Enzyme-assisted glucose quantification for a painless Lab-on-PCB patch implementation

Abstract

In the context of an integrated Lab-on-PCB wearable patch extracting interstitial fluid from the patient via integrated microneedles, the requirements from the integrated biosensing part are quite special compared to static glucose electrochemical biosensors. Hence, in this study, a fully PCB-integrated enzymatic glucose quantification Lab-on-Chip device is presented and evaluated considering these special requirements for such a patch implementation: a) range and limit of detection compatible with interstitial fluid glucose levels of diabetic patients and b) effect of sample flow rate on the biosensing platform performance. This work employs a chronoamperometric approach for glucose detection based on covalently immobilized glucose oxidase on PCB-integrated electrodes. The chronoamperometric measurements show that this platform exhibits μM range sensitivity, high specificity, and good reproducibility, and the assay can detect glucose from 10 μM to 9 mM with a lower limit of detection of 10 μM. The demonstrated detection range under continuous flow proved compatible with interstitial fluid glucose levels of diabetic patients. The sample-to-answer time of our Lab-on-PCB device is less than 1 min (sample delivery of few seconds and 20 s for electrochemical measurement), employing sample volumes of 50 μL in this instance. Increased flow rates substantially improve the platform sensitivity (1.1 μA/mM @0 μL/min to 6.2 μA/mM @10 μL/min), with the measured current increasing exponentially to the flow rate, as opposed to the theoretically expected much lower dependence. This work demonstrates the feasibility of Lab-on-PCB patches in terms of biosensing performance, paving the way for the first cost-effective, painless diabetes management microsystem.

Keywords: Chronoamperometry; Electrochemical biosensor; Flow rate dependence; Glucose; Lab-on-PCB; Microfluidics.