Preparation And Biological Evaluation Of Plasma Polymeric Films With Promoting-Endothelialization

Medical stainless steel is widely used as clinical implantable and interventional devices.However,once blood contact with biomaterials, complicated interaction will happen on the interface so as to form coagulating reaction and thrombus.It is believed that the endothelialization of the blood contacting device surface may overcome the problem.Biomolecule immobilization on the material surface may be an important method to improve the endothelialization.There are few functional groups on the surface of medical stainless steels,so how to get reactive functional groups and immobilize biomolecules on the surface of medical stainless steels become challenging.In this paper,the polyallylamine films containing primary amine groups and polymerized acrylic acid(PPAA) films containing carboxyl groups on the surface of medical stainless steels were obtained by radio frequency(RF) plasma polymerization by controlling the duty cycle and the RF-power,and the gelatin molecule was further covalently immobilized on the surface of the polymerized films.The-NH₂ and-COOH retention of the coatings were investigated by XPS (X-ray photoelectron spectroscopy) and FTIR(Fourier transform infrared spectroscopy).The highest content of primary amine(-NH₂/C)was 2.16%and carboxyl groups(-COOH/C) was 7.22%.Atomic force microscopy(AFM) showed that the polyallylamine film is continuous and pinhole-free.The plasma polymerized acrylic acid film has the dynamic stability in water.FTIR indicated there were typical characteristic absorption peaks of amideâ… and amideâ…¡which were ascribed to the gelatin.There is new peak of N1s in the survey spectra of XPS,which is from the gelatin.The analysis of FTIR and XPS also showed that the gelatin molecules were effectively immobilized on the surface of polymerized films.Contacting angle measurement indicated the polymerized films immobilized by the gelatin molecule presented better hydrophilicity and higher surface energy.In vitro endothelial cell(EC) adhesion test and Alamar Blue test showed the polymerized films immobilized by the gelatin promoted ECs adhesion and had better EC activity.The cell attachment ratio of the pulsed plasma polyallylamine film(85.73%) which immobilized gelatin was the higher than that of the continuous plasma polyallylamine film(82.73%).It is because that there were more active sites(-NH₂) on the surface of the pulsed plasma polyallylamine films, so the density of the gelatin chains immobilized on the the pulsed plasma polyallylamine films than that of the continuous plasma polyallylamine films.The viability of ECs increased about 41.9%after 72h cultivation on the G-P-PPAA-1(duty cycle 50%) than the G-P-PPAA-2(duty cycle 75%).The reason may be that there was more the active sites(-COOH) on the surface of the G-P-PPAA-1 than the G-P-PPAA-2,so the density of the gelatin chains immobilized on the G-P-PPAA-1 than that of the G-P-PPAA-2.