Functional Polydopamine Coatings And Nanoparticles For Biomedical Applications

Polydopamine(PDA),polymerized by mussel-inspired dopamine(DA),has become the research focus because of a variety of advantages,such as polymerization under mild conditions,good bio/cytocompatibility,and secondary reaction property.PDA has thus been used for surface modification and preparation of nanoparticles in the field of biomaterials and biomedical application.In this thesis,four studies based on PDA were carried out for different biomedical applications.1.One of the most importances for surface mediated gene delivery system is how to immobilize the gene on the material surfaces efficiently.In this research,nanocomposites,protamine/plasmid DNA(PrS/pDNA),was immobilized on PDA coating surfaces simply and effectively by using the secondary reaction property of PDA.The results of cell experiment showed that PDA surfaces modified by PrS/pDNA promoted the adhesion and spreading of endothelial cells(EC)and smooth muscle cells(SMC).The gene on the PDA surfaces transfected cells efficiently.When hepatocyte growth factor plasmid DNA(HGF-pDNA)was used in this PDA gene delivery system,the HGF secretion of EC and SMC were increased about 43.3%and 36.5%,respectively.The PDA coatings immobilized by PrS/HGF-pDNA enhanced the EC competitiveness compared to SMC because HGF can accelerate EC proliferation selectively.In 3 days EC and SMC co-culture experiment,the ratio of EC/SMC was increased from 1:1 to 4:1.Our findings demonstrated that PDA coatings have the potential to be an efficient gene-immobilization platform on surface gene delivery system.2.Surface structure of a biomaterial is the most important factors to control cell behaviors.In this research,a PDA-involved multilayer with surface nano-/microstructure was constructed through the layer-by-layer(LbL)assembly of carbon nanotubes(CNTs)and poly-L-lysine(PLL).Firstly,CNTs@PDA was preparing by coating PDA on CNTs.Then,PLL/CNTs@PDA multilayer film with surface nano-/microstructure was constructed through LbL assembly.The reaction between CNTs@PDA and PLL would be the main driving force.The PLL/CNTs@PDA multilayer film showed good biocompatibility,and enhancing EC and SMC adhesion,similar to the traditional flat PDA coating.However,difference effects of PLL/CNTs@PDA film on EC and SMC proliferation were observed.EC proliferation on PLL/CNTs@PDA surfaces was inhibited,while SMC proliferation on PLL/CNTs@PDA surfaces was preserved In addition,the PLL/CNTs@PDA film can enhance the adhesion and synapsis growth of pheochromocytoma 12(PC 12)cells.3.It is a challenge to endow PDA with new functions in molecule level.By electrochemical polymerization,pyrrole(Py)was used to react with dopamine for preparing polydopamine-pyrrole(PDA-PPy)coating.The data showed that the PDA-PPy coating had good electrical conductivity and secondary reaction property,which might be attributed to PPy and PDA,respectively.By using the secondary reaction property,vascular endothelial growth factor(VEGF)molecules were immobilized on the PDA-PPy coating successfully.4.Adding new functions into PDA functional material on molecule level is an important research area in PDA coatings and nanoparticles.In this research,the chelation DA-BTZ was constructed,through the coordination reaction between anti-cancer drug bortezomib(BTZ)and DA.The DA-BTZ was further polymerized into PDA-BTZ nanoparticles,a new kind of PDA nanoparticles showed double stimuli-responsive property.The sizes of PDA-BTZ nanoparticles were around 80nm,and the BTZ-loading rate of the nanoparticles was 36.7%.These PDA-BTZ nanoparticles had both pH-sensitive and near-infrared(NIR)light photothermal conversion properties which promoted the release of BTZ by reducing pH value(from 7.4 to 5.7)or NIR irradiation.In 72h,the release of BTZ reached 33.2%and 37.2%,respectively.Further,the release of BTZ was enhanced significantly to 79.2%at the condition of NIR irradiation and pH 5.7.The PDA-PPy nanoparticles can induce apoptosis of MCF-7 cells in vitro.In vivo experiment,the PDA-BTZ nanoparticles showed good capability to reduce the size of tumor with NIR irradiation.