近年来，医用不锈钢材料被广泛的应用于心血管植介入器械。然而当其与血液接触时，在界面上会形成一系列的复杂的相互作用，导致凝血反应和血栓的形成。生物材料表面覆盖内皮细胞层是改善材料血液相容性的理想方法，但直接把内皮细胞种植在医用不锈钢材料表面不仅增殖速度慢，而且内皮细胞在短的时间内就容易脱落分离。因此如何通过表面处理，在医用不锈钢表面形成一定浓度的反应性官能团，并通过官能团有效的固定促内皮化生物分子明胶来构建具有促内皮化功能的材料表面，从而提高医用不锈钢材料表面的生物相容性成为研究的重点。
本文采用等离子体聚合沉积方法，通过调控脉冲占空比和放电功率，以烯丙胺和丙烯酸为反应单体在医用不锈钢表面合成含有伯胺基和羧基的聚合薄膜，并以伯胺基和羧基为反应的位点在聚合薄膜表面固定了明胶分子。衰减全反射傅立叶红外光谱（ATR-FTIR）和X射线光电子能谱(XPS)的分析结果表明两种聚合薄膜表面分别含有伯胺基团和羧基官能团，相对含量分别达到最大值2.16%（NH2/C）和7.22%（COOH/C）；原子力显微镜照片表明等离子体聚烯丙胺薄膜都表现为连续、无针孔的致密薄膜；等离子体聚合沉积的聚丙烯酸薄膜在水中具有较好的动态稳定性；明胶分子固定的聚烯丙胺和聚丙烯酸薄膜的ATR-FTIR图谱中出现了酰胺I和酰胺II峰；明胶分子固定的聚丙烯酸薄膜的XPS全谱中出现了N1s吸收峰，且明胶分子固定的聚烯丙胺和聚丙烯酸薄膜表面的C1s谱出现了酰胺键的结合能288.2eV，这表明且明胶分子有效地固定到了聚合薄膜表面，静态接触角测试结果表明固定了明胶分子的聚合薄膜表现出较好的亲水性。
体外内皮细胞粘附实验及Alamar Blue评价结果表明固定了明胶分子的聚合薄膜均表现出良好的内皮细胞粘附性能，且内皮细胞表现出更高活性。明胶分子固定的脉冲射频等离子体聚烯丙胺薄膜表面的内皮细胞粘附率为85.73%，高于连续波射频等离子体聚烯丙胺薄膜表面皮细胞粘附率82.73%，这可能是由于脉冲射频等离子体聚合能在薄膜表面能保持更高的胺基浓度，从而使薄膜表面固定的明胶分子浓度更高。通过制备两种脉冲占空比（50%和75%）的等离子体聚丙烯酸薄膜P-PPAA-1和P-PPAA-2并分别固定明胶分子，体外体外内皮细胞粘附实验及Alamar Blue评价均表明低占空比下合成的聚丙烯酸薄膜固定明胶分子后表面内皮细胞粘附能力更强，72h在其表面粘附的细胞增长率为41.9%。这可能是由于低占空比下射频等离子体聚合薄膜表面具有更高的羧基浓度，从而具有更高浓度的明胶分子固定。

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 amide I and amide II 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.