Analysis of poly(ethylene glycol)-diacrylate macromer polymerization within a multicomponent semi-interpenetrating polymer network system

Semi-interpenetrating polymer networks (semi-IPNs) containing poly(ethylene glycol)-diacrylate (PEGdA) and modified gelatin were prepared with 2,2-dimethoxy-2-phenylacetophenone (DMPA) as a photoinitiator. The effect of (i) initiator and PEGdA concentration, and (ii) weight ratio and type of modified gelatin on the conversion of PEGdA functional end groups was monitored in situ using attenuated total reflectance-Fourier transform infrared (ATR-FTIR). Reaction induction time was dependent on DMPA concentration and increased with decreasing DMPA concentration. Relative reaction rate was strongly dependent on both DMPA and PEGdA concentrations. Gelatin weight ratio and modification did not significantly affect reaction induction time, relative reaction rate, or reaction end time. Swelling/degradation kinetics at various aqueous conditions sought to establish relationships between diacrylate conversion and the resulting semi-IPN physical properties. Semi-IPN swelling weight ratio was strongly dependent on solvent conditions and semi-IPN exposure to gamma-irradiation. Gelatin backbone modification and UV exposure time exhibited no effect on semi-IPN swelling weight ratio. In conclusion, ATR-FTIR presents a viable means of monitoring the conversion of PEGdA functional end groups within a complex mixture. UV exposure >10 s did not significantly affect the weight swelling ratio, and supports our ATR-FTIR results that network formation reached completion before 3 min of UV exposure.     

Poly(N-isopropylacrylamide)-based semi-interpenetrating polymer networks for tissue engineering applications. Effects of linear poly(acrylic acid) chains on rheology

Semi-interpenetrating polymer networks (semi-IPNs), comprised of poly(N-isopropylacrylamide-co-acrylic acid) (p(NIPAAm-co-AAc)) hydrogels and linear p(AAc) chains, were synthesized, and the effects of the p(AAc) chains on semi-IPN rheology were examined. Oscillatory shear rheometry studies were performed and the rheological data were analyzed as a function of temperature, frequency, and p(AAc) chain amount (weight average molecular weight (Mw) 4.5 x 10(5) g/mol). At 22 degrees C, the semi-IPNs, as well as control p(NIPAAm-co-AAc) hydrogels, demonstrated rheological data that were representative of soft, loosely cross-linked solids. Furthermore, only the highest p(AAc) chain amount tested affected the rigidity of the p(NIPAAm-co-AAc)-based semi-IPNs, as compared to the p(NIPAAm-co-AAc) hydrogels. At 37 degrees C, the complex shear moduli (G*) demonstrated by the p(NIPAAm-co-AAc)-based semi-IPNs were significantly greater than G* exhibited by the p(NIPAAm-co-AAc) hydrogels, and the semi-IPN G* values significantly increased with increasing p(AAc) chain amount. These results can be used to develop p(NIPAAm)-based semi-IPNs with tailored mechanical properties that may function as scaffolds in tissue engineering initiatives.     

Novel poly(HEMA-co-METAC)/alginate semi-interpenetrating hydrogels for biomedical applications: synthesis and characterization

Novel p(HEMA-co-METAC)/alginate semi-interpenetrating hydrogels (semi-IPNs) were developed in the attempt to improve poly(hydroxyethylmethacrylate) biological response, extending its applications in the biomedical field. Materials with different alginate contents were synthesized by copolymerization of 2-hydroxyethylmethacrylate and 2-methacryloxy ethyltrimethyl ammonium chloride monomers in the presence of aqueous solutions of alginate and characterized with respect to p(HEMA-co-METAC) synthesized in the presence of water. Swelling studies in water revealed high values of water uptake (>100%) with marked differences in the swelling degree at increasing polysaccharide content. The effect of ionic strength and of pH on the swelling behavior of hydrogels was also investigated. Higher ionic strengths resulted in a minor swelling degree accordingly with hydrogels polyelectrolyte nature. The introduction of the natural ionizable polysaccharide into the network made the semi-IPNs swelling depending on pH values of the solutions. A biological characterization was performed in terms of protein absorption on hydrogel surfaces, cytotoxicity (ISO 10993-5) and cell adhesion and proliferation studies using both murine 3T3 and human fibroblasts. Hydrogels proved noncytotoxic; moreover, semi-IPN surfaces allowed cell attachment and proliferation, thus supporting their potential biomedical use.     

