Capacitive immunosensing at gold nanoparticle-decorated reduced graphene oxide electrodes fabricated by one-step...

Nanostructured electrochemical biosensors have ushered in a new era of diagnostic precision, offering enhanced sensitivity and specificity for clinical biomarker detection. Among them, capacitive biosensing enables ultrasensitive label-free detection of multiple molecular targets. However, the complexity and cost associated with conventional fabrication methods of nanostructured platforms hinder the widespread adoption of these devices. This study introduces a capacitive biosensor that leverages laser-engraved reduced graphene oxide (rGO) electrodes decorated with gold nanoparticles (AuNPs). The fabrication involves laser-scribed GO-Au³⁺ films, yielding rGO-AuNP electrodes, seamlessly transferred onto a PET substrate via a press-stamping methodology. These electrodes have a remarkable affinity for biomolecular recognition after being functionalized with specific bioreceptors. For example, initial studies with human IgG antibodies confirm the detection capabilities of the biosensor using electrochemical capacitance spectroscopy. Furthermore, the biosensor can quantify CA-19-9 glycoprotein, a clinical cancer biomarker. The biosensor exhibits a dynamic range from 0 to 300 U mL^-1, with a limit of detection of 8.9 U mL^-1. Rigorous testing with known concentrations of a pretreated CA-19-9 antigen from human fluids confirmed their accuracy and reliability in detecting the glycoprotein. This study signifies notable progress in capacitive biosensing for clinical biomarkers, potentially leading to more accessible and cost-effective point-of-care solutions.