Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Hydrogels”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 181 records · Page 10Linked to original sources
PubMedDate not supplied

Adhesion behavior of peritoneal cells on the surface of self-assembled triblock copolymer hydrogels.

Adhesion behavior of cells to the surface of physical hydrogel membranes prepared by water-induced self-organization of precisely synthesized ABA-triblock copolymers comprised of poly(beta-benzyl L-aspartate) (PBLA) as A segment and poly(ethylene oxide) (PEO, molecular weight = 20 000) as the B segment were investigated. The cast film from the methylenechloride solution of these copolymers swelled in water very rapidly forming hydrogels (100-400% water content of total weight). The content of PBLA affected the strength, the hydrophobicity, and the amount of water involved in the hydrogel surface. During the early stage of cultivation with murine peritoneal cells, cell adhesion on the hydrogels of PEO and PBLA with 18 (20K18) and 25 (20K25) monomeric units was not observed, while adhesion on the hydrogels of PEO and PBLA with 32 (20K32) and 55 (20K55) monomeric units was successful, suggesting more than 12 mol % in PBLA content is necessary for adhesion of these cells. Although cell spreading on the hydrogels of 20K18, 20K25, and 20K32 was not sufficient, the hydrogel of 20K55 allowed cell adhesion and spreading to be bipolar with leading edge whose raffling is active with pseudopodium and lamellipodium as well as PBLA homopolymer, suggesting active motility of these cells. Remarkably, prolonged incubation restored adhesiveness onto the films at 20K18 in contrast to adhesion with 20K25 despite low hydrophobicity. It is conceivable that adaptation of proteins and chemical changes to the surface during the culture period may participate in these phenomena. Mechanical properties and interaction between cell and these copolymer hydrogels could be controlled by composition of block segments, and optimization for implants could also be attainable.

Adhesiveness↗
PubMed2004

Tethered protein/peptide-surface-modified hydrogels.

We investigated a wet chemistry method to covalently bond polyethylene glycol (PEG)-tethered extracellular matrix (ECM) proteins (laminin and fibronectin) or peptide (fibronectin-adhesion-peptide sequence) onto the surface of a poly(2-hydroxylethyl methacrylate-co-methylacrylic acid) (PHEMA/MAA) hydrogel that could potentially be used as a replacement for corneal tissue in the eye. An essential requirement for the success of such a surface in the biological environment is its ability to support the growth and attachment of corneal epithelial cells; ECM proteins are known to promote cellular attachment and growth. We hypothesized that the use of tethers or long hydrophilic chains would allow the attached ECM protein/peptide molecules to move two-dimensionally in space, thereby increasing their ability to bind with epithelial cell membranes. Additionally, the tethers would prevent the specifically added growth-enhancing factors from being obscured by any non-specific protein binding occurring on the hydrogel surface. In this surface-modification study, carbodiimidazole (CDI) was used to activate the carboxylic groups (-COOH) on the hydrogel surface in anhydrous dimethylsulfoxide (DMSO) before addition of the PEGylated proteins/peptide. The resulting tethered protein/peptide surface-modified hydrogels were analyzed in terms of percent grafting efficiency, biological activity and mechanical properties. X-ray photoelectron spectroscopy (XPS) and 125I radioactive labeling demonstrated the successful covalent bonding between the moieties and the hydrogel surface. Radiolabeling and enzyme-linked immunosorbent assay (ELISA) studies indicated that the tethered proteins attached to the hydrogel surface at a concentration of approx. 0.1 microg/cm2. ELISA testing further showed that tethered proteins remained biologically active. However, mechanical tensile testing indicated that the mechanical properties of these chemically modified hydrogels were somewhat altered in comparison with the unmodified hydrogel. Future studies will evaluate the cellular response to these surface-modified materials in vitro and in vivo.

Biocompatible Materials↗
PubMed2005

Cell viability of chitosan-containing semi-interpenetrated hydrogels based on PCL-PEG-PCL diacrylate macromer.

