Label-Free Colorimetric Detection of Gelatinases on Nanoporous Silicon Photonic Films

We report the development of a sensor platform for detection of gelatinases based on porous silicon photonic films. The sensor is made by spin-coating gelatin, a substrate protein to gelatinases, onto the porous silicon, which forms a thin, uniform, and smooth gel layer where samples can be directly spotted. The digestion products of gelatin by the active gelatinase present in the sample are able to enter the pores and induce color changes that can be detected by the naked eye. Using this sensor, we have demonstrated the detection of matrix metalloproteinase-2 (MMP-2)-an important gelatinase closely associated with tumor aggressiveness and metastatic potential-with concentrations varying from 0.1 to 1000 ng/mL in samples with volumes as small as 1 microL. The detection limit of this method, in terms of the minimum quantity of active MMP-2 in the sample that can be detected, is 2 orders of magnitude lower than what has been reported for zymography.