Temperature-sensitive PVA/PNIPAAm semi-IPN hydrogels with enhanced responsive properties

A series of temperature-sensitive hydrogels of semi-interpenetrating polymeric networks (semi-IPN) composed of poly(N-isopropylacrylamide) (PNIPAAm) and poly(vinyl alcohol) (PVA) were prepared by radical polymerization. The PNIPAAm networks were cross-linked by N,N'-methylenebisacrylamide in the presence of linear PVA. The reaction processes were investigated by rheometry using oscillatory deformation tests. It was found that gelations were very fast and the modulus reached equilibrium within about 12.5min. The prepared semi-IPN hydrogels were characterized for their morphologies and thermal behaviors by scanning electron microscopy and differential scanning calorimetry, respectively. The interior network structures of the semi-IPN matrix became more porous with increasing PVA. In comparison to the conventional PNIPAAm gel, the newly reported semi-IPN hydrogels exhibited the same lower critical solution temperature. Their swelling properties, such as temperature dependence of equilibrium swelling ratio, shrinking kinetics and reswelling kinetics in water, were also studied. Experimental data indicated that the shrinking and reswelling rates of the semi-IPN hydrogels were much faster than those of the conventional PNIPAAm hydrogels. With this novel approach, water absorption and response properties could be adjusted by tuning the feed ratio of NIPAAm and PVA. These fast responsive hydrogels exhibited improved temperature sensitivity and swelling properties compared to the conventional PNIPAAm hydrogel, which would be critical and desirable for a gel to find potential applications in biomedical fields, such as drug delivery systems and sensors.     

Controlled immobilization of chondroitin sulfate in polyacrylic acid networks

Novel semi-interpenetrating polymer networks (semi-IPNs) of chondroitin sulfate (ChS) and acrylic acid (AA) were prepared with the aim of obtaining a hydrogel for use as a colon-specific drug carrier. By controlling the concentrations of cross-linking agent, diethylene glycol dimethacrylate (DEGDA), as well as the reaction solvent, high swelling percentages were obtained (approx. 1600%). However, the highest sol percent obtained for these hydrogels was approx. 70%, and most of the chondroitin sulfate remained soluble and could be extracted. Therefore, an alternative approach was adopted: methacrylate-grafted ChS (ChSMA) was synthesized and then co-polymerized with acrylic acid (AA) at a molar ratio of 1:5 with various concentrations of AA. The sol content of these ChSMA-AA hydrogels was reduced to approx. 20%, and the cross-linking densities were almost 100-fold higher than those of the semi-IPNs. FT-IR spectra showed that the H-bonding interactions between ChS and PAA and the spectra of the semi-IPNs were similar to that of PAA itself after sol extraction. In contrast, the FT-IR spectra of ChSMA-AA remained intact after sol extraction. Ketoprofen was used as a model drug to test the sustained release behavior of these hydrogels.     

pH- and Temperature-Responsive P(DMAEMA-GMA)-Alginate Semi-IPN Hydrogels Formed by Radical and Ring-Opening Polymerization for Aminophylline Release

A novel poly((2-dimethylamino) ethyl methacrylate-glycidyl methacrylate)-alginate (P(DMAEMA-GMA)alginate) semi-IPN hydrogel was synthesized via radical polymerization of the double bonds and ring-opening of the epoxy groups without using catalyst and cross-linker. ¹H-NMR, FT-IR and DSC data were consistent with the expected structures for the hydrogels. The interior morphology of the hydrogels was also investigated by SEM. The swelling ratio and compressive strength of the hydrogels were measured. The semi-IPN hydrogel had pH and temperature sensitivity, and pH-sensitive points of all hydrogels were found to be at pH 5.0. The release behavior of the model drug, aminophylline, was found to be dependent on the hydrogel composition and environment pH, which manifests that these materials have potential applications as intelligent drug carriers.     

