Synthesis And Characterization Of Biodegradable Poly(amide-imide)s

As implant materials in spinal surgery,although one of the most widely used polyetheretherketones?PEEK?is biocompatible,chemically stable and has an elastic modulus similar to that of human bones,it is not biodegradable along with the absorption of bone graft at the later stage of implantation,which may result in stress shielding for bone grafts and slow down fusion rate in PEEK clinical applications.One the other hand,PEEK is biologically inert as its limited bioactivity and poor ability of bone integration,which is unfavorable for its stable integration with adjacent bone tissues upon implantation in the specified time.In order to solve this problem,in this article,we incorporated L-amino acid into the polymer chain to synthesize a novel biodegradable L-amino acid derived poly?amide-imide??PAI?,and then introduced the biologically active substance SiO₂ into the polymer matrix to make a novel PAI/SiO₂ composites with both biodegradable and bioactive to provide a new implant material for spinal surgery.The specific contents include following aspects:?1?Three kinds of L-amino acids based diacid monomers were successfully synthesized by solution condensation of L-glycine,L-leucine,L-phenylalanine and3,3',4,4'-biphenyltetracarboxylic dianhydride?BPDA?in the solvent of acetic acid,respectively.The molecular weight distribution of diacid monomer is homogeneous,and both ends of the molecule contain functional groups that can be used to react with the terminal amino group,which would be expect to provide a reaction site for subsequent polymerization.?2?Varieties of L-amino acid based novel poly?amide-imide?s?PAIs?were synthesized by reactions of three different prepared diacid monomers with4,4'-diaminodipheny ether?ODA?by the direct polycondesention in a medium consisting of molten tetrabutylammonium bromide?TBAB?and triphenyl phosphite?TPP?under N₂ atmosphere.In addition,no L-amino acids containing pure PAI,which structure is similar to the novel PAI,was successfully synthesized by a three step method.?3?Thermogravimetric analysis,hydrophilic analysis,mechanical property testing,in vitro biodegradability analysis and in vitro biocompatibility evaluation were conducted to characterize the properties of all novel PAIs and pure PAI.The testing results showed that the novel PAIs exhibited more dramatic mechanical flexibility,hydrophilicity,thermal stability and biodegradability when compared to those of the pure PAI.The in vitro degradation data showed that the average degradation rates of the novel PAIs were about 1.2-2.4 times faster than those of the pure PAI.The preliminary biocompatibility studies of bone marrow mesenchymal stem cells revealed that the all the novel PAIs were cell compatible.While one of the novel PAIs incorporated with L-phenylalanine showed higher cell adhesion,proliferation and differentiation than those of pure PAI and the other two novel PAIs,indicating that the different L-amino acids incorporation in the novel PAIs change the cell growth environment somehow.?4?Choose out the best performance novel PAI.To provide a reaction site for subsequent synthesis of novel PAI/SiO₂ composites,it is necessary to end-capping modify the polymer matrix firstly by using silane coupling agent which contains terminal amino group.Then,a series of novel PAI/SiO₂ composites with different amount of SiO₂ were successfully synthesized by sol-gel technique with modified novel PAI as the continuous phase and SiO₂ as the dispersed phase.The test results exhibited that the SiO₂ generated in situ dispersed homogenously in polymer matrix,the hydrophilicity of the composites had shown a trend of decreasing firstly and then increasing slowly with the addition of SiO₂,and the novel PAI/SiO₂ composites are biodegradable and have good biocompatibility.