Interpenetrating Polymer Network Hydrogels Research Articles

Enhancing protein resistance of hydrogels based on poly(2‐hydroxyethyl methacrylate) and poly(2‐methacryloyloxyethyl phosphorylcholine) with interpenetrating network structure

AbstractIn this work, sequential interpenetrating polymer networks (IPNs) based on poly(2‐hydroxyethyl methacrylate) (PHEMA) and poly (2‐methacryloyloxyethyl phosphorylcholine) (PMPC) were prepared with improved protein resistance. The bulk properties of the IPN hydrogels such as water content, ion permeability and mechanical strength were determined by the gravimetric method, ionoflux measurement technique and tensile tester respectively. The surface characteristics of the IPNs were investigated by X‐ray photoelectron spectroscopy (XPS) and contact angle measurements. XPS analysis suggested that PMPC was present on the surface and in the bulk material. The IPN hydrogels possessed more hydrophilic surface than PHEMA revealed by contact angle measurements. Bovine serum albumin was used as a model protein to evaluate protein resistance by bicinchoninic acid assay method. The result revealed that the protein adsorption on the IPNs showed dramatically reduction compared to PHEMA. These results suggest that the IPNs based on PHEMA and PMPC may be further developed as ophthalmic biomaterials. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Preparation and properties of temperature‐sensitive soy protein/poly(N‐isopropylacrylamide) interpenetrating polymer network hydrogels

AbstractTemperature‐sensitive interpenetrating polymer network (IPN) hydrogels based on soy protein and poly(N‐isopropylacrylamide) were successfully prepared. The structure and properties were systematically characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry and thermogravimetric analysis, and the swelling and deswelling behavior was also investigated. It was found that the hydrogels had good miscibility, thermal stability and temperature sensitivity, and the lower critical solution temperature was ca 32 °C. Changing the content of soy protein or crosslinker could be used to control the swelling behavior, water retention and network structure of the IPN hydrogels. The results show that the novel IPN hydrogels may be of potential interest in drug delivery systems. Copyright © 2011 Society of Chemical Industry

Thermosensitive soy protein/poly(n‐isopropylacrylamide) interpenetrating polymer network hydrogels for drug controlled release

AbstractA series of the thermosensitive interpenetrating polymer network hydrogels composed of soy protein and poly(N‐isopropylacrylamide) were successfully prepared. The structure and properties were systematically characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and differential scanning calorimetry. It was found that the hydrogels had good miscibility and high porosity, and the volume phase transition temperatures of the hydrogels were around 32°C. The release behavior and the release mechanism of a model protein, bovine serum albumin (BSA), were also investigated in detail. The results indicated that the release behavior of BSA had strong temperature dependence and the release percentage of BSA could be controlled by modulating the amount of soy protein or crosslinking agent. The analysis of the release mechanism revealed that the Fickian diffusion controlled release was dominant under the experimental conditions. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.

Synthesis and characterization of photocrosslinkable gelatin and silk fibroin interpenetrating polymer network hydrogels

To effectively repair or replace damaged tissues, it is necessary to design scaffolds with tunable structural and biomechanical properties that closely mimic the host tissue. In this paper, we describe a newly synthesized photocrosslinkable interpenetrating polymer network (IPN) hydrogel based on gelatin methacrylate (GelMA) and silk fibroin (SF) formed by sequential polymerization, which possesses tunable structural and biological properties. Experimental results revealed that IPNs, where both the GelMA and SF were independently crosslinked in interpenetrating networks, demonstrated a lower swelling ratio, higher compressive modulus and lower degradation rate as compared to the GelMA and semi-IPN hydrogels, where only GelMA was crosslinked. These differences were likely caused by a higher degree of overall crosslinking due to the presence of crystallized SF in the IPN hydrogels. NIH-3T3 fibroblasts readily attached to, spread and proliferated on the surface of IPN hydrogels, as demonstrated by F-actin staining and analysis of mitochondrial activity (MTT). In addition, photolithography combined with lyophilization techniques was used to fabricate three-dimensional micropatterned and porous microscaffolds from GelMA–SF IPN hydrogels, furthering their versatility for use in various microscale tissue engineering applications. Overall, this study introduces a class of photocrosslinkable, mechanically robust and tunable IPN hydrogels that could be useful for various tissue engineering and regenerative medicine applications.

