A Microfluidic Device Integrating a Glucose Sensor and Calibration Function for Cell-Based Assays

Abstract

Microphysiological systems (MPS) incorporating microfluidic technologies offer improved physiological relevance and real-time analysis for cell-based assays, but often lack non-invasive monitoring capabilities. Addressing this gap, we developed a microfluidic cell-based assay platform integrating an electrochemical biosensor for real-time, non-invasive monitoring of kinetic cell status through glucose consumption. The platform addresses the critical limitations of traditional cell assays, which typically rely on invasive, discontinuous methods. By combining enzyme-modified platinum electrodes within a microfluidic device, our biosensor can quantify dynamic changes in glucose concentration resulting from cellular metabolism. We have integrated a calibration function that corrects sensor drift, ensuring accurate and prolonged short-term measurement stability. In the validation experiments, the system successfully monitored glucose levels continuously for 20 h, demonstrating robust sensor performance and reliable glucose concentration predictions. Furthermore, in the cell toxicity assays using HepG2 cells exposed to varying concentrations of paraquat, the platform detected changes in glucose consumption, effectively quantifying the cellular toxicity responses. This capability highlights the device's potential for accurately assessing the dynamic physiological conditions of the cells. Overall, our integrated platform significantly enhances cell-based assays by enabling continuous, quantitative, and non-destructive analysis, positioning it as a valuable tool for future drug development and biomedical research.

Keywords: biosensor; calibration; cell-based assay; glucose oxidase; microfluidic system; microphysiological system (MPS); paraquat.

Figure 1

The cell-based assay platform consists of a microfluidic device with a glucose biosensor, a fluidic system, and a potentiostat. (A) Experimental setup: The microfluidic device, connected to syringe pumps and a potentiostat, was installed in an incubator. (B) Schematic image of the microfluidic device. (C) The geometry of the microfluidic device with the integrated glucose sensor.

Figure 2

Automatic calibration procedure during prolonged short-term measurement. (A) During cell dynamics measurement, the sample culture medium comes from the cell culture chamber at a rate of 8.8 μL/min (1). During calibration, first, a calibration solution with a glucose concentration of 2 mM is introduced from calibration solution inlet A at a rate of 8.8 μL/min for 10 minutes (2). After that, a calibration solution with a glucose concentration of 8 mM is introduced at a rate of 8.8 μL/min from calibration solution inlet B for 10 minutes. Through these operations, the biosensor is calibrated every 2 h during prolonged short-term measurement. (B) Laminar flow of the solutions in the biosensor chamber during calibration using colored water. To prevent backflow, two ports other than the main port are also flowed at 0.1 μL/min in each phase.

Figure 3

Biosensor outputting current density versus glucose concentration in DMEM (pH 7.4) at 37 °C. Values indicate mean ± standard deviation.

Figure 4

Results of prolonged short-term glucose concentration monitoring to evaluate the calibration function without cells. (A) Time course of the sensor response current in the culture medium with low-glucose DMEM containing 5.6 mM glucose at 37 °C with the calibration function. (B) Time course of the calculated glucose concentration using calibration data in the culture medium with low-glucose DMEM containing 5.6 mM glucose at 37 °C.

Figure 5

Results of prolonged short-term glucose concentration monitoring in a cell toxicity experiment. (A) Time course of the sensor response current for cells without paraquat, cells with 5 mM paraquat, and cells with 10 mM paraquat in a culture medium (low-glucose DMEM containing 5.6 mM glucose), with automatic calibration performed every 2 h. (B) Time course of the glucose consumption for cells without paraquat, cells with 5 mM paraquat, and cells with 10 mM paraquat in the culture medium, as determined by automatic calibration. Values indicate the moving average. The relative glucose consumption value was normalized with the initial glucose consumption value.