Colloids and Surfaces B, Biointerfaces vol:126 pages:481-488
Most current bone implants with open porosity enable fast osseointegration, but also present an increased risk of biofilm-associated infection. We designed a novel implant material consisting of a mesoporous SiO2 diffusion barrier with controlled drug release functionality integrated in a macroporous Ti load bearing structure. The fully interconnected macroporous Ti substrates had an open porosity of 30% with an interconnecting pore window size ranging from 0.5 to 2.0 µm. Almost complete filling of this Ti structure by SiO2 injection was achieved. The obtained SiO2 diffusion barrier had a mean pore diameter of approximately 6.4 nm and a specific surface area of 144 m²/g SiO2. An in vitro test tool consisting of Ti/SiO2 in an insert set-up, disks through which antibiofilm molecules can diffuse from the feed side to the release side, was manufactured. A continuous release without initial burst effect of the antibiofilm compound toremifene through Ti/SiO2 disks was sustained for at least 9 days, with higher release concentrations (up to 17 µM per day) for increasing toremifene feed concentrations (up to 4 mM). The toremifene diffusivity through the SiO2 phase into H2O was estimated to be in the order of 10-13 m²/s, suggesting configurational diffusion through mesopores. Candida albicans biofilm growth on the toremifene-release side of the Ti/SiO2 disks was significantly inhibited.
This establishes a proof-of-concept for attaining drug delivery functionality by the incorporation of mesoporous SiO2 into a high-strength macroporous Ti carrier material. Next-generation implants made of this composite material and equipped with an internal reservoir (feed side) can yield long-term controlled release of antibiofilm compounds, effectively preventing or treating implant infections on the implant surface (release side) over a prolonged time.