In situ forming IPN hydrogels of calcium alginate and dextran-HEMA for biomedical applications

In situ forming hydrogels, which allow for the modulation of physico-chemical properties, and in which cell response can be tailored, are providing new opportunities for biomedical applications. Here, we describe interpenetrating polymer networks (IPNs) based on a physical network of calcium alginate (Alg-Ca), interpenetrated with a chemical one based on hydroxyethyl-methacrylate-derivatized dextran (dex-HEMA). IPNs with different concentration and degree of substitution of dex-HEMA were characterized and evaluated for protein release as well as for the behavior of embedded cells. The results demonstrated that the properties of the semi-IPNs, which are obtained by dissolution of dex-HEMA chains into the Alg-Ca hydrogels, would allow for injection of these hydrogels. Degradation times of the IPNs after photocross-linking could be tailored from 15 to 180days by the concentration and the degree of substitution of dex-HEMA. Further, after an initial burst release, bovine serum albumin was gradually released from the IPNs over approximately 15days. Encapsulation of expanded chondrocytes in the IPNs revealed that cells remained viable and, depending on the composition, were able to redifferentiate, as was demonstrated by the deposition of collagen type II. These results demonstrate that these IPNs are attractive materials for pharmaceutical and biomedical applications due to their tailorable mechanical and degradation characteristics, their release kinetics and biocompatibility.

Improved oxygen permeability and mechanical strength of silicone hydrogels with interpenetrating network structure

The interpenetrating polymer network (IPN) silicone hydrogels with improved oxygen permeability and mechanical strength were prepared by UV-initiated polymerization of monomers including methacryloxypropyl tris(trimethylsiloxy)silane (TRIS), 2-hydroxyethylmethacrylate (HEMA) and N-vinyl pyrrolidone (NVP) in the presence of free radical photoinitiator and cationic photoinitiator. The polymerization mechanism was investigated by the formation of gel network. The structure of IPN hydrogels was characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). The results showed that the IPN hydrogels exhibited a heterogeneous morphology. The mechanical properties, surface wettability and oxygen permeability were examined by using a tensile tester, a contact angle goniometer and an oxygen transmission tester, respectively. The equilibrium water content of the hydrogels was measured by the gravimetric method. The results revealed that the IPN hydrogels possessed hydrophilic surface and high water content. They exhibited improved oxygen permeability and mechanical strength because of the incorporation of TRIS.

Ionotropically cross-linked pH-sensitive IPN hydrogel matrices as potential carriers for intestine-specific oral delivery of protein drugs

Background: The oral delivery of proteins and peptide drugs is considered a major challenge. These types of therapeutics are readily degraded, if taken orally, due to the harsh high acidity of stomach and enzymatic attack in the upper small intestinal tract. Methods: Water-soluble copolymers of sodium acrylate (AAs) grafted onto carboxymethyl cellulose (CMC) were prepared and characterized using Fourier transform spectroscopy, differential scanning calorimetry, and X-ray diffraction. The obtained graft copolymers were then used in a combination with sodium alginate to develop a new series of pH-sensitive interpenetrating polymeric network (IPN) hydrogels through ionotropic gelation with divalent ions (Ca2+). Morphology of the developed hydrogels was investigated using SEM. Swelling characteristics, at distinct compositions, were also studied at 37°C in two consecutive buffer solutions of pH 2.1 and 7.4 (similar to that of gastric and intestinal fluids, respectively). The release profiles of bovine serum albumin, as a model protein, from test IPN hydrogel films were studied in simulated gastric and intestinal fluids. In addition, the drug release process was confirmed by means of SEM. Results: Swelling studies of the developed IPN hydrogels at different pH values confirmed their pH-sensitive nature. The equilibrium swelling extents of the hydrogels were found to be dependent on the grafting yield of CMC/AAs graft copolymer. The IPN hydrogels attained equilibrium swelling percentages in the range 445–740%. In addition, the amount of bovine serum albumin released within 2 hours in pH 2.1 was relatively low (less than 18.1%). This amount increased up to 68% after 8 hours in pH 7.4. Conclusions: From the obtained preliminary data, it seems that the IPN hydrogels developed in this contribution can be tailored to act as good potential carriers for oral delivery of protein drugs. These hydrogels showed a promising protection of protein drugs from the harsh acidity of stomach and, at the same time, they conferred sustained drug release in the intestinal fluid.

