Diagnosis of viral infectious diseases through sensitive detection of human serum antibodies using a modified label-free electrochemical biosensor

Rapid virus identification is crucial for preventing outbreaks. The COVID-19 pandemic has highlighted the critical nature of rapid virus detection. Here, we designed a label-free electrochemical biosensor modified with gold nanoparticles (AuNPs) to detect IgG antibodies from human serum, enabling rapid point-of-care diagnostics. AuNPs were synthesized and characterized. A multivariate optimization was carried out to determine the optimal condition for functionalizing AuNPs with anti-IgG. Subsequently, using a glassy carbon electrode (GCE), a modified AuNPs/GCE electrochemical biosensor was developed for IgG detection. The results indicated that AuNPs displayed a spherical morphology with a size distribution of 19.54 nm. Additionally, the zeta potential was recorded at −7.84 mV. Central composite design (CCD) analysis determined the optimal conditions for functionalizing AuNPs to be an anti-IgG concentration of 320 µg mL⁻¹, a temperature of 25 °C, and pH of 7.4. The characterization study confirmed the successful synthesis and functionalization of AuNPs. Through electrochemical impedance spectroscopy measurement, the biosensor demonstrated a limit of detection (LOD) of 0.2 ng mL⁻¹ and limit of quantification (LOQ) of 0.8 ng mL⁻¹. Furthermore, tests in real samples showed the interaction between IgG antibodies in serum samples and AuNPs/GCE, confirming the biosensor's ability to detect and quantify IgG in clinical samples.