Rapid screening test for detection of oxytetracycline residues in milk using lateral flow assay

- A semi-quantitative lateral flow assay (LFA) was developed to detect the oxytetracycline antibiotics residues in milk samples.
- For the first time membrane components required for LFA in milk system was optimized and reported.
- This method can be used as a screening assay for oxytetracycline residues in milk at all the level of milk supply.
- This method is sensitive enough to detect 30 ppb oxytetracycline in milk, which is much lower than the Codex prescribed maximum residue limit.

A rapid, semi-quantitative lateral flow assay (LFA) was developed to screen the oxytetracycline (OTC) antibiotics residues in milk samples. In this study a competitive immuno-assay format was established. Colloidal gold nano-particles (GNP) were prepared and used as labelling material in LFA. Polyclonal antibodies were generated against OTC molecule (anti-OTC), purified and the quality was assessed by enzyme linked immuno sorbet assay. For the first time membrane components required for LFA in milk system was optimized. GNP and anti-OTC stable conjugate preparation method was standardized, and then these components were placed over the conjugate pad. OTC coupled with carrier protein was placed on test line; species specific secondary antibodies were placed on the control line of the membrane matrix. Assay was validated by spiking OTC to antibiotic free milk samples and results could be accomplished within 5 min. without need of any equipment. The visual detection limit was 30 ppb.