Design and Evaluation of a Microfluidic Device Such As a Self-Powered Glucose Biosensor Using a Solution of Glucose and Human Blood
Authors: Escalona-Villalpando Ricardo , Sandoval-García Alicia , Espinosa-Lumbreras José , Miranda-Silva Mireya , Arriaga Luis , Minteer Shelley D. , ledesma-García J. 
Published: July 2022

Glucose sensors have been seen as a greater research interest because they are related to type I diabetes disease and because individuals diagnosed with this disease are more susceptible to complications, such as high blood pressure, high cholesterol levels, eye problems, and even death. Self-powered glucose biosensor (SPGB) based on biofuel cells (BFCs) combine the operational systems of a BFC and a biosensor in where the energy could be used for glucose quantification as an SPGB and operate the sensor without the need for any external energy source. This strategy could have certain advantages as the sensor is limited to two electrodes without applying an external voltage, it can be fed with the same biological fluid with the prospect of being implanted, the interferers can be decreased by not applying a potential, and a single concentration of the substrate is sufficient to calibrate the system. In this context, the microfluidics has proven to be an important technology in the area of biosensors and has been used to transport or mix the sample, this device using different and independent electrolytes depends on the enzyme to improve performance, reported in the work group before. The glucose oxidase (GOx) bioanode was prepared using dimethylferrocene-modified linear polyethyleneimine (FcMe2-LPEI). On other hand, the laccase (Lc) biocathode was prepared using anthracene-modified MWCNTs (AnMWCNTs). The microfluidic device consisted of two parts fabricated from PMMA using a micromilling system CNC (Computer Numerical Control). For the calibration curve, it was used as anolyte PBS pH 7.4 (0.1 M) using 0, 1, 3, 5, 7, 10, and 20 mM glucose and PBS pH 5.6 (0.1 M). In the case of the real samples, the anolyte was blood or serum, and the catholyte was PBS pH 5.6. The electrolytes were fed using a syringe pump (Kd Scientific) at a flow rate of 3 mL h-1. Polarization curves for microfluidic self-powered glucose biosensing (m-SPGB) were obtained by linear polarization from OCP to 0 V at 2 mV s-1. All experiments were performed in triplicate, and the average ± standard deviation was reported. The interferers evaluated in the m-SPGB were 0.025 mM ascorbic acid (AA), 0.1 mM uric acid (UA) and 0.5 mM dopamine (DA) and arranged in the anolyte prepared with PBS pH 7.4 (0.1 M). The architecture of the m-SPGB device is defined mainly by two modules: the sensor unit and the Wi-Fi transmission/reception unit. The electrochemical characterization of the FcMe2-LPEI/GOx bioanode and AnMWCNT/Lc biocathode immobilized on TCP was performed by cyclic voltammetry (CV), showing activity towards glucose oxidation and oxygen reduction respectively. Confirming the electrocatalytic activity of the bioelectrodes, both were used in the m-SPGB using PBS pH 7.4 and different concentrations of glucose in the anolyte and PBS pH 5.6 as the catholyte. Under these operating conditions, the average OCP was 0.81 ± 0.021 V constant voltage at the different glucose concentrations evaluated. The result is important because the system is sensitive to low glucose concentrations of 1 mM and 3 mM, and an increase in the current is observed, differentiating very well in each concentration from 0 to 20 mM. Plots of the comparative responses to the increase in current and power in the m-SPGB versus glucose concentration. The linear ranges of both parameters were 0–10 mM with correlation coefficients (R2) of 0.9907 and 0.9913, respectively; in both cases, they were within the range to measure blood or serum glucose. On the other hand, the sensitivity was higher, at a current of 1.24 μA mM-1, while the power was 0.19 μW mM-1, with a better limit of detection (LOD) of 0.48 mM vs. 0.76 mM of the power. The electronic device connected to the m-SPGB was used for the quantification of the different glucose concentrations, sending the wireless-type information to a laptop for processing and more efficient interpretation without the need for a potentiostat/galvanostat and the connection between the electronic device for sending and processing the information and the microfluidic device where the enzymatic reactions are carried out. In summary, the results, in general, are comparable and superior to other SPGBs published by other authors and show their importance in using a microfluidic system.