tunable microlenses prepared by the method used in Chapter 2. In this chapter the microlenses are subjected to various pH and temperature in aqueous solutions. Chapter 4 describes that the microlens arrays constructed on Au nanoparticle-functionalized glass substrates by self-assembly display dramatic changes in lensing power in response to an impingent frequency-doubled Nd:YAG laser. The microlens photoswitching is highly reversible, with sub-millisecond lens switching times. Chapter 5 describes the development of bioresponsive hydrogel microlenses as a new protein detection technology. The microlens method is shown to be very specific for the target protein, with no detectable interference from nonspecific protein binding. Chapter 6 describes the use of bioresponsive hydrogel microlenses as a label-free biosensing scaffolding. These microstructures simultaneously act as the biosensors scaffolding/immobilization architecture, transducer, amplifier, and also allow for broad tunability of the analyte concentration to which the microlens is sensitive.
4
Pareek, Pradeep. "Photo-crosslinked Surface Attached Thin Hydrogel Layers." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2005. http://nbn-resolving.de/urn:nbn:de:swb:14-1115623310082-44480.
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Stimuli sensitive polymers and hydrogels respond with large property changes to small physical and chemical stimuli (e.g. temperature, pH, ionic strength). The bulk behavior of these polymers is widely studied and they show an isotropic swelling. However, thin hydrogel layers of polymers on a substrate show a swelling behavior, which is constrained in some way. Therefore, size, confinement, patternability, response time and transition temperature of thin hydrogel layers are the most important parameters in technological applications and this study focuses on the investigation of these above-mentioned parameters. The aim of this study involves synthesis, characterization and application of thin photo-crosslinked hydrogel layers. Dimethylmaleimide (DMI) moiety was incorporated in the polymers chains and was used to introduce photo-crosslinking by [2+2] cyclodimerization reaction in the presence of UV irradiation. The following photo-crosslinkers based on DMI group were synthesized ? - Acrylate photo-crosslinker (DMIAm) - Acrylamide photo-crosslinker (DMIAAm) - Polyol photo-crosslinker (DMIPA, DMIPACl) The conventional free radical polymerization of above listed photo-crosslinker with its respective monomer resulted in formation of photo-crosslinkable polymers of (a) HEMA, (b) DMAAm, (c) NIPAAm/DMAAm, (d) NIPAAm/Cyclam. The properties of these polymers were investigated by NMR, UV-VIS spectroscopy, GPC and SPR. Thin hydrogel layers were prepared by spin coating on gold-coated LaSFN9 glass. The covalent attachment to the surface was achieved through an adhesion promoter. Swelling behavior of the thin polymer layers was thoroughly investigated by Surface Plasmon Resonance (SPR) Spectroscopy and Optical Waveguide Spectroscopy (OWS). SPR and OWS gave a wide range of information regarding the film thickness, swelling ratio, refractive index, and volume degree of swelling of the thin hydrogel layer. For hydrophilic photo-crosslinked hydrogel layers of HEMA and DMAAm, it was observed that the volume degree of swelling was independent of temperature changes but was dependent on the photo-crosslinker mol-% in the polymer. These surface attached thin hydrogel layer exhibited an anisotropic swelling. For NIPAAm photo-crosslinked hydrogel layers with DMAAm as a hydrophilic monomer, it was observed that both transition temperature (Tc) and volume degree of swelling increases with increase in the mol-% of DMAAm. To study the effect of film thickness on Tc and volume degree of swelling, hydrogels with wide range of film thickness were prepared and investigated by SPR. These results provided vital information on the swelling behavior of surface attached hydrogel layer and showed the versatility of SPR instrument for studying thin hydrogel layers. Later part of project involved synthesis of multilayer hydrogel assembly involving a thermoresponsive polymer and a hydrophilic polymer. The combination of two layers with photo-crosslinkable DMAAm polymer as base layer and photo-crosslinkable NIPAAm polymer as top layer formulate a multilayer assembly where, the base layer only swells in response to temperature and the top layer shows temperature dependent swelling. Photo-crosslinked hydrogel layers of NIPAAm, DMAAm and HEMA shows a high-resolution patterns when irradiated by UV light through a chromium mask. At last this study focused on an important application of these hydrogel layers for cell attachment processes. Cell growth, proliferation and spreading shows a biocompatible nature of these hydrogel surfaces. Such thermoresponsive photo-crosslinkable multilayer structure forms bases for future projects involving their use in actuator material and cell-attachment processes.
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Trinh, Quang Thong. "Hydrogel based piezoresistive pH sensors." Dresden TUDpress, 2006. http://deposit.d-nb.de/cgi-bin/dokserv?id=2860048&prov=M&dok_var=1&dok_ext=htm.
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Al-Shohani, Athmar Dhahir Habeeb. "Hydrogel formulations for ophthalmic delivery." Thesis, University College London (University of London), 2017. http://discovery.ucl.ac.uk/1540916/.
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Going blind is incomprehensible and with an aging population the number of people with blinding disease is increasing. Glaucoma and age related macular degeneration (AMD) are two major causes of blindness affecting people as they age. The only proven treatment for glaucoma is lowering of the intraocular pressure (IOP) which is best done by surgically placing a channel from the anterior chamber to allow aqueous outflow to drain into the subconjunctival space. The drainage channel can be formed by the use of a glaucoma drainage device (GDD) or by glaucoma filtration surgery (GFS). Both GFS and the use of a GDD often fail over time because local fibrosis (scarring) in the subconjunctival space blocks aqueous outflow resulting in the increase of IOP and disease progression. It was hypothesised that a more biocompatible GDD could be fabricated from a hydrogel, and that the hydrogel material could be used to restrict aqueous outflow to control the IOP. Hydrogels are widely used in ophthalmic applications including contact lens and intraocular lens. Since hydrogels are widely examined for use in drug delivery, it was also hypothesised that a hydrogel implant could be made for the subconjunctival space after GFS to stop tissue adhesion and to deliver locally an anti-fibrotic or anti-inflammatory drug to increase the chances for long-term surgical success. For AMD, the current treatment is intravitreal (IVT) injections of anti-VEGF antibodies approximately every 4-6 weeks. IVT injections are an invasive procedure and associated with some complications, but it is also becoming apparent that many healthcare systems around the world cannot cope with the increasing demands for IVT injections to treat AMD. To reduce the frequency for IVT injections, there is a need to develop formulations that allow a longer duration of action for therapeutic proteins in the back of the eye. Maintaining protein stability is a major challenge in formulation science and clinical use. It was further hypothesied that injectable hydrogels could also be used to formulate an antibody for IVT injection to display an extended residence time in the vitreous cavity. Free radical polymerisations of 2-hydroxyethyl methacrylate (HEMA) and 2-methacryloyloxyethyl phosphoryl choline (MPC) in the presence of a cross-linker, poly¬(ethylene glycol diacrylate) (PEGDA) were conducted to prepare HEMA-MPC co-polymer hydrogel films. Both HEMA and MPC are widely used in ophthalmic hydrogel products and MPC is known to be exceptionally biocompatible, although it must only be used as a co-polymer to ensure there are suitable processing and mechanical properties in the resulting hydrogel. Different HEMA-MPC hydrogels with increasing relative stoichiometries of MPC (0%-100% (w/w)) were prepared and characterised to determine if water flow through the gel was possible. Unfortunately the hydrogel films formed have low permeability (1.1×10-18 m2 s-1 pas-1) compared to the permeability required to control flow at a rate of 2 μL/min under 10-15 mmHg IOP, which is (6 ×10-14 m2 s-1 pas-1). Although the HEMA-MPC hydrogel films could not be used for flow control, they were further examined for use as potential implants for local tissue site drug delivery in subconjunctiva. HEMA-MPC hydrogels with 10% MPC were found to offer the best balance between water content, mechanical strength and drug loading and release that was required for the possible implantation drug loaded films derived from a range drugs (dexamethasone, pirfenidone and doxycycline). The process used for drug loading of dexamethasone was optimised by using, methanol and the in vitro half-life of DEX was increased from 1.8 to 9.1 days with release being sustained for more than 3 weeks. There are other causes of subconjunctival scarring, in particular trachoma, which is the main cause of blindness due to infection. Doxycycline is thought to be a good candidate drug for treating patients after trachoma surgery because it has both anti-bacterial and anti-fibrotic properties. As a water-soluble drug, doxycycline release could not be sustained for more than 3 days, so the 10% MPC films were modified with the incorporation of β-cyclodextrin (β-CD) in an effort exploit the possible affinity of doxycycline with β-CD to prolong doxycycline release. Several methods were examined to introduce β-CD into the HEMA-MPC films including the formation of HEMA-MPC films with pendant β-CD, the embedding of β-CD cross-linked particles within the hydrogel network and formation of an interpenetrating network (IPN) of β-CD and HEMA-MPC. Unfortunately, the release profile of doxycycline was similar in the modified and non-modified HEMA-MPC hydrogels. To evaluate hydrogels for use in IVT injections of antibodies, N-isopropylacylamide (NIPAAm) thermoresponsive hydrogels were evaluated. Three different macromolecular hydrophilic cross-linkers were evaluated; PEGDA, phosphorylcholine 3059 (PC 3059) and acrylated hyaluronic acid (Ac-HA). The prepared hydrogels were characterised regarding physical properties such as water content, water retention thermoresponsivness and protein release. The thermal responsiveness decreased with increasing cross-linker percentage. Modification in the type and percentage of cross-linker used allowed the preliminary screening of the different formulations. Hydrogel formulations made with 40 mg NIPAAm as monomer and 8 μL PEGDA, 20 mg PC3059 or 4 mg Ac-HA were able to sustain the release of antibodies for a month in a validated in vitro model of the eye.
