<i>Old is Gold</i>: Electrolyte Aging Influences the Topography, Chemistry, and Bioactivity of Anodized TiO₂ Nanopores.

Abstract

Titanium dioxide (TiO2) nanostructures including nanopores and nanotubes have been fabricated on titanium (Ti)-based orthopedic/dental implants via electrochemical anodization (EA) to enable local drug release and enhanced bioactivity. EA using organic electrolytes such as ethylene glycol often requires aging (repeated anodization of nontarget Ti) to fabricate stable well-ordered nanotopographies. However, limited information is available with respect to its influence on topography, chemistry, mechanical stability, and bioactivity of the fabricated structures. In the current study, titania nanopores (TNPs) using a similar voltage/time were fabricated using different ages of electrolyte (fresh/0 h to 30 h aged). Current density vs time plots of EA, changes in the electrolyte (pH, conductivity, and Ti/F ion concentration), and topographical, chemical, and mechanical characteristics of the fabricated TNPs were compared. EA using 10-20 h electrolytes resulted in stable TNPs with uniform size and improved alignment (parallel to the underlying substrate microroughness). Additionally, to evaluate bioactivity, primary human gingival fibroblasts (hGFs) were cultured onto various TNPs in vitro. The findings confirmed that the proliferation and morphology of hGFs were enhanced on 10-20 h aged electrolyte anodized TNPs. This pioneering study systematically investigates the optimization of anodization electrolyte toward fabricating nanoporous implants with desirable characteristics.