Synthesis,Characterization and Properties of 2‐(Perfluorooctyl)ethylacrylate Grafted Segmented Polyurethaneureas

We report herein that 2‐(perfluorooctyl)ethylacrylate (PFEA) was successfully grafted onto a segmented polyurethaneurea (SPUU). We found that certain PFEA orientated onto the grafted SPUU film surface could significantly improve hemocompatibility. 1,2‐Propanediamine (PD) as a chain extender was used to synthesize the SPUU, which was based on diphenylmethane diisocyanate (MDI), vinyl group‐containing poly(butadiene) diol (PBD), and hydrogenated poly(isoprene) diol (HPIP). PFEA was copolymerized with the SPUU using α,α′‐azobis(isobutyronitrile) (AIBN) as a radical initiator. Various feed ratios of PFEA grafted polymers were synthesized (SPUU‐F‐0.5, SPUU‐F‐0.75, and SPUU‐F‐1.0) while non‐grafted SPUU was abbreviated as NG‐SPUU. The bulk characteristics of the resulting polymers were investigated by infrared spectroscopy (IR) measurement. Mechanical properties of the typical PFEA grafted SPUU were measured by dynamic viscoelasticity and tensile measurements. We found that PFEA orientated on the surface, as revealed by attenuated total reflectance‐Fourier transform infrared spectroscopy (ATR‐FTIR), electron spectroscopy for chemical analysis (ESCA), and water contact angle measurements. The hemocompatibility in vitro was evaluated with rabbit platelet‐rich plasma (PRP) contact tests and viewed by electron probe microanalyzer (EPM) using NG‐SPUU as a reference. We found that fewer platelets adhered to the PFEA grafted surfaces. New polymer SPUU‐F‐0.5 showed the best hemocompatibility in the tested samples. Platelet adhesion to PFEA grafted polymers SPUU‐F‐0.5, SPUU‐F‐0.75, and SPUU‐F‐1.0 was inhibited 91%, 58%, and 50% compared with NG‐SPUU. The relative clotting time of the cast films in contact with cow platelet‐poor plasma (PPP) was 3.26, 2.94, 1.95, 2.39 and 1.00 for SPUU‐F‐0.5, SPUU‐F‐0.75, SPUU‐F‐1.0, NG‐SPUU, and glass, respectively. The new polymers also showed the common characters of fluorinated polymers as revealed by water vapor transmission, dielectric constant, and index of refraction measurements.

Structure of the synthesized PFEA Grafted SPUU.     

Lateral augmentation of the mandible in minipigs with a synthetic nanostructured hydroxyapatite block

In this study, the effect of feed composition, degree of hydrophilicity, and internal morphology has been investigated for cell proliferation potential of the polyacrylamide/gelatin (PAm/G) semi-interpenetrating polymeric network (semi-IPNs). Polycaprolactone diacrylate was used to cross-link polyacrylamide chains. Scanning electron microscopy (SEM) micrographs demonstrate uniformly distributed porous structure with internal diameter in the range of 75-175 μm, dependent on matrix compositions. Water-air contact angle was found in the range of 49° ± 0.22 to 89° ± 0.14 (p < 0.02) suggesting varying degree of hydrophilicity of the hydrogel surface. In addition, protein adsorption study showed 45 ± 0.14 μg to 64 ± 0.12 μg (p < 0.01) of protein adsorbed per cm2 of hydrogel. Quantitative estimation of cell adhesion and proliferation was carried out by DNA quantification using fluorimetric assay method (p < 0.02). Microscopic images of proliferative cells on semi-IPNs by fluorescent and inverted phase contrast supported the findings of DNA quantification. Contact angle in the range of 63-69° in association with 52-59 μg/cm2 protein absorption and 115-150 μm pore size was found optimum for fibroblast proliferation on PAm/G semi-IPN scaffolds. The newly developed semi-interpenetrating network may serve as a potential scaffold for soft tissue-engineering applications.     