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Read, Helen E. S. B. Massachusetts Institute of Technology. "Rheometric measurement of hydrogel toughness." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/127870.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, May, 2020Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 11-12).
As soft physical gels become more popular due to their biological applications, there is increased interest in measuring mechanical properties such as toughness. However, traditional tensile testing methods do not work for such materials due to the intrinsic softness of the material. We present a novel method for measuring fracture energy using a rheometer and show it is broadly consistent with the pure shear test, a standard method where the material exhibits mode I fracture. This method has potential applications in characterizing a wide range of soft and transient gels.
by Helen E. Read.
S.B.
S.B. Massachusetts Institute of Technology, Department of Mechanical Engineering
8
Hamilton, C. J. "Transport phenomena in hydrogel membranes." Thesis, Aston University, 1988. http://publications.aston.ac.uk/9719/.
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In this thesis the factors surrounding the permeation of alkali and alkaline earth metal salts through hydrogel membranes are investigated. Although of relevance to aqueous separations in general, it was with their potential application in sensors that this work was particularly concerned. In order to study the effect that the nature of the solute has on the transport process, a single polymer matrix, poly (2-hydroxyethyl methacrylate), was initially studied. The influence of cation variation in the presence of a fixed anion was looked at, followed by the effect of the anion in the presence of a fixed cation. The anion was found to possess the dominant influence and tended to subsume any influence by the cation. This is explained in terms of the structure-making and structure-breaking characteristics of the ions in their solute-water interactions. Analogies in the transport behaviour of the salts are made with the Hofmeister series. The effect of the chemical composition of the polymer backbone on the water structuring in the hydrogel and, consequently, transport through the membrane, was investigated by preparing a series of poly (2-hydroxyethyl methacrylate) copolymer membranes and determining the permeability coefficient of salts with a fixed anion. The results were discussed in terms of the `free-volume' model of permeation and the water structuring of the polymer backbone. The ability of ionophores to selectively modulate the permeation of salts through hydrogel membranes was also examined. The results indicated that a dualsorption model was in operation. Finally, hydrogels were used as membrane overlays on coated wire ion-selective electrodes that employed conventional plasticised-PVC-valinomycin based sensing membranes. The hydrogel overlays were found to affect the access of the analyte but not the underlying electrochemistry.
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Huettner, Nick. "Developing hydrogel systems for Biofabrication." Thesis, Queensland University of Technology, 2019. https://eprints.qut.edu.au/126397/1/Nick_Huettner_Thesis.pdf.
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The two research projects cover the versatile applications of hydrogels in biofabrication. Hydrogels find application as synthetic matrices in bioprinting, can be easily modified with bioactive motifs and processed by robotic systems, enabling high-throughput screening (HTS) approaches. The first project targeted cellular response to cell adhesion peptides in poly(ethylene glycol)-based hydrogels. An upscalable platform using a robotic system was developed, enabling HTS of the peptide-modified hydrogel matrices, tailorable to different cell types. The second project aimed to develop a tailorable physical hydrogel for bioprinting, based on different architectures of a poly(2-oxazoline)-b-poly(2-oxazine) copolymer. Hydrogel properties were evaluated by rheology.
10
Gholap, S. G. "Hydrogel membranes for bio-separations." Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 2005. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/2436.
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GUPTA, PREETI. "HYDROGEL BASED WOUND DRESSING MATERIAL." Thesis, DELHI TECHNOLOGICAL UNIVERSITY, 2021. http://dspace.dtu.ac.in:8080/jspui/handle/repository/18806.
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Weak mechanical strength of hydrogels in wet condition limits their use for load
bearing applications. Their mechanical strength can be raised by grafting them over
some support or by converting them into nanofibrous form. Present thesis is focused on
the preparation of poly (acrylamide-co-acrylic acid) hydrogel grafted over cotton fabric
using two different cross-linkers i.e. PEG and MBAAm for making medicated dressing
and nanofibers of hydrogel of poly (acrylamide-co-acrylic acid). FTIR was used to
confirm the insertion of cross-links into the polymer chains. Grafting of uniform
hydrogel layer on cotton surface and formation of hydrogel nanofibers were confirmed
by using SEM. The average fibre diameter was found to be 275±94.5 nm.
Swelling of composite prepared using PEG followed first-order kinetic model
at acidic and neutral pH whereas second-order kinetic model at pH 8.5 while that
prepared using MBAAm followed second-order kinetic equation at all the pHs studied.
The kinetics of swelling was also governed by Peppas model at all pHs. Release of drug
from both the composites was studied in phosphate buffers having pH 5.5,7 and 8.5 at
37±0.1°C and observed that it was fastest in phosphate buffer having pH 7. On fitting
drug release data into different models, it was observed that drug release was diffusion
controlled and followed Fickian diffusion mechanism in case of composite prepared by
using PEG as cross-linker whereas it was controlled by diffusion as well as chain
relaxation in case of composite prepared by using MBAAm. Mechanical testing using
Universal Testing Machine supported a higher mechanical strength of the hydrogel
composite as compared to its film. Swelling behaviour of Nanofibrous mats was found to be highest at neutral pH and it followed second order kinetics at all pHs. The drug release kinetics was further
evaluated and found that it took place by Fickian diffusion (n < 0.5) and followed
second order release kinetics. Antimicrobial tests were performed to show the
effectiveness of drug loaded within the hydrogel samples.
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Bibi, Nurguse. "Elastase responsive hydrogel dressing for chronic wounds." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/elastase-responsive-hydrogel-dressing-for-chronic-wounds(f2a1f950-d38d-4cb2-8b8e-3c1e10ef7910).html.
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Chronic wounds are a major financial and clinical burden causing the deaths of millions per year. Over expression of elastase is well documented as the main culprit that delays the normal wound repair process within chronic wounds. The aim of this thesis is to design a responsive chronic wound dressing based on the hydrogel polymer, PEGA (polyethylene glycol acrylamide) in the form of particles to mop-up excess elastase by exploiting polymer collapse in response to elastase hydrolytic activity within sample fluids mimicking the environment of chronic wounds. PEGA particles were functionalised with enzyme cleavable peptides (ECPs) containing charged residues. Upon cleavage the charge balance changes, causing polymer swelling and consequent elastase entrapment. The pH range of chronic wounds is reported in the range of 5.45 - 8.65. Due to its pI which is around 8.3, within this range elastase exist both in its cationic and anionic forms. To accommodate a hydrogel dressing that could selectively entrap excess elastase both in its cationic and anionic, oppositely charged ECPs were designed. In its cationic form, elastase was found to have a high preference of cleaving ECPs and penetrating into PEGA particles bearing negative charges. In contrast, in its anionic form the opposite effect was observed, wherein elastase preferred to cleave ECPs and penetrate PEGA particles bearing positive charges. The diffusion, accessibility and entrapment of elastase into functionalised PEGA particles was explored using various fluorescence microscopy techniques. Removal of the charged residue by elastase showed a reduction in particle swelling causing the pores of PEGA particles to become restricted. In this manner, cleaved PEGA particles prevented the accessibility of molecules with a molecular weight as low as 20 kDa into the cleaved PEGA particles. Since elastase has a molecular weight of 25.9 kDa the collapsing of the pores within PEGA particles entrapped elastase inside the interior of cleaved PEGA particles. In its cationic form (at pH 7.4) elastase was found to penetrate and become trapped more into both negative and positive PEGA particles compared to neutral particles. The negative particles were shown to trapped cationic elastase within 2 minutes compared to the positive particles. In contrast, the neutral particles failed to retain and encapsulate elastase as the fluorescence inside the neutral particles was found to decrease. Coinciding with these observations, after sample fluids containing elastase were treated with functionalised PEGA particles, the residual elastase activity in sample fluids was reduced more by the charged PEGA particles compared to neutral particles. The cell culture studies demonstrated that the elastase activity observed in human dermal fibroblasts (HDF) was also reduced more by the charged particles compared to the neutral particles. However, the positive particles were found to significantly reduced HDF-elastase activity compared to both the negative and neutral PEGA particles. Overall, this thesis exemplifies that on the basis of charge selective cleaving of ECPs coupled to PEGA particles can be exploited to selectively remove excess proteases such as elastase from sample fluids mimicking the environment of chronic wounds.