Interpenetrating polymer network hydrogels based on silicone and poly(2-methacryloyloxyethyl phosphorylcholine)

In the present work, sequential interpenetrating polymer networks (IPNs) based on silicone and poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) were developed with improved protein resistance. The structure and morphology of the IPNs were characterized by Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The results showed that the IPNs exhibited heterogeneous morphology. The bulk properties such as water content, ion permeability, and mechanical strength of the IPNs were determined by gravimetric method, ionoflux measurement technique, and tensile tester, respectively. The surface characteristics of the IPNs were investigated by X-ray photoelectron spectroscopy (XPS) and contact angle measurements. XPS analysis suggested that PMPC was present on the surface as well as in the bulk material. The IPNs possessed more hydrophilic surface than pristine silicone revealed by contact angle measurements. Bovine serum albumin (BSA) was used as a model protein to evaluate protein resistance by a bicinchoninic acid assay method. The result revealed that the protein adsorption on the IPNs was significantly reduced compared to pristine silicone. These results suggest that the IPNs based on silicone and PMPC may be developed as novel ophthalmic biomaterials. Copyright © 2010 John Wiley & Sons, Ltd.

Effect of the presence of lignin or peat in IPN hydrogels on the sorption of heavy metals

The adsorption of metal ions Cu2+ and Ni2+ from contaminated simulated water was studied using new starch/acryl amide-based hydrogels in the presence of lignin or peat to create an interpenetrating polymer network (IPN). The chemical structure of the materials was studied using infrared spectroscopy and their morphology was observed by scanning electron microscopy (SEM). The behavior of hydrogels in water and the water transport mechanisms were characterized using Fick’s law. Metal ion sorption was analyzed using inductively coupled plasma spectrometry. Hydrogels showed maximum water absorption values at about 100 h and all of them showed a Fickean water transport mechanism. On one hand, SEM confirmed that the new material is in fact an IPN and, on the other, that the internal porosity shown is responsible for the water absorption. On the other hand, the hydrophobic nature of the dispersed phase and its concentration in the hydrogel formulation seem to influence this process, which could also influence or facilitate the diffusion/sorption of metal ions. Peat-containing hydrogels showed a slightly lower absorption capacity of these ions than lignin-containing formulations. These hydrogels have a high potential to obtain metal ion-collector membranes.

Preparation and antidehydration of interpenetrating polymer network hydrogels based on 2‐hydroxyethyl methacrylate and N‐vinyl‐2‐pyrrolidone

AbstractThis work reports the preparation of 2‐hydroxyethyl methacrylate (HEMA)/N‐vinyl‐2‐pyrrolidone (NVP) interpenetrating polymer network (IPN) hydrogels by UV‐initiated polymerization in the presence of free radical photoinitiator Darocur 1173 and cationic photoinitiator 4,4′‐dimethyl diphenyl iodonium hexafluorophosphate. The polymerization mechanism was investigated by the formation of gel network. The structure and morphology of the HEMA/NVP IPN hydrogels were characterized by fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM). The results showed that the IPN gels exhibited homogeneous morphology. The dehydration rates of HEMA/NVP IPN hydrogels were examined by the gravimetric method. The results revealed that the hydrogels had a significant improvement of antidehydration ability in comparison with poly(2‐hydroxyethyl methacrylate)(PHEMA) hydrogel embedded physically with poly(N‐vinyl‐2‐pyrrolidone)(PVP). © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Preparation and characterization of interpenetrating polymer network silicone hydrogels with high oxygen permeability

AbstractIn the current work, interpenetrating polymer network (IPN) silicone hydrogels are prepared by UV‐initiated polymerization of acrylate monomers including siloxane macromer, methacryloxypropyl tris (trimethylsiloxy) silane (TRIS) and N,N‐dimethylacrylamide (DMA)/N‐vinyl‐2‐pyrrolidone (NVP) in the presence of free radical and cationic photoinitiators. The polymerization mechanism is investigated preliminarily by the formation of gel network. The morphology of the hydrogels is characterized by fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and transmission electron microscope (TEM). The results show that the IPN hydrogels exhibit a heterogeneous morphology. The surface wettability is examined by the contact angle goniometer. The result reveals that the IPN silicone hydrogels possess hydrophilic surfaces with the lowest water contact angle of 59°. Furthermore, the oxygen permeability of the hydrogels is measured by an oxygen transmission tester. The results indicate that the IPN silicone hydrogels have excellent oxygen permeability with the highest Dk of 226 barrer. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Interpenetrating polymeric network hydrogel for stomach-specific drug delivery of clarithromycin: Preparation and evaluation