Chitosan-modified biodegradable hydrogels were prepared by UV irradiation of solutions in mild aqueous acidic media of poly(caprolactone)-co-poly(ethylene glycol)-co-poly(caprolactone) diacrylate (PCL-PEG-PCL-DA) and chitosan. Hydrogels obtained were characterized using FT-IR, DSC, TGA and XPS. FT-IR, TGA and DSC revealed the semi-interpenetrating polymer network structure formed in the hydrogel. Though the water swelling degree of these chitosan-modified hydrogels was substantial in the range of 322-539%, it was found that fibroblasts could still attach, spread and grow on them; this is in contrast to the commonly investigated PEG-diacrylate hydrogel. The MTT assay demonstrated that cells could grow better on 3 or 6% chitosan-modified hydrogel than unmodified PCL-PEG-PCL-DA hydrogels or low-content (1%) chitosan-modified PCL-PEG-PCL-DA hydrogel. Increased chitosan content resulted in increased cell interaction and also decreased water swelling, both of which results in increased cell attachment and spread.

Acrylates↗
PubMed2001

Biocompatible hydrogel supports the growth of respiratory epithelial cells: possibilities in tracheal tissue engineering.

Extensive tracheal defect reconstruction is a major challenge in plastic and reconstructive surgery. The lack of an epithelial lining on the luminal surfaces of tracheal prostheses is among the major causes of their failure. Chitosan-gelatin hydrogels were synthesized for the development of biocompatible, growth-supportive substrata for respiratory epithelial cells. We employed J774 macrophages to test the immunocompatibility of this gel. The hydrogel did not exert a cytotoxic effect on macrophages, as confirmed by tetrazolium reduction and neutral red uptake assay. Flow cytometric analysis of macrophages cultured on the hydrogel showed a comparable expression of activation markers CD11b/CD18, CD45, and CD14 to the control. Semiquantitative RT-PCR results showed an absence of upregulation of interleukin-6 (IL-6) and TNF-alpha in these macrophages with respect to the controls. Primary human respiratory epithelial cells cultured on the hydrogel showed proper attachment, normal morphology, and growth. A small proportion of cells on the hydrogel showed synchronously beating cilia. RT-PCR analysis showed that cells on the hydrogel expressed mucins 2 and 5 and cytokeratin 13, which are markers for secretory goblet and squamous cells, respectively. All these results demonstrate that the hydrogel supports the growth of a mixed population of differentiated epithelial cells. This hydrogel is suitable as a culture substratum for respiratory epithelial cells and could be used as a potential candidate for coating tracheal prostheses.

Biocompatible Materials↗
PubMed2003

Adhesion and migration of marrow-derived osteoblasts on injectable in situ crosslinkable poly(propylene fumarate-co-ethylene glycol)-based hydrogels with a covalently linked RGDS peptide.

Marrow-derived osteoblasts were cultured on poly(propylene fumarate-co-ethylene glycol) (P(PF-co-EG)) based hydrogels modified in bulk with a covalently linked RGDS model peptide. A poly(ethylene glycol) spacer arm was utilized to covalently link the peptide to the hydrogel. Three P(PF-co-EG) block copolymers were synthesized with varying poly(ethylene glycol) block lengths relative to poly(ethylene glycol) spacer arm. A poly(ethylene glycol) block length of nominal molecular weight 2000 and spacer arm of nominal molecular weight 3400 were found to reduce nonspecific cell adhesion and show RGDS concentration dependent marrow-derived osteoblast adhesion. A concentration of 100 nmol/mL RGDS was sufficient to promote adhesion of 84 +/- 17% of the initial seeded marrow-derived osteoblasts compared with 9 +/- 1% for the unmodified hydrogel after 12 h. Cell spreading was quantified as a method for evaluating adhesivity of cells to the hydrogel. A megacolony migration assay was utilized to assess the migration characteristics of the marrow-derived osteoblasts on RGDS modified hydrogels. Marrow-stromal osteoblasts migration was greater on hydrogels modified with 100 nmol/mL linked RGDS when compared with hydrogels modified with 1000 nmol/mL linked RGDS, while proliferation was not affected. These P(PF-co-EG) hydrogels modified in the bulk with RGDS peptide are potential candidates as in situ forming scaffolds for bone tissue engineering applications.

Animals↗
PubMed2007

Polyethylene glycol-based cationically charged hydrogel beads as a new microcarrier for cell culture.