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Yata, Tomoya. "Development of efficient amplification method of DNA hydrogel and composite-type DNA hydrogel for photothermal immunotherapy." 京都大学 (Kyoto University), 2016. http://hdl.handle.net/2433/215494.
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Rutschilling, Ryan R. "Evaluation of Wear Experience with Silicone Hydrogel Lenses in Current Silicone Hydrogel Planned Replacement Lens Wearers." The Ohio State University, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=osu1618559832574561.
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Walia, Rashi. "Solid-Hydrogel Hybrid Structural Materials for Biomedical Devices and Applications." Thesis, The University of Sydney, 2022. https://hdl.handle.net/2123/29549.
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Hybrid combinations of hydrogels and solid materials allow a high level of functionality for devices such as tissue engineering scaffolds and soft machines. This thesis reports a versatile strategy to develop mechanically robust solid-hydrogel hybrid materials using surface embedded radicals generated through plasma immersion ion implantation (PIII) of polymeric surfaces. Acrylamide and silk hydrogels were formed on PIII activated polytetrafluoroethylene (PTFE), polyethylene (PE) and polystyrene (PS) surfaces without any external crosslinking agents or initiators. X-ray photoelectron spectroscopy (XPS) and attenuated total reflection (ATR)-Fourier transform infrared (FTIR) spectrometry confirmed the formation of the acrylamide hydrogels. The amount of hydrogel formed on the substrate increased with incubation time, monomer concentration and temperature. Stability tests indicated that 95% of the hydrogel coating was retained even after 4-months of incubation in PBS solution. Adhesive T-peel tests results demonstrating adhesion strength of the hydrogel on the PIII-treated PTFE (PIII PTFE) interface of over 300-340 N/m. Hydrogels synthesised with fibronectin enabled cell adhesion and spreading. Thesis results show that polymers functionalized with surface-embedded radicals provide excellent solid platforms for the generation of robust and functional solid-hydrogel hybrid structures for biomedical applications.
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Salehpour, Somaieh. "Synthesis of Stimuli-responsive Hydrogels from Glycerol." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/20584.
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Due to an increased environmental awareness and thus, concerns over the use of fossil-based monomer for polymer production, there is an ongoing effort to find alternatives to non-renewable traditional monomers. This has ushered in the rapid growth in the development of bio-based materials such as green monomers and biodegradable polymers from vegetable and animal resources. Glycerol, as a renewable bio-based monomer, is an interesting candidate for sustainable polymer production. Glycerol is a renewable material that is a by-product of the transesterification of vegetable oils to biodiesel. Utilization of the excess glycerol derived from the growing biodiesel industry is important to oleochemical industries. The main objective of this thesis was to produce high molecular weight polyglycerol from glycerol and synthesize stimuli-responsive polyglycerol hydrogels. The work began with an investigation of the step-growth polymerization of glycerol to relatively high molecular weight polyglycerol using several catalysts. The catalytic reaction mechanisms were compared and the polymer products were fully analyzed. High molecular weight partially branched polyglycerol with multimodal molecular weight distributions was obtained. The polymerization of glycerol proceeded fastest with sulphuric acid as catalyst as indicated by the highest observed conversion of monomer along with the highest molecular weights. Theoretical models were used to predict the gel point and to calculate monomer functionality. High molecular weight polyglycerol was used to synthesize novel stimuli-responsive hydrogels. Real-time monitoring of step-growth polymerization of glycerol was investigated using in-line and off-line Attenuated Total Reflectance/Fourier Transform infrared (ATR-FTIR) technique.
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Habánková, Eva. "Reologické hodnocení fotogelace termocitlivých makromonomerů ve vodném prostředí." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2017. http://www.nusl.cz/ntk/nusl-316431.
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Táto práca si dáva za cieľ chemicky zasieťovať biodegradovateľný makromonomér ,-itaconyl-PLGA–PEG–PLGA vo vodnom roztoku pri teplote okolia a pri teplote tela (37 °C). ,-itaconyl-PLGA–PEG–PLGA makromonomér môže vo vode vytvárať fyzikálnu sieť vďaka hydrofóbnym interakciám medzi hydrofóbnym PLGA a hydrofilným PEG. Vďaka dvojitej väzbe kyseliny itakonovej, ktorá je k makromonoméru pripojená na jeho koncoch, sa naskytuje možnosť dodatočného chemického zasieťovania fotopolymerizáciou. Výsledkom je hybridná sieť, ktorá zvyšuje mechanickú stabilitu a životnosť hydrogélu. Na priame sledovanie formovania siete prostredníctvom zmeny mechanických vlastností bola v práci použitá fotoreológia.
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Zainuddin. "Synthesis and calcification of hydrogel biomaterials /." [St. Lucia, Qld.], 2005. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18693.pdf.
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Lorentz, Holly. "Lipid Deposition on Hydrogel Contact Lenses." Thesis, University of Waterloo, 2006. http://hdl.handle.net/10012/2963.
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The primary objective of this study was to quantify and characterise lipid deposition on soft (hydrogel) contact lenses, particularly those containing siloxane components. Studies involving a variety of in vitro doping and in vivo worn contact lenses were undertaken, in which lipid deposition was analyzed by either TLC or HPLC. Specific experiments were completed to optimize a method to extract the lipid from the lens materials, to compare the total lipid deposition on nine different hydrogel lenses and to analyze the effect that lipid deposition had on wettability. A method for extracting lipid from contact lenses using 2:1 chloroform: methanol was developed. This study also showed that siloxane-containing contact lens materials differ in the degree to which they deposit lipid, which is dependent upon their chemical composition. Small differences in lipid deposition that occur due to using variations in cleaning regimens were not identifiable through TLC, and required more sophisticated analysis using HPLC. Contact lens material wettability was found to be influenced by in vitro lipid deposition. Specifically, conventional hydrogels and plasma surface-treated silicone-hydrogel materials experienced enhanced wettability with lipid deposition. Reverse-phase HPLC techniques were able to quantify lipid deposits with increased sensitivity and accuracy. From the HPLC studies it was found that contact lens material, concentration of the lipid doping solution, and the composition of the lipid doping solution in in vitro deposition studies influenced the ultimate amount and composition of lipid deposits. In vivo HPLC studies showed that the final lipid deposition pattern was influenced by the interaction between the composition of the tear film and the various silicone hydrogel contact lens materials. In conclusion, HPLC analysis methods were more sensitive and quantitative than TLC. Lipid deposition was ultimately influenced by the concentration and composition of the lipid in the tear film and the contact lens material. Contact lens wettability was influenced by the presence and deposition of lipid onto the contact lens surfaces. Finally, this reverse-phase HPLC lipid analysis protocol was not the most sensitive, robust, or accurate. In the future, other methods of analysis should be explored.
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Nkhwa, Shathani. "Hydrogel biocomposites for bone tissue regeneration." Thesis, King's College London (University of London), 2016. https://kclpure.kcl.ac.uk/portal/en/theses/hydrogel-biocomposites-for-bone-tissue-regeneration(ad423107-672f-4269-9aa0-5e4eb949dfd5).html.
