Opto-Active Polyurethane Urea-Based Fluorescent Materials for Protease Detection

Biosensing polymers have a wide range of in vitro and in vivo biomedical applications, such as detecting cancer biomarkers. Here, an opto-active polymeric material was fabricated and characterized for its ability to detect proteolysis in the presence of trypsin, a commercially available proteolytic enzyme, or when exposed to metastatic cancer cells. Opto-active (OA) polymeric casts incorporate DQ gelatin, a fluorogenic, polypeptide substrate standardly used to detect protease activity, in a polyurethane urea (PUU) elastomer network, providing an immobilized substrate that better mimics extracellular matrix properties compared to free-floating DQ gelatin. Both polymer swelling and proteolytic degradation lead to an increase in the fluorescence of the opto-active polymeric cast. When cells are grown on the opto-active cast, the use of fluorescent microscopy instead of conventional spectroscopy allowed for simultaneous measurement of the protease activity from the fluorescent response of OA casts and monitoring cell dynamics, growth, and viability over multiple days. MDA-MB-231 breast metastatic cancer cells seeded on opto-active casts exhibited normal morphology and proliferation, demonstrating the biocompatibility of the OA casts. Finally, this study shows that the sensitivity of OA casts is sufficient to detect proteases secreted by proliferating cells, illustrating the great potential of an opto-active cast platform for implementing responsive in vitro models with further multiplexing capabilities.