An enzyme immunoassay for serum tobramycin.

A heterogeneous enzyme immunoassay for serum tobramycin was developed using tobramycin-beta-D-galactosidase conjugate as the labelled antigen and 4-methylumbelliferyl-beta-D-galactoside as the fluorescence substrate. B/F separation was carried out using an immobilized second antibody, Immunobead. The minimal detectable level was 10 pg/tube or 0.2 microgram/ml of serum. Assay recovery was excellent and the intra-assay and inter-assay variances were 4.41% and 12.6%, respectively. The values from the enzyme immunoassay agreed well with those from radioimmunoassay and bioassay. This assay system is highly sensitive and can be easily applied to other drugs and hormones.