The aim of this study was to develop a controlled release system targeting antibiotic delivery to the stomach. The hydrogels were synthesized by using chitosan, poly (acrylic acid) and poly (vinyl pyrrolidone) polymers crosslinked with glutaraldehyde and N,N’-methylenebisacrylamide. Interpenetrating polymeric network (IPN) hydrogels were prepared by varying the concentration of crosslinking agent (glutaraldehyde). The amount of chitosan, poly (acrylic acid), poly (vinyl pyrrolidone) and N,N’-methylenebisacrylamide were kept constant in all formulations. The effect of glutaraldehyde concentration on the swelling and release characteristics were evaluated. Modalities used to assess the most optimal hydrogel formulation included high liquid chromatography, FTIR analysis, differential scanning calorimetry, swelling studies, in vitro drug release study, mucoadhesive study and scanning electron microscopy. The result showed that IPN hydrogels were greater in swelling, more mucoadhesive and released more drug at lower pH values. Thus, it is believed that the antibiotic concentration in the stomach might be sustained through this formulation.

Interpenetrating polymeric network hydrogel for stomach-specific drug delivery of clarithromycin: Preparation and evaluation

The aim of this study was to develop a controlled release system targeting antibiotic delivery to the stomach. The hydrogels were synthesized by using chitosan, poly (acrylic acid) and poly (vinyl pyrrolidone) polymers crosslinked with glutaraldehyde and N,N’-methylenebisacrylamide. Interpenetrating polymeric network (IPN) hydrogels were prepared by varying the concentration of crosslinking agent (glutaraldehyde). The amount of chitosan, poly (acrylic acid), poly (vinyl pyrrolidone) and N,N’-methylenebisacrylamide were kept constant in all formulations. The effect of glutaraldehyde concentration on the swelling and release characteristics were evaluated. Modalities used to assess the most optimal hydrogel formulation included high liquid chromatography, FTIR analysis, differential scanning calorimetry, swelling studies, in vitro drug release study, mucoadhesive study and scanning electron microscopy. The result showed that IPN hydrogels were greater in swelling, more mucoadhesive and released more drug at lower pH values. Thus, it is believed that the antibiotic concentration in the stomach might be sustained through this formulation.

Comparative delivery of Diltiazem hydrochloride through synthesized polymer: Hydrogel and hydrogel microspheres

AbstractIn this study, interpenetrating polymer network (IPN) hydrogel based on polyvinyl alcohol (PVA) networking with polyacrylic acid (PAA) were prepared by a non‐conventional emulsion method without any added crosslinker, using benzoyl peroxide as initiator and sodium chloride (NaCl) as additive. The IPN hydrogel was characterized by using Fourier transformed infrared (FTIR) spectrophotometry, Thermo gravimetric analysis (TGA), and Scanning electron microscopy (SEM). (PVA‐co‐PAA)/NaCl normal IPN hydrogel (H) were fabricated into hydrogel microspheres (HM) by modified emulsion crosslinking method using glutaraldehyde‐saturated toluene as crosslinker and were loaded with Diltiazem hydrochloride (DL). The IPN hydrogel showed more swelling in simulated intestinal fluid (SIF). (PVA‐co‐PAA)/NaCl HM formulation A1 showed comparatively higher DL entrapment (79%) and better control over DL release up to 24 h. By comparing antihypertensive activity of DL loaded two formulations in normotensive rats, HM formulation A1 found more effective in reducing blood pressure to 40.1%. The experimental results demonstrated that (PVA‐co‐PAA)/NaCl HM had the greater potential than normal hydrogel to be used as a drug carrier. A single use of the prepared hydrogel microsphere system of DL can effectively control hypertension in rats. The system holds promise for clinical studies. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

