Near-infrared photothermal immunoassay for pancreatic cancer biomarker CA 19-9 on a digital thermometer.

A near-infrared (NIR) photothermal immunoassay was designed for the sensitive monitoring of CA 19-9 on the capture antibody-coated microplate, coupling a 3D-printed device with a digital thermometer in this work. Prussian blue nanoparticles (PBNPs)-encapsulated CaCO3 microspheres were not only utilized for labeling of detection antibody, but used as the photo-heat conversion materials for the signal amplification. With the sandwiched immunocomplex, the as-released PBNPs under acidic conditions adsorbed and converted NIR-light wavelength to heat under 808-nm laser irradiation, thereby resulting in the temperature change of the detection solution. Under optimum conditions, a linear range from 1.0 U mL-1 to 100 U mL-1 and a detection limit of 0.83 U mL-1 were acquired for the CA 19-9 detection on the portable photothermal immunosensing platform with PBNP-CaCO3-labeling system. Relative standard deviations for reproducibility were ≤9.7% for intra-assay and ≤11.9% for inter-assay. High specificity, long-time storage stability (>10 months) and good accuracy (relative to gold standard with commercial human ELISA kit) with the photothermal immunoassay were encountered for the evaluation of target CA 19-9 in complex system.