An Immune‐Enhancing Injectable Hydrogel Loaded with Esketamine and DDP Promotes Painless Immunochemotherapy to Inhibit Breast Cancer Growth

Abstract Chemotherapy is the cornerstone of triple‐negative breast cancer. The poor effectiveness and severe neuropathic pain caused by it have a significant impact on the immune system. Studies confirmed that immune cells in the tumor microenvironment (TME), have critical roles in tumor immune regulation and prognosis. In this study, it is revealed that the painless administration of Esketamine, combined with Cisplatin (DDP), can exert an anti‐tumor effect, which is further boosted by the hydrogel delivery system. It is also discovered that Esketamine combined with DDP co‐loaded in Poloxamer Hydrogel (PDEH) induces local immunity by increasing mature Dendritic Cells (mDCs) and activated T cells in PDEH group while the regulatory T cells (Tregs) known as CD4 + CD25 + FoxP3 + decreased significantly. Finally, , CD8 + and CD4 + T cells in the spleen exhibited a significant increase, suggesting a lasting immune impact of PDEH. This study proposes that Esketamine can serve as a painless immune modulator, enhancing an anti‐tumor effect while co‐loaded in poloxamer hydrogel with DDP. Along with improving immune cells in the microenvironment, it can potentially alleviate anxiety and depression. With its outstanding bio‐safety profile, it offers promising new possibilities for painless clinical therapy.