Preparation Of Mussel-Inspired Conductive Oligoaniline Biomaterials For Tissue Engineering Applications

With the development of biomedical polymer materials,conductive polymers,such as polyaniline and polythiophene have been paid more attention due to their unique physicochemical properties such as reversible redox,induction of cell growth and differentiation.The most important issue related to restricting the applications of conductive polymers is the lack of biodegradability,absorbability and processability.Therefore,the numerous conductive and electroactive biodegradable materials have been designed and synthesized.Among them,aniline oligomer(such as aniline trimer and aniline tetramer,etc.)with defined molecular structure,good electrical activity and biocompatibility,can be removed from the body through the kidney under physiological conditions.Therefore,biodegradable functional scaffold materials based on aniline oligomer have been widely used in tissue engineering.External electrical stimulus(ES)can effectively regulate cell behavior and promote tissue regeneration.Additionally,the conductive biomaterials containing the oligoanilines,could localize ES and improve the efficiency of ES,then contribute to better regulate the cellular activities including cell adhesion,migration,proliferation and differentiation.However,the synthesis of conductive and electroactive polymers with biocompatibility and good formation through the simple fabricated strategy,still remains a challenge for tissue engineering,and needs further design and development.Therefore,we designed a series of novel conductive and electroactive polymer materials,fabricated micropatterned conductive nanofiber mesh and electroactive microsphere through electrospinning technology and high-voltage electrostatic(HVE)technique,respectively,and then systematically evaluated their potential biomedical applications through in vitro and in vivo study.This dissertation mainly includes the following four parts.(1)A series of conducting random copolymer materials poly(ATMA-co-DOPAMA-co-PEGMA)(PAT)based on aniline tetramer,dopamine and PEG were successfully synthesized through free radical addition polymerization.The functional materials exhibited excellent conductivity,electroactivity,hydrophilicity,adhesiveness and hemocompatibility.The conductive polymers combined with ES could synergistically enhance cell proliferation,ALP activity,calcium ion content,and expression of osteogenic genes.More importantly,the adhesiveness and biocompatibility of dopamine endows PAT modifiability on a variety of materials.(2)In sodium periodate solution,electroactive microspheres were prepared by immobilizing electroactive PAT on the biodegradable PLGA/HA microspheres through oxidative polymerization of DOPA in PAT.The YKYKY-containing recombinant insulin-like growth-factor-1(IGF-1)was hydroxylated through tyrosinase treatment to obtain DOPA-IGF-1 for the surface modification of electroactive scaffolds,thus the biodegradable microsphere with electroactivity and bioactivity was achieved.The as-prepared microsphere with good biocompatibility exhibited significant cell proliferation and enhanced osteogenic differentiation.The functional microspheres were injected into the areas of rat critical-sized(5 mm)calvarial bone defects.At 8 weeks,the electroactive and bioactive microspheres showed excellent repair ability with formation larger of neo-osteogenesis in bone defect site.(3)A micropatterned conductive nanofiber mesh was constructed by the conductive composite(PCL/PAT)and electrospinning technology,and NGF was immobilized onto nano fiber mesh by the redox reaction of DOPA in PAT for nerve tissue engineering applications.The nanofiber mesh possessed a regularly aligned valley and ridge structure.Combining ES with nanofiber mesh coated with NGF could synergistically promote proliferation and further differentiation of NSCs into neurons,and the formation of astrocytes was also suppressed,indicating the nerve repair ability.(4)The conducting polymers based on conductive aniline trimer and PCL,were successfully synthetized via a one-pot step-growth addition polymerization reaction.The conductive shape memory elastomer films were prepared by using a high temperature solvent evaporation method,and their biocompatibility in vitro was preliminarily explored.These copolymer films possessed porous structure of uniform size,and exhibited excellent stretchability and good shape memory effect.The conductive elastomer materials upon ES significantly promoted cell growth and osteogenic differentiation of MC3T3-E1 cells,in terms of ALP activity,calcium deposition,and bone-related protein and gene expression levels.In summary,the conductive and electroactive biomaterials with various forms of application could promote transport of intercellular electrical signals,and combining with ES could well modulate cellular events at the implant-materials interface,thereby promoting the differentiation of cells and supporting the generation of functional tissue.