Highly sensitive nano-ELISA for detecting 19-nortestosterone in beef

It is challenging to achieve a highly sensitive enzyme-linked sorbent immunoassay (ELISA) method for rapid screening 19-nortestosterone (19-NT) residue in animal tissues. This paper demonstrated that utilising a bioconjugate of gold nanoparticles and enzyme-labelled antibodies as signal probe have increased the sensitivity of a traditional ELISA for 19-NT by 10 times. The sensitivity of this ELISA was 0.01 ng/mL in buffer and the detection limit (LOD) of 0.3 µg/kg could be obtained after the beef samples were simply pre-treated. This new method was facile and has the potential application for improving the sensitivity of ELISA methods against various small molecular contaminants.