Dongqi Li, Jia Hu, Yingshu Cui, Qian Li, Xiaosong Li
Malignant tumors remain one of the most serious challenges to global health. Although chemotherapy and targeted therapy are available treatment options, their effectiveness is often limited by the complexity of the tumor microenvironment (TME). In recent years, immunotherapy has demonstrated significant potential in harnessing the immune system to combat cancer. Polymeric nanoparticles (PNPs) have emerged as versatile platforms for cancer immunotherapy, offering favorable biocompatibility, tunable size, and surface functionalization for targeted delivery. In this review, we critically evaluate PNP design strategies, emphasizing stimuli-responsive release mechanisms that enable spatiotemporally controlled drug delivery within the TME, thereby enhancing efficacy and minimizing systemic toxicity. We further highlight PNP-enabled synergistic therapies, including photodynamic, chemodynamic, and sonodynamic therapies, that induce immunogenic cell death (ICD) and potentiate antitumor immunity, as well as PNP-based vaccines (RNA, peptide, and in situ) that activate dendritic cells (DCs) and cytotoxic T lymphocytes (CTLs). Nevertheless, the clinical translation of PNP-based therapies is constrained by multiple factors, including manufacturing scalability, emulsifier-related toxicity, rapid RES clearance, inherent immunogenicity, and the heterogeneity of the TME. By bridging material engineering with immunological barriers and translational challenges, this review provides a critical framework for designing next-generation PNP immunotherapies toward personalized cancer treatment.