Schematic overview of the STNPCR-LFBA principle for detecting <i>Alternaria panax</i> Whetz.

(A) Using the target DNA template, PCR amplification using the external primer pair (F1 and R1) will generate a PCR product that will be used for amplification by the inner primer pair (F2 and R2) in a single tube. The labeled single-stranded PCR product is hybridized with the labeled probe to form a nucleic acid hybridization complex (labeled with Biotin and Fam). (B) After placing the solution of the hybridization complex onto the sample pad of the biosensor, driven by the running stream, this complex is bound to a colloidal gold particle-streptavidin particles (AuNPs-SA) on the conjugate pad of the biosensor, followed by migrated further with the buffer stream, and the sample is trapped by the mouse anti-Fam antibody on the test line (T line) of the biosensor, the T line turns red. The excess unbound AuNPs-SA migrated and it can be captured by biotin on the control line (C line). The result is positive when both the T and C lines are red. The result is negative if only the C line is red.