Self-powered sensor for naked-eye detection of serum trypsin

Here, we report a device for the detection of the proteolytic enzyme trypsin, which is a biomarker for pancreatitis. The sensor is self-powered, easy to use, and signals the presence of trypsin via a light-emitting diode (LED) that is visible to the unaided eye. Assay time is ∼3 h, and the limit of detection is 0.5 μg/mL, which is within the range required for detection of trypsin at levels signaling acute pancreatitis. The sensing mechanism relies on trypsin digestion of a gelled protein layer. Partial digestion of the protein layer permits hydroxide penetration and subsequent etching of an underlying Al membrane. Degradation of both the protein and Al layers exposes an underlying Mg anode and closes an electrochemical circuit that produces ∼2.2 V. This is sufficient voltage to illuminate the LED. A logarithmic relationship is observed between the time required for LED illumination and trypsin concentration. The device is equally effective for trypsin dissolved in buffer or serum media.