Figure 1
Schematic illustration of the design of the mammalian biosensor system. The approach combines the amplification features of LAMP with the visual detection on a LFD to screen and identify mammals or red meat within processed meats rapidly. Generally, mammalian include the red meat, so that the mammalian was drawn in red with pictorial diagram. By contrast, other species was presented in dark blue diagram. Genomic DNA was analyzed to seek the endogenous reference gene, and used to determine the specificity, allelic variation and sensitivity by LAMP. For LAMP approach, in the presence of mammalian, FITC- and BIO-labeled products were obtained by modified primers. And there were only free labelled-primers in the closed tube in absence of mammalian. For LFD strategy, Anti-biotin-labeled Au-NPs, anti-FITC antibodies and secondary antibody were pre-immobilized on the conjugate pad, test line (T) and control line (C) of the LFD, respectively. Then, the products with running buffer were applied on the sample application pad of LFD. Typically, when the solution with double-labelled products migrates by capillary action and passes the conjugate pad, the biotin on the products and primers reacted with the anti-biotin on the Au-NP surface to form a DNA-biotin–anti-biotin–Au-NP complex and continued to migrate along the strip. Then the positive complexes were captured on the test line by the immunoreactions between anti-FITC on the test line and the FITC in the positive complexes. The accumulation of Au-NPs is visualized as a characteristic red band on test line. The excess anti-biotin–Au-NPs continued to move and were captured on the control line by immunoreactions between the secondary antibody and anti-biotin on the Au-NPs, forming another red band. In the absence of mammalian, there was no dual-labeled product in the solution; therefore, no anti-biotin–Au-NP conjugate was captured on the test line of the LFD, and no red band was observed on the test line. For this method, a red band on the control line showed that the LFD was working properly.
