New electrochemical biosensor for the early diagnosis of dengue virus based on a mimetic peptide immobilized on a polymeric nanocomposite.

Early diagnosis of Dengue fever is critical for effective patient management and outbreak control. This study presents an electrochemical biosensor based on a mimetic peptide (MPDV) covalently immobilized on a gold electrode modified with reduced graphene oxide (r-GO) and poly(3-hydroxyphenylacetic acid). The sensing mechanism is based on the specific binding of anti-DENV IgM antibodies by the LLRNAST core epitope-mimicking recognition motif within the MPDV peptide. This biological interaction modulates the intrinsic electrooxidation of the peptide's cysteine residues, resulting in a sensitive label-free and mediator-free signal. Surface characterization by AFM, CV, and EIS confirmed the successful layer-by-layer assembly of the sensing interface and effective peptide immobilization. The r-GO/poly(3-HPA) nanocomposite promoted a 19-fold enhancement of the electroactive charge, significantly increasing sensitivity. Molecular dynamics simulations demonstrated stable peptide orientation, ensuring the accessibility of the binding motif. The biosensor exhibited a linear response toward anti-DENV IgM in human serum over the dilution range from 1:50 to 1:10,000, with a correlation coefficient (R2) of 0.999. The limit of detection (LOD) was 0.30 ng mL-1 and the limit of quantification (LOQ) was 0.99 ng mL-1. Selectivity was validated against symptomatic negative controls and co-circulating flaviviruses, supported by preliminary immunoassay data, demonstrating negligible non-specific interactions. The biosensor retained approximately 91% of its initial response after 40 days of storage under dry storage at 8 °C. By integrating a structurally stable mimetic peptide with a nanostructured conductive interface, this study establishes a highly sensitive strategy for selective anti-DENV IgM detection. The combination of experimental and theoretical modeling provides a robust platform for early dengue diagnosis and highlights the potential of this mediator-free biosensor for point-of-care applications.