Biological properties of direct grafting by ultraviolet irradiation of vinyl benzyl phosphonic acid onto titanium surfaces

Abstract

Titanium (Ti) and its alloys are the most effective metals for structural implantable device applications. However, Ti-based materials are passively integrated into the bone, resulting in a purely mechanical attachment. Consequently, the loss of osseointegration often leads to implant failure. Therefore, enhancing bone formation surrounding the implant is primordial. In previous investigations conducted in our laboratory, grafting bioactive polymers with sulfonate groups, such as poly(sodium styrene sulfonate) (polyNaSS), was demonstrated to increase the adherence and differentiation of osteoblast cells. In this context, this contribution proposes to functionalize Ti with a phosphonic acid-based polymer, poly(vinyl benzyl phosphonic acid) (poly(VBP)). A two-step UV-initiated grafting polymerization was developed to covalently graft VBP into Ti surfaces. The surfaces were characterized using colorimetry, Fourier-transformed infrared spectra recorded in an attenuated total reflection (FTIR-ATR), X-ray photoelectron spectroscopy (XPS) techniques, and water contact angle (WCA) measurements. The Ti substrates were evaluated for cell viability, spreading, alkaline phosphatase activity, and calcium formation using MC3T3-E1 osteoblast cells. The interaction of Ti grafted samples with osteoblast cells, was significantly improved as well as the cell/surface interaction. Together, these findings demonstrated that poly(VBP) grafted on Ti surfaces improved osteoblasts' early cell adhesion and spreading activities, crucial for osseointegration applications.