Immobilization Of Biological Protein On Titanium And Research Of Their Biological Activity

Titanium and its alloys have been applied in clinic more and more owing to their good biocompatibility and mechanical properties. Surface bioactivating engineering could change the surface states of titanium and its alloys and improve their bioactivity. The main objective of this paper is to deposit a polymer nano-film containing functional group (carboxyl or amido) on titanium surface through low temperature plasma polymerization technology. Then bioactive proteins (bovine serum albumin (BSA), collagen I (CI) and fibronectin (FN)) were immobilized on the titanium surface through those functional groups. In the end, the bioactivity and biocompatibility of samples were studied based on apatite precipitation and osteoblast culture in vitro.During the low temperature plasma polymerization, different factors (reaction power, pulse duty factor, reaction time, bias voltage and pressure) were investigated to get the best film. The results of X-ray photoelectron spectroscopy (XPS) and Fourier transformed infrared spectoscopy (FTIR) implied that polymer nano-film containing carboxyl or amido were deposited successfully by using allylamine or acrylic acid as a reagent, respectively. The results of surface profilometer showed that the thickness of the film was from 50nm to 200nm. And the data of contact angle indicated that the hydrophilicity of the titanium surface decreased obviously after the plasma polymerization. After immobilized proteins, the corresponding functional groups were detected by FTIR. The high-resolution XPS spectra of C and N elements indicated that proteins were immobilized by condensation reaction between proteins and functional groups on titanium surface.The results of in vitro biomimetic mineralization showed that the proteins immobilized on titanium surface were beneficial to hydroxyapatite (HA) deposition and grain refinement. From SEM, the micromorphology of HA was porous spherical. The behavior of the osteoblast on samples before and after modification was investigated through culture of osteoblast. The results showed that the activity of cell on the protein modified surface was higher than that on the pure titanium. The ranking of the activity is as follows: 1^st, samples with FN immobilized; 2^nd samples with CI immobilized; 3^rd samples with BSA immobilized. And on the whole, the activity of samples containing carboxyl is higher than samples containing amido. It indicated that the proteins (especially FN) can promote cell adhesion, spread and colonization.