Analgesic and potentiated photothermal therapy with ropivacaine-loaded hydrogels

Rationale: Tumor ablation can cause severe pain to patients, but there is no satisfactory means of analgesia available. In addition, recurrence of residual tumors due to incomplete ablation threatens patient safety. Photothermal therapy (PTT), a promising approach for tumor ablation, also faces the aforementioned problems. Therefore, developing novel photothermal agents that can efficiently relieve PTT-associated pain and potentiate the PTT efficacy are urgently needed. Methods: The Pluronic F127 hydrogel doped with indocyanine green (ICG) was served as photothermal agent for PTT. Mouse model that inoculation of tumor near the sciatic nerve was constructed to assess the PTT-evoked pain. Subcutaneous and sciatic nerve vicinal tumor-bearing mice were used to test the efficacy of PTT. Results: PTT-evoked pain depends on an increase in tumor temperature and is accompanied by the activation of TRPV1. A simple introduction of local anesthetic (LA) ropivacaine into ICG-loaded hydrogels relieves PTT-induced pain and exerts long-lasting analgesia compared with opioid analgesia. More interestingly, ropivacaine upregulates major histocompatibility complex class I (MHC-I) in tumor cells by impairing autophagy. Therefore, a hydrogel co-doped with ropivacaine, TLR7 agonist imiquimod and ICG was rationally designed. In the hydrogel system, imiquimod primes tumor-specific CD8⁺ T cells through promoting DCs maturation, and ropivacaine facilitates tumor cells recognition by primed CD8⁺ T cells through upregulating MHC-I. Consequently, the hydrogel maximumly increases CD8⁺ T cells infiltration into tumor and potentiates PTT efficacy. Conclusion: This study for the first time provides an LA-dopped photothermal agents for painless PTT and innovatively proposes that a LA can be used as an immunomodulator to potentiate the PTT efficacy.