Osteoblast response to titanium surfaces coated with strontium ranelate-loaded chitosan film

Improving the peri-implant bone quality has notable clinical value in cases of osteoporosis following implant insertion.

In this study, strontium ranelate-loaded chitosan film was produced on a titanium surface in different concentrations of strontium ranelate (SR) (0, 2, 20, 40, and 80 mmol/L of the strontium ion [Sr2+]) with the expectation of utilizing the bone healing-enhancement effect of Sr2+. The physicochemical properties of SR-loaded chitosan films were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). The release/dissolution mechanism was tested by inductively coupled plasma optical emission spectrometry (ICP-OES), and in vitro cell responses were evaluated using primary osteoblasts (POBs) in terms of cell proliferation, alkaline phosphatase (ALP) activity, and quantitative analysis of key osteoblastic gene expression.

XRD and FTIR observation showed that only a few SRs reacted chemically with chitosan through hydrogen bonds or conjugate action. The initial burst release (70% to 85%) of Sr2+ occurred in the first 3 days and was followed by a slower release stage. At a low concentration (2 mmol/L or 20 mmol/L), SR-loaded chitosan film promoted cell responses of POBs with enhanced proliferation, ALP activity, and expression levels of bone morphogenetic protein 2 (BMP-2), runt-related transcription factor 2 (Runx-2), ALP, and osteocalcin, but at a high concentration (40 mmol/L or 80 mmol/L), it inhibited POB growth.

These results indicated that SR-loaded chitosan film on a titanium surface promotes osteoblast proliferation and differentiation in a dose-dependent manner, which may represent a new approach in the treatment of a titanium implant.