Hollow metal–organic nanoparticles as redox species for label-free voltammetric immunoassay of prostate specific antigen

Abstract

A new kind of hollow cadmium–organic coordination nanoparticle (CdOP) was prepared by connecting Cd²⁺ with 2-aminoterephthalic acid which exhibited strong electrochemical redox activity at −0.71 V. The obtained nanoparticles were used to construct a redox substrate for label-free voltammetric immunoassay of prostate specific antigen (PSA) by drop-coating CdOPs onto the surface of a glassy carbon electrode (GCE). Then, the CdOP film was covered with a mixture of Nafion and graphene oxide (GO) due to their good film-forming properties and excellent biocompatibility. Based on the electrostatic interaction between the membrane and anti-PSA, a label-free voltammetric immunosensor was fabricated simply by immobilizing anti-PSA on the modified GCE. The determination linear range for PSA was from 0.01 ng mL⁻¹ to 100 ng mL⁻¹ and a detection limit of 0.97 pg mL⁻¹ (S/N = 3) was achieved. Importantly, the results of human blood serum samples by this biosensor were in good agreement with the enzyme linked immunosorbent assay results, indicating that the biosensor possessed high reliability for protein determination.