A gold-based immunochromatographic strip for the specific detection of tacrolimus in whole blood

Tacrolimus is a macrolide immunosuppressant widely used in organ transplantation. Due to the narrow treatment window, therapeutic drug monitoring of the clinical application of tacrolimus is necessary. In this study, a carboxyl group introduced at the hydroxyl or carbon positions of tacrolimus was used to couple with carrier protein to synthesize complete antigens. After screening different immunogens and coating antigens, a highly-sensitive and specific monoclonal antibody (mAb) 4C5 was obtained, with a half inhibitory concentration (IC50) value of 0.26 ng mL(-1) determined by indirect competitive enzyme-linked immunosorbent assay (ic-ELISA). A colloidal gold-based immunochromatographic strip (CG-ICS) was established to monitor tacrolimus in human whole blood based on the mAb 4C5. Through visual observation, it was found that the visual limit of detection (vLOD) and cut-off value of qualitative detection were 1.0 and 20.0 ng mL(-1), respectively. The calculated LOD (cLOD) value of quantitative detection was 0.16 ng mL(-1), and the linear range was 0.48-7.57 ng mL(-1). In addition, the results of the CG-ICS for analyzing real positive samples of human whole blood were basically consistent with those of LC-MS/MS. Therefore, the CG-ICS was suitable for rapid and accurate clinical monitoring of tacrolimus.