Foreign Body Reaction to Biomaterial Nanotubular Surface and the Influence of Silver Loading

The impacts of biomaterial surface properties (i.e., surface nanotopography) and dopants (i.e., silver (Ag)) on the biomaterial-associated foreign body reaction (FBR) remain unclear. In this study, an in vivo FBR that was induced by a titania nanotube array (NT) on titanium was examined with and without Ag loading. An NT with an 80 nm diameter that was fabricated by anodization, and the NT samples that were loaded with two Ag concentrations (NT-AgH and NT-AgL) and formed by electrodeposition exhibited high hydrophilicities. A relatively rapid initial Ag+ release with a subsequent gradual reduction was observed for NT-AgH and NT-AgL; the Ag+ release was higher for NT-AgH than for NT-AgL. We found that the NT decreased the biomaterial-associated FBR, evidenced by a decreased fibrous capsule thickness and a number of recruited macrophages. The effect of Ag loading on the FBR was considered acceptable because the FBR induced by the NT-Ag samples was still less severe than that of the PT control. Additionally, the temporary increases in the blood, brain, liver and kidney Ag+ concentrations did not produce general side effects and were considered to be in the safe range. This study demonstrates the ability of nanotopography to alleviate the biomaterial-associated FBR and provides further evidence for future clinical applications of biomaterials with nanostructures and Ag loading.