Enhanced Osseointegration of Porous Titanium Modified with Zeolitic Imidazolate Framework-8

Nanoscale zeolitic imidazolate framework-8 (ZIF-8)-modified titanium (ZIF-8@AHT) can enhance osteogenesis in vitro. In this study, we systematically and quantitatively examined the effects of ZIF-8@AHT on osteogenesis, and investigated its ability to form bone in vivo. First, we coated various quantities of nanoscale ZIF-8 crystals on alkali- and heat-treated titanium (AHT) by controlling the concentration of the synthesis solution. We then characterized the ZIF-8@AHT materials using scanning electron microscopy (SEM), powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and determination of the sessile drop contact angle. To illustrate the combined effects of micro/nanotopography and ZIF-8@AHT composition on bone regeneration, we cultured MC3T3-E1 preosteoblast cells on various titanium substrates in vitro by setting pure titanium (Ti) and AHT as control groups. The ZIF-8@AHTs enhanced cell bioactivity compared with AHT and Ti, as evidenced by increased extracellular matrix (ECM) mineralization, collagen secretion and the upregulated expression of osteogenic genes (Alp, Col1, Opg, and Runx2) and osteogenesis-related proteins (ALP and OPG). ZIF-8@AHT-1/8 exhibited better osteogenic activity compared with the other ZIF-8@AHT groups investigated. We subsequently inserted Ti, AHT, and ZIF-8@AHT-1/8 implants into the healed first molars (M1s) of mice, and found that ZIF-8@AHT-1/8 also promoted osseointegration at the bone-implant interface. These results suggest that ZIF-8@AHT-1/8 has great potential for practical application in implant modification.