Biodegradable interpenetrating polymer network (IPN)-structured hydrogels consisting of gelatin (Gtn) and dextran (Dex) were prepared by sequential crosslinking reactions of Gtn and methacryloylated Dex. Phase separation of these hydrogels is dominated by preparation conditions, i.e., above or below the sol-gel transition temperature (Ttrans) of Gtn. Enzymatic degradation by either α-chymotrypsin or dextranase is hindered for the IPN-structured hydrogel prepared below Ttrans whereas this hydrogel is perfectly degradable in the presence of both enzymes. Such a specific feature of enzymatic degradation was not observed for the hydrogel prepared above Ttrans. These results suggest that double-stimuli-responsive degradation of IPN-structured hydrogels is related to their phase separation. 相似文献
Chemically crosslinked dextran hydrogels were prepared for application in the controlled delivery of bioactive proteins. Dextran was functionalized by reacting with glycidyl acrylate to introduce reactive double bonds. Upon exposure to γ-irradiation the functionalized dextran formed a crosslinked gel which could be degraded by dextranase. The effect of dextranase-induced degradation on the swelling kinetics of the prepared hydrogels was examined. Enzymatic degradation of the gels became slower as the γ-irradiation dose increased for the formation of the gels. The dextran hydrogels were examined as a potential delivery system for proteins by using invertase as a model protein. Invertase was incorporated into the hydrogel by mixing it with the purified, functionalized dextran before exposure to γ-irradiation. The effect of γ-irradiation on the bioactivity of the incorporated invertase was determined. The γ-irradiation did not change the bioactivity of the incorporated invertase as long as the total γ-irradiation dose was limited below 0.4 Mrad. The release study showed that the release of invertase from the dextran gel was controlled by dextranase-induced degradation rather than diffusion through the dextran network. The release study also showed that the invertase release was pulsatile. Parameters such as the degree of functionalization, dextran molecular weight, and γ-irradiation dose can be adjusted to prepare delivery systems which meet the desired degradation kinetics and protein release profiles. 相似文献
A series of biodegradable hydrogels based on dextran and poly(L-glutamic acid) were fabricated for effective vancomycin loading and release. The preparation of hydrogels was simply achieved by photo cross-linking of methacrylated dextran and poly(L-glutamic acid)-g-hydroxyethyl methacrylate (PGH) in the presence of photoinitiator 12959. The structures of hydrogels were characterized by FTIR and SEM. The swelling and enzymatic degradation behaviors of hydrogels were examined to be dependent on the poly(L-glutamic acid) content in the hydrogels. The higher content of poly(L-glutamic acid) in the gel, the higher swelling ratio and quicker degradation were observed. More interestingly, the hydrogel with higher PGH ratio showed higher vancomycin (VCM) loading content, which might be due to the electrostatic interaction between carboxylate groups in hydrogel and ammonium group of VCM. In vitro drug release from the VCM-loaded hydrogels in aqueous solution exhibited sustained release of VCM up to 72 h, while the in vitro antibacterial test based on the VCM-loaded hydrogel showed an efficient Methicillin-Resistant S. aureus (MRSA) inhibition extending out to 7 days. These results demonstrated that the biodegradable hydrogels which formed by in situ photo-cross linking would be promising as scaffolds or coatings for local antibacterial drug release in tissue engineering. 相似文献
Summary: Specific temperature‐responsive biodegradable hydrogels were synthesized and characterized in terms of their regulation of enzymatic accessibility based on the physical properties of the temperature‐responsive polymers. The hydrogels consist of glycidyl methacrylate‐modified dextran grafted with the poly(N‐isopropylacrylamide) (PNIPAAm) homopolymer, and cross‐linked by co‐polymerization with NIPAAm and N,N‐dimethylacrylamide (DMAAm). The coil‐globule change in the grafted poly(NIPAAm) chains and only a slight dehydration of the poly(NIPAAm‐co‐DMAAm) cross‐linkers are effective in controlling the enzymatic degradation over a specific temperature range.
