(280d) Rapid, Continuous Monitoring of Protein Levels in Food Matrices By Combining Microfluidics and Printed Electronics

Ensuring the safety and quality of food products requires a rapid and accurate diagnostic platform that operates with minimal user input when measuring toxin or pathogen levels. We have developed such a biosensor by combining printed electronic and microfluidic technologies to measure the concentration of ricin, a toxic protein, in aqueous buffer, orange juice, and milk. The label-free detection strategy transduces protein binding at a floating-gate electrode via a previously presented mechanism [1] giving a quantitative electronic readout that correlates with the amount of protein in solution. Specificity for ricin is achieved by functionalizing the gold floating gate with an aptamer that is selective to the target protein ricin but the underlying mechanism is interchangeable with other protein or nucleic acid targets. The principal advantage is the ability to decouple the electronic transducer from the microfluidic capture interface so that the protein can be measured from complex matrices such as orange juice and milk. This feature allows the sensor to be configured in-line with current manufacturing processes thus providing a continuous monitor for toxin levels, an example of which is ricin.

We were able to achieve limits of detection as a low as 1 ng/mL in buffer and 10 ng/mL in milk and orange juice by operating the printed electronic device at 13 Hz, rather than the common DC limit. This AC operation improves the signal-to-noise allowing for smaller amounts of bound protein to be identified. Additionally, the parallel fabrication strategy and microfluidic control of complex fluids minimizes the background noise from device-to-device variations, electrode instability, and non-specific adsorption. As little as 1 ng of ricin is necessary to generate a signal that arises in less than 45 minutes. These performance metrics demonstrate the potential for this technology to impact the food safety industry by providing manufacturers with more information from less time/labor leading to safer products sent to the public.