Surface Modification Of Biomedical Poly(Lactic Acid)by Polysaccharide And Enzyme

Biomedical polymer material is a kind of advanced material which have special functions on reparation, replacement and regeneration of organic tissues. In recent years, it has become one of the most fast growing biological materials.For the biomedical polymer materials, their biological properties not only depend on its own nature, to a large extent, it also depend on the chemical nature and physical properties of the surface. Therefore, the surface modification is an important and useful method to improve the surface properties of material. In this study, lentinan was extracted from shiitake mushroom at first, then, two kinds of lentinan derivatives were prepared. Finally, these polysaccharides were immobilized onto the surface of poly(lactic acid)(PLA) by different methods.Carboxymethylated lentinan (LC) was covalently immobilized onto the surface of aminated PLA substrates via chemical grafting method. In addition, LC and chitosan were alternatively deposited on the aminated PLA substrates via layer-by-layer assembly method (LbL). The LC was proved by infrared spectroscopy. The modified and unmodified PLA surfaces were investigated by scanning electron microscope (SEM) and water contact angle measurements. The hemolysis test, thrombus test, and the antibacterial activity against Escherichia coli of modified and unmodified PLA were tested in vitro, respectively. Then, the surface properties of PLA modified by different modification methods were evaluated and compared. The results showed that the hydrophilicity, blood compatibility, and antibacterial activity against Escherichia coli of PLA modified by LbL assembly and chemical grafting were both improved.Sulfated lentinan (LS) and lysozyme were deposited on the aminated PLA through LbL method. The test results showed that the modified surface became more hydrophilic. Moreover, the hemolysis test demonstrated the modified poly(lactic acid) had a better blood compatibility. In addition, the antibacterial activity against Escherichia coli and Staphylococcus aureus were improved after modification.This work provides scientific data and valuable experiences for preparing biocompatible materials with multi-function and specific bioactivity. It also can provide an effective method for the immobilization of bioactive polysaccharide derivative and enzyme on polymeric biomaterials.