Bioactivity on alkali-treated NAZOZR and titanium surfaces with nanonetwork structures

Abstract

Herein we focused on NANOZR, which has high fracture toughness and elasticity, to create a new implant material by applying surface structure control via concentrated alkali treatment. We investigated the initial adhesion of bone marrow cells and the ability of this material to induce hard tissue differentiation. Two experimental samples were used: NANOZR treated with a concentrated alkali at room temperature and titanium treated with an alkali solution. A commercially available NANOZR plate with a mechanically polished surface was used as a control. Analysis was performed using scanning electron microscopy (SEM) and scanning probe microscopy (SPM), as well as X-ray photoelectron spectroscopy (XPS) for surface analysis. In addition, the contact angle of distilled water on the surface of each group was measured, and the initial adhesion of bovine serum albumin was investigated. After bone marrow mesenchymal cells were collected from the bilateral femurs of 7-week-old male Sprague-Dawley rats, a primary culture was established, and the third generation was used for the experiment. We also measured alkaline phosphatase activity at 14 and 21 days after culturing, the amount of osteocalcin produced, and the amount of calcium precipitated after 21 and 28 days. In addition, the expression of gene markers related to differentiation induction was examined from the mRNA obtained after reverse transcription from the cells 3 days after culture. Observation using SEM and SPM showed that a nanometer-level network structure was formed on the alkali-treated titanium, but there was no change in the NANOZR. In XPS observations, it was found that a deep oxide film layer was formed on the alkali-treated titanium and alkali-treated NANOZR. The expression of various differentiation-inducing markers and gene markers was higher in the experimental group than in the control group at all measurement times, and there was no difference in the values between the alkali-treated titanium and the alkali-treated NANOZR. Based on the above results, it is suggested that nano-level surface modification may be useful for improving the differentiation-inducing ability of bone marrow cells in alkali-treated NANOZR, similar to the case of titanium.