Catalytic FeCo Prussian blue analogue nanozyme for sandwich immunoassay on commercial bandage model substrate

Herein, we developed a bandage-based colorimetric immunoassay for the visual and quantitative detection of prostate-specific antigen (PSA) by utilizing the cotton fiber region of a commercial adhesive bandage as an antibody immobilization substrate and integrating FeCo Prussian blue analog (FeCo-PBA) nanozymes for signal amplification. FeCo-PBA nanozymes were synthesized through a simple aqueous-phase method and employed as catalytic labels in a sandwich immunoassay. Upon PSA recognition, FeCo-PBA-labeled antibodies were captured on the fiber surface and catalyzed the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H 2 O 2 , producing a visible blue color signal, while a smartphone-assisted platform was established to extract red value ( R -value) for quantitative analysis. The FeCo-PBA nanozymes exhibited a high peroxidase-like activity of 10.43 U mg −1 , which was 2.9 times higher than that of Fe-based Prussian blue nanoparticles, and a lower activation energy of 7.62 kJ mol −1 , indicating enhanced catalytic efficiency. Owing to the improved catalytic performance, the sensor enabled quantitative PSA detection over a range of 0.1–50 ng mL −1 based on the correlation between the R -value and PSA concentration, while also demonstrating good selectivity and accuracy. This work provides a simple and low-cost strategy for converting commercial bandages into quantitative biosensing platforms and offers a promising approach for portable point-of-care cancer biomarker detection. Graphical abstract