Tissue anti-adhesion potential of ibuprofen-loaded PLLA-PEG diblock copolymer films

This study was designed to evaluate the effect of polyethylene glycol (PEG) and nonsteroidal anti-inflammatory drug (ibuprofen) on the prevention of postsurgical tissue adhesion. For this, poly(L-lactic acid) (PLLA)-PEG diblock copolymers were synthesized by ring opening polymerization of L-lactide and methoxy polyethylene glycol (Mw 5000) of different compositions. The synthesized copolymers were characterized by gel permeation chromatography and 1H-nuclear magnetic resonance spectroscopy. PLLA-PEG copolymer films were prepared by solvent casting. The prepared copolymer films were more flexible and hydrophilic than the control PLLA film, as investigated by the measurements of glass transition temperature, water absorption content, and water contact angle. The drug release behavior from the ibuprofen (10 wt%)-loaded copolymer films was examined by high performance liquid chromatography. It was observed that the drug was released gradually up to about 40% of total loading amount after 20 days, depending on PEG composition; more drug release from the films with higher PEG compositions. In vitro cell adhesions on the copolymer films with/without drug were compared by the culture of NIH/3T3 mouse embryo fibroblasts on the surfaces. For in vivo evaluation of tissue anti-adhesion potential, the copolymer films with/without drug were implanted between the cecum and peritoneal wall defects of rats and their tissue adhesion extents were compared. It was observed that the ibuprofen-containing PLLA-PEG films with high PEG composition (particularly PLLA113-PEG113 film with PEG composition, 50 mol%) were very effective in preventing cell or tissue adhesion on the film surfaces, probably owing to the synergistic effects of highly mobile, hydrophilic PEG and anti-inflammatory drug, ibuprofen.     

Effect of solvent evaporation rate on microphase-separated structure of segmented poly(urethane-urea) prepared by solution casting

A useful instrument for polymer film preparation by solution casting was employed in this study. It enabled us to control the solvent evaporation rate of the polymer solution. By using this instrument, the aggregation of hard segments in segmented poly(urethane-urea) (SPUU) was investigated. SPUU was prepared from poly(tetramethy1ene oxide), 4,4′-diphenylmethane diisocyanate and ethylenediamine. The effect of solvent evaporation rate on the microphase-separated structure of SPUU was elucidated by dynamic mechanical analysis, tensile test, differential scanning calorimetry analysis, small-angle X-ray scattering measurement, IR and IR dichroism analyses. The aggregation of hard segments in SPUU was observed to be affected considerably by the solvent evaporation rate of the cast film during the preparation. It was found that the slower the solvent evaporation rate, the higher the aggregation of hard segments to form rigid hard segment domains in SPUU. Nine months after casting, this casting effect still remained on the aggregation state of hard segments of SPUU films, although the interdomain spacing was not influenced by its rate.     

Porous Agarose-Based Semi-IPN Hydrogels: Characterization and Cell Affinity Studies

Abstract

Hydrogels are frequently considered for medical applications due to the ease of preparation in different forms and high water content that makes them comparable to natural tissues. However, these general properties are not sufficient to make any hydrogel suitable for cell attachment and growth which are necessary for their use in tissue regeneration. Besides, the high water content makes the hydrogels mechanically weak. The formation of semi-interpenetrating networks (semi-IPNs) can be used in attempts to enhance physical, mechanical and thermal properties. In this study, semi-IPNs of agarose were prepared with chitosan and alginate, two polyelectrolytes that are positively and negatively charged under physiological conditions, respectively. Zeta potential was used to confirm the formation of charged hydrogels. All hydrogels had ultimate compression strengths in the range of 91–210 Pa where the value for pure agarose was about 103 Pa. Chitosan increased the compressive strength about two folds whereas the alginate had opposite effects. The amount of strongly bound water present in the hydrogels were estimated from TGA and DSC analysis and the highest value was found for alginate-agarose hydrogels as about 15%. The attachment and the migration of L929 fibroblasts were monitored in vitro using the MTS assay and confocal microscopy. The highest cell proliferation and penetration were observed for positively charged chitosan-agarose semi-IPN hydrogels.     

