Rapid detection of Escherichia coli O157:H7 in milk, bread, and jelly by lac dye coloration‐based bidirectional lateral flow immunoassay strip

Abstract

Lac dye, a kind of food additive and textile dye, is extracted from lac insect secretions. The ability of lac dye to stain bacteria was firstly found. Based on the discovery, a new bidirectional lateral flow immunoassay strip (BLFIS) for detecting Escherichia coli O157:H7 (E. coli O157:H7) was successfully developed. The BLFIS has two sheets of nitrocellulose (NC) membranes separated by a sample pad. The anti‐E. coli O157:H7 monoclonal antibodies (McAb) were oppositely dispensed on the NC membranes as the control line and test line, respectively. On the side of the control line, a conjugation pad immobilized with pre‐stained E. coli O157:H7 was assembled. The detection limit of BLFIS was 106 CFU/ml. Furthermore, after pre‐incubation in food sample, the detection sensitivity was significantly increased to 100 colonies of the initial bacterial count. This method may be an improvement over traditional colloidal gold lateral flow immunoassay strips, which does not require the pairing of two antibodies to complete the detection, nor the chromogenic nanomaterials to report the detection results, such as gold nanoparticles. And the BLFIS might provide technical support for detecting E. coli O157:H7 in food and ensuring food safety.

An intelligent readable and capture-antibody-independent lateral flow immunoassay based on Cu2−xSe nanocrystals for point-of-care detection of Escherichia coli O157:H7

“…The Cu 2− x Se-LFIA method displays the advantages of simple probe synthesis and does not require professional instruments and experimental personnel. In addition, compared with the traditional colloidal gold-based LFIA method 17 and lac dye coloration-based bidirectional lateral flow immunoassay strip, 40 the Cu 2− x Se-LFIA method exhibited a superior sensitivity and a linear range. Moreover, the operation process of this method was simple since it did not require an capture antibody labeling sensing carrier.…”

A review on urinary tract infections diagnostic methods: Laboratory-based and point-of-care approaches

“…The sensitivity of the tests performed with PdNPs-HRP LFTS resulted in a detection 5-10-fold higher than that of AuNPs based assays. Liu et al, developed a label-free bidirectional LFA based on antigenantibody reaction and "lac dye" coloration, without resorting to the use of nanomaterials and double antibody sandwiches, and reducing the difficulty and cost of the test [70]. Lac dye is a natural dye extracted from lac insect secretions and was firstly found by this research group to have the ability to dye E. coli O157:H7.…”

Recent Advances in Microfluidic Devices for Contamination Detection and Quality Inspection of Milk

“…Thus, the problem of developing microfluidic platforms for the on-site detection of common foodborne pathogens in milk samples has attracted great interest in the recent literature. Typically, these platforms have been designed for the detection of E. coli [ 86 , 90 , 91 , 92 , 93 ], S. aureus [ 94 , 95 , 96 ], Listeria [ 97 , 98 , 99 ], and Salmonella [ 100 , 101 , 102 , 103 , 104 ].…”

“…However, in severe cases, it can cause more serious problems such as sepsis and hemolytic uremic syndrome [ 105 ]. Various microfluidic platforms have been developed for the detection of E. coli in milk samples, including lab-on-a-chip devices combined with immunoassay [ 78 ], aptamer and fluorescence detection [ 76 ], rolling circle amplification (RCA), and fluorescence detection [ 91 ], and lab-on-paper devices based on RCA and colorimetric detection [ 105 ], colorimetric detection [ 86 , 106 ], and immunoassay [ 90 , 92 , 93 ]. Sun et al [ 105 ] developed a folding microfluidic lab-on-paper RCA device with DNAzyme-containing DNA superstructures for E. coli detection in juice and milk samples.…”