This kit employs a solid-phase enzyme-linked immunosorbent assay (ELISA) utilizing a double-antibody sandwich technique to quantify residual host cell proteins (HCPs) originated from the CHO-K1 cell line.

A sheep polyclonal antibody specific to CHO-K1 HCPs was employed in the assay to capture any remaining HCPs in the samples. Calibration standards or test samples, along with the HRP-labeled anti-CHO-K1 HCP antibody, were simultaneously added to the microtiter plate pre-coated with the affinity purified capture antibody, and followed by incubation and washing. TMB (3,3',5,5'-tetramethylbenzidine) substrate was added into the reaction, catalyzed by the HRP oxidation to produce a blue-colored product (maximum absorption peak at 655 nm). Then the stop solution was added to terminate the enzymatic reaction, resulting in a yellow-colored product (maximum absorption peak at 450 nm). The absorbance values at 450 nm wavelength was positively correlated with the HCPs concentration in the calibration standard and the samples. The concentration of HCPs in the samples can be calculated using a dose-response curve.