All-in-one microfluidic device with an integrated porous filtration membrane for on-site detection of multiple salivary biomarkers

A hand-held microfluidic device is developed with an integrated filtration membrane for electrochemical monitoring of multiple salivary biomarkers. The platform consists of array of screen-printed electrodes, integrated with a high throughput microfluidic system that was developed via clean-room free 3D-printing technique. A ‘channel-inside-channel’ configuration is introduced to facilitate pump-less passive flow of saliva at the broad sensing chambers. In order to eliminate the salivary protein based biofouling problems, a flexible porous filtration membrane is integrated at the microfluidic inlet that avoids the passage of bulkier protein constituents. As the presence of separate insulator layer on the sensing electrodes adversely affects its integration with the fluidic channel, the electrode substrate itself is utilized as the insulator by exposing the bottom region of the printed electrodes as active region. Enzyme based electrochemical sensors are developed with suitable nanomaterials for monitoring glucose, lactate, cholesterol and uric acid from collected saliva samples. The device showed distinct differences in salivary glucose levels for healthy subjects before and after consuming glucose-rich drinks. The glucose sensor responses are validated with high performance liquid chromatography and commercial colorimetric assay methods, and observed good correlation with parallel finger prick blood glucose measurements with an average Pearson coefficient of 0.9161, demonstrating its efficacy in saliva based point-of-care analysis.