Fluorescein-Labeled Thiacalix[4]arenes as Potential Theranostic Molecules: Synthesis, Self-Association, and Antitumor Activity

In this paper, a series of thiacalix[4]arenes were synthesized as potential theranostic molecules for antitumor therapy. We propose an original strategy for the regioselective functionalization of thiacalix[4]arene with a fluorescent label to obtain antiangiogenic agent mimetics. The aggregation properties of the synthesized compounds were determined using the dynamic light scattering. The average hydrodynamic diameter of self-associates formed by the macrocycles in 1,3-alternate conformation is larger (277–323 nm) than that of the similar macrocycle in cone conformation (185–262 nm). The cytotoxic action mechanism of the obtained compounds and their ability to penetrate into of human lung adenocarcinoma and human duodenal adenocarcinoma cells were established using the MTT-test and flow cytometry. thiacalix[4]arenes in 1,3-alternate conformation did not have a strong toxic effect. The toxicity of macrocycles in cone conformations on HuTu-80 and A549 cells (IC(50) = 21.83–49.11 µg/mL) is shown. The resulting macrocycles are potential theranostic molecules that combine both the pharmacophore fragment for neoplasmas treatment and the fluorescent fragment for monitoring the delivery and biodistribution of nanomedicines.