Strain-Influenced Degradation of Native Collagenous Tissue in a Very-Low Volume, Environmentally-Controlled Bioreactor

We have hypothesized that collagenous matrix is an intrinsically smart biomaterial which resists enzymatic attack when under tensile strain. Testing this hypothesis requires the ability expose native tissue to low volumes of enzyme (due to their expense) while tracking mechanical response. In this study, we have developed an environmentally-controlled, mechanochemical bioreactor which permits load/strain tracking and direct observation of degrading tissue (polarization pictures) in a very small volume chamber (∼ 500 ul). In the device, the chamber “reaction volume” is formed between two layers of inert immiscible fluids. The device permitted exposure of the native tissue strips (∼6.0 mm × 0.7 mm × 13.5 mm) to small volumes of enzyme solution while it tracked the degradation-induced stress relaxation (to 0.01N accuracy) and provided direct observation of the tissue polarization signal. As expected in this small series, tissue with the higher (4% and 8%) strain degraded much more slowly compared to the lower (2%) strain. The new method successfully tracked collagen degradation (at high resolution) induced by a small volume of enzyme. The ability to perform these tests will permit the use of more expensive and physiologically relevant MMPs.