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The biomedical burden of large bone defects caused by trauma, infection, tumours or inherent genetic disorders remains a clinical challenge. Autologous bone or autograft continue to be the clinical “gold standard” for most effective bone regeneration, which is limited by bone supply and donor site morbidity. Thus, current synthetic substitutes need to be improved to match the performance of autografts. Bone tissue engineering is an attractive approach for regeneration of bone especially in relation to critical sized defects and a scaffold with osteoinductive properties and adequate mechanical properties is expected to enhance bone formation. The aim of the study is to enhance bone regeneration and the concept is based on adequate design of three dimensional scaffolds that mimic the structure of bone, which by virtue of its inherent properties have the ability to localise fluids rich in osteoinductive factors. The hydrogels and composites were all synthesized with a base polymer polyvinyl alcohol (PVA), which is both robust, biocompatible and FDA approved material. Facile methods of crosslinking such as air-drying and freeze-drying which introduces a level of porosity in the materials due to the lyophilisation process, were used to render the hydrogels insoluble, and conditions optimised to yield materials with properties suitable for soft bone tissue applications. PVA hydrogels were synthesized and characterised, results indicated that water uptake, glass transition and tensile strength were influenced by varying concentration of the polymer solution. A new type of dual network (DN) hydrogel composed of PVA and alginate was developed and optimised. Characterisations by spectral and thermal analysis, confirmed incorporation of alginate within the PVA network structure. Hydration dynamics and tensile properties, indicated that DN formed from a PVA base crosslinked by two freeze thaw cycles yielded tough hydrogels with controlled swelling, making them suitable for soft tissue applications as well as the diversity of being further incorporated with ceramic fillers for the development of bone composite substitutes. Incorporation of bioglass® 45S5 within the polymeric network structure of the DN led to enhancement of the mechanical properties such as tensile strength and fracture toughness as well as imparting bioactivity within the hydrogel composites, which was demonstrated by the development of hydroxy carbonated apatite on the surface and internal structure of the composites, this result was further corroborated by the increase in tensile strength and stiffness of the composites when placed in simulated body fluid over a period of 28 days. The second group of hydrogel composites was composed of a PVA fluid phase and calcium metaphosphate (CMP) ceramic phase, crosslinked by freeze drying. This hydrogel composite was developed to have a high mineral content with properties that closely resemble the properties of bone based on its inorganic/organic nanocomposite structure. Compression and water uptake behaviour of the composite could be modulated by varying concentration of PVA and the composite system properties were found to be suitable and lie within the range values for trabecular bone. In vitro cell culture tests were used to assess biocompatibility and the selected scaffolds were seeded with human osteoblast cells (HOB) and were evaluated by MTT, and live dead staining. All the systems were found to be biocompatible and cells were able to attach and proliferate within the scaffolds. Biofunctionality was assessed on the scaffolds which all showed a peak increase in alkaline phosphatase activity (ALP) at day 14, an important bone marker indicating osteoblast differentiation.
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Ling, Yibo. "Hydrogel cell encapsulation for tissue engineering." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/44456.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.Vita.
Includes bibliographical references (leaves 116-123).
The engineering of artificial tissues for restoration or replacement of organ function holds the potential to alter the landscape of medical therapeutics. In many tissue engineering approaches, cells seeded within 3D porous structures are expected to remodel into tissue-like structures. Despite significant progress, difficulties in lack of control over tissue architecture as well as vascularization continue to limit the efficacy of engineered constructs. This thesis describes work aimed at tackling these two problems. First, two techniques for generating size- and shape-controlled cell-laden hydrogels are described in the context of potential modular assembly for conferring greater control over the geometry of homotypic and heterotypic cell arrangements within engineered tissues. Then, a method for producing cell-loaded microfluidic agarose hydrogels for tissue engineering is described.
by Yibo Ling.
S.M.
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Yang, Pei. "Iontophoretic drug transport through hydrogel membranes." Scholarly Commons, 2001. https://scholarlycommons.pacific.edu/uop_etds/2628.
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Hydrogel membranes with different charge properties, positively charged 2-(N, N-Dimethylamino)ethyl methacrylate-co-butyl acrylate (DMEMA-co-BuA), neutral 2-hydroxyethyl methacrylate-co-butyl acrylate (HEMA-co-BuA), and negatively charged acrylic acid-co-butyl acrylate (AA-BuA) were designed and synthesized for investigation of the transport mechanism of iontophoresis. The hydrogels were characterized by determination of the equilibrium hydration and dimensional change. To study the different crucial factors influencing iontophoretic transport, three model compounds, positively charged phenylpropanolamine (PPA), zwitterionic phenylalanine (Phe), and negatively charged 3-phenylpropionic acid (3-PPA) were selected. These compounds have similar structure and molecular weight but different charge properties. Three transport conditions, passive diffusion, anodal and cathodal iontophoretic transport, were used in this dissertation. A novel parameter, E v , was developed to quantitatively evaluate the enhancement of transport due to the electro-osmotic flux. E v values were obtained by comparing the enhancement/hindrance factor (E-value) through charged membrane to that through neutral membrane with comparable hydration. The model compounds, hydrogel membranes, and transport conditions used in this study made the iontophoretic transport a complicated system with twenty-seven possible different combinations. The E v values can be used to determine the electro-osmotic effect under various iontophoretic conditions with different permeants. The results showed that E v values of permeants with similar structure and molecular weight are robust to permeant charge. Passive diffusion and anodal/cathodal iontophoretic transport of PPA through HEMA-co-BuA and AA-co-BuA of different compositions were conducted. Linear relationships were established between the reciprocal of hydration and the logarithm of flux, E-value, and E v value. It is found that iontophoretic transport of drug through hydrogels is governed by free volume theory. To explore the pH effect on iontophoretic transport through hydrogel, the transport behaviors of Phe through HEMA-co-BuA under three transport conditions in the pH range of 1.5 to 11.2 were investigated. A mathematical model was developed to describe the effect of pH on iontophoretic transport. This model has successfully predicted the total permeability of Phe at various pH values. The distribution and charge of species depended on pH and thus affected iontophoretic transport. The passive, anodal and cathodal transport behaviors of 3-PPA through negatively charged human skin were in agreement with those through the negatively charged hydrogel membrane AA-co-BuA (60:40). It was shown that the negatively charged hydrogel membrane could be used as a model membrane to study transport behavior through human skin.
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Hanning, Christopher Douglas. "Development of the morphine hydrogel suppository." Thesis, University of Leicester, 1996. http://hdl.handle.net/2381/34094.
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Corbett, Daniel James. "Functional hydrogel coatings for Biomedical applications." Thesis, Queen's University Belfast, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.676276.
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Biomedical devices are commonly used in all areas of healthcare, These devices, which range from contact lenses through to endotracheal tubes, are most often fashioned from materials which allow the device to carry out its function thoroughly, but in doing so render the device susceptible to a number of complications. Two of the most major complications are that of device infection and poor frictional behaviour at the interface of the device and human tissue. This thesis details the development and characterisation of various polymeric systems which allow the resolution of these problems. With regard to infection, well established photodynamic techniques are further developed to provide a system which can bring about effective prevention of infection for prolonged durations of time, leading to a wide range of advantages, potentiating the function of the device. Biomaterial frictional behaviour is improved in a number of ways, including the development of next generation device coatings which are more easily wetted, offer improved biocompatibility, and also offer an improved tenacity of effect. Moreover, further work in this thesis has led to the development of successful photochemical attachment pathways for the addition of such coatings to the surface of commonly used biomaterial substrates.
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Deng, Kangfa, Gerald Gerlach, and Margarita Guenther. "Force-compensated hydrogel-based pH sensor." SPIE, 2015. https://tud.qucosa.de/id/qucosa%3A35185.
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This paper presents the design, simulation, assembly and testing of a force-compensated hydrogel-based pH sensor. In the conventional deflection method, a piezoresistive pressure sensor is used as a chemical-mechanical-electronic transducer to measure the volume change of a pH-sensitive hydrogel. In this compensation method, the pH-sensitive hydrogel keeps its volume constant during the whole measuring process, independent of applied pH value. In order to maintain a balanced state, an additional thermal actuator is integrated into the close-loop sensor system with higher precision and faster dynamic response. Poly (N-isopropylacrylamide) (PNIPAAm) with 5 mol% monomer 3-acrylamido propionic acid (AAmPA) is used as the temperature-sensitive hydrogel, while poly (vinyl alcohol) with poly (acrylic acid) (PAA) serves as the pH-sensitive hydrogel. A thermal simulation is introduced to assess the temperature distribution of the whole microsystem, especially the temperature influence on both hydrogels. Following tests are detailed to verify the working functions of a sensor based on pH-sensitive hydrogel and an actuator based on temperature-sensitive hydrogel. A miniaturized prototype is assembled and investigated in deionized water: the response time amounts to about 25 min, just half of that one of a sensor based on the conventional deflection method. The results confirm the applicability of the compensation method to the hydrogel-based sensors.
