Preparation And Properties Of Biomaterials Based On Thiol-ene Click Chemistry

In recent years,"click"chemistry has become one of the most useful and attractive synthetic concepts in many fields such as drug development and biomedical materials,due to its high reaction efficiency,good environmental adaptability?water resistance,oxygen and various chemicals?.It also has the advantages of high selectivity,pure products,and so on.The polymer with special structure can be designed and prepared by"click"chemistry,which can be used for surface biomodification and in-situ hydrogel preparation.Many biomolecules?amino acids,peptides,proteins,etc.?contain thiol groups,that can also be used to design biomolecule-polymer hybrid materials with controllable properties.Polydopamine?PDA?has excellent biocompatibility and low cytotoxicity.Therefore,the deposition of PDA on substrate surfaces can get a hydrophilic and biological surface.PDA coating can promote cell adhesion,proliferation and differentiation.In addition,PDA has the properties of amphoteric ions and it is sensitive to external pH.PDA can also be used in drug controlled release and biochip applications.Polydimethylsiloxane?PDMS?is widely used in cell culture and biochip preparation due to its adjustable hardness,easy forming,good optical transparency and non-toxicity.However,its inherent hydrophobic surface is not conducive to cell growth,so the surface modification of PDMS is necessary for effective cell adhesion.In this dissertation,we used a vinyl silicone oil blended PDMS macro-monomer to give PDMS a certain reactivity without affecting curing and other properties of the PDMS.Then we completed the amino modification of PDMS surface through thiol-ene"click"chemistry by using mercaptoethylamine.And finally,the PDA with different morphology was successfully grafted by the Schiff base reaction/Michael addition.The hydrophobicity of the modified PDMS could be controlled by adjusting the morphology of the PDA.The tests of contact angle,frictional wear,protein absorption all verified the pH sensitiveness of the modified surface?PDA/PDMS?.In addition,cell culture and western blotting also showed that could greatly promote the cell growth and differentiation.So the PDA modification was a simple and effective method to getting a biological material.Inspired by the success of the above work,we also prepared a high precision rapid prototyping hyaluronic acid hydrogel using thiol-ene"click"chemistry.Hyaluronic acid?HA?is a well-known biomaterial that widely existed in mammalian extracellular matrix?ECM?.It is a completely natural linear polymer with non-immunogenicity,biocompatibility and biodegradability.It can promote skin repair and wound healing effectively.It also plays an important role in many biological processes,such as tissue engineering,drug delivery,immune regulation and so on.But the texture of hyaluronic acid hydrogel is brittle and its mechanical properties are weak commonly.It is necessary to improve the strength by a series of modification methods such as cross-linking or copolymerization.Firstly,we synthesized methacrylated hyaluronic acid?HAMA?and a four-arm base-linking agent?PE?NAC?₄?.The hydrogel could be quickly cured by mixing the HAMA and PE?NAC?₄ under the action of 405 nm light by thiol-ene"click"chemistry.The hyaluronic acid hydrogel?HAMA/PE?NAC?₄?had the characteristics of high-precision forming,the precision could reach 25?m.The rheological test and the compression test proved that the mechanical property of the HAMA/PE?NAC?₄hydrogel could be successfully adjusted by regulating the amount of the cross-linking agent PE?NAC?₄.The hydrogel was a completely biogenic green material and had little or no residual biological harmful molecules.Besides,it could be completely biodegraded.We used the HAMA/PE?NAC?₄ hydrogel to release vascular endothelial growth factor?VEGF?.The results showed that the hyaluronic acid gel could support cell growth and promote the release of VEGF?386 pg/mL?.The rapid light-curing material is expected to be used in the wound dressing in the future.