Optimal Zn-Modified Ca-Si-Based Ceramic Nanocoating with Zn Ion Release for Osteoblast Promotion and Osteoclast Inhibition in Bone Tissue Engineering

Abstract

We investigated the slow release of Zn ion (Zn2+) from nanocoatings and compared the in vitro response of osteoblasts (MC3T3-E1) and proosteoclasts (RAW 264.7) cultured on Ca2ZnSi2O7 nanocoated with different Zn/Ca molar ratios on a Ti-6Al-4V (i.e., Ti) substrate to optimize cell behaviors and molecule levels. Significant morphology differences were observed among samples. By comparing with pure Ti and CaSiO3 nanocoating, the morphology of Ca2ZnSi2O7 ceramic nanocoatings was rough and contained small nanoparticles or aggregations. Slow Zn2+ release from nanocoatings was observed and Zn2+ concentration was regulated by varying the Zn/Ca ratios. The cell-response results showed Ca2ZnSi2O7 nanocoating at different Zn/Ca molar ratios for osteoblasts and osteoclasts. Compared to other nanocoatings and Ti, sample Zn/Ca (0.3) showed the highest cell viability and upregulated expression of the osteogenic differentiation genes ALP, COL-1, and OCN. Additionally, sample Zn/Ca (0.3) showed the greatest inhibition of RAW 264.7 cell growth and decreased the mRNA levels of osteoclast-related genes OAR, TRAP, and HYA1. Therefore, the optimal Zn-Ca ratio of 0.3 in Ca2ZnSi2O7 ceramic nanocoating on Ti had a dual osteoblast-promoting and osteoclast-inhibiting effect to dynamically balance osteoblasts/osteoclasts. These optimal Zn-Ca ratios are valuable for Ca2ZnSi2O7 ceramic nanocoating on Ti-coated implants for potential applications in bone tissue regeneration.