Detection of Wild-Type Hypoxanthine Guanine Phosphoribosyl Transferase of Lymphocytes in Gamma-Irradiated Mice with Surface Plasmon Resonance

A quick and sensitive detection of the wild-type hypoxanthine guanine phosphoribosyl transferase (HPRT), which is known as a biomarker for radiation exposure, was developed. The conventional HPRT measurement technique is to detect the mutant HPRT, which is time-consuming and has low sensitivity. In this study, the wild-type HPRT was detected as a gamma radiation biomarker using a surface plasmon resonance (SPR) biosensor with 6-thioguanine (6-TG) as a probe and the anti-HPRT antibody as a signal amplification factor. First, we used this system to measure the wild-type HPRT dissolved in PBS. Six-TG immobilized on the surface can specifically detect the wild-type HPRT, and the anti-HPRT antibody enhances about 10 times the primary signal produced by the binding of the wild-type HPRT with 6-TG. A linear relationship (r = 0.991) was obtained between the concentration of the wild-type HPRT and the enhanced signal. The low detection limit (LDL) is 2.1 ng/mL. The regeneration using glycine-HCl was also investigated. Six-TG immobilized on the surface can be used in 9 injection-regeneration cycles. The relative standard deviation (RSD) of baseline changes after regenerations is 2.8%. The applicability of the method to real samples has been demonstrated with comparative analyses of lymphocyte extracts in gamma irradiated and unirradiated mice. The irradiated sample displays a significantly lower level of the wild-type HPRT compared to that in the unirradiated sample. The single sample detection only needs about 20 min. Thus, the SPR biosensor could potentially serve as an attractive technique for rapid and sensitive detection of the wild-type HPRT, a gamma radiation biomarker.