Determination of biological activity of human insulin by a homogeneous time-resolved fluorescence method

We developed an in-vitro bioassay for determining the bioactivity of human insulin by homogeneous time-resolved fluorescence immunoassay. CHO-INSR B1284 transgenic cells were used as target cells. Key assay parameters, including the cell density, the range of working concentrations, and the stimulation time were optimized. The specificity, relative accuracy, intermediate precision, linearity, and range of the method were validated, as well as the passage stability of the CHO-INSR B1284 cell line. The national standard of recombinant human insulin was used as the benchmark to evaluate the relative potency of insulin analogues and drugs. The drugs and the reference human insulin showed a dose-response relationship, R² > 0.995, which conforms to the four-parameter equation: y = (A - D) / 1 + (x/C)^B + D. Specificity of the method was good. The geometric mean, relative bias, and geometric coefficient of variation (GCV, %) of the five concentrations (n = 8, 64%, 80%, 100%, 125% and 156%) met the requirements of the General Rules of Chinese Pharmacopoeia, 2020 edition, Volume IV (9401). In summary, a bioassay for determining the in vitro bioactivity of human insulin based on a homogeneous time-resolved fluorescence technique was established; the method was simple, time-saving, accurate and precise, and could be used for the evaluation of biological activity and quality.