Hydrogel-mediated tri-modal nanoplatform for localized colorectal cancer therapy via smart chemo-photothermal-radiotherapy.

Colorectal cancer (CRC) remains difficult to eradicate locally because chemotherapy, photothermal therapy (PTT), and radiotherapy each have distinct limitations when used alone. Here, we engineer an injectable, mucoadhesive hydrogel-mediated tri-modal nanoplatform designed for localized CRC therapy by integrating smart chemotherapy delivery with externally activatable PTT and radiosensitization. Core-shell AuNP@mesoporous silica nanoparticles were loaded with 5-fluorouracil (5-FU) and functionalized with a pH/ROS-responsive linker and hyaluronic acid (HA) to enable CD44-mediated tumor targeting and microenvironment-triggered "uncapping"/drug release. The targeted nanocarriers were embedded within a chitosan/acellular fish skin (CS/AFS) hydrogel to form a local depot intended to prolong tumor-site residence and reduce systemic exposure. In vitro, the complete nine-group panel demonstrated stepwise gains from targeting, hydrogel confinement, and external activation. The tri-modal condition (Gel-tNP + 808-nm NIR + 2-Gy X-ray) produced the strongest cytotoxicity, approaching near-complete ablation in HCT-116 cells and reproducing the efficacy hierarchy in a second CRC line (SW480), while normal colon epithelial cells (NCM460) maintained higher viability across matched conditions, supporting an initial therapeutic window. Mechanistically, the tri-modal regimen generated the highest intracellular ROS levels, amplified early γH2AX DNA double-strand break signaling and increased damage persistence, and drove extensive cell death consistent with synergistic chemo-photothermal-radiotherapy action (e.g., ~ 9% viability and ~ 5.6-fold LDH release vs. control in the tri-modal group). Collectively, this work advances an engineering framework for localized, externally programmable tri-modal CRC therapy using a stimuli-responsive, HA-targeted nanocarrier embedded in an injectable bioadhesive hydrogel depot.