Sequential antibiotic and growth factor releasing chitosan-PAAm semi-IPN hydrogel as a novel wound dressing

The aim of this study is to prepare a novel wound dressing material which provides burst release of an antibiotic in combination with sustained release of growth factor delivery. This might be beneficial for the prevention of infections and to stimulate wound healing. As a wound dressing material, the semi-interpenetrating network (semi-IPN) hydrogel based on polyacrylamide (PAAm) and chitosan (CS) was synthesized via free radical polymerization. Ethylene glycol dimethacrylate was used for cross-linking of PAAm to form semi-IPN hydrogel. The hydrogel shows high water content (～1800%, in dry basis) and stable swelling characteristics in the pH range of the wound media (～4.0–7.4). The antibiotic, piperacillin–tazobactam, which belongs to the penicillin group was loaded into the hydrogel. The therapeutic serum dose of piperacillin–tazobactam for topic introduction was reached at 1st hour of the release. Additionally, in order to increase the mitogenic activity of hydrogel, epidermal growth factor (EGF) was embedded into the CS–PAAm in different amounts. Cell culture studies were performed with L929 mouse fibroblasts and the simulated cell growth was investigated by 3-(4,5-dimethylthiazol-2-yl)-diphenyltetrazolium bromide assay. The successful sustained release behavior of CS–PAAm hydrogel for EGF maintained the presence of EGF in the culture up to 5?days and the highest mitochondrial activities were recorded for the 0.4?μg EGF-loaded/mg of hydrogel group. In conclusion, CS–PAAm semi-IPN hydrogel loaded with piperacillin–tazobactam and EGF could be proposed for an effective system in wound-healing management.     

A novel controlled drug delivery system based on pH-responsive hydrogels included in soft gelatin capsules

pH-sensitive hydrogels based on methacrylic acid (MAA) and poly(ethylene glycol) macromonomer (PEGMEMA) entrapping diltiazem hydrochloride (DIL·HCl) were synthesized inside soft gelatin capsules for use as a new dosage form for oral drug administration. Different monomer compositions were used to evaluate their swelling and release behavior in two media: at low pH, simulating the acid pH of the stomach, and at pH 7, simulating the higher pH environment of the intestine. Both the swelling process and DIL·HCl release strongly depended on pH and monomer composition. Hydrogels with intermediate compositions showed diminished DIL·HCl release at pH 1.2. This fact was related to the formation of an impermeable outer skin, observed by magnetic resonance imaging (MRI). At pH 7 similar shaped release profiles were found for the four hydrogel compositions under investigation. At this neutral pH slow protonation of the carboxylate groups of MAA led to a swelling front and a dry core, also observed by MRI. As a consequence of this anomalous swelling, release curves exhibited a long period of zero order kinetics. This shows that the system could be a suitable candidate to develop a zero order release dosage form for oral administration of DIL·HCl. The swelling and dissolution processes were analyzed by different mathematical approaches.     

Interpenetrating hydrogel networks based on polyacrylamide and poly(itaconic acid): synthesis and characterization

The synthesis of sequential and simultaneous semi-interpenetrating hydrogel networks (IPNs) based on polyacrylamide (PAAm) and poly(itaconic acid) (PICA) is described. Polyacrylamide was used as a host polymer. Physical properties of IPN hydrogels were determined by IR, swelling, extraction and density measurements. No indication for the formation of hydrogen-bonded complexation was observed by IR spectroscopy. The extraction results showed that the grafting level between the two components of PAAm/PICA in simultaneous semi-IPN is higher than that observed in sequential IPNS. These results confirm that the decrease in swelling ratios with PICA contents is probably due to the entanglement effect. The properties of IPN hydrogels were found to be dependent on the composition and the type of IPN. Both sequential and simultaneous IPNs have quite different morphologies compared to the pure PAAm host hydrogel.     

