Zwitter-repel: An anti-fouling coating promoting electrochemical biosensing in biological fluids

This is the authors' abstract. We don't add key points for this paper.

Most electrochemical biosensors require sample processing to reduce biofouling induced by the complex composition of biological samples that typically causes a decrease in the target-to-blank signal. Herein, we report a zwitterionic copolymer bearing sulfobetaine, carboxylic, aldehyde, and thiol groups as a thin (∼16 nm) anti-fouling coating for electrochemical biosensing platforms. The resulting polymer-coated electrodes reduced protein adsorption by ∼ 67 % compared to the bare-gold surface when incubated with radiolabeled human serum albumin (HSA) protein-spiked human plasma, while cyclic voltammetry yielded a 5 % increase in anodic current signal after incubation in 1 % HSA for 1 h compared to the 83 % decrease in anodic current observed with bare gold electrodes. The polymer-coated electrode facilitated the detection of redox-labeled DNA in buffer, as well as in unprocessed and undiluted plasma with detection limits of 23 nM and 21 nM, respectively; detection of 104 cp mL−1 lentivirus pseudotyped with the Omicron spike protein of SARS-CoV-2 in unfiltered 50 % saliva was also achieved within 5 min with improved target-to-blank ratios and reproducibility relative to the well-established PEG-based biosensing platform for detecting COVID-19. On this basis, the Zwitter-repel coating offers potential to sensitively detect other disease biomarkers/analytes while eliminating or reducing the need for sample pre-processing and/or the use of additional backfilling/blocking agents.