Mimicking physiological flow conditions to study alterations of bioactive glass surfaces in vitro.

Bioactive glasses form a strong bond with surrounding tissue and slowly degrade when implanted in vivo, stimulating the host bone to regenerate itself. We investigated the behaviour of microstructured bioactive glass surfaces (13-93) in an SBF reactor, which mimics physiological flow conditions. The structures were developed to potentially influence cell-biological long term processes such as osteogenic differentiation. It is therefore important that the structures withstand a certain time in SBF or body fluids. The experiments revealed that these structures were preserved up to 30 days. Although macroscopically stable, mass loss under flowing conditions was 2-2.5%, in contrast to <1% under static conditions. Polished samples in flowing medium lost 2.7% up to day 7 and then regained mass, resulting in overall 0.5% mass loss after 30 days. Thicker calcium phosphate rich layers for the samples in flowing medium were detected, demonstrating better bone bonding capacity than predicted conventionally. The hydroxyapatite conversion in the reactor was comparable to published in vivo data. We conclude that surface alterations that occur in vivo can be better mimicked by using the proposed flow bioreactor than by the established SBF method in static medium.