Multifunctional Nanoparticle Loaded Injectable Thermoresponsive Hydrogel as NIR Controlled Release Platform for Local Photothermal Immunotherapy to Prevent Breast Cancer Postoperative Recurrence and Metastases

For breast cancer patients who have undergone breast‐conserving surgery, effective treatments to prevent local recurrences and metastases is very essential. Here, a local injectable therapeutic platform based on a thermosensitive PLEL hydrogel with near‐infrared (NIR)‐stimulated drug release is developed to achieve synergistic photothermal immunotherapy for prevention of breast cancer postoperative relapse. Self‐assembled multifunctional nanoparticles (RIC NPs) are composed of three therapeutic components including indocyanine green, a photothermal agent; resiquimod (R848), a TLR‐7/8 agonist; and CPG ODNs, a TLR‐9 agonist. RIC NPs are physically incorporated into the thermosensitive PLEL hydrogel. The RIC NPs encapsulated PLEL hydrogel (RIC NPs@PLEL) is then locally injected into the tumor resection cavity for local photothermal therapy to ablate residue tumor tissues and produce tumor‐associated antigens. At the same time, NIR also triggers the release of immune components CPG ODNs and R848 from thermoresponsive hydrogels PLEL. The released immune components, together with tumor‐associated antigens, work as an in situ cancer vaccine for postsurgical immunotherapy by inducing effective and sustained antitumor immune effect. Overall, this work suggests that photothermal immunotherapy based on local hydrogel delivery system has great potential as a promising tool for the postsurgical management of breast cancer to prevent recurrences and metastases.