Due to the complexity of tumor pathology, the demand for the combined use of multiple drugs in clinical treatment has become increasingly clear-cut. Multi-drug combination can act on multiple pathways and multiple targets simultaneously to exert synergistic effects. However, the current delivery strategy for multi-drug combination still needs to be optimized. Nano-drug delivery systems can carry drugs to overcome physiological and pathological barrier to target tumor tissues and cells, achieve the goal of continuous, controllable, and targeted delivery, and enhance the efficacy of anti-tumor synergism and detoxification. To meet the new requirements for smarter and more accurate antitumor multi-drug combinational therapy, the nano-drug delivery system has been well-designed to realize more functions. For instance, delivery of multiple drugs in accurate proportions and doses can make the multi-drug synergistic effect more precise; stimulus-responsive drug release can improve selectivity and reduce side effects; controlling the time-course relationship of multiple drugs can realize sequential drug combination effect. It has shown broad prospects in the field of tumor multidrug therapy and has become one of the new directions of research and development. This article reviews the recent developments in the application of tumor drug combination therapy strategies and their delivery systems, and analyzes the new requirements and challenges of multidrug combination for the development of nano-drug delivery systems.

Tumor immune checkpoint therapy is a clinical treatment strategy developed based on the new principle of the inhibition of negative immune regulation. In this article, the tumor immune checkpoint therapy and the drug delivery strategies were reviewed, mainly including immunity and tumor therapy, tumor immune checkpoint therapy and its mechanism of action, clinical application of tumor immune checkpoint therapy and therapeutic drugs, immune resistance of programmed cell death protein 1 (PD1)/programmed cell death ligand 1 (PDL1) treatment and countermeasures, drug delivery strategies for tumor immune checkpoint therapeutic agents, etc. As a revolutionary new immunotherapy strategy, tumor immune checkpoint therapy has shown obvious superior therapeutic efficacy in a variety types of tumor. However, tumor immune checkpoint therapy is also faced with a big challenge, namely, immunotherapy resistance. With the discovery of new mechanism, the continuous development of new therapeutic drugs and delivery strategies, tumor immune checkpoint therapy is expected to further improve the clinical efficacy of tumor.

Polydopamine (PDA) is a novel type of polymer synthesized inspired by adhesion proteins in mussels. It has been widely used in tumor-targeting drug delivery systems due to its natural advantages such as good biocompatibility, excellent photothermal conversion performance, adhesion, high chemical reactivity and multiple drug release response mechanisms. This review summarizes the applications of PDA-based tumor-targeting drug delivery in recent years, hoping to provide references for designing a more reasonable and effective PDA-based multifunctional collaborative tumor therapy platform.

At present, cancer is still one of the most serious threats to human health. Despite the wide application of multiple cancer therapies in clinical practice, the therapeutic effects of most cancers are still far from satisfactory. In recent years, the discovery of regulated cell death may be a good first step on the road to treat cancer. Ferroptosis is triggered by lipid peroxidation of unsaturated fatty acids in cell membrane catalyzed by iron ion. It has been widely concerned as an emerging target for cancer therapy. With the booming of biomedical nanotechnology, ferroptosis as an emerging therapeutic target has attracted extensive attention. Here, we review the advance on the intersection of ferroptosis and biomedical nanotechnology. First, the research background of ferroptosis and nano-preparation as well as the feasibility of ferroptosis-based nano-drug delivery systems (nano-DDS) for cancer treatment are presented and analyzed. Then, the strategies for inducing ferroptosis based on nano-DDS are summarized, mainly including: the promotion of Fenton reaction, the inhibition of glutathione peroxidase 4 (GPX-4) and the restriction of the cysteine-glutamate exchange transporter (system Xc^-). Furthermore, the combination therapy strategies based on biomedical nanotechnology induced ferroptosis are also discussed. Finally, we shine the spotlight on the prospects and challenges of ferroptosis-based nanotherapeutics in clinical application.

In recent years, immunotherapy has made great progress in clinical cancer therapy. However, the poor tumor specificity, low intra-tumoral penetration, and low cellular uptake in the systemic delivery of immunotherapeutic drugs lead to low efficacy and poor safety, limiting the development of immunotherapy. Active tumor-targeting nano drug delivery systems (aNDDS) can enhance the concentration of drugs in target cells through the interaction between surface-conjugated antibodies or ligands and the receptors on target cell membranes, providing a viable strategy for specific and efficient drug delivery. In addition, some specific types of cell membranes with the natural targeting ability have been exploited for the construction of biomimetic nanocarriers to improve the drug delivery efficiency. In view of the many advantages of active tumor-targeting nanocarriers, researchers also have designed a series of aNDDS for promoting antitumor immune responses and proved that they improved the efficacy and safety of immunotherapy. In this review, we summarize the recent progress on aNDDS for improving the tumor immunotherapy and look forward to the main challenges and future directions in this field.

As a basic amino acid, histidine has a pK_a close to the acidity of the tumor microenvironment, thus the charge and solubility of histidine are able to vary as the pH changes. Under a neutral environment, histidine is not charged and exhibits hydrophobic properties, while it can be protonated and becomes hydrophilic when exposed to mildly acidic pH, such as tumor microenvironment. Therefore, histidine is widely used in the design of drug delivery systems to target the mildly acidic pH of tumor microenvironment. This article reviews the recent progresses of histidine-based tumor-targeting drug delivery systems, and summarizes the principles on promoting internalization and tuning drug release by taking advantage of histidine. Finally, we point out the common issues on histidine application and illustrate its future prospects.

