An electrochemical microfluidic device for non-enzymatic cholesterol determination using a lab-made disposable electrode

Cholesterol is an important steroid and hormone precursor, and its levels in the blood are associated with risk factors for cardiovascular diseases. In this work, a non-enzymatic methodology for cholesterol determination in serum samples is described. First, a working electrode was constructed using homemade ink and a plastic substrate by a simple dunking process. Next, the dunked electrode (DWE) was modified with nickel ions (Ni-DWE) and combined with a low-cost microfluidic platform, resulting in a thread-based electroanalytical device (& mu;TED). The arrangement of & mu;TED consists of two coupled electrodes (one reference in the inlet reservoir and an auxiliary electrode against the outlet reservoir) and a mobile support for facile working electrode exchange. After optimization of construction parameters, the system was applied for non-enzymatic determination of cholesterol under alkaline conditions using the redox pair Ni(ii)/Ni(iii) as a mediator. Under the best analytical conditions, a calibration curve was constructed with a linear dynamic range (LDR) from 0.25 to 25.0 & mu;mol L-1, and the calculated limits of detection (LOD) and quantification (LOQ) were 0.074 and 0.24 & mu;mol L-1, respectively. No effects of possible interferents on electrochemical response were found in the presence of ascorbic acid, uric acid, dopamine, cysteine, and glucose, suggesting that the proposed device can be used for the determination of cholesterol without significant matrix effects of human plasma. Finally, cholesterol analysis was carried out using spiked plasma samples, and good recovery values were achieved.

Automated summary

This study describes a non-enzymatic method for determining cholesterol concentration in serum samples. A working electrode was created using homemade ink and a plastic substrate, and then modified with nickel ions and combined with a low-cost microfluidic platform to create a thread-based electroanalytical device. The device showed good performance for cholesterol determination in human plasma.