This study has demonstrated that the miniature bioreactor is capable of applying load and measuring the displacement with very high temporal, spatial and force resolution. The data captured from the experiments by the bioreactor are repeatable and demonstrate the effect of tensile strain on the rate of degradation of collagen in native tissue. Previous studies (including our own) have asserted that strain can stabilize the collagen molecule against enzymatic attack. Earlier data demonstrate that tensile load somehow changes the physicochemistry of the enzyme kinetics and leads to delay in the degradation of collagen fibrils. In this investigation, we conclude thatloads over a fairly large range do not alter the degradation rate at high strain for bacterial collagcnase. However, early in each experiment (when strains are low), there arc some interesting dynamics which suggest that higher loads lead to faster degradation (the opposite of our own hypothesis). Nonetheless, we have developed a device capable of detecting the effect of fixed load on degradation rates with high fidelity.It should be noted that crude bacterial collagenase is a non-specific enzyme capable of degrading collagen in addition to many other molecules. It contains up to 18 different enzymes which result in rales and patterns of collagen degradation that are drastically different from in vivo digestion (by MMPs or cathepsin). It is clear that moving to a more physiologically relevant enzyme (MMP or cathepsin) will produce results that arc more comparable with the in vivo remodeling process. In addition, since strain control provides a "static" geometry under which to view degradation, it is important to convert the protocol to use that mechanical test mode as well.
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