Radiolabeling of Trastuzumab With Technetium‐99m [99mTc] as a Radioligand for Screening Mentha pulegium on HER‐2 Receptors

ABSTRACT The use of medicinal plants as anti‐cancer agents has attracted the attention of researchers. A method is needed for screening the anti‐cancer effects on HER‐2 receptors. In this study, a simple method based on radioligand binding studies was developed for primary screening of medicinal plants on HER‐2 receptors in vitro. Trastuzumab was conjugated to HYNIC in a chemical reaction using NHS‐HYNIC. HYNIC‐Trastuzumab was radiolabeled with [99mTc] using SnCl 2 as a reducing agent and tricine as a coligand. Biological activities of [99mTc]Tc‐HYNIC‐Trastuzumab were determined in saturation binding studies using the SKBR3 cell line. The IC 50 of Mentha pulegium was determined in competition with [99mTc]Tc‐HYNIC‐Trastuzumab on the SKBR3 cell line. Radiochemical purity was ≥ 90% ± 2.08%. Based on the results, radiolabeled Trastuzumab maintained its biological activity after labeling (immunoreactivity = 83%, K d = 7.049 ± 1.861 nM). The IC 50 of Mentha pulegium was 31.3 ± 1.3 μg/mL. [99mTc]Tc‐HYNIC‐Trastuzumab can be used as a radioligand in competition binding studies for primary screening of medicinal plants, peptides, and small molecules in vitro on HER‐2 receptors.