Copper doped NH2-metal-organic frameworks as co-reactant modulating unit for sensitive electrochemiluminescence immunoassay

Abstract

A facile electrochemiluminescence (ECL) immunosensor for the sensitive detection of prostate specific antigen (PSA) was constructed based on a co-reactant modulating strategy using Cu²⁺-modified NH₂-metal-organic frameworks (NMOF@Cu²⁺) nanoprobes as modulating units. In this proposal, the biconical NMOF@Cu²⁺ nanoprobes possess a large number of carboxyl groups, which could be labeled by the targets PSA to form PSA-NMOF@Cu²⁺ conjugates. Moreover, the nanoprobes could consume K₃[Fe(CN)₆] and result in a lower signal of the ECL system of luminol-K₃[Fe(CN)₆]. The bioassay was executed in a split-type mode. First, the competitive immunological recognition reaction with PSA-NMOF@Cu²⁺ conjugates as the signal probes were performed in the antibody labeled 96-well plate. Upon the targets PSA were present, PSA will compete with the PSA-NMOF@Cu²⁺ conjugates for immobilization, which determined the amount of PSA-NMOF@Cu²⁺ conjugates immobilized in the plate and resulted in different amounts of the prefilled K₃[Fe(CN)₆] being consumed. Then, the above reacted solution was transferred in the detection cell for ECL test, the ECL signal from luminol/K₃[Fe(CN)₆] system will reflect the content of PSA. The developed ECL immunosensor showed high sensitivity for PSA with a linear response range of 1.0 pg·mL⁻¹ ‒ 10 ng·mL⁻¹ and a detection limit of 0.5 pg·mL⁻¹. Moreover, the applicability of the present method was demonstrated in the determination of PSA in human serum.