Ultra-dense vertical electrochemical biosensors enable single-response multiplexed diagnosis
The central problem motivating this project is the rapid, accessible, and accurate diagnosis of diseases, either in a laboratory setting or at the point of need. In this context, platforms with high testing capacity emerge as essential tools to expedite diagnosis and enhance clinical accuracy, enabling the simultaneous and sequential assessment of distinct biomarkers. Electrochemical label-free biosensors (BELF) offer high analytical performance combined with speed, simplicity, portability, and low cost, but they have not yet successfully reached the commercial market beyond the personal blood glucose assays. In response to this gap, we present a new configuration of an electrochemical device that (i) performs serial analysis of a high number of sensors, (ii) combines high reproducibility with simplicity of use and reduced cost, and (iii) introduces something unprecedented in electrochemistry: the simultaneous and independent monitoring of distinct redox reactions from a single square wave voltammetry (SWV) scan, using a single working electrode (WE). Abbreviated as SERM (single-response multiplexing), this strategy promises to propel advances in multiplexed systems by enabling the use of BELFs for the simultaneous detection of multiple analytes from single-channel portable potentiostats. Produced through microfabrication techniques, the sensors consist of only 2 electrodes comprising vertical thin films of Au separated by a dielectric (SU-8) and arranged in a mesh. This configuration contributes to the integration capacity of sensors (many sensors per area), resulting in a significant reduction in the final cost of chips. Considering an industrial infrastructure and 48 sensors per wafer, the unit cost was estimated at R$3.55. In this study, as a proof of concept, we evaluated the device's performance as a biosensor by modifying the WEs with peptides (recognition element) for the detection of COVID-19 IgG antibodies in real samples. Through this innovative approach, we were able to double processing capacity while simultaneously achieving 100% accuracy in serum samples. We envision the platform to enable broad applications in high-testing capacity approaches, as it can be tailored to other biosensing devices and formats.