Lateral Flow Assay-Based Rapid Detection of Cephalexin in Milk

Abstract

A rapid and semiquantitative lateral flow assay has been developed for detection of cephalexin (CFX) in milk. The assay is based on a competitive format using polyclonal antibodies. Antibodies were raised in rabbits against CFX-keyhole limpet hemocyanin. The specificity of antibodies was ascertained by direct enzyme-linked immunosorbent assay. The laboratory prepared gold nanoparticles coupled to anti-CFX antibodies, which competed for free CFX in sample and CFX-bovine serum albumin conjugate on the test line of a lateral flow strip. The control line of the lateral flow strip consisted of species-specific antibody. The assay was validated with spiked milk samples and involved application of skim milk to the adsorbent pad followed by visualization of red color on test and control lines within 8min. The lower detection limit of CFX was 30ppb in milk, which is lower than the Codex prescribed maximum residue limit. The storage stability of the prepared strip was also established.