A Biodegradable Thermosensitive Hydrogel Preparation And Performance

Thermo-sensitive hydrogels possess greater potential applications infields such as drug delivery, owing to their volume transition under lowercritical solution temperature (LCST). However, they are notbiodegradable and then applications were limited. The multifunctionalmacromolecule poly(N-isopropylacrylamide-co-methylacrylate-co-hydrazide)(PNMH) was prepared and used to cross link oxidized sodiumalginate(OSA) to form biodegradable and thermo-sensitivegels(PNMH-OSA). In addition, the thermo-sensitivity of PNMH andPNMH-OSA gels,degradation and drug releasing of PNMH-OSA gelswere studied in this article.The structure of PNMH and PNMH-OSA gel was characterized andanalyzed by infrared spectroscopy,LCRS, and so on. It was showed thatPNMH with crossing-linking groups-NHNH₂ was synthesized byhydrazine partially substituting methoxymethane; OSA-PNMH hydrogelswere chemically crosslinked hydrogels which was formed by creatingC=N bonds between the -NH₂ groups of side groups of PNMH and theavailable aldehyde of OSA. PNMH possessed thermo-sensitivity andLCST of PNMH solution went down with increasing concentration ofPNMH solution,decreasing NIPA,strengthening ion intensity,andshorter substituting time. OSA-PNMH hydrogels still showedthermo-sensitive property and thermo-sensitivity of hydrogels becameweaken with increasing the weight ratio of OSA and PNMH.The degradation of PNMH-OSA gel was due to break of C=N bonds.Experimental results showed that with increasing PNMH content, degradation time of gel became longer; OSA-PNMH hydrogel withweight ratio of OSA: PNMH=2: 8 could completely degradate at 25℃anddissolved faster than at 37℃, but the other hydrogels needed longer timeto degradate at 25℃than at 37℃; the higher degree of oxidation of SAand the lower degree of substitution of PNMH were, the shorter the timeof degradation was; the degradation of gel became difficult withincreasing quantity of MA monomer; in acid and alkali medium, hydrogel was easy to degradate; the degradation time of gel became longer whenstrengthening ion intensity and reducing water content of gel; thehydrogels with smaller slice or volume were easier to degradate.The Experimental results of drug releasing showed that the releaseof low molecule weight drug MB was controlled primarily by diffusing, but high molecule weight drug BSA was released through degradation ofgel mainly; the accumulative release of gels with weight ratio ofOSA: PNMH=6: 4 was close to that with weight ratio of OSA: PNMH=4: 6in the beginning, but that of gel with weight ratio of OSA: PNMH=6: 4was markedly higher than the gel with weight ratio of OSA: PNMH=4: 6subsequently; the accumulative release of gel at 37℃was higher than at25℃.