The thermo‐responses of the graft chains (steric hindrance) and the crosslinkers (slight deswelling of the hydrogel networks) control the enzymatic degradation of the hydrogel. 相似文献
The aim of the present work was to prepare a well-defined hydrogel of chemically cross-linked and organ-metallic complexed interpenetrating PEG networks. The hydrogel was synthesized via the reaction of copper(I)- catalyzed 1,3-dipolar azide-alkyne cycloaddition(CuA AC) with poly(ethylene glycol)-dopamine(PEG-DA)("Click Chemistry") followed by complexation with Fe~(3+) ions to crosslink the polymeric network. The chemical composition and morphology of the resulting hydrogels were characterized by Fourier transform infrared spectroscopy(FTIR), ~1H-NMR and scanning electron microscopy(SEM). Swelling ratio, mechanical strength, conductivity, and degradation behaviors of the hydrogels were also studied. The effect of the polymer chain length on properties of hydrogels was explored. The compressive strength of hydrogels could reach as high as 13.1 MPa with a conductivity of 2.2 × 10~(-5) S·cm~(-1). The hydrogels also exhibited excellent thermal stability even at a temperature of 300 °C, whereas degradation of the hydrogel after 7 weeks was observed under a physiological condition. In addition, the hydrogel exhibited a good biocompatibility based on its in vivo performance through an in vivo subcutaneous implantation model. No inflammation and no obvious abnormality of the surrounding tissue were observed when the hydrogel was subcutaneously implanted for 2 weeks. This work is a step towards creating a new pathway to synthesize hydrogels of interpenetrating networks which could be of important applications in the future research. 相似文献
Poly(N-isopropylacrylamide) (PNIPA) hydrogels with varied degree of crosslinking (DC) were synthesized by using poly(ethylene glycol) (PEG) as an additive. A phase separated ("macroporous") morphology was formed when using PEG contents of > or = 20 wt.-%. Temperature-dependent degrees of swelling had been measured, and average mesh sizes of the swollen polymer network had been calculated. The loading of the hydrogels with labelled dextrans with various molar masses and bovine serum albumin (BSA)-via swelling of the shrunken gel in a cold solution-and their subsequent unloading-via immersion in hot water-were studied in detail. The loading efficiencies were close to zero for PNIPA prepared at PEG contents of < or = 10 wt.-%, and they increased sharply to about 100% for PNIPA prepared with PEG contents of > or = 20 wt.-%. A complete unloading was achieved as well. For macroporous PNIPA prepared at 40 wt.-% PEG content, the loading efficiency was a function of the DC, and the "cut-off" observed as a function of dextran or protein size correlated with the mesh size of the hydrogel. The function of these "smart" hydrogels can be explained by the temperature-induced "pumping" of the solution into the gel bulk via the permanent pores, along with an uptake into the adjacent hydrogel network. Those materials could be used as matrices for the efficient and reversible immobilization of (bio)macromolecules. 相似文献
The present study describes the synthesis and characterization of dextran hydrogels produced by photocrosslinking of dextran chains. The hydroxyl groups of native dextran were converted to acrylate groups to make hydrogel precursors with different substitution degrees. The hydrogels were photopolymerizated in the presence of a suitable photoinitiator system (thionine/triethylamine) and characterized by 13C,1H NMR, and infrared spectroscopy. The information about microenvironment formed in hydrogel solutions was obtained by fluorescence spectroscopy using pyrene and nabumetone probes. This technique was used also to study the crosslinking process. The results about the solubility and swelling index data of hydrogels showed that their use as models of drug delivery is technically feasible. 相似文献
Microbial infections continually present a major worldwide public healthcare threat, particularly in instances of impaired wound healing and biomedical implant fouling. The development of new materials with the desired antimicrobial property to avoid and treat wound infection is urgently needed in wound care management. This study reports a novel dual‐functional biodegradable dextran‐poly(ethylene glycol) (PEG) hydrogel covalently conjugated with antibacterial Polymyxin B and Vancomycin (Vanco). The hydrogel is designed as a specialized wound dressing that eradicates existing bacteria and inhibits further bacteria growth, while, ameliorating the side effects of antibiotics and accelerating tissue repair and regeneration. The hydrogel exhibits potent antibacterial activities against both gram‐negative bacteria Escherichia coli (E. coli) and gram‐positive bacteria Staphylococcus aureus (S. aureus) with no observable toxicity to mouse fibroblast cell line NIH 3T3. These results demonstrate the immense potential of dextran‐PEG hydrogel as a wound dressing healthcare material in efficiently controlling bacteria growth in complex biological systems. 相似文献