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Immunotherapy as an alternative treatment strategy for B-cell lymphoma is undesirable because of tumor heterogeneity and immune surveillance. Spermidine (SPM), as a regulator of the tumor microenvironment (TME), can facilitate the release of damage-associated molecular patterns (DAMPs) from cancer cells, promote immune recognition, and thus alleviate immune surveillance in the TME. Hence, in this work, self-assembled spermidine-based metal-immunopeptide nanocomplexes (APP-Fe NCs; APP is anti-programmed death ligand-1 peptide) with pH-responsive release kinetics were prepared via the flash nanocomplexation (FNC) technique based on the noncovalent interaction between APP-SPM-dextran (DEX) and sodium tripolyphosphate (TPP) and coordination between Fe3+ and TPP. An in vitro study suggested that APP-Fe NCs effectively induce strong oxidative stress and mitochondrial dysfunction and subsequently lead to ferroptosis in cells by interfering with homeostasis in lymphoma cells. Further investigation on lymphoma mice models demonstrated that APP-Fe NCs effectively inhibited the growth and liver metastasis of lymphomas. Mechanistically, by triggering ferroptosis in tumor tissues, these spermidine-containing APP-Fe NCs efficiently facilitated the release of DAMPs and ultimately reshaped TME to enhance immunotherapy efficacy in lymphoma. Combined with its good histocompatibility and facile preparation technique, this pH-responsive APP-Fe NCs with regulation on TME may hold potential for cascade amplification on the combinative immunotherapy of lymphoma in the clinic.

Poly(disulfide)s-based systems with repetitive disulfide bonds in their backbones are emerging as promising tumor microenvironment responsive platforms for drug delivery. However, complicated synthesis and purification processes have restricted their further application. Herein, we developed redox-responsive poly(disulfide)s (PBDBM) by one-step oxidation polymerization of a commercially available monomer, 1,4-butanediol bis(thioglycolate) (BDBM). PBDBM can self-assemble with 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-poly(ethylene glycol)(3400) (DSPE-PEG(3.4k)) by the nanoprecipitation method and be formulated into PBDBM NPs (sub 100 nm). It can also be loaded with docetaxel (DTX), a first-line chemotherapy agent for breast cancer, to form DTX@PBDBM NPs with a loading capacity of 6.13%. DTX@PBDBM NPs with favorable size stability and redox-responsive capability exhibit superior antitumor activity in vitro. In addition, owing to the different glutathione (GSH) levels in normal and tumor cells, PBDBM NPs with disulfide bonds could synergistically increase intracellular ROS levels, further inducing apoptosis and cell cycle arrest in the G2/M phase. Moreover, in vivo studies revealed that PBDBM NPs could accumulate in tumors, suppress 4T1 tumor growth, and significantly attenuate the systemic toxicity of DTX. Thus, a novel redox-responsive poly(disulfide)s nanocarrier was successfully and facilely developed for cancer drug delivery and effective breast cancer therapy.