Endoplasmic reticulum (ER), a multifunctional organelle in eukaryotic cells, is responsible for protein synthesis and intracellular signal transduction, which dominates cell function, survival, and apoptosis. Disequilibrium of ER homeostasis may induce ER stress, which closely intertwines with tumor occurrence and progress. A few clinical-used drugs (such as anthraquinones and oxaliplatin) can mediate the immunogenic cell death of tumor cells through excessive ER stress, and sequentially stimulate anti-tumor immune responses as well as long-term immune memory. However, these drugs often exhibit poor targeting ability and extremely low ER accumulation in tumor cells, limiting their clinical efficacy. Therefore, the researches of ER-targeted delivery of these drugs will significantly benefit the efficient and precise anti-tumor immunotherapy. In this review, we introduce the relationship between ER and tumor immunity, and summarize the ER targeting strategies for anti-tumor immunotherapy in recent years. Furthermore, we discuss the problems of existing ER targeting strategies and look into its broad prospects of application.

The development of nanotechnology has made it possible to develop safe, efficient, precise and controllable drug delivery system (DDS). Among them, organic or inorganic synthetic nanocarriers have been widely reported and used for the delivery of tumor therapeutic agents. However, some of carriers have several problems, such as easily eliminated by the body's immune system, difficult to preparation or poor safety in vivo. In recent years, with the development of biomedicine, biomimetic technology based biomembrane-mediated nanodrug delivery has organically integrated the low immunogenicity of natural biomembrane, cancer targeting, and the controllable and multifunctional of smart nanocarrier design. It will achieve a new breakthrough of nanotechnology in cancer targeted therapy. Based on the recent advances of cell membrane-derived biomimetic nanotechnology and the nanomedicine in the field of cancer therapy, this review discusses the three aspects including the experimental basis of cell membrane-derived biomimetic nanotechnology, the classification of biomimetic nanodrug delivery platforms, and the application in cancer targeted therapy. Therefore, the review will provide reference for the design of smart drug delivery system and its development in cancer targeted treatment.

Tumor microenvironment (TME) is composed of abnormal tumor vasculature, extracellular matrix components, endothelial cells, pericytes, tumor associated fibroblasts, smooth muscle cells and immune cells, which is characterized by hypoxia, acidosis and high interstitial fluid pressure. Hypoxia and acidosis within the TME trigger an adjustment of the extracellular matrix (ECM), a response from neighbor stromal cells (e.g., fibroblasts) and immune cells (lymphocytes and macrophages), inducing tumor growth, angiogenesis, and ultimately, resulting in metastasis. What's more, the components of TME including abnormal tumor vasculature, rich composition of the ECM, and abundant stroma cells impair tumoral distribution and penetration of the drugs. At the same time, this stromal microenvironment plays a vital role in creating an immunosuppressive environment.Over the past years, more and more researches focus on targeting and remolding TME to improve therapeutic effects against tumors. Herein, we reviewed current strategies developed to target and remodel TME, including modulating tumor hypoxia, tumor vasculature, tumor associated fibroblasts, extracellular matrix components, tumor associated macrophage phenotypes and dendritic cells. Also, potential problems and future directions are pointed out in this review.

Cancer is considered as one of the major diseases endangering human health in the world, it is urgent to find a safer and more efficient treatment for cancer therapy. Gene therapy with ribonucleic acid (RNA) drugs could regulate the expression of tumor related genes, and exhibit good anti-tumor therapeutic potential in preclinical and clinical trials. Based on the differences between tumor tissues and normal tissues in microenvironment signal characteristics such as pH, specific enzyme concentration or redox gradient, various microenvironment responsive nanocarriers had been studied and developed to deliver RNA drugs to tumor tissues and cells, improving the anti-tumor efficacy of RNA drugs and reducing toxic and side effects. This paper reviews the pathophysiological characteristics of tumor microenvironment and various strategies of tumor microenvironment responsive nanocarriers, in order to provide reference for the design of safe and efficient RNA drug delivery system for cancer therapy.

Natural killer (NK) cells, as an essential part of innate immunity, can directly identify and kill tumor cells after being activated by the synergistic action of surface inhibitory receptors and activated receptors. It can secrete cytokines to recruit dendritic cells (DCs), induce DCs maturation and enhance adaptive immune response. It can target cancer stem cells (CSCs) and circulating tumor cells (CTCs) to inhibit cancer metastasis. NK cells have a unique inflammatory tendency, which can respond to cytokines and chemokines released from tumor sites and migrate to tumor sites, making them occupy an important advantage in cancer targeted therapy. The research on cancer targeted therapy of NK cells as drug delivery carriers, NK cell membrane-coated biomimetic nanoparticles, and NK cell extracellular vesicles (NKEVs) has attracted more and more attention. The article will focus on the mechanism of NK cells inhibiting cancer, and summarize the research progress of cancer targeted therapy of NK cells.

Nanotechnology has shown broad application prospects in the diagnosis and treatment of cancer. Currently, nearly 80 cancer nanomedicines are under clinical investigation, and many have been approved with enhanced anti-tumor efficacy and decreased side effects. However, the presence of various barriers in related basic research, process control and clinical trials lead to extremely low translation rate. From the perspective of clinical commercialization, we summarized the progress, clinical status, challenges and opