A molecule capturer analysis system for visual determination of avian pathogenic Escherichia coli serotype O78 using a lateral flow assay

A method for rapid and accurate determination of avian pathogenic Escherichia coli serotype O78 (APEC O78) by the gold nanoparticle-labeled lateral flow strip method, entitled molecule capturer analysis system (MCAS), is described. Target virulence-associated gene of APEC O78 is adopted as the analyte. After pre-amplification with the designed functional primer set, numerous new-formed amplicons are simultaneously labeled with fluorescein isothiocyanate (FITC) and digoxin. AuNPs with a diameter of 18 nm and the characteristic plasmonic peak at 526 nm are utilized for labeling. These two labels of FITC and digoxin are further captured and measured with the AuNP-labeled lateral flow strip, and the AuNPs are retained on the test line through the immunoreaction for signal output. Under optimized conditions, this MCAS protocol can determine the target APEC O78 with excellent determination limit of 4.3 cfu mL⁻¹ based on the optical density of AuNPs on the test line of lateral flow strips. The working range is 2.52 × 10¹ to 1.63 × 10⁷ cfu mL⁻¹. Spiked serum samples are rapid and accurately measured, and the results are highly correlated with those of the real-time PCR. With this MCAS protocol, rapid and on-site determination of APEC O78 can be realized without expensive instruments or professional personnel. This MCAS protocol can be easily applied to other analytes by just replacing the traditional primer set with functionalization primer set.