A new polyethylene glycol (PEG) based microcarrier was designed and examined by the attachment and growth of mouse fibroblast cells. In the design of microcarrier, a PEG-based macromonomer, polyethyleneglycol methacrylate (PEGMA), was selected as the main component of hydrogel beads since PEG is known as a nontoxic and biocompatible material. A relatively new cationic comonomer, N-[3-(dimethylamino)propyl]methacrylamide (DMAPM), with higher ionization ability with respect to the similar comonomers was used for providing cationic charge to the hydrogel structure. In the first part, a suspension copolymerization method was developed for the production of cationically charged hydrogel beads as a potential microcarrier for cell culturing. The suspension copolymerization by using ethylene dimethacrylate (EDM) as cross-linking agent and cyclohexanol as the diluent provided spherical, polydisperse poly(PEGMA-DMAPM-EDM) hydrogel beads with an average size of 121 microm. The hydrogel beads exhibited a pH-dependent swelling behavior. The L929 mouse fibroblast cells were cultured on poly(PEGMA-DMAPM-EDM) hydrogel beads with an initial concentration of 200,000 cells/mL. The cells were incubated in Dulbecco's modified Eagle's medium during 5 days and the cell proliferation was investigated at every 24 h. An effective cell attachment and growth up to 3.5 x 10(6) cells/mL were observed with the poly(PEGMA-DMAPM-EDM) hydrogel beads. The results indicated that the proposed microcarrier was a significant alternative to the hydrogel beads obtained by the copolymerization of 2-hydroxyethyl methacrylate and 2-dimethylaminoethylmethacrylate commonly used in microcarrier-facilitated cell culturing studies.

Animals↗
PubMed2005

Controlling drug release from imprinted hydrogels by modifying the characteristics of the imprinted cavities.

The aim of this study was to analyse the influence of the template/functional monomer proportion on the achievement of molecularly imprinted hydrogels with cavities with a high enough affinity for the drug to sustain drug release. Imprinted hydrogels were prepared from N,N-dimethylacrylamide and tris(trimethylsiloxy)sililpropyl methacrylate (DMAA and TRIS; main components), methacrylic acid (MAA; functional monomer), ethylene glycol dimethacrylate (EGDMA; cross-linker), and timolol (template drug). Photo-polymerization of the monomer solutions was carried out in poly(propylene) molds (0.3 mm thickness) to obtain contact lens-like devices. Non-imprinted control hydrogels were also prepared in the same way but without the addition of timolol. The imprinted hydrogels showed a higher affinity for timolol and a slower release rate than the non-imprinted hydrogels. The release rate decreased by increasing the MAA/timolol ratio in the gel recipe. Hydrogels prepared with 400 x 10(-3) M MAA, 600 x 10(-3) M EGDMA, and a timolol/MAA mole ratio of 1:16-1:32 had drug diffusion coefficients two orders of magnitude below those of non-imprinted hydrogels. The results obtained clearly indicate that the timolol release rate is critically affected by the conditions under which the hydrogels were synthesized. These effects are discussed on the basis of the influence of drug proportion on the conformation of the imprinted cavities.

Adsorption↗
PubMed2006

Improved systemic safety and risk-benefit ratio of topical 0.1% timolol hydrogel compared with 0.5% timolol aqueous solution in the treatment of glaucoma.

