Exploring C4D detection for the development of innovative and low-cost microfluidic biosensors

Abstract

Total analysis microsystems (uTAS) are a trend of Modern Chemistry due to the extremely low sample consumption (pL to nL), its portability potential and the integration of several processes into a single device. However, with the miniaturization of analytical systems, several challenges have also arisen, with the main ones being adequate fluid manipulation and the development of detection methods to be used for an accurate and simple analysis. Currently, electrochemical techniques are the commonly applied in uTAS due to its high sensitivity and miniaturization potential. In particular, capacitively coupled contactless conductivity detection (C4D) has been quickly growing in the literature because it does not require electrodes to be in direct contact with the solution, avoiding a number of problems such as electrolysis and metal degradation. However, it is, in principle, a universal detection technique, capable of detecting signals related to any compound with conductivity different from the electrolyte used. Therefore, it has been commonly used along with separation methods, being mainly coupled to capillary electrophoresis (CE-C4D). We propose here the improvement of a new class of innovative biosensors based on the detection of biomolecules selectively and accurately using the C4D technique (uBIA-C4D). For this end, microfluidic devices will be constructed with three gold electrodes: one responsible for sample excitation (eexc), one to act as reference, measuring the basal conductivity of the solution (err), and another to act as a working electrode (erw), evaluating the interactions between the biomolecules. The electrodes will be isolated from the solution by deposition of a SiO2 layer, which will be modified with specific antibodies only on the erw region. It is expected that the difference between the signal obtained by erw and err will vary linearly with the analyte concentration. Previous work by our group shows that the project has great potential to generate successful results. Therefore, we hope to improve this new strategy based on C4D detection for the development of precise, simple, and low cost biosensors to be applied in uTAS.