Tissue adhesive indocyanine green‐locking granular gel‐mediated photothermal therapy combined with checkpoint inhibitor for preventing postsurgical recurrence and metastasis of colorectal cancer

Developing effective therapy to inhibit postoperative recurrence and metastasis of colorectal cancer (CRC) is challenging and significant to reduce mortality and morbidity. Here, a granular hydrogel, assembled from gelatin microgels by dialdehyde starch and interpenetrated with in situ polymerized poly(sulfobetaine methacrylate‐co‐N‐isopropylacrylamide) (P(SBMA‐co‐NIPAM)), is prepared to load and lock Food and Drug Administration (FDA)‐approved indocyanine green (ICG) with definite photothermal function and biosafety for photothermal therapy (PTT) combining with checkpoint inhibitor. The presence of P(SBMA‐co‐NIPAM) endows granular hydrogel with high retention to water‐soluble ICG, preventing easy diffusion and rapid scavenging of ICG. The ICG‐locking granular hydrogel can be spread and adhered onto the surgery site at wet state in vivo, exerting a persistent and stable PTT effect. Combined with αPD‐L1 treatment, ICG‐locking granular hydrogel‐mediated PTT can eradicate postsurgery residual and metastatic tumors, and prevent long‐term tumor recurrence. Further mechanistic studies indicate that combination treatment effectively promotes dendritic cells maturation in lymph nodes, enhances the number and infiltration of CD8+ T and CD4+ T cells in tumor tissue, and improves memory T cell number in spleen, thus activating the antitumor immune response. Overall, ICG‐locking gel‐mediated PTT is expected to exhibit broad clinical applications in postoperative treatment of cancers, like CRC.