PURPOSE: The purpose of the study was to compare the systemic safety and risk-benefit ratio of 0.1% timolol hydrogel and 0.5% aqueous timolol eye drops in the treatment of glaucoma. METHODS: An 8-week randomised, double-blind, cross-over, multicentre study. A total of 25 patients with primary open-angle glaucoma, exfoliation glaucoma, or ocular hypertension was enrolled. After completing a wash-out period, patients were randomly chosen to receive either 0.1% timolol hydrogel once daily or 0.5% aqueous timolol eye drops twice daily. Intraocular pressure and heart rate during rest and exercise, head-up tilt test results, spirometry readings, and plasma concentrations of timolol were recorded. The risk-benefit ratio was determined by calculating the ratio between several heart rate endpoints and the change in intraocular pressure (IOP). RESULTS: The mean drug-induced change in the peak heart rate during exercise was -13.5 beats/min (SD 7.6) in the 0.5% aqueous timolol group and -5.1 beats/min (SD 6.7) in the 0.1% timolol hydrogel group (P<0.001; 95% CI 4.06-12.18). There was no significant difference in the IOP-reducing efficacy between these compounds. The risk-benefit ratio was significantly improved when 0.1% timolol hydrogel was used, compared with 0.5% aqueous timolol in the exercise test. In the head-up tilt test the risk-benefit ratio was significantly improved at rest (P<0.05), at 1 min (P<0.05) and at 5 min (P<0.001) after patients had received 0.1% timolol hydrogel. There were, however, no differences in spirometry readings. After patients had been treated with 0.1% timolol hydrogel, plasma concentrations of timolol were 1/6 (at peak) and 1/50 (at trough) of those of 0.5% aqueous timolol. CONCLUSIONS: Drug-induced changes in the peak heart rate, and head-up tilt test results as well as plasma concentrations of timolol, were significantly more pronounced after treatment with 0.5% aqueous timolol than with 0.1% timolol hydrogel. Because of the statistically similar IOP-reducing efficacy of these formulations the risk-benefit ratio was significantly improved when patients used 0.1% timolol hydrogel instead of 0.5% aqueous timolol.

Administration, Topical↗
PubMed2006

Hyaluronic acid hydrogel immobilized with RGD peptides for brain tissue engineering.

In this paper, hyaluronic acid hydrogels with open porous structure have been developed for scaffold of brain tissue engineering. A short peptide sequence of arginine-glycine-aspartic acid (RGD) was immobilized on the backbone of the hydrogels. Both unmodified hydrogels and those modified with RGD were implanted into the defects of cortex in rats and evaluated for their ability to improve tissue reconstruction. After 6 and 12 weeks, sections of brains were processed for DAB and Glees staining. They were also labeled with GFAP and ED1 antibodies, and observed under the SEM for ultrastructral examination. After implanting into the lesion of cortex, the porous hydrogels functioned as a scaffold to support cells infiltration and angiogenesis, simultaneously inhibiting the formation of glial scar. In addition, HA hydrogels modified with RGD were able to promote neurites extension. Our experiments showed that the hyaluronic acid-RGD hydrogel provided a structural, three-dimensional continuity across the defect and favoured reorganization of local wound-repair cells, angiogenesis and axonal growth into the hydrogel scaffold, while there was little evidence of axons regeneration in unmodified hydrogel.

Absorbable Implants↗
PubMed2006

New cyclodextrin hydrogels cross-linked with diglycidylethers with a high drug loading and controlled release ability.

PURPOSE: The goal of the study is to develop new hydrogels based on cyclodextrins cross-linked with ethyleneglycol diglycidylether (EGDE) under mild conditions, to be used as carriers of amphiphilic drugs. Also, it aims to characterize the cross-linking and the drug loading and release processes. METHODS: The cross-linking of hydroxypropyl-beta-cyclodextrin (HPbetaCD) with EGDE, in the absence or presence of hydroxypropylmethylcellulose (HPMC) Methocel K4M, was optimized applying oscillatory rheometry and Fourier transform infrared. Hydrogels were characterized regarding swelling in water, ability to load diclofenac, and release after different drying treatments. RESULTS: Solutions of HPbetaCD (14.28%), without or with HPMC (0.2-1.0%), provided firm and transparent hydrogels after cross-linking with EGDE (14.28%), in which around two thirds of the OH groups were cross-linked. The incorporation of HPMC progressively reduced the gel time and the swelling degree of hydrogels. HPbetaCD hydrogels efficiently loaded diclofenac and sustained the release for several hours. The presence of HPMC slowed the release from swollen hydrogels, but promoted it from hydrogels dried before the loading and also before the release. CONCLUSIONS: HPbetaCD hydrogels with good mechanical properties and tunable loading and release ability can be obtained by direct cross-linking with EGDE.

2-Hydroxypropyl-beta-cyclodextrin↗
PubMed2006

A material decoy of biological media based on chitosan physical hydrogels: application to cartilage tissue engineering.

