Abstract
Microfluidic devices are well suited for use in field applications, including for point-of-care (POC) diagnosis and therapy monitoring. Advantages of the use of microfluidics include small sample volumes, rapid sample to answer times, and disposable test cards combined with minimal portable instrumentation. A continuing challenge is detection from a complex sample, like saliva, which often requires extensive manual preprocessing to reduce background from interferents and for which analytes are often at lower concentrations than in blood. Further, coupling electrochemical detection to microfluidic devices has shown promise for multiple applications, but most often has been demonstrated with benchtop potentiostats rather than POC-compatible instrumentation. In the current report, we demonstrate a disposable microfluidic flow cell paired with a portable, miniature potentiostat for electrochemical measurement of the anticonvulsant drug carbamazepine in a background of human saliva. Specific highlights of the device include the small input volume of 12 μL of saliva, the absence of any manual preprocessing of the saliva sample, and carbamazepine quantification using an inexpensive polymeric laminate flow cell with stencil-printed electrodes and miniature potentiostat. With this system, accurate and robust quantification of carbamazepine drug level was achieved at therapeutically relevant concentrations of 2.5 μM to 15 μM carbamazepine in saliva. Further, functional dry storage of the microfluidic flow cells was demonstrated over 90 days.