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Samchenko, Yu M., S. O. Kryklia, T. P. Poltoratska, Леонід Федорович Суходуб, Леонид Федорович Суходуб, Leonid Fedorovych Sukhodub, Yu O. Isheikina, V. I. Makarenko, and V. V. Konovalova. "Hybrid Hydrogel Materials with Incorporated Nanoparticles." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35464.
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Synthesis and physico-chemical studies of new promising hybrid hydrogels based on polyvinyl alcohol (PVA) acetales and copolymer hydrogels based on vynil monomers have been studied. Acrylamide and Acrylnitrile were used as some of components that carry various fillers . Sponge acetales of polyvinyl alco-hol were used as enforcing net. The synthesized composites demonstrated high strength as compared to standard hydrogels- Yung-module varied in the range of 80 to 300 kPa depending on the extent of PVA ac-etale matrix filling with hydrogel component. The materials showed high sorbability to water and water solutions. Study of swelling kinetics as compared to solvents of various nature (water, ethanol, sunflower oil ) was carried out.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35464
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Huang, Yujian. "Bioinspired Tunable Hydrogel for Biomedical Applications." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1513874923888155.
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Niu, Ye. "Microparticulate Hydrogel Materials Towards Biomedical Applications." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1586094812805108.
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Lu, Xihua. "Polymer hydrogel nanoparticles and their networks." Thesis, University of North Texas, 2002. https://digital.library.unt.edu/ark:/67531/metadc3232/.
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The thermally responsive hydroxypropyl cellulose (HPC) hydrogel nanoparticles have been synthesized and characterized. The HPC particles were obtained by chemically crosslinking collapsed HPC polymer chains in water-surfactant (dodecyltrimethylammonium bromide) dispersion above the lower critical solution temperature (LCST) of the HPC. The size distributions of microgel particles, measured by dynamic light scattering, have been correlated with synthesis conditions including surfactant concentration, polymer concentration, and reaction temperature. The swelling and phase transition properties of resultant HPC microgels have been analyzed using both static and dynamic light scattering techniques. By first making gel nanoparticles and then covalently bonding them together, we have engineered a new class of gels with two levels of structural hierarchy: the primary network is crosslinked polymer chains in each individual particle, while the secondary network is a system of crosslinked nanoparticles. The covalent bonding contributes to the structural stability of the nanostructured gels, while self-assembly provides them with crystal structures that diffract light, resulting in colors. By using N-isopropylacrylamide copolymer hydrogel nanoparticles, we have synthesized nanoparticle networks that display a striking iridescence like precious opal but are soft and flexible like gelatin. This is in contrast to previous colored hydrogels, which were created either by adding dyes or fluorescent, or by organic solvent or by embedding a colloidal crystal array of polymer solid spheres . Creating such periodic 3D structures in materials allows us to obtain useful functionality not only from the constituent building blocks but also from the long-range ordering that characterizes these structures. Hydroxypropyl cellulose (HPC) and poly (acrylic acid ) (PAA) complexes were studied using turbidity measurement and laser light scattering. The phase transition temperature of the complexes is found to depend on pH and molecular weights of PAA and HPC. The driving force for this phenomenon is due to the hydrogen bonding and hydrophobic interaction of the macromolecules. Based on the principle of the PAA/HPC complexes, the PAA nanoparticles were synthesized in 0.1wt % HPC aqueous solution at room temperature.
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Trevett, Adrian S. "The mechanical properties of hydrogel polymers." Thesis, Aston University, 1991. http://publications.aston.ac.uk/9692/.
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Spinelli, Frances Josephine. "Characterization of heparin-based hydrogel networks." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 102 p, 2009. http://proquest.umi.com/pqdweb?did=1663116581&sid=6&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Cho, Eunhee. "Hydrogel compositions for nonviral gene delivery." Connect to this title online, 2009. http://etd.lib.clemson.edu/documents/1263395173/.
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Gaulding, Jeffrey Clinton. "Hydrogel nanoparticles and assemblies for bioapplications." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/52155.
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Hydrogels are cross-linked networks of highly hydrophilic polymer chains. When reduced to colloidal dimensions, particles of this sort are termed “microgels�? and both discrete particles and ensembles have intriguing properties. Microgels can be made to be susceptible to numerous environmental stimuli, such as temperature and pH. The resultant changes in the network hydration lead to characteristic swelling responses which can have great impact on properties of the gel network such as the porosity, hydrophilicity, stiffness, or particle-particle packing. The multitude of responsive stimuli; the architectural versatility of discrete particles; and the variety of particle ensembles have made the study of microgels and their assemblies a very rich field. Primarily due to their physiological softness and the aforementioned versatility, responsive microgels are of great interest as a material to address the daunting challenges facing the next generation of healthcare.
This dissertation describes investigations into hydrogel nanoparticles and assemblies thereof, with the goals of expanding their utility in applications such as drug delivery and non-fouling interfaces through the development of novel materials to both extend their synthetic versatility and to probe their underlying properties. Physiologically-relevant degradable cross-linking within microgels is studied, though the incorporation of hydrolytically degradable or reduction-responsive cross-links. More complex structures are demonstrated for both types of cross-linking as synthetic and architectural control enables additional functional microgel designs.
Microgel assemblies, particularly thin films, have been demonstrated to have numerous desirable properties for biological applications, such as reduced cell attachment, drug delivery, and self-healing capabilities. This dissertation includes additional fundamental studies of microgel films, both in their synthesis, such as methods for depositing films onto colloidal substrates, and in their application, as investigations into the origins and critical factors for self-healing films. Further, the cell-resistant properties of microgel multilayers are studied and evidence suggests that the viscoelastic or mobile character of the films is likely the main factor that directs cell adhesion.
The work in this dissertation serves to both expand our toolset with regard to the functional synthesis of microgels and assemblies and to improve our fundamental understanding of phenomena of interest for a variety of potential applications. Both of these should serve to allow the enormous potential of hydrogel nanoparticles and their assemblies to be more efficiently tapped for a wide range of applications in the field of biomaterials.
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Ehrenhofer, Adrian, Alice Mieting, Sascha Pfeil, Johannes Mersch, Chokri Cherif, Gerald Gerlach, and Thomas Wallmersperger. "An automatically rainproofing bike helmet through light-sensitive hydrogel meshes: Design, modeling and experiments." SPIE, 2020. https://tud.qucosa.de/id/qucosa%3A74218.
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For everyday cycling, one needs to carry rainproof clothing just for the case of unexpected downpours. In the present research, we present a concept for a helmet which is automatically rainproof when the rain starts. When the sun comes out, the helmet is breathable again even before it completely dries up. This functionality is provided by active hydrogel meshes. Hydrogel meshes offer great advantages due to their ability to change the aperture size with swelling and deswelling. In our current work, we present the design and modeling steps for hydrogel-layered active meshes which use (i) swelling and deswelling in hydrated state and (ii) swelling starting from the dry state. The main goal is to close the air openings of a bicycle helmet when rain starts as an automatic rainproofing. This can be achieved through the swelling of the hydrogel pNiPAAM-co-chlorophyllin in the meshes, which leads to closing when hydrated. At the same time, the light-sensitive behavior leads to opening of the apertures under direct sun exposure, i.e. when the sun appears again after the rain. We present the steps of modeling and design using the Normalized Extended Temperature-Expansion-Model (NETEM) to perform simulations in Abaqus. The model is capable of describing both the swelling of the hydrogel under light stimulus and the volume change due to hydration. It is based on the analogy between free swelling and thermal expansion and defined for nonlinear displacements. We also discuss the fabrication process of hydrogel-layered fibers and challenges in their application and simulation. As a proof of concept for hydrogel-layered meshes, we show preliminary experimental results of a poly(acrylamide)/poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAAm/PAMPS) hydrogel with semi-interpenetrated network (SIPN) structure and its swelling capacities on a mesh. Starting from the active hydrogel meshes as presented in the current work, the next step can be smart textiles that harness the power of hydrogels: the adaptation to combinations of stimuli - like humidity, temperature and brightness - that define environments.