The cartilage tissue has a limited self-regenerative capacity. Tissue-engineering represents a promising trend for cartilage repair. The present study was aimed to develop a biomaterial formulation by combining fragments of chitosan hydrogel with isolated rabbit or human chondrocytes. We first reported the properties of the constructs elaborated with rabbit chondrocytes and pure chitosan physical hydrogels with defined molecular weight, acetylation degree and polymer concentration. Morphological data showed that chondrocytes were not penetrating the hydrogels but tightly bound to the surface of the fragments and spontaneously formed aggregates of combined cell/chitosan. A significant amount of neo-formed cartilage-like extracellular matrix (ECM) was first accumulated in-between cells and hydrogel fragments and furthermore was widely distributed within the neo-construct. The optimal biological response was obtained with hydrogel fragments concentrated at 1.5% (w/w) of polymer made from a chitosan with a degree of acetylation between 30 and 40%. Such hydrogels were then mixed with human chondrocytes. The phenotype of the cells was analyzed by using chondrocytic (mRNA expression of mature type II collagen and aggrecan as well as secretion of proteoglycans of high molecular weight) and non chondrocytic (mRNA expression of immature type II collagen and type I collagen) molecular markers. As compared with human chondrocytes cultured without chitosan hydrogel which rapidly dedifferentiated in primary culture, cells mixed with chitosan rapidly loose the expression of type I and immature type II collagen while they expressed mature type II collagen and aggrecan. In these conditions, chondrocytes maintained their phenotype for as long as 45 days, thus forming cartilage-like nodules. Taken together, these data suggest that a chitosan hydrogel does not work as a scaffold, but could be considered as a decoy of cartilage ECM components, thus favoring the binding of chondrocytes to chitosan. Such a biological response could be described by the concept of reverse encapsulation.

Acetylation↗
PubMed2005

Sequential formation of covalently bonded hydrogel multilayers through surface initiated photopolymerization.

A novel method for the sequential formation of hydrogel multilayers is described. Formation of the first layer is based on surface initiated photopolymerization of hydrogel precursors on eosin derivatized surfaces. In order to attach subsequent layers it is necessary to be able to functionalize intermediate hydrogel layers with eosin. In the present work, this is accomplished by introducing poly(ethylene glycol) amino acrylate (NH2-PEG-Acr) along with other hydrogel precursors such as poly(ethylene glycol) diacrylate (PEG-DA) on the intermediate layers. The pendant amine groups allow functionalization of the intermediate layers with eosin for subsequent photopolymerization of new hydrogel layers. The process can be repeated sequentially to construct multilayered hydrogel membranes. The NH2-PEG-Acr monomer can be formed by coupling cysteamine to PEG-DA by a conjugate addition reaction. The approach to multilayer formation could allow the incorporation of specific functionalities or compositions within each hydrogel layer so that multifunctional membranes can be formed. It could also be implemented, through proper photopatterning procedures, for the formation of 3-D hydrogel structures. The mild photopolymerization conditions employed using visible (514 nm), rather than ultraviolet light would make this technique especially attractive for tissue engineering, drug delivery, biomaterials, biosensor development and other situations where the elements incorporated are sensitive to UV light exposure.

Eosine Yellowish-(YS)↗
PubMed2004

Modeling of swelling and drug release behavior of spontaneously forming hydrogels composed of phospholipid polymers.

Physically cross-linked hydrogel had been investigated in order to make use of oral polypeptide drug delivery carrier. By using 2-methacryloyloxyethyl phosphorylcholine (MPC) copolymer, we had prepared a spontaneously forming hydrogel showing controllable dissociation via pH changes. In this study, the dissociation and release of polypeptide drugs from the MPC polymer hydrogel loaded with polypeptide drugs, which had been prepared from aqueous solutions containing water-soluble poly[MPC-co-methacrylic acid (MA)] (PMA) and poly[MPC-co-n-butyl methacrylate (BMA)] (PMB) had been executed. The polymer concentration was 10 wt.% and PMA/PMB feed ratio (A/B feed ratio) was 5/5. Insulin labeled with fluorescein-4-isothiocyanate (FITC) and cytochrome c had been loaded for the examination of the release behavior. The hydrogel in pH 1.8 aqueous solution would be swelling, for the hydrogel would absorb outside water. However, during this process, the polymer is dissoluting out from the hydrogel due to the widening of the polymer network. The cytochrome c followed anomalous transport while insulin depended on the swelling and dissolution of the polymer chains. The hydrogel showed surface erosion in neutral condition, although the hydrogel is composed of two different polymer possessing divergent physical properties. The release followed anomalous transport, but the erosion rate slightly changed with as the hydrophobicity of the loaded drugs. The total amount of the drugs released in neutral condition was larger compared to the acidic condition. When the eroded percentage and the release percentage were compared with each other, it showed that release was slightly slower than erosion, indicating that the erosion was controlling the release phenomenon.