Functionalized chitosan/NIPAM (HEMA) hybrid polymer networks as inserts for ocular drug delivery: synthesis, in vitro assessment, and in vivo evaluation

A series of hybrid polymeric hydrogels, prepared by the reaction of acrylic acid-functionalized chitosan with either N-isopropylacrylamide or 2-hydroxyethyl methacrylate monomers, were synthesized, pressed into minitablets, and investigated for their ability to act as controlled release vehicles for ophthalmic drug delivery. For comparison, interpolymeric complex analogues synthesized using the same monomers and pure, unfunctionalized chitosan were examined by means of an identical characterization protocol. The effects of network structure and composition upon the swelling properties, adhesion behavior, and drug release characteristics were investigated. Comparative in vitro studies employing chloramphenicol, atropine, norfloxacin, or pilocarpine informed the selection of drug-specific carrier compositions for the controlled delivery of these compounds. In addition, in vivo (rabbit model) experiments involving the delivery of pilocarpine indicated that chitosan-based hybrid polymer networks containing 2-hydroxyethyl methacrylate are useful carriers for the delivery of this therapeutic agent.     

Synthesis, properties and controlled release behaviors of hydrogel networks using cyclodextrin as pendant groups

Based on inclusion character of beta-cyclodextrin (beta-CD) with drug molecule and low glass transition temperature of poly(2-hydroxyethyl acrylate) (PHEA), a series of hydrogels with different compositions were synthesized by the copolymerization of a monovinyl cyclodexrin monomer with 2-hydroxyethyl acrylate (HEA). The structure and properties of the hydrogels were characterized by FTIR, DSC, TGA and swelling measurements. It is found that swelling ratios of these beta-CD hydrogels can keep a relative stability in the range of pH from 1.4 to 7.4, and are not sensitive to change in NaCl concentration. Using drug N-acety-5-methoxytryptamine (melatonin, MEL) as a model molecule, the controlled drug release behaviors of these hydrogels were investigated. The results indicate that the diffusion and permeation of MEL from the hydrogels may be a dominant factor for its release. Owing to the formation of MEL/beta-CD retarding diffusion rate of MEL, a sustained release of MEL from hydrogel with high content of beta-CD can be obtained compared with hydrogel PHEA without beta-CD.     

Drug release from starch-acetate microparticles and films with and without incorporated alpha-amylase

Acetylation of starch considerably decreases its swelling and enzymatic degradation. Thus, starch-acetate (SA) based delivery systems may be suitable for controlled drug delivery. The aim of the present study was to evaluate drug release from the SA microparticles (SA mps) and SA films. The average degree of acetyl substitution (DS) per glucose residue in the starch was either 1.9 (SA DS 1.9) or 2.6 (SA DS 2.6). Timolol (mw 332), calcein (mw 623) and bovine serum albumin (BSA, mw 68,000) were used as model drugs. A continuous timolol release from the both SA mps was observed in phosphate buffer solution (PBS) pH 7.4 (50-days incubation). The release of timolol was faster from the SA DS 1.9 mps than from the SA DS 2.6 mps. Calcein release from both SA mps was continuous in PBS pH 7.4 (5-days incubation). But, calcein release profile from the SA DS 2.6 film in PBS pH 7.4 showed discontinuities. However, the release of calcein from both SA films was continuous in human serum in vitro during the 7-day incubation, i.e. enzymes enhanced calcein release. Thus, alpha-amylase was incorporated into the SA films in order to enhance drug release from the films. However, the effects of incorporation of alpha-amylase on the model macromolecule (BSA) release from the SA films were modest. In conclusion, this study demonstrates the achievement of slow release of different molecular weight model drugs from the SA mps and films as compared to fast release from the native starch preparations. DS of SA, physicochemical properties of a drug and the presence of enzymes can all affect drug release profiles from SA based preparations.     