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Boisselier, Julie. "Mise en œuvre d’un système de confinement et de délivrance moléculaire pour la production in situ de glucose au sein d’un hydrogel conçu pour l'ingénierie tissulaire." Thesis, Cergy-Pontoise, 2016. http://www.theses.fr/2016CERG0830/document.
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En ingénierie tissulaire, la survie in vivo de cellules souches implantées au sein d’un biomatériau est limitée par les conditions d’un environnement ischémique qui se caractérise par un déficit en oxygène et en nutriments. Récemment, dans le cadre d’un projet de recherche dédié au développement d’un hydrogel composite à base de fibrine, biomatériau conçu pour améliorer la survie de cellules souches post-implantation, il a été mis en évidence la nécessité de contrôler dans le temps et l’espace la disponibilité du glucose au sein de ce matériau. Cet apport in situ de glucose est réalisé par dégradation contrôlée de l’amidon, un polymère de glucose. Cette production est assurée par action enzymatique d’un catalyseur spécifique de l’hydrolyse de l’amidon, l’amyloglucosidase (AMG).Toutefois, il convient de maitriser différents paramètres tels que la fuite de l’AMG en dehors de l’hydrogel ou encore sa perte d’activité au cours du temps. Dans ce contexte, l’encapsulation de l’AMG dans des nanoparticules d’un polymère biodégradable et biocompatible, ici l’acide poly(lactique-co-glycolique) (PLGA), devrait permettre le contrôle des paramètres susmentionnés.Des nanoparticules de type core-shell contenant l’AMG (NPe) ont été synthétisés par l’adaptation d’un protocole de double émulsion (water-oil-water). Différentes méthodes ont été développées pour déterminer les propriétés physico-chimiques et biochimiques des nanoparticules produites. Le protocole de synthèse a été optimisé afin de produire des nanoparticules reproductibles et stériles utilisables dans des hydrogels implantables in vivo.Le cahier des charges de l’hydrogel enrichi en amidon et en NPe impose un apport continu du glucose pendant 1 mois. La stabilité des nanoparticules a été étudiée en solution et dans les hydrogels. La production de glucose grâce à ces NPe a été investiguée en solution et en hydrogel mettant en avant l’intérêt de ces nanoparticules au sein du dispositifIn tissue engineering, the in vivo survival of stem cells located within a biomaterial is limited by an ischemic environment characterized by a low supply of oxygen and nutrients. Recent studies on fibrin based hydrogels (designed to improve stem cells survival after implantation) have highlighted the need to control the spatiotemporal availability of glucose within a biomaterial scaffold. Glucose release occurs through the degradation of starch, a glucose polymer, at a rate controlled by the action of the enzyme amyloglucosidase (AMG), a specific catalyst for the hydrolysis of starch.In order to eventually be of clinical impact, critical parameters must be tuned, such as the AMG leakage outside the hydrogel and its loss of activity over time. In this context, AMG encapsulation within nanoparticles of a biodegradable and biocompatible polymer, here poly(lactic-co-glycolic acid) (PLGA), is a promising means toward controlling the above parameters.The AMG-containing core-shell type nanoparticles (NPe) were synthesized by an adaptation of the double emulsion technique (water-oil-water). Different methods have been developed to determine the physicochemical and biochemical properties of the resulting nanoparticles. The synthesis was optimized to produce sterile and reproducible nanoparticles appropriate for in vivo implantable hydrogels.Nanoparticle stability and glucose release were investigated in solution and in hydrogels. A key specification of the hydrogel system, enriched in starch and NPe, is the continuous supply of glucose over 1 month. Glucose production was observed to meet this specification, highlighting the potential advantages of this approach
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Kim, Sangjoon. "The Development and Characterization of Double Layer Hydrogel for Agricultural and Horticultural Applications." University of Toledo / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1279116187.
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Zacher, Thomas. "Utilisation of evanescent fields for the characterisation of thin biosensing layer systems." [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=964808854.
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Kazek, Maciej. "Wpływ odmiany, inokulacji i hydrożelu na plonowanie i jakość nasion konwencjonalnej soi (Glycine max (L.) Merr.)." Rozprawa doktorska, Uniwersytet Technologiczno-Przyrodniczy w Bydgoszczy, 2020. http://dlibra.utp.edu.pl/Content/3214.
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Jin, Tuo. "A novel hydrogel anchored lipid bilayer system." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ27670.pdf.
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Hui, Andrew J. "Hydrogel-based artificial heart valve stent material." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0018/MQ58005.pdf.
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Chen, Michael C. W. "Hydrogel-based microfluidic system for cell culture." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/7209.
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Traditionally, cell culture has been done in culture flasks or well plates where the volumes and length scales involved in the culture environment are many orders of magnitude larger than the size scale of individual cells. To better tailor medical care to an individual patient, it may be necessary to carry out genetic, physiological, and biochemical analyses on very small cell samples and to have an in vitro cell culture environment that more closely approximates the in vivo conditions.
A microfluidic device that integrates both cell handling and long-term 3-D cell culture techniques is presented. The designed microdevice traps cells with alginate, an ionically cross-linking hydrogel, which mimics the extra cellular matrix within our body. To encapsulate the cells, a solution of calcium ions is introduced in parallel with the alginate precursor cell suspension. Alginate hydrogel forms at the interface and as the region of gel grows it traps cells inside. This is a reversible process; the gel matrix can be dissolved and the cells can be released by the addition of ethylene-diaminetetraacetic acid (EDTA), a calcium chelator.
To show that the microfluidic device is reliable for long term mammalian cell culture, hepatocytes and breast tumor cells were cultured within the alginate gel layer inside the microfluidic device for more than two weeks. Hepatocytes were able to form three-dimensional aggregates within the microfluidic hydrogel environment. We further demonstrate the possibility of performing anticancer agent screening within this device. Breast tumor cells seeded in the microchannel were treated with doxorubicin, a common chemotherapy drug. Compared to controls, the doxorubicin inhibited cell proliferation.
In future, this system will have applications in cell-based testing and in studies involving small cell populations, such as cancer cells obtained from needle biopsies of tumors.
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Wang, Chih-Ying. "Diffusion in hydrogel-supported lipid bilayer membranes." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=123227.
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Biomimetic membranes are powerful tools for fundamental studies of transmembrane proteins, and they can be used in sensing and separation technologies. This thesis presents theoretical models and experimental studies of diffusion in hydrogel-supported lipid bilayer membranes. Three hydrodynamic models are developed to assess tracer diffusion in (i) an hydrogel-supported single-leaflet membrane; (ii) a solid-supported dual-leaflet membrane; and (iii) an hydrogel-supported dual-leaflet membrane. The hydrogel-supported single-leaflet model describes transmembrane protein (tracer) diffusion in lipid bilayer membranes, and the hydrogel-supported dual-leaflet model generalizes this single-leaflet model, including inter-leaflet friction. The solid-supported dual-leaflet model allows tracers to span either one or both leaflets. The models quantify how the tracer diffusion is affected by hydrogel concentration, inter-leaflet friction, and a dimensionless parameter Λ. Thus, the models predict tracer diffusion coefficients based on key system parameters. In addition to theory, experiments were undertaken to measure lipid (PE-CF) and lipopolymer (DSPE-PEG2k-CF) self-diffusion coefficients in hydrogel-supported membranes, using fluorescence recovery after photo-bleaching (FRAP). The results show that polyacrylamide and agarose hydrogels can enhance tracer diffusion in DOPC bilayers, relative to their glass-supported counterparts. Moreover, the hydrogels impart size-exclusion and Brinkman screening effects, which may benefit membrane-based molecular-separation and sensing platforms.Les membranes biomimétiques sont des outils puissants pour des études fondamentales sur des protéines transmembranaires, et pourraient être utilisées par les technologies de détection et de séparation. Cette thèse présente trois modèles théoriques et les études expérimentales de diffusion avec les membranes bicouches lipidiques soutenus par hydrogels. Trois modèles hydrodynamiques adresse la diffusion du traceur dans: (i) une membrane à feuillet unique soutenus par hydrogel, (ii) une membrane à double feuillet soutenus par solide, et (iii) une membrane à double feuillet soutenus par hydrogels. Le modèle à feuillet unique hydrogel soutenu décrit la diffusion de protéine transmembranaire (traceur) dans les membranes bicouches lipidiques, et le modèle à double feuillet hydrogel soutenu généralise ce modèle avec feuillet unique, dont la friction se prèsente inter-feuillet. Le modèle à double feuillet solide soutenu permet les traceurs de durée une ou deux feuillets bicouches lipidiques. Ces trois modèles wxpliquent comment la diffusion traceur est affectée par la concentration de l'hydrogel, et quantifiet les frottements entre feuillet, et un paramètre sans dimension Λ. Ces modèles peuvent ê tre utilisés pour prédire les coefficients de diffusion de traceurs grâce à des paramètres clés du système. Les expériences comprennent la diffusion des lipides (PE-CF) et diffusion lipopolymère (DSPE-PEG2k-CF) dans des bicouches lipidiques hydrogel soutenus, mesurée par la récupération de fluorescence après photoblanchiment. Les résultats expérimentaux montrent que le hydrogels polyacrylamide et agarose peuvent améliorer la diffusion de traceur dans des bicouches DOPC, par rapport à leurs homologues verre soutenus. Les hydrogels présentent également d'exclusion de taille et les effets de dépistage Brinkman. Les applications peuvent bénéficier des séparations moléculaires.
