Opto-active (OA) polymeric systems have potential applications in many areas such a textile materials, coatings, and fluorescent probes. Of great interest in the area of molecular biology, the incorporation of proteolytic specific substrates is an attractive platform as they have the potential to measure biological responses real-time. Proteases such matrix metalloproteinases (MMP) have been implicated in a wide range of diseases including cancer. The ability to detect secreted MMP-9 activity real-time would provide dynamic MMP-9 measurements in response to biological cues. OA polymers are a promising platform for detecting real-time MMP-9 activity as they can be biocompatible, possess tunable mechanical properties, and can release biological molecules.<br/>In this study, OA casts were fabricated from the incorporation of DQ-substrates (i.e., gelatin or elastin) in a polyurethane (PUR) network. The PUR network comprised of polycaprolactone, hexamethylene diisocyanate (HDI) or methylene diphenyl diisocyanate (MDI). These opto-active casts were fabricated using various concentrations of DQ-substrate, from 0 to 500 micro-g substrate/(mL PUR). All composites were mixed in a speed mixer. Casts were prepared using tetrahydrofuran (THF) or dimethyl sulfoxide (DMSO) solvent casting to produce an optically clear material. FTIR suggests that DQ-gelatin is conjugated in the PUR network as a decrease in the urethane carbonyl group (at 1680 cm<sup>-1</sup>) was observed with an increase of DQ-gelatin concentration in the opto-active material. Thermal gravimetric analysis (TGA) suggests that the PUR NCO/OH ratio affects the OA casts thermal stability. OA casts incorporating DQ-gelatin produced a fluorescent signal when exposed to recombinant MMP-9 (100 ng/mL), suggesting that the DQ-gelatin degradation products maintained its fluorescent activity in the opto-active material. Preliminary cell culture results have suggested that opto-active casts (DQ-gelatin) are capable of detecting secreted protease activity when RAW 264.7 cells are seeded on the material surface. Ongoing studies include additional thermal analysis and detection limit analysis.

Engineered opto-active polymeric systems for protease detection

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