A simple route to high-strength hydrogel with an interpenetrating polymer network

AbstractHydrogels have potential applications in many fields, but the poor mechanical strength has limited their further development. In this article, we designed a simple route to high-strength interpenetrating polymer network (IPN) hydrogel from polyacrylamide (PAAm) and poly(vinyl alcohol) (PVOH). The highest tensile strength and elongation were 2.4 Mpa and 4300 %, respectively. It was found that the hydrogel strength depended on the chemical crosslinking, physical entanglement and PVOH precipitates. Because of the hydrogen bonding interactions and self-crosslinking, the structure of PVOH transferred from crystal to amorphous. PVOH precipitates scattered in the crosslinked PAAm matrix which dispersed the stress and improved the hydrogel toughness. The simple method is versatile in synthesizing high-strength IPN hydrogels using many kinds of polymer species.

Collagen and glycopolymer based hydrogel for potential corneal application

6-Methacryloyl-α-d-galactopyranose (MG) was synthesized, and characterized by Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectrometry, and single-crystal X-ray diffraction. A series of interpenetrating polymer network (IPN) hydrogels was fabricated by simultaneously photocuring MG crosslinked by poly(ethylene glycol) diacrylate and chemically crosslinking type I collagen with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide. The successful incorporation of the glycopolymer, polymer MG, into collagen hydrogel was confirmed by FTIR and solid-state 13C NMR. The optical characteristics of the IPN hydrogels are comparable to those of human corneas. The tensile strength and modulus of the hydrogels are enhanced by incorporation of polymer MG in comparison to that of the control collagen hydrogel. Biodegradation results indicated that polymer MG enhanced the stability of the composite hydrogels against collagenase. In vitro results demonstrated that the IPN hydrogel supported the adhesion and proliferation of human corneal epithelial cells and outperformed human cornea in blocking bacteria adhesion. Taken together, the IPN hydrogel might be a promising material for use in corneal lamellar keratoplasty.

Release of BSA from porous matrices constituted of alginate–Ca 2+ and PNIPAAm-interpenetrated networks

The synthesis of thermosensitive Interpenetrating Polymer Network (IPN) hydrogels and the release of Bovine Serum Albumin (BSA) from the hydrogels were reported. The hydrogels, constituted of poly(N-isopropyl acrylamide) PNIPAAm network interpenetrated in alginate–Ca 2+ network, were synthesized in a two-stepped process. In the first step, PNIPAAm network was synthesized from an aqueous solution containing N-isopropyl acrylamide (NIPAAm) monomers and N,N′-methylene-bis-acrylamide (MBAAm) co-monomers, and sodium alginate (SA) (1 or 2% w/v). The concentration of NIPAAm monomers in the hydrogel-forming solution was always 2.5, 5.0 or 10.0% (w/v). In the second step, alginate–Ca 2+ networks were formed by immersion of the membrane, obtained on the first step, in a 1.0% (w/v) aqueous calcium chloride. The IPN hydrogels were characterized as a function of temperature (from 25 to 45 °C) through the following measurements: drop water contact angle (DWCA), compression elastic modulus ( E) and cross-linking density ( ν e). The morphology was investigated using scanning electronic microscopy (SEM). In vitro release of BSA from the hydrogels was monitored by UV–Vis spectroscopy at 22 °C and 37 °C. DWCA results showed a decrease in the hydrogel hydrophilicity when the temperature and/or the PNIPAAm amount on hydrogels were increased. PNIPAAm-loader hydrogels are more compacted and presented elevated rigidity, mainly above 35 °C. This trend was attributed to the collapsing of PNIPAAm chains as the hydrogels were warmed above its Lower Critical Solution Temperature (LCST), which in aqueous solution is ca. 32–33 °C. The amount of BSA released from the alginate–Ca 2+/PNIPAAm hydrogels changes inversely to both amount of PNIPAAm and temperature. The transport of BSA from the hydrogels was evaluated through a conventional model. In the lesser-compacted hydrogels the release occurs mostly by diffusion. In the more compacted ones the chain relaxation contributes to the BSA release. Thus, the alginate–Ca 2+/PNIPAAm IPN-typed matrixes may be considered as smart hydrogels for the release of BSA, because the amount and rate of BSA released may be tailored by both the NIPAAm concentration in the hydrogel-forming solution and the control of temperature of hydrogel.

