Calcium-phosphate slurry processing: A novel chemical treatment technique to activate osteogenesis on titanium

摘要

Titanium (Ti) implants have become essential medical products in surgery and dentistry as substitutes for hard tissues. However, it is difficult to achieve a strong mechanical interface between the implant and the surrounding hard tissue because osteogenesis does not progress easily on Ti. This paper presents a novel chemical treatment technique, called calcium-phosphate slurry processing, to activate osteogenesis on Ti substrate, developed by our research group. The calcium-phosphate slurry processing is a simple technique, and it involves burying a Ti substrate in calcium phosphate slurry prepared by mixing calcium phosphate powder with distilled water and then heated at 973 K in air. This process induces the substrate to react with the reagent efficiently and crystallizes the surface layer in one step. By treating with the slurry prepared by mixing 1 g of tribasic calcium phosphate (3Ca_3(PO_4)_2·Ca(OH)_2) powder with 1.5 mL of distilled water, a composite coating comprising calcium phosphate and titanium dioxide (TiO_2) was fabricated on a Ti substrate. The thickness of the coating, estimated from a transition electron microscopic (TEM) image, was approximately 300 nm, and the average roughness (Ra) of the treated surface, calculated from the scanning probe microscopic (SPM) image, was slightly increased as compared to that of a non-treated surface. After the sterilization, osteoblast-like MC3T3-E1 cells were seeded on the treated and non-treated Ti substrates and then cultured for 3 d. There was no difference in the attached cell numbers between the non-treated and treated substrates, indicating that the treated Ti surface will not show the cytotoxicity. The cells were thereafter differentiation-induced on the substrates. The calcifications of the cells at 27 d after differentiation-incubation are shown in Fig. 1. The calcified deposits were stained by alizarin red S. The clustered deposits were observed only on the treated Ti substrate. This result indicates that osteogenesis on Ti is activated by treating with calcium-phosphate slurry. On the basis of these experimental results, we propose that calcium-phosphate slurry processing is one of the hopeful surface treatment techniques to activate osteogenesis of Ti implants. Fig. 1. Photograph of calcified deposits in MC3T3-E1 cells stained with a 1% alizarin red S solution. Cells were differentiation-induced on (a) non-treated Ti, and (b) treated Ti for 27 d.