Fiber-optic protease sensor based on the degradation of thin gelatin films

Despite increasing interest in situ monitoring of proteolytic activity in chronic wound is not possible and information can only be obtained by sampling wound exudate. In this context, we developed an evanescent wave (EW) fiber-optic sensor to quantify protease activity directly in the wound bed. Detection is based on the degradation of thin gelatin films deposited on the fiber core by dip-coating, which serve as a substrate for proteases. After staining with a chlorophyllin copper sodium salt biocompatible dye, EW absorption occurs proportionally to the dye concentration, which is detected by the variation in light transmission intensity. The sensor response varies proportionally to enzymatic activity, showing sensitivity against MMP-2 and MMP-9 down to 2 μg/mL and 10 μg/mL, respectively. In addition, it is sensitive to film thickness and crosslink density, thus allowing tuning of the sensitivity and lifetime. Designed to be totally biocompatible and low cost, this miniature sensor has potential for use as a point-of-care disposable device in a clinical environment to assist physicians with quantitative information about the wound healing process.