Preparation and characterization of a positive thermoresponsive hydrogel for drug loading and release

AbstractA positive thermoresponsive hydrogel composed of poly(acrylic acid)‐graft‐β‐cyclodextrin (PAAc‐g‐β‐CD) and polyacrylamide (PAAm) was synthesized with the sequential interpenetrating polymer network (IPN) method for the purpose of improving its loading and release of drugs. The structure and properties of the PAAc‐g‐β‐CD/PAAm hydrogel (IPN hydrogel) were characterized with Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), and swelling measurements. FTIR studies showed that the IPN hydrogel was primarily composed of an IPN of PAAc‐g‐β‐CD and PAAm. The data from DSC and swelling measurements indicated that the phase‐transition temperature or upper critical solution temperature (UCST) of the IPN hydrogel was approximately 35°C. Through the measurement of the temperature dependence of the swelling, increases in the UCST and non‐sensitivity to changes in the salt concentration were observed for the IPN hydrogel versus the normal IPN hydrogel poly(acrylic acid)/PAAm (without β‐cyclodextrin). Furthermore, the swelling/deswelling kinetics of the IPN hydrogel also exhibited an improved controllable response rate versus the normal IPN hydrogel. Ibuprofen (IBU) was chosen as the model drug for examining loading and release from the IPN hydrogel. The experimental data proved that the IPN hydrogel provided a positive drug release pattern; the IBU released faster at 37°C than at 25°C, and improved drug loading and controlled release were achieved by the IPN hydrogel versus the normal IPN hydrogel. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Hydrogel based on interpenetrating polymer networks of dextran and gelatin for vascular tissue engineering

Hydrogel networks are highly desirable as three-dimensional (3-D) tissue engineering scaffolds for cell encapsulation due to the high water content and ability to mimick the native extracellular matrix. However, their application is limited by their nanometer-scale mesh size, which restricts the spreading and proliferation of encapsulated cells, and their poor mechanical properties. This study seeks to address both limitations through application of a novel cell-encapsulating hydrogel family based on the interpenetrating polymer network (IPN) of gelatin and dextran bifunctionalized with methacrylate (MA) and aldehyde (AD) (Dex–MA–AD). The chemical structure of the synthesized Dex–MA–AD was verified by 1H-NMR and the degrees of substitution of MA and AD were found to be 14 and 13.9 ± 1.3 respectively. The water contents in all these hydrogels were approximately 80%. Addition of 40 mg/ml to 60 mg/ml gelatin to neat Dex–MA–AD increased the compressive modulus from 15.4 ± 3.0 kPa to around 51.9 ± 0.1 kPa (about 3.4-fold). Further, our IPN hydrogels have higher dynamic storage moduli ( i.e. on the order of 10 4 Pa) than polyethylene glycol-based hydrogels (around10 2–10 3 Pa) commonly used for smooth muscle cells (SMCs) encapsulation. Our dextran-based IPN hydrogels not only supported endothelial cells (ECs) adhesion and spreading on the surface, but also allowed encapsulated SMCs to proliferate and spread in the bulk interior of the hydrogel. These IPN hydrogels appear promising as 3-D scaffolds for vascular tissue engineering.

Bioactive interpenetrating polymer network hydrogels that support corneal epithelial wound healing

The development and characterization of collagen-coupled poly(ethylene glycol)/poly(acrylic acid) (PEG/PAA) interpenetrating polymer network hydrogels is described. Quantitative amino acid analysis and FITC-labeling of collagen were used to determine the amount and distribution of collagen on the surface of the hydrogels. The bioactivity of the coupled collagen was detected by a conformation-specific antibody and was found to vary with the concentration of collagen reacted to the photochemically functionalized hydrogel surfaces. A wound healing assay based on an organ culture model demonstrated that this bioactive surface supports epithelial wound closure over the hydrogel but at a decreased rate relative to sham wounds. Implantation of the hydrogel into the corneas of live rabbits demonstrated that epithelial cell migration is supported by the material, although the rate of migration and morphology of the epithelium were not normal. The results from the study will be used as a guide toward the optimization of bioactive hydrogels with promise in corneal implant applications such as a corneal onlay and an artificial cornea.