OPEN ACCESS Jacobs Journal of Nanomedicine and Nanotechnology Establishment of a Highly Specific Enzyme Immunoassay for Digoxin in Human Serum

We previously developed a radioimmunoassay for digoxin using an antiserum raised against digoxin 3’-hemisuccinate -bovine serum albumin. In the present study, we aimed to establish an enzyme immunoassay (EIA) for measuring serum digoxin level in patients, using digoxin 3’-hemisuccinate-β-D-galactosidase as an enzyme-labeled antigen. The developed enzyme immunoassay showed a quantification range of 0.2 to 10 ng/ml and exhibited high specificity for digoxin, with low levels of cross-reaction to dihydrodigoxin (12.3%), digitoxin (7.84%), digoxigenin bisdigitoxoside (0.31%), digoxigenin monodigitoxoside (0.19%), and digoxigenin (0.05%). Compared with a commercial anti-digoxin antiserum clinically used to monitor digoxin concentration in human serum, our antiserum showed much higher specificity for intact digoxin. Intra-assay and inter-assay variations were less than 9.3% and 8.8%, respectively. Recovery was within the range of 96.0 -105.0%. Mean digoxin concentrations measured in serum samples (n=42) from digoxin-treated patients by EIA using the new antiserum and the commercial anti-digoxin antiserum were 1.26 and 1.39 ng/ml, respectively. The present EIA, which is superior to RIA in terms of convenience and disposal of waste materials, is expected to be practically useful to monitor intact digoxin in human serum.