Preparation And Property Of Chitosan-casein Phosphopeptides Biocomposite Film On The Surface Of Titanium Alloy

Titanium (Ti) and its alloys have been applied in orthopedics as one of the most popular biomedical metallic implant materials. Generally, the surface characteristics of implant materials, such as surface structure and physicochemical property, have a great effect on the biological behaviors. At present, it has been demonstrated that the modification of Ti and its alloys by using of biochemical methods has become an effective way to enhance tissue integration, shorten implant cycle and improve success rate.In this work, in order to combine the good biocompatibility of Ti alloy and biospecificity of bioactive molecules, the surface of Ti alloy pre-modified by silane coupling agent and glutaraldehyde was covalently grafted with chitosan (CS) via biochemical multistep self-assembled method. Then, for the first time, the achieved surface was further immobilized with casein phosphopeptides (CPP) molecules, which are one group of bioactive peptides released from caseins in the digestive tract and can facilitate the calcium adsorption and usage, to form CS-CPP biocomposite films. The structure and composition of the prepared films were characterized by X-ray photoelectron spectroscopy (XPS), contact angle measurement, attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and atomic force microscopy (AFM). At the same time, cytocompatibility and bioactivity of the fabricated films were evaluated through cultivation of the osteoblasts in vitro.The main results are drawn as follows:as pointed out by XPS characterization, the chemical composition and the chemical state of main elements on the surfaces were changed after each modifying step. From ATR-FTIR analysis, it was found that some typical chemical groups could be detected. These results demonstrated that multi-step assembly was successfully performed, and the CS and CPP were assembled onto the Ti alloy surface orderly. The wettability of the functionalized Ti surfaces was also investigated. The CS-CPP biocomposite films modified surface is extremely hydrophilic with the water contact angles is about 26°, indicating that the end groups on modified surface have a great on surface wettability. The changes of surface morphologies were observed with AFM after each modifying step on silicon substrate. It is obvious that a relatively regular surface with even spherical particles formed after grafting CS, and then the surface recovered relatively flat after CPP was further modified, because of the filling of CPP molecules, finally, a continuous CPP layer was formed. The osteoblasts culture test indicated that the activity of cells on the CPP modified Ti surface was higher than that on the pure Ti. Namely, the prepared CS-CPP biocomposite films can promote cell adhesion, spread and proliferation, the cells volume increased significantly and cells fully stretched, exhibiting rougher surface profile and fuzzy boundaries. Therefore, the construction of CS-CPP biocomposite films is an effective way to improve bone cell function and enhance biological properties of Ti alloy.