Investigation of initial pellicle formation on modified titanium dioxide (TiO2) surfaces by reflectometric interference spectroscopy (RIfS) in a model system

Objectives. Plaque accumulation, leading to inflammatory processes and bone loss, is one of the main reasons for failure of dental implants. Pellicle formation plays a key role in bacterial adhesion and plaque accumulation. The influence of experimental bioactive implant surface coatings on the initial process of pellicle formation was investigated in a model system. Methods. TiO2-films were modified by covalent binding of laminin and human epidermal growth factor (EGF) to promote adhesion of epithelial cells. Adsorption and dissociation behavior of bovine serum albumin (BSA) and salivary proteins on these surfaces were monitored by time-resolved reflectometric interference spectroscopy (RIfS). Results. The thickness of the irreversibly adsorbed salivary protein layer was reduced from 2.78±0.71 nm on unmodified TiO2 to 0.78±0.22 nm on laminin-coated surfaces and to 1.18±0.29 nm on EGF-coated surfaces. The percentage of initially adsorbed proteins remaining irreversibly bound was reduced from 51±8% on titanium to 23±5% by laminin coating and to 44±11% on EGF-coated surfaces. The highest reduction of protein adsorption (layer thickness lower than 0.05 nm) was achieved on DC-PEG-layers used as spacer for protein coupling. Significance. Laminin and EGF were shown to be promising candidates for use as biological coatings on the transmucosal part of titanium dental implants where the objective is to enhance epithelial adhesion and inhibit adsorption of salivary proteins and bacteria.