Self-Assembling Benzothiazole-Based Gelators: A Mechanistic Understanding of in Vitro Bioactivation and Gelation

Low molecular weight gelators (LMWGs) of chemotherapeutic drugs represent a valid alternative to the existing polymer-based formulations used for targeted delivery of anticancer drugs. Herein we report the design and development of novel self-assembling gelators of the antitumor benzothiazole 5F 203 (1). Two different types of derivatives of 1 were synthesized, formed by an amide (2) and a carbamate (3a-3d) linker, respectively, which showed potent in vitro antitumor activity against MCF-7 mammary and IGROV-1 ovarian carcinoma cells. In contrast, MRC-5 fibroblasts were inherently resistant to the above derivatives (GI₅₀ > 10 μM), thus revealing stark selectivity against the malignant cell lines over the nontransformed fibroblasts. Western blots assays demonstrated induction of CYP1A1 by 1 and its derivatives only in sensitive malignant cells (MCF-7), corroborating conservation of a CYP1A1-mediated mechanism of action. The ability to form stable gels under relatively high strains was supported by rheological tests; in addition, their inner morphology was characterized as possessing a crossed-linked nanostructure, with the formation of thick aggregates with variable widths between 1100 and 400 nm and lengths from 8 to 32 μm. Finally, in vitro dissolution studies proved the ability of hydrogel 2 to release 48% of 2 within 80 h, therefore demonstrating its ability to act as a platform for localized delivery.