Microfluidic Paper-Based Electrochemical Immunosensor for the Detection of Prostate-Specific Antigen (PSA) Based on Modified Flexible Screen-Printed Carbon Electrodes

Abstract

A microfluidic paper-based electrochemical immunosensor (μPAD) presents a promising platform for detecting prostate-specific antigen (PSA), a key biomarker for prostate cancer. Detection is based on the unique antigen-antibody binding, which restricts electron transfer at the electrode's surface. In this study, we developed a label-free immunosensor using ferri-/ferrocyanide ([Fe-(CN)₆]^3-/^4-) as a redox probe to monitor current changes before and after antigen immobilization. The screen-printed carbon electrode (SPCE) was modified with mesoporous carbon (MC) to boost the electrochemical signals due to its high surface area and functional carboxylic acid groups for efficient antibody attachment. By integrating this with a μPAD, sample handling and preparation were simplified. A commercial laser printer was used to create hydrophobic zones, offering a cost-effective and straightforward fabrication method. The synthesized MC was further combined with carbon nanotubes (CNT) and graphene oxide (GO) to construct the immunosensor. Under optimized conditions, the sensor exhibited a linear response for PSA concentrations ranging from 10 to 1000 ng/mL, with a detection limit of 2.16 ng/mL. Additionally, the sensor demonstrated excellent reproducibility, selectivity, and stability, making it a potential alternative analytical tool for PSA detection in real samples.