Optimization of amino group density on surfaces of titanium dioxide nanoparticles covalently bonded to a silicone substrate for antibacterial and cell adhesion activities

A composite consisting of titanium dioxide (TiO₂) particle, the surface of which was modified with amino groups, and a silicone substrate through covalent bonding at their interface was developed, and antibacterial and cell adhesion activities of the composite were evaluated. The density of the amino groups on the TiO₂ particle surface was controlled by the reaction time of the modification reaction. The degradation rate of CH ₃CHO in the presence of the TiO₂ particles under UV irradiation decreased with an increase in the amino group density on the TiO₂ surface. On the other hand, the number of L929 cells adhering on the TiO₂/silicone composite increased with an increase in the amino group density. From the above two results, the optimum density of amino groups for both photoreactivity and cell adhesiveness was estimated to be 2.0-4.0 molecules/ nm². The optimum amino group-modified TiO ₂/silicone composite sheet (amino group density, 3.0 molecules/nm²) showed an effective antibacterial activity for Escherichia coli bacteria under UV irradiation.