Nanogel delivered benzimidazole-triazole hybrids as potent multitarget inhibitors of topoisomerase and tubulin in triple-negative breast cancer.

Breast cancer remains a major therapeutic challenge due to poor selectivity, multidrug resistance, and systemic toxicity of conventional chemotherapeutics. Here, we report the design, synthesis, and nanogel-based delivery of benzimidazole-triazole hybrids (HSRA1,2, and 3) for targeted anticancer therapy. Structurally, HSRA1 is a bis-N/S-triazole amide bearing fluorinated aromatic substituents, HSRA2 incorporates a methyl-substituted nucleoside-like triazole, while HSRA3 is a minimal S-triazole amide scaffold. Chitosan/polyvinyl pyrrolidone (Cs/PVP) nanogels encapsulated these compounds efficiently, yielding spherical nanoparticles of 230-275 nm with narrow PDI (<0.3). Nanogel encapsulation significantly enhanced cytotoxic potency against MDA-MB-231 triple-negative breast cancer cells, reducing IC₅₀ from 18.1 to 66.1 μM (free drugs) to 3.5-6.9 μM (NGs). SAR analysis highlighted that the bis-triazole substitution in HSRA1 confers optimal polarity, hydrogen-bonding, and π-π stacking, driving superior anticancer activity and selectivity (SI ≈ 10). HSRA2 showed moderate activity linked to sterically hindered nucleoside-triazole substitution, while HSRA3 remained less potent due to insufficient electronic and steric contributions. Mechanistic studies confirmed G0/G1 arrest and apoptosis induction, while enzymatic assays established HSRA1 as a strong dual topoisomerase I/II (>70% inhibition) and tubulin polymerization inhibitor (∼48%). Docking revealed that HSRA1 retains key interactions with ASP533 and LYS532 of Topo I, although it misses binding to ARG364. Collectively, these results identify HSRA1 nanogel as a multitarget, structurally optimized anticancer candidate with superior potency, tumor selectivity, and safety compared to its free form and reference agents.