Preparation Of Temperature-Sensitive Injectable Hydrogel And Relevant Study On Its Properties

Injectable hydrogels have played many competent roles as scaffold material for vocal cord tissue engineering.They provide a good transmission channel and plentiful water environment for cell metabolism, contact well with tissues, and can be situ injected. Hyaluronan(HA), a main sort of consistent proteoglycans in extracellular matrix, has wonderful physicochemical properties and biocompatibility, which is promised to be developed as scaffold for vocal cord tissue engineering, However, natural HA is easy to degrade in tissues, so chemical cross-linking modification is needed to enlarge the molecular weight of HA, delay the degradation and improve its stability. In addition, as scaffold of tissue engineering, thermo dynamical reversibility is essential for injectable hydrogels. PNIPAAm, cross-linked from NIPAAm, is a typical non-degradable temperature-sensitive material, and its LCST is about 32℃, with good biocompatibility; Methylcellulose(MC) is a biodegradable temperature-sensitive material with advantages of high water content, flexible similar to tissues, good biological compatibility, et al. The study aim at exploring the condition of cross-linking of HA. We synthesize XLHA-PNIPPAAm and XLHA-MC injectable hydrogels through blending crosslinked HA (XLHA) and two temperature-sensitive materials differed in degradation. The physicochemical properties and biocompatibili-ty of the two hydrogels are also studied.(1) Cross-linking of HAUsing BDDE as cross-linking agent, with temperature controlled through waterbath, HA is cross-linked under alkaline environment. We discuss the influence of initial concentration of HA (the systemic pH), reaction time, the quantum of cross-linking agent and reaction temperature. Based on the swelling ratio of hydrogels.We assess the crosslinking degree of the products and obtain the best condition of reaction, which in our study is:initial concentration of HA is 10%(prepared by 0.2M NaOH); reaction temperature is 50℃; reaction time is 6h; BDDE/HA(M/M)=1. The Mc of XLHA prepared under such condition is 1.749×106. The preparation of PNIPAAm by Co60γradiationPoly(N-isopropylacrylamide) with different crosslinking density are synthesized by radiation. Influence of monomer concentration, dose radiation and the quantum of cross-linking agent are also observed. Swelling Ratios under different temperature of hydrogels are tested. Through injection property test, we obtain the hydrogels with injectability, which will be blended with XLHA to form XLHA-PNIPAAm injectable hydrogels.(3) The physicochemical properties of XLHA-PNIPAAm and XLHA-MCXLHA-PNIPAAm and XLHA-MC injectable hydrogels are prepared through blending XLHA and two temperature-sensitive materials differed in degradation Poly(N-isopropylacrylamide)(PNIPAAm) and Methylcellulose (MC) with certain process, respectively. We test the injectablility, enzymatic biodegradability, structure and temperature-sensitivity of the two injectable hydrogels.The results show that the addition of both non-degradable material PNIPAAm and degradable material MC could postpone the degradation of HA effectively. XLHA-PNIPAAm blending XLHA and PNIPAAm prepared with 5kGy radiation, MBAAm/NIPAAm (M/M)=0.015, monomer concentration is 3% showed the best enzyme biostability and better than that of XLHA-MC. DSC results show that the LCST of PNIPAAm is about 32℃, while the LCST of MC is 67.5℃. they also shows that the addition of HA(XLHA) had little impact on the LCST of PNIPAAm hydrogel, while the addition of XLHA results in disappearance of LCST of MC at a certain temperature range in DSC. The injectability test shows that XLHA-MC hydrogel has temperature-sensitivity. FTIR shows that no obvious structure changes between constituents were observed for both XLHA-PNIPAAm and XLHA-MC.(2) Biocompatibility evaluation of XLHA-PNIPAAm and XLHA-MC hydrogelsCytotoxicity test and Hemolytic test are used for the preliminary biology evaluation on injectable hydrogels XLHA-PNIPAAm and XLHA-MC. The results show that XLHA-PNPAAm and XLHA-MC injectable hydrogels are both qualified in hemolysis and cytotoxicity test, up to revelent standard, what's more, The biocompatibility of XLHA-PNIPAAm hydrogel shows better than XLHA-MC hydrogel.