Combined Detection of CA19-9 and MUC1 Using a Colorimetric Immunosensor Based on Magnetic Gold Nanorods for Ultrasensitive Risk Assessment of Pancreatic Cancer.

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 NaBH 4 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 NaBH 4 , 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.