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Wasbrough, Matthew. "Nanostructured hydrogel films for encapsulation and release." Thesis, University of Bath, 2011. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.545323.
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We have been investigating solutions of surfactants and polyelectrolytes that are able to spontaneously form micron thick hydrogel films at the air/solution interface. Previous research within the group has shown that the surfactant can act as a templating agent for the polymer hydrogel, leading to well ordered mesostructured films similar to those seen in surfactant templated inorganic materials or polymeric layer-by-layer films, which have both been highly active areas of research over the past 20 years. This project built on the previous research within the group to develop a greater understanding of these films and how they may be controlled and used for real world applications. This thesis concentrates on two areas; the first is films made from a cationic surfactant/polymer system and the second from a cat-anionic surfactant/polymer system. Using the cationic surfactant/polymer system, we built on the previous research by altering the head group area to tail volume ratio of the surfactants being used to allow control over the final mesostructure within the films. Small angle neutron scattering (SANS) was used to study the bulk solution while neutron and x-ray reflectivity and grazing incidence diffraction were used to study the films. Using this system we have also developed the previous work, studying the incorporation of sparingly soluble species in films, by studying the encapsulation of hydrophobic and amphiphilic species into the surfactant micelles and therefore into the films as a function of micelle and film structure. We have also studied, using Fluorescence spectroscopy, the subsequent release of these species from the films. The cat-anionic surfactant/polymer system was discovered more recently and therefore has not had as much previous research performed on it. It is of particular interest because it allows films to be formed from a variety of different polymers where the cationic system currently has only been found to form films with one polymer. Using this cat-anionic system we have studied the surfactant interactions in the bulk with SANS, ultra-SANS and spin-echo-SANS to determine the structure over a wide length range. This data is compared to cryo-SEM results. In particular cryo-SEM and USANS have been used to validate modelling from the new technique of SESANS. We then studied the film formation with x-ray and neutron reflectivity. As well as forming from a wider range of polymers, these films are much thicker and more robust, which may be due to the larger scale aggregates formed in solution.
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Mattern, Kristin J. (Kristin Julie). "Permeability studies in biomimetic glycosaminoglycan-hydrogel membranes." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/42940.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2008.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 272-280).
The rates of water and solute transport tend to be lower in fibrous materials than in bulk solution. This phenomenon of "hindered transport" is caused by steric, hydrodynamic, and electrostatic interactions between the solvent, the solute, and the fibers. In this research the effect of these interactions were studied using charged, fibrous agarose-glycosaminoglycan (GAG) membranes. The work was motivated by current research into the role of the glomerular capillary wall (GCW) in ultrafiltering blood plasma, which is the first step in the processing of blood by the kidney. The GCW is composed of three layers in series: an endothelium, a basement membrane, and an epithelium. Intreasing evidence from experimental results and theoretical models of the GCW indicate that the endothelial layer and its associated glycocalyx may significantly limit the transport of macromolecules across the glomerular barrier. The glycocalyx is primarily composed of proteoglycans, a fibrous mixtures of proteins and anionic GAG. GAG fibers are present in many other biological materials, such as basement membranes and cartilage, making the current studies in agarose-GAG relevant to a variety of biological systems. Agarose-GAG membranes were synthesized by using 1-cyano-4-(dimethylamino)pyridinium tetrafluoroborate (CDAP) to create reactive sites in thin agarose hydrogels. Chondroitin sulfate GAG was then covalently bound to the reactive sites via their terminal amine group. By manipulating the temperature and duration of key reaction steps, the synthesis was optimized to provide high bound GAG yields and a spatially uniform distribution of GAG throughout the membrane. Models of the coupling reaction were developed to guide the synthesis conditions, resulting in 70-115 [mu]m-thick membranes composed of 2-4 v% agarose and 0-0.4 v% GAG.
(cont.) The Darcy (or hydraulic) permeabilities of the membranes with variable GAG content were measured with buffer solutions over a range of ionic strengths. In 3 v% agarose gels, the addition of even a small amount of GAG (0.4 v%) resulted in a two-fold reduction in the Darcy permeability. Electrokinetic coupling, caused by the flow of ions past the charged GAG fibers, resulted in an additional two-fold reduction in the opencircuit hydraulic permeability when the solution ionic strength was decreased from 1 M to 0.011 M. A microstructural model was used to understand these phenomena, accounting for the charge of the GAG fibers, heterogeneities in the agarose gels, and the mixture of agarose and GAG fibers. Several "mixing rules" from the literature were compared to predict the permeability of a mixture of fibers from structural models for a single fiber type. A fiber volume-weighted averaging of each fiber resistivity was found to be reasonably reliable, with a root-mean-squared error of 24% for 64 cases of fiber mixtures with differing radii, orientation, and/or charge. The microstructural model, using this mixing rule, accurately predicted the Darcy permeability when charge effects were suppressed at high ionic strengths; however, this model underestimated the reduction in permeability at lower ionic strengths when the effects of the GAG charge were significant. A macroscopic approach to electrokinetic effects using Donnan equilibria better captured the decrease in Darcy permeability with decreasing ionic strength. Studies of equilibrium partitioning and sieving were performed with BSA (an anionic globular protein) and Ficoll (an uncharged spherical polysaccharide). The effects of charge were studied by varying the ionic strength in experiments with BSA; the effects of solute size were examined by using Ficolls with radii ranging from 2.7 to 5.9 nm.
(cont.) Solute permeability studies were performed in 4 v% agarose gels with 0 or 0.2 v% GAG. Partition coefficients (F) for BSA were measured for ionic strengths of 0.5 to 0.011 M. For BSA in agarose gels with no GAG, F = 0.65 ± 0.02 (standard error) and did not vary with ionic strength. In gels with 0.2 v% GAG, F = 0.54 ± 0.02 at ionic strengths = 0.2 M, but decreased by nearly two-fold at 0.011 M. For the same Stokes-Einstein radius (3.5-3.6 nm), the partition coefficients of BSA at neutral conditions and of Ficoll were similar in blank agarose gels, but differed by 15% in agarose-GAG gels. The partition coefficients for Ficolls decreased with increasing solute radius. A microstructural model for partitioning in fibrous materials was evaluated against the experimental observations. The experimental data were most consistent models that had a nearly homogeneous fiber density. The model was in good agreement for partition coefficients of Ficolls with various radii. The decrease in BSA partition coefficient at low ionic strengths was well captured by both microstructural and Donnan models of charge effects. The sieving coefficient (T), or ratio of downstream to upstream solute concentrations, was measured at moderately high Péclet number where T = FKc, where Kc is the convective hindrance factor. It has been hypothesized by others that Kc is independent of charge, such than any charge effects in T are caused by F. Sieving coefficients were measured under similar conditions as partition coefficients. Like partitioning, ionic strength had little effect on the sieving of BSA through blank agarose, but T was decreased by over half from 0.1 M to 0.011 M in gels with 0.2 v% GAG. In these agarose-GAG gels, there was not a statistically significant effect of ionic strength on Kc. Models used for agarose-GAG membranes were applied to a simple model of the glomerular endothelial glycocalyx.