Cytochromes c↗
PubMed2005

Dynamic swelling behavior of gamma-radiation induced polyelectrolyte poly(AAm-co-CA) hydrogels in urea solutions.

The aim of this study was to investigate the equilibrium swelling properties in urea solutions of gamma-radiation induced polyelectrolyte copolymeric hydrogels consisting of acrylamide (AAm) and crotonic acid (CA). Poly(acrylamide-co-crotonic acid), poly(AAm-co-CA) hydrogels containing different amounts of CA were obtained in the form of rods after radiation. Swelling experiments were performed in aqueous urea solutions at 25 degrees C, gravimetrically. The hydrogels showed large extents of swelling in aqueous (urea/water) media the swelling being highly dependent on the chemical composition of the hydrogels and irradiation dose. The percentage swelling of poly(AAm-co-CA) hydrogels was between 1160 and 4250%, while that of the AAm hydrogels was between 670 and 900%. The diffusional exponent values (n) are between 0.51 and 0.66, hence the diffusion of urea/water into the hydrogels is non-Fickian. Equilibrium urea/water contents of the hydrogel systems were changed between 0.870 and 0.977.

Acrylamides↗
PubMed2006

Acrylic/cyclodextrin hydrogels with enhanced drug loading and sustained release capability.

The influence of the proportion of acrylamidomethyl-gamma-cyclodextrin (gamma-CD-NMA) on loading and release of the hydrophobic triamcinolone acetonide (TA) and the hydrophilic propranolol (PR) by acrylic acid hydrogels was evaluated. gamma-CD-NMA was synthesized by condensation of gamma-cyclodextrin (gamma-CD) with N-(hydroxymethyl) acrylamide. Hydrogels were prepared with gamma-CD-NMA and sodium acrylate (3 M or 4 M), using N,N'-methylen(bisacrylamide) (BIS) as cross-linker, by free radical polymerization into glass moulds of 2 mm wide and were cut as discs (10 mm diameter). gamma-CD-NMA did not modify the pH-dependent swelling of the hydrogels, but significantly increased the swelling degree in the 40:60 ethanol:water, medium in which TA can be dissolved. Hydrogels prepared with gamma-CD-NMA above 5% (w/w of total monomers) showed a remarkably higher capacity to load TA, e.g., 33 mg/g dry hydrogel versus 0.6 mg/g dry hydrogel without gamma-CD-NMA. This is explained by the formation of 1:1 inclusion complexes of TA with gamma-CD mers that overcomes the lack of interactions with the acrylic groups of the network. The release of TA in water, 0.1 N HCl, or pH 6.8 phosphate buffer was sustained for at least 24 h, whatever the pH and the composition of the medium used. In contrast, loading of PR from the water solutions was greater for hydrogels prepared with 3 M acrylate than with 4 M acrylate, irrespective to their content in gamma-CD-NMA, and in less than 2 h ca. 80% PR was released. The lower affinity of PR for the gamma-CD cavities, compared to the strong intensity of the electrostatic interactions with the acrylic acid groups, explains why the incorporation of gamma-CD-NMA did not increased the loading and control release capacity of the hydrogels of this hydrophilic drug. In summary, the copolymerisation of CD with acrylic monomers can provide highly hydrophilic pH-sensitive networks which load large amounts of hydrophobic drugs and release them in a sustained way.

Calorimetry, Differential Scanning↗
PubMed2006

Characterization of insulin protection properties of complexation hydrogels in gastric and intestinal enzyme fluids.

