Preparation And Properties Of Cross-linkable Cyclotriphosphazene Derivative

Cyclo-or polyphosphazene derivatives as biomedical materials are promising intissue engineering scaffold materials and drug delivery, because of their excellentbiocompatibility and biodegradability.In this thesis, hex[4-(monomethyl maleate) phenoxy]cyclotriphosphazene (C3) wassynthesized by hexachlorocyclotriphosphazene and characterized by FT-IR, NMR and MS.This cyclotriphosphazene derivative can be crosslinked in situ with N-vinyl pyrrolidone(NVP) by radical polymerization. The mechanical property, swelling and degradationbehavior in pH=7.4and pH=2.0solutions of the crosslinked products were studiedpreliminarily. The drug release behavior of the pH-sensitive crosslinked products with5-Fluorouracil (5-Fu) was also investigated.The results showed that the crosslinking reaction can occurred at37℃with less heatreleasing, and the setting time was between5to10minutes, which meets the clinicalrequirements. Compressive strength and compressive modulus of the crosslinked productsincreased with the increasing amount of C3. Maximum compressive strength andcompressive modulus values were21.0±1.6MPa and361.0±37.4MPa, which were close tothose of human trabecular bones. The equilibrium swelling of crosslinked products inpH=7.4solution took about12hours. With the increasing content of C3, the swelling ratioincreased, and the largest swelling ratio was250%. It nearly can not swell in pH=2.0solution. The degradation rate of crosslinked products in5M NaOH is faster than that of in5M HCl. More than550hours were needed for the complete degradation both in pH=7.4and in pH=2.0solution. The degradation process can divide into two stages, fast diffusionof the residual free molecule in the first stage and decomposition of polymer network inthe second stage. The drug release rate of crosslinked products in pH=2.0solution was slower than that of in pH=7.4solution. Because in pH=7.4solution swelling and diffusioncan all promote the drug release, but in pH=2.0solution the drug release was onlycontrolled by diffusion. Before the balance of drug release, the lowest content of C3hadthe fastest drug release rate in both of the pH.The above results preliminary indicated that the crosslinked products of C3and NVPcan degrade and the drug release behavior had certain pH sensitivity. Therefore it has agood application prospect in the fields of injectable bone tissue engineering and drugrelease.