Enhanced Immunosensor Using a Handheld pH Meter for the Point‐of‐Care, Sensitive Detection of Prostate Specific Antigen

An enhanced handheld pH meter based immunosensor was proposed for point‐of‐care, quantitative determination of prostate specific antigen (PSA). Monoclonal antibody‐functionalized magnetic beads (MB‐Ab1) were prepared to capture PSA in sample, and subsequently bond to polyclonal antibody‐immobilized gold nanoparticles‐polyamide‐amine dendrite‐lead ion (GO‐PAMAM‐Pb2+) and dispersed in H2S solution. Based on negative Gibbs free energy of formation, PbS (solubility product constant Ksp=8.0×10−28 was formed by reaction of Pb2+ and H2S. Hence, the pH of solution increased due to the H+ appeared, and the resulting pH value was monitored by a handheld pH meter.