The objective of this study was to elucidate the mechanisms contributing to oral bioavailability of insulin by poly(methacrylic acid grafted with poly(ethylene glycol)) (P(MAA-g-EG)) hydrogels using the gastric and intestinal fluids from rats. P(MAA-g-EG) hydrogels successfully protected the incorporated insulin from enzymatic degradation by forming interpolymer complexes in the gastric fluid. The hydrogels also showed the insulin protection ability by itself. In the intestinal fluid, P(MAA-g-EG) hydrogels significantly decreased the insulin degradation rate and calcium ion levels, while protein levels was not changed. Insulin protecting effects were dependent on the fraction of the carboxylic group in the polymer networks. Moreover, the insulin degradation inhibitory effect was significantly correlated with Ca2+ deprivation ability of P(MAA-g-EG) hydrogels in the intestinal fluid, implying that the Ca2+ deprivation ability plays an important role in the inhibition of the intestinal enzyme activities. Insulin-loaded P(MAA-g-EG) (ILPs) hydrogels showed a rapid and almost complete insulin release even in the presence of intestinal proteases. These results suggested that the insulin protection ability of the hydrogels contributed to improve oral insulin absorption and that P(MAA-g-EG) hydrogels can be an excellent carrier for protecting insulin during their transit through the GI tract.

Animals↗
PubMed2005

The enhancement of cell adherence and inducement of neurite outgrowth of dorsal root ganglia co-cultured with hyaluronic acid hydrogels modified with Nogo-66 receptor antagonist in vitro.

Hyaluronic acid hydrogels modified with polyclonal anti-Nogo-66 receptor antibody were developed in order to promote regeneration in the injured CNS. These modified hydrogels were intended not only to deliver antibodies, but also to serve as a scaffold for neural regeneration following their implantation into injured tissue. Since unmodified hyaluronic acid-hydrogels do not support cell attachment, the gels were modified with polyclonal anti-Nogo-66 receptor with the aim of altering the surface properties of the gels in such a way as to improve neuronal adherence and survival. After evaluating the immobilization efficiency of the system, chicken dorsal root ganglia and dorsal root ganglia cells were planted on the surface of the modified gels to determine cell viability. Dorsal root ganglia were also cultured close to the gels in order to assay the inducement of neurite outgrowth. In dorsal root ganglia and cell viability assay, dorsal root ganglia and neuron cells could adhere to the modified hydrogels and survive well, but it did not happen to unmodified hydrogels. After 72 h, these attached cells were stained positively with immuno-staining for neurofilament. Neurite outgrowth inducement assay showed that the number and length of dorsal root ganglia neurites on the side toward modified hydrogels were significantly more than that on the opposite side (both P<0.01). The results reveal that hyaluronic acid-hydrogels modified with anti-Nogo-66 receptor can support neural cell attachment and survival in vitro. Furthermore, this system can greatly induce neurite outgrowth. The results also indicate that this modified hydrogels have potential to repair injury in the CNS.

Animals↗
PubMed2004

Sustained release of vascular endothelial growth factor from calcium-induced alginate hydrogels reinforced by heparin and chitosan.

A possible alternative for immunosuppression is a microencapsulation technique using hydrogels, which have been utilized for cell immobilization and drug delivery systems. Angiogenesis is crucial for delivery of the metabolic products to the host tissues as well as to supply oxygen and nutrients to cells. The local delivery of angiogenic growth factors, such as VEGF and basic FGF, has been recently studied to enhance angiogenesis on peripheral tissue of graft. In this study, we evaluated sustained VEGF release with a model using hydrogels coated with chitosan and heparin in vitro. We fabricated calcium alginate gels and chitosan-coated calcium alginate gels. Heparinized chitosan-coated calcium-induced alginate hydrogel beads were prepared by soaking chitosan-coated calcium alginate gels in heparin solution. We compared the stability and VEGF release manner between three kinds of hydrogels. To compare the stability, 5 mL of each hydrogel was incubated with 20 mL PBS under the rotational culture. Compression forces were measured using a rheometer. The amount of VEGF released from the gels was measured by ELISA. The heparin-coated chitosan alginate hydrogels showed the highest surface stability among the three hydrogels. VEGF from the heparinized gel was released in sustained manner up to 10 days in vitro. Chitosan-coated alginate gels released 90% of loaded VEGF within 5 days. These results suggest that local delivery of VEGF using a heparinized hydrogel may provide a long-term supply of angiogenic growth factor that might induce new vessel formation in vivo.

Alginates↗