Integration of Carboxylate Carbon Dot-Supported Gold Nanoparticles with Boron Nitride Nanosheets for Electrochemical Sensing of Prostate-Specific Antigen via Sandwich Immunoassays

An electrochemical sandwich immunoassay was fabricated to measure the prostate-specific antigen (PSA) biomarker. The PSA immunosensor was developed by altering the surface of a glassy carbon electrode (GCE) with a nanocomposite comprising carboxyl-functionalized carbon dots that support gold nanoparticles (AuNPs), which were then combined with hydroxylated boron nitride nanosheets (HO-BN). This construction possesses distinctive signal enhancement characteristics and was prepared via a facile method. Considering the high biological affinity of AuNPs for biomolecules, carbon dots (CDs) with carboxyl (COOH) groups make a suitable substrate for electrode modification. This alteration allows for the PSA antibody (Ab1) attachment, resulting in a sandwich-like configuration. Additionally, carbon dot-stabilized AuNPs integrated into HO-BN nanosheet nanocomposites considerably boost the electron transfer rate, leading to remarkable potential in sensor applications. By utilizing horseradish peroxidase (HRP)-conjugated antifree PSA antibody (Ab2), a reduction in hydrogen peroxide (H₂O₂) was achieved within the electrochemical cell. This reduction led to increased current, attributed to the increased PSA concentration, which is required for the biosensor analysis to perform properly. The developed immunosensor revealed a linear correlation with PSA concentrations ranging from 1.0 to 3500 pg mL^-1, achieving a low detection limit of 0.136 pg mL^-1. Furthermore, the PSA aptasensor demonstrates excellent selectivity, remarkable stability, and commendable reproducibility, indicating its significant potential for clinical research and diagnostic applications.