Bifunctional competitive antigen enhanced DLS Immunosensor for the ultrasensitive detection of furosemide in slimming products.

A bifunctional competitive antigen-enhanced dynamic light scattering (BCA-DLS) immunosensor was developed for the ultrasensitive detection of furosemide in slimming products. The bifunctional competitive antigen (Furo@BSA@GA) was synthesized by co-labeling furosemide and gallic acid with a cis-diol structure on bovine serum albumin (BSA). This innovative BCA-DLS immunosensor employs monoclonal antibody-coated magnetic nanoparticles (MNP@mAbs) as DLS probes to competitively bind the furosemide with bifunctional competitive antigen. Then, the polyvalent phenylboronic acid-labeled bovine serum albumin (PBA@BSA) further triggers the aggregation of the MNP@mAbs and Furo@BSA@GA complex, and the variation in the hydrodynamic diameter of the DLS probe is inversely proportional to the concentration of furosemide. The highly efficient boronate-affinity interaction between PBA@BSA and Furo@BSA@GA significantly reduces the detection time to 25 min and significantly improves the sensitivity of the DLS immunosensor, achieving a detection limit of 196.33 fg mL-1, which is 1251 times lower than that of traditional enzyme-linked immunosorbent assays.