We herein report a facile approach for developing an enzyme-free colorimetric immunosensor based on a magnetic iron oxide (IO)-coated gold nanorod (MGNR) nanocomposite with high electron transfer ability to accelerate the color bleaching reaction of methyl orange (MO) in the presence of NaBH4 for ultrasensitive detection of cancer antigens. In the case of MO, the reaction rate of MGNRs showed approximately 45.6-fold and 1520.8-fold higher than that of Cys-GNRs and NaBH4, respectively. The proposed colorimetric immunosensor was demonstrated to enable simple, cost-effective, sensitive, and specific carbohydrate antigen 19-9 (CA19-9) and mucin 1 (MUC1) detection for risk evaluation of pancreatic cancer (PC) with a small volume of serum sample without the use of any enhancing solutions or enzymes. By increasing the concentration of CA19-9 and MUC1, more MGNRs remained in the plate well to enhance the color bleaching of MO. As a proof-of-concept, the limit of detection (LOD) of 3.5 × 10-5 U/mL for CA19-9 and 5.2 × 10-6 U/mL for MUC1 was obtained with a wide linear quantification range from 8.6 × 10-5 U/mL to 1.4 × 10-2 U/mL for CA19-9 and 1.3 × 10-5 U/mL to 2.1 × 10-3 U/mL for MUC1, suggesting potential clinical applications for the early risk evaluation of PC.
Keywords: carbohydrate antigen 19−9 (CA19−9); colorimetric biosensor; enzyme-free; mucin 1 (MUC1); pancreatic cancer.