The site-directed modification of nanobodies through a genetic engineering technology for the fluorescent test strip...

The lateral flow immunochromatography assay (LFIA) offers a rapid and on-site method for food safety. However, the current LFIA shows a limitation due to the random binding between the label and antibodies resulting in target recognition sites on the antibody being occupied yielding false-negative outcomes. To address these issues, this study utilized genetic engineering technology to integrate the super folded green fluorescent protein (SGFP) gene into the sequence of a specific nanobody for fenpropathrin, a Nb-SGFP fluorescent probe, realizing site-directed modification to avoid the block of recognition sites. Meanwhile, it also minimizes potential antibody performance issues during the process that may affect antibody affinity. Based on this, a fluorescent strip detection method was established, providing a new strategy for efficient and convenient detection of fenpropathrin. The detection limit of the method was 1.2 ng mL^-1, which adequately met the sensitivity requirements for fenpropathrin detection. To validate its accuracy, the fluorescent test strip method was compared with GC-MS/MS analysis. The strong correlation between the two methods confirms that our approach enables rapid detection of fenpropathrin residues in fruits and vegetables.