New hybrid radio-fluorescent probes [(131)I]-BPF-01 and [(131)I]-BPF-02 for visualisation of cancer cells: Synthesis and preliminary in vitro and ex vivo evaluations

We synthesised and biologically evaluated two new hybrid probes [(131)I]BPF-01 and [(131)I]BPF-02 which were built from three structural entities: benzothiazole-phenyl, fluorescein isothiocyanate (FITC), and iodine-131. These probes were designed for potential applications in assisting surgical procedures of solid cancers. The cytotoxicity study demonstrated that fluorescent probes BPF-01 (31.23 μg/mL) and BPF-02 (250 μg/mL) were relatively not toxic to normal immortalized human keratinocytes (HaCaT) cells, as indicated by the percentage of cell survival above 50 %. Furthermore, both probes displayed low to moderate anticancer activity against the breast cancer cells (MDA-MB-231) and prostate cancer cells (LNCaP and DU-145). The probe BPF-01 apparently showed an accumulation in the tumour tissues, as suggested by ex vivo fluorescence examinations. In addition, the cellular uptake study suggests that hybrid probe [(131)I]-BPF-01 was potentially accumulated in the MCF-7 cell line with the highest uptake of 16.11 ± 1.52 % after 2 h of incubation, approximately 50-fold higher than the accumulation of iodine-131 (control). The magnetic bead assay suggests that [(131)I]-BPF-02 and [(131)I]-BPF-02 showed a promising capability to interact with translocator protein 18 kDa (TSPO). Moreover, the computational data showed that the binding scores for ligands 7–8, BPF-01 and BPF-02, and [(131)I]-BPF-01 and [(131)I]-BPF-02 in the TSPO were considerably high. Accordingly, fluorescent probes BPF-01 and BPF-02, and hybrid probes [(131)I]BPF-01 and [(131)I]BPF-02 can be further developed for targeting cancer cells during intraoperative tumour surgery.