Rapid detection and quantification of tumor marker carbohydrate antigen 72-4 (CA72-4) using a superparamagnetic immunochromatographic strip.

Rapid and quantitative detection of biomarkers with high sensitivity and specificity has become a common practice in the clinical diagnosis and treatment of cancer. Herein, a quantitative lateral flow immunoassay (LFIA) based on superparamagnetic nanoparticles (SPMNPs) was developed for detection of carbohydrate antigen 72-4 (CA72-4) in human serum. This direct and rapid method did not involve any sample preparation and was accomplished using a test strip in which a sandwich reaction was performed. Probes on the conjugate pad were prepared by coupling monoclonal antibody CC49 specific to CA72-4 onto SPMNPs. Coupled monoclonal antibody B72.3 and goat anti-mouse IgG were loaded onto a nitrocellulose (NC) membrane, serving as the test and control lines, respectively. Initially, results were evaluated by macroscopic observation. Afterwards, the magnetic signal strength of the reaction area was quantified using a magnetic assay reader (MAR). Several parameters that may influence the detection sensitivity were studied and optimized. Under optimal conditions, the proposed method was capable of detecting as low as 0.38 IU/mL of CA72-4 in 20 min and had a wide detection linearity range (0-100 IU/mL). We evaluated 100 clinical samples (70 positive and 30 negative) to assess the validity of these test strips, which exhibited high sensitivity (99%) and specificity (97%). The results indicated a high rate of accuracy (98.4-102%) and a low relative standard deviation according to the average recovery test. In conclusion, the test strips based on SPMNP probes are a rapid, sensitive, and quantitative method for the detection of CA72-4 and possess great potential in point-of-care testing (POCT).