(cont.) The composition and structure of the glycocalyx are not well characterized, but some of its properties can be inferred from the properties of the entire capillary wall and the other capillary layers. Models of the hydraulic permeability of the endothelium suggest that the glycocalyx may be up to several hundred nanometers thick, but the GAG density is probably less than 4 v%. To determine if sieving through such a layer would contribute to glomerular selectivity, improved models for hindered transport coefficients are needed for fibrous systems where the fiber spacing is on the same scale as the solute size.
by Kristin J. Mattern.
Ph.D.
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Dennison, Kathleen Anne. "Radiation crosslinked poly(ethylene oxide) hydrogel membranes." Thesis, Massachusetts Institute of Technology, 1986. http://hdl.handle.net/1721.1/15047.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1986.MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE.
Bibliography: leaves 360-367.
by Kathleen Anne Dennison.
Ph.D.
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Martin, Mackenzie Marie. "Synthetic polypeptide-based hydrogel systems for biomaterials." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/91120.
Full textAbstract:
Thesis: S.M., Massachusetts Institute of Technology, Department of Chemistry, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 27-28).
Hydrogels formed from synthetic polypeptides generated by ring opening polymerization (ROP) of a-amino acid N-carboxyanhydrides (NCAs) present a robust material for modeling the interaction between extracellular matrix (ECM) properties and cellular phenomena. The unique properties of the polypeptide backbone allow it to fold into secondary structures and the ability to modify the side chain presents the opportunity to display chemical functionalities that dictate cellular signaling. The ability to induce cells to form tissue is a chemical and engineering challenge due to the fact that cells need physical support in the form of a 3D scaffold with both chemical and mechanical signals. The Hammond group previously reported the combination of synthetic polypeptides with modified side chains available for click chemistry at quantitative grafting efficiencies. Herein, new schemes for hydrolytically stable versions of the polymer system with click functionality are introduced. Additionally, a new random copolymer, poly(y-propargyl-L-glutamate-co-[gamma]-allyl-L-glutamate) (PPALG) is presented that exploits both the azide-alkyne and thiol-ene click reactions to allow orthogonal side chain modification to increase chemical complexity and ultimately allow a library of "designer" gel systems to be generated.
by Mackenzie Marie Martin.
S.M.
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Herrmann, Anna [Verfasser]. "Surface-Bound Functional Hydrogel Networks / Anna Herrmann." Berlin : Freie Universität Berlin, 2020. http://d-nb.info/1219070157/34.
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Caffarel-Salvador, E. "Hydrogel-formimg microneedles for therapeutic drug monitoring." Thesis, Queen's University Belfast, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.669672.
Full textAbstract:
Therapeutic drug monitoring (TOM) focuses on measurement of drugs with narrow therapeutic windows. Inappropriate concentrations of these drugs can elicit either an absence of therapeutic response or toxic effects. Microneedles (MN) have previously been studied for their ability to painlessly penetrate the stratum corneum, allowing transdermal delivery of various compounds. Interest in MN technology to sample analytes is increasing due to their minimally-invasive characteristics when compared to conventional needles. . . To overcome problems associated with the use of conventional needles, this study aimed to identify the most suitable polymeric MN array design and utilise this, for the first time, as a sampling device capable of imbibing large amounts of fluid for TOM. Hydrogel-forming MN arrays were fabricated from blends of poly(methyl vinyl ether-eo-maleic acid) crosslinked with poly(ethylene glycol) both with and without pore-forming agents. These MN were used in combination with reverse iontophoresis and hygroscopic Iyophilised tablets to further enhance fluid uptake by polymeric matrices. Theophylline, a bronchodilator with a narrow therapeutic window, was chosen as the model drug of the study. A high-performance liquid chromatography (HPLC) method was developed and validated for detection of theophylline. This study proved the capacity of hydrogel-forming MN to take up theophylline, in vitro and in vivo, and release it in water solution for HPLC quantification. Theophylline was successfully detected and quantified from 12 of 24 MN after 1 h insertion in the back of rats dosed with 10 mg theophylline/kg body mass. While this study posed certain challenges, including problems optimising HPLC methodology and difficulties designing a method to extract theophylline in vivo, the potential of MN as a novel in vivo TOM technology with significant clinical potential was proven. Ideally, given the findings of this study, future work will focus on the use of hydrogel-forming MN for TOM in human volunteers.
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Ekblad, Tobias. "Hydrogel coatings for biomedical and biofouling applications." Doctoral thesis, Linköpings universitet, Sensorvetenskap och Molekylfysik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-54304.
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Many applications share a substantial and yet unmet need for prediction and control of interactions between surfaces and proteins or living cells. Examples are blood-contacting biomaterials, biosensors, and non-toxic anti-biofouling coatings for ship hulls. The main focus of this thesis work has been the synthesis, characterization and properties of a group of coatings, designed for such applications. Many types of substrates, particularly plastics, were coated directly with ultrathin, hydrophilic polymer coatings, using a newly developed polymerization method initiated by short-wavelength ultraviolet light. The thesis contains eight papers and an introduction aimed to provide a context for the research work. The common theme, discussed and analyzed throughout the work, has been the minimization of non-specific binding of proteins to surfaces, thereby limiting the risk of uncontrolled attachment of cells and higher organisms. This has mainly been accomplished through the incorporation of monomer units bearing poly(ethylene glycol) (PEG) side chains in the coatings. Such PEG-containing “protein resistant” coatings have been used in this work as matrices for biosensor applications, as blood-contacting inert surfaces and as antibiofouling coatings for marine applications, with excellent results. The properties of the coatings, and their interactions with proteins and cells, have been thoroughly characterized using an array of techniques such as infrared spectroscopy, ellipsometry, atomic force microscopy, surface plasmon resonance and neutron reflectometry. In addition, other routes to fabricate coatings with high protein resistance have also been utilized. For instance, the versatility of the fabrication method has enabled the design of gradients with varying electrostatic charge, affecting the protein adsorption and leading to protein resistance in areas where the charges are balanced. This thesis also describes a novel application of imaging surface plasmon resonance for the investigation of the surface exploration behavior of marine biofouling organisms, in particular barnacle larvae. This technique allows for real-time assessment of the rate of surface exploration and the deposition of protein-based adhesives onto surfaces, a process which was previously very difficult to investigate experimentally. In this thesis, the method was applied to several model surface chemistries, including the hydrogels described above. The new method promises to provide insights into the interactions between biofouling organisms and a surface during the critical stages prior to permanent settlement, hopefully facilitating the development of antibiofouling coatings for marine applications.
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Monteiro, Maria Inês Gonçalves. "Forward osmosis membranes tailored by hydrogel coatings." Master's thesis, Faculdade de Ciências e Tecnologia, 2012. http://hdl.handle.net/10362/9833.
Full textAbstract:
Dissertação para obtenção do Grau de Mestre
em Engenharia Química e BioquímicaForward osmosis (FO) is a promising process to substitute reverse osmosis (RO), as a lower cost and more environmentally friendly desalination process. However, FO still presents some drawbacks, in particular the several internal concentration polarization (CP) effects and insufficient salt selectivity. In order to overcome these disadvantages, this study focuses on the use of hydrogel surface-coated FO membranes to minimize internal CP effect in water purification, and also to improve membrane salt rejection. For this, a series of crosslinked poly(ethylene glycol) (PEG)-based hydrogels were synthesized, by the photopolymerization of poly(ethylene glycol) diacrylate (PEGDA) and the monomer (PEG) in the presence of a photoinitiator. The water uptake and salt permeability of the resulting films were controlled by manipulating the composition ratio of PEGDA and the monomer PEG, by varying the water content in the prepolymerization mixture and the UV-exposure time. High water uptake and low salt permeability values were observed for the films prepared with 50wt% of water content(50%PEGDA). The hydrogels were applied using different techniques (pressure, soaking and coating) to a cellulose acetate (CA) membrane prepared by phase inversion. However, only one technique was effective, surface coating. The CA membranes coated with these hydrogels materials showed an improvement in NaCl rejection (≅100%) and in some cases an enhancement of 100 and 120% of the original water flux (50% PEGDA coating on the active layer and on the porous support, respectively; in PRO mode). The 50%PEGDA coated membrane (with a coating on the porous support) has also shown reduction of the internal CP effects.