Transition And Properties Of Thermo-sensitive Methylcellulose-based Hydrogels

Methylcellulose(MC) can have water solubility with an optimum level of thedegree of methyl substitution (typically, DS between 1.7-2.0). MC solutions willundergo a completely reversibly sol-gel phase transition upon heating. Thisthermo-sensitive MC hydrogels have many advantages as tissue engineering materials:high water content, the good elasticity similar to tissues, and good biocompatibility,which will be widely used in macromolecular drug delivery, drug release ,tissuebarriers and tissue engineering because of their simplicity and safety.In this paper, the mechanism of sol-gel transition was studied by usingmicro-Differential Scanning Calorimetry(micro-DSC) method, rheological methodand so on. The results showed that the transition was caused by the the dynamicequilibrium between the hydrogen bonds and methoxyl hydrophobical interactions ata certain temperature.Also the effects of concentration of MC and various additives tothe gel properties(such as the gel temperature and the gel strength) were discussed,using the test tube inversion method and the breakthrough vacuum method.In this paper, the network structures of MC-glycerol hydrogels were characteredby a rheological method , also a rubber elasticity theory used to the physical hydrogelsprepared in the presence of a solvent was cited to analyze the effects of variousglycerol volume ratios on the structure of hydrogels. Based on the analysis of thecreep of the MC-glycerol hydrogels, mathematic models fit to the determinate curveswere inferred, thus the mechanical model for the MC-glycerol hydrogels was gained.Also water-soluble salicylic acid was choosed to study the release rates and releasemodels of MC hydrogels, MC-glycerol hydrogels, and the MC-glycerol-PVPhydrogels. The results showed that the drug in all the systems was released on theswollen mechanism, but the addition of glycerol can delay the release rate and extendsthe zero order release period. Due to the interaction with the drug, the release rate ofthe systems including polyvinylpyrrolidone(PVP) was slower .