The development of a multi-nitroimidazole residue analysis assay by optical biosensor via a proof of concept project to develop and assess a prototype test kit.

An assay based on optical biosensor technology has been developed to detect a broad range of nitroimidazole drug residues and their metabolites (dimetridazole (DMZ), metronidazole (MNZ), ronidazole (RNZ), hydroxymetronidazole (HO-MNZ) and hydroxydimetridazole (HO-DMZ)) in chicken muscle. The detection limit for the procedure was determined as 0.5 ppb for DMZ and detection capabilities (CCbetas) ranged from <1 ppb for DMZ, MNZ and RNZ to <2 ppb for HO-MNZ and HO-DMZ. Intra-assay variation (n=6) was calculated as 11.6% at a concentration of 1 ppb DMZ and 4.7% at a concentration of 2 ppb DMZ. Inter-assay variation (n=3) was determined to be 14.2% at a concentration of 1 ppb DMZ and 3.5% at a concentration of 2 ppb DMZ. A prototype kit based on this assay was produced and a multinational study was undertaken to independently evaluate its performance. The resulting data showed that the kit can be implemented with little difficulty in laboratories of varying expertise and is sensitive enough to meet the standards required by international law. Feedback from this study led to the incorporation of some minor improvements to the kit. The commercial partner in the project, XenoSense Ltd., was consulted with regards to producing a commercial test kit based on the prototype assay. As feedback from the collaborative study had been positive with respect to speed, ease of use and performance of the kit, the decision to commercialise the kit was taken. In conclusion, the prototype nitroimidazole kit was shown to offer numerous advantages over existing analytical techniques.