Hierarchical pluronic F127-chitosan hydrogel embedding gallium-doxorubicin co-loaded nanocapsules enables dual-responsive release and apoptosis in triple-negative breast cancer cells.

Localized chemotherapy is hampered by rapid clearance, systemic toxicity, and poor tumor retention, motivating depots that maintain site-specific exposure. We introduce a hierarchical nanocapsule-in-hydrogel platform built from chitosan conjugated to Pluronic F127 derivatives for co-delivery of doxorubicin (DOX) and gallium nitrate (Ga(NO₃)₃). Succinic-acid-modified F127-chitosan (SAF-C) self-assembles into ∼34 nm nanocapsules, while alanine-modified F127-chitosan (ADF-C) forms an injectable, thermogelling network via covalent crosslinking. Embedding SAF-C within ADF-C yields a dual-responsive depot that suppresses burst release and enables staged, pH- and temperature-sensitive delivery: proton-labile coordination accelerates Ga³ ⁺ release, whereas DOX follows diffusion-limited kinetics, extending liberation from hours to days. Both carriers show high in-vitro biocompatibility (>90 % viability in NIH-3T3, HeLa, and 4T1). In 4T1 triple-negative breast cancer cells, the depot sustains apoptotic signaling and reduces viability to < 10 %, while free DOX or Ga³ ⁺ cause transient necrosis with partial recovery. Fluorescence imaging reveals delayed yet enhanced nuclear DOX accumulation and intracellular Ga³ ⁺ retention, indicating spatiotemporal synergy between gallium's metabolic interference and DOX-mediated DNA damage. By biasing cell death toward apoptosis over necrosis, this nanocapsule-in-hydrogel platform offers a generalizable design principle for localized multi-agent delivery.