High-index {hk0} faceted platinum concave nanocubes with enhanced peroxidase-like activity for an ultrasensitive colorimetric immunoassay of the human prostate-specific antigen.

Developing simple, high-efficiency non-enzyme bioassays is of great importance for modern analytical systems, but remains a significant challenge. One promising route is to utilize highly efficient nanocatalysts with the exposure of active crystal facets. Herein, we for the first time propose a novel colorimetric immunoassay for the ultrasensitive detection of the human prostate-specific antigen (PSA) based on using a unique type of nanolabel - high-index {hk0} faceted platinum concave nanocubes (HIF-Pt-CNCs). The proposed HIF-Pt-CNCs exhibit superior peroxidase-like catalytic activity that is ∼1500- and ∼4-fold higher than that of natural horseradish peroxidase and Pt nanospheres, respectively, and thereby can provide powerful signal amplification by catalyzing the oxidation of peroxidase substrates in the presence of hydrogen peroxide. Using the HIF-Pt-CNC-labelled anti-PSA detection antibody as a signal probe, the immunoassay is carried out in anti-PSA capture antibody-immobilized microplate wells in a sandwich-type detection mode. Under optimal conditions, the developed immunoassay is able to achieve high sensitivity and specificity for PSA detection in a linear range of 20-2000 pg mL-1 and with an ultralow detection limit of 0.8 pg mL-1, which is much lower than that of conventional enzyme-linked immunosorbent assay (ELISA). Moreover, the method is validated for the analysis of 10 PSA clinical serum specimens, and the results agree very well with those obtained by using a commercialized ELISA kit. Therefore, this new, facile and efficient immunoassay is a promising technique with potential applications in medical science research and clinical diagnosis.