Rapid, Selective, Label-Free Aptameric Capture and Detection of Ricin in Potable Liquids Using a Printed Floating Gate Transistor

We report a label-free method to quantify protein levels using a combination of printed electronic and microfluidic technologies. The protein, in this case, ricin, is captured by a floating electrode functionalized with a DNA aptamer. The binding is transduced into an amplified potentiometric signal by a printed, electrolyte-gated transistor (EGT). Microfluidic channels physically separate the active sensor surface from the EGT-transducer, permitting the capture of ricin down to 30 pM (1 ng/mL) in buffer and 300 pM (10 ng/mL) in orange juice and milk in the absence of preconcentration. The assay is flow-based, leading to measurement in minutes since no preprocessing, enzymatic reaction, or rinsing steps are needed. Its easy fabrication, multiplexability, simple operation, and facile analysis, combined with rapid quantitation at clinically relevant levels, make this strategy a promising approach to parallelized monitoring of toxin levels in food and other environmental samples.