A solid-phase fluoroimmunoassay of tobramycin.

A solid-phase fluoroimmunoassay has been developed for the determination of tobramycin in serum. The principle of this method is based on direct competition of a fluorescein-labeled and unlabeled hapten for a fixed amount of specific antibody immobilized on a dipstick sampler. The bound and free labeled hapten are separated simply by removing the sampler from the reaction mixture. The fluorescence signal from the bound fluorescein-labeled hapten is measured with a FIAX fluorometer. The fluorescein-labeled tobramycin, which is easily prepared, has excellent shelf life. The assay is fast and simple, involves only one pipetting step, and avoids the use of radiochemicals. Within-assay coefficients of variation are less than 10%. The assay correlates well with radioimmunoassay (r = 0.97) and radioenzymatic assay (r = 0.96).