Time-resolved single-step protease activity quantification using nanoplasmonic resonator sensors.

Protease activity measurement has broad application in drug screening, diagnosis and disease staging, and molecular profiling. However, conventional immunopeptidemetric assays (IMPA) exhibit low fluorescence signal-to-noise ratios, preventing reliable measurements at lower concentrations in the clinically important picomolar to nanomolar range. Here, we demonstrated a highly sensitive measurement of protease activity using a nanoplasmonic resonator (NPR). NPRs enhance Raman signals by 6.1 x 10(10) times in a highly reproducible manner, enabling fast detection of proteolytically active prostate-specific antigen (paPSA) activities in real-time, at a sensitivity level of 6 pM (0.2 ng/mL) with a dynamic range of 3 orders of magnitude. Experiments on extracellular fluid (ECF) from the paPSA-positive cells demonstrate specific detection in a complex biofluid background. This method offers a fast, sensitive, accurate, and one-step approach to detect the proteases' activities in very small sample volumes.