Novel etherified locust bean gum-alginate hydrogels for controlled release of glipizide

On many occasions, homopolysaccharide hydrogel networks alone are not suitable for controlled drug delivery. In this study, interpenetrating networks (IPNs) of sodium alginate (ALG) and etherified locust bean gum (ELBG) were developed through ionotropic gelation with Al³⁺ ions, tested for glipizide release, and were compared with homopolymer hydrogel networks. The degree of reticulation in IPNs was explained by the neutralization equivalent, tensile strength measurement, and drying kinetics of drug-free hydrogels. IPNs afforded a maximum of 94.40?±?0.35% drug entrapment efficiency and exhibited slower drug release profiles up to 8?h. Al³⁺-ALG network almost completed the release of embedded drug in 3.5?h; however, the homopolymer Al³⁺-ELBG network discharged their content at a slow, uniform rate up to 8?h like the IPNs. All the networks appeared spherical under scanning electron microscope. In all cases, a faster drug release rate was assumed in phosphate buffer (pH 7.4) than in KCl/HCl buffer (pH 1.2) solution. The pH-responsive swelling of the beads was responsible for the variable drug release rate in different media. NonFickian diffusion mechanism was operative for the transport of drug from the IPNs. Moreover, IPNs gained appreciation for their better mechanical strength (63.79?±?1.59?MPa) than Al³⁺-ELBG network. Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry, and X-ray diffraction analyses indicated a compatible environment for drug encapsualtion and release from the IPNs. The drug release curves of Al³⁺-ELBG and IPNs were found similar to a reference product. Hence, Al³⁺-ELBG and IPNs could be useful in controlling diabetes over longer periods.     

A preliminary report on the biocompatibility of photopolymerizable semi-interpenetrating anhydride networks

A new family of poly(anhydrides) (PA) has been developed which can be cured photochemically to produce degradable networks. These degradable anhydride networks may be useful in orthopaedics as bone cements and as matrices for drug delivery. This system, which is a semi-interpenetrating network (semi-IPN), has been evaluated for biocompatibility in subcutaneous tissue in rats and appears to undergo degradation primarily by surface erosion. The inflammatory response to the semi-IPN implants was minimal at both short (3 and 6 weeks) and long (28 weeks) time points and the fibrotic response was largely absent throughout the duration of this study. Furthermore, the OrthoCure implant material integrated well with the surrounding tissue and was invaded with vascularized connective tissue. For reference, linear PA controls were tested and showed a foreign body response culminating in the formation of relatively avascular fibrous capsule several cell layers thick, which became thicker over time, a response similar to what is typically observed in FDA approved implantable polymeric device systems.     

The effect of composition of poly(acrylic acid)-gelatin hydrogel on gentamicin sulphate release: in vitro

Hydrogels based on poly(acrylic acid) and gelatin crosslinked with N,N'-methylene bisacrylamide (0.5mol%) and glutaraldehyde (4%), respectively, forming an interpenetrating network were employed as matrices, for studying the loading and release of gentamicin sulphate. The release kinetics of gentamicin sulphate was evaluated in water (pH approximately 5.8), phosphate buffer (pH 7.4) and citrate buffer (pH 4) at 37+/-0.1 degrees C. The drug release in phosphate buffer was faster as compared to water or citrate buffer. Fitting the data of release studies in Peppas model indicated that the release of drug from full IPNs in phosphate buffer (pH 7.4), water (pH approximately 5.8) and citrate buffer (pH 4) were diffusion controlled. However, semi-IPNs showed both anomalous and Fickian diffusion mechanisms. With increasing gelatin percentage in the polymer, rate of drug release was faster and almost 85% of the loaded drug was released within 7 days in phosphate buffer (pH 7.4).