Abstract: Stable type Ⅰ collagen layer was formed on PLLA membrane surface by using the grafting-coating method. First, polymethacrylic acid (PMAA) was grafted on the PLLA membrane to yield carboxyl groups on the PLLA surface. Then, water-soluble carbodiimide was used as condensing agent to catalyze the reaction between the carboxyl groups and the amino groups to graft the collagen covalently on the PLLA-g-PMAA surface. Meanwhile, the collagen solution physically coated on the PLLA membrane surface was preserved to form coated collagen layer. XPS spectroscopy was used to verify the occurrence of the grafting reaction. The density of the carboxyl groups on the PLLA-g-PMAA surface was determined by colorimetric method. The surface density of the collagen coated on the PLLA surface was determined by ninhydrin method. The stability of the collagen layer was studied by incubating the collagen-coated membrane in phosphate buffer saline (PBS, pH=7.4). The surface density of the collagen decreased very slightly after the incubation, indicating the good stability of the coated collagen layer. The cell culture results showed that the growth rate of chondrocytes increased significantly on the collagen-coated PLLA membrane compared with that under the control. On the control of PLLA membrane, the cells were round shaped and easy to accumulate with each other, while on the collagen-coated PLLA membrane, the cells were spread out and evenly distributed. In conclusion, using grafting-coating method, stable collagen layer can be produced on the hydrophobic PLLA surface to improve the cytocompatibility obviously.

Key words: Poly(lactic acid), Surface modification, Grafting, Biomaterials, Cytocompatibility