Bisphosphonates on Smooth TiO2: Modeling and Characterization

This paper presents insights into surfaces properties of sputter-deposited titania modified with bisphosphonates, including zeta potential measurements in a pH range. Functionalization was investigated through simulation and experimental approaches to model the adsorbate and evaluate structure-response relationships. Molecules of etidronic, alendronic, and risedronic acids were investigated through density functional theory. The molecules vary their reactivity through similar structures considering different scenarios. X-ray photoelectron spectroscopy of titania/BP systems demonstrated that functionalization occurs in a short time and resulted in a predominantly "side-on" adsorbate configuration after two hours of immersion. Zeta potential showed the predominancy of negative charges deprotonated free phosphonates. Water contact angle demonstrated that titania surfaces are hydrophilic after overnight functionalization. Atomic force measurements of bisphosphonates layers suggested that the molecular anions follow the surface topography, unchanging the surface roughness.