Fluorimetric ex vivo quantification of protease debriding efficacy on natural substrate.

Debridement is the process of removal of necrotic and infected tissue to clean a wound or burn and expedite healing. Proteases such as papain, bromelain, and collagenase that promote debridement by degrading proteins in the dead tissue are in use today. However, the only method to measure debriding efficacy in vitro is the fluorescent monitoring of the digestion of an Artificial Wound Eschar (AWE) substrate. This AWE substrate contains a pellet of only three eschar matrix proteins collagen, elastin, and fibrin which do not account for the complexity and the composition of necrotic tissue. Here, we describe an ex vivo method using dry necrotic full thickness human skin and ortho-phthalaldehyde (OPA), a molecule commonly used for sensitive fluorimetric protein detection to monitor debridement activity. We advocate this simple yet sensitive approach to detect debridement efficacy that can readily be used commercially to benchmark products prior to in vivo testing.

Retaining in-gel zymographic activity of cysteine proteases via a cysteine-supplemented running buffer.

Zymography is a powerful technique to separate and identify different enzymatic activities on a standard acrylamide gel. For oxidation prone enzymes such as cysteine proteases however, the oxidizing species generated by electrolysis of the gel running buffer may result in partial or complete inactivation, thus compromising the final readout. This can be only partially remedied by subsequent treatment of the gel with reducing agents. We demonstrate the generation of reactive oxidizing species during electrophoresis and discovered that supplementation of the gel running buffer with a minimum of 5 mM cysteine prevents enzyme inactivation and allows retention of proteolytic activity as measured by zymography on model substrate N α-benzoyl-l-arginine p-nitroanilide, without at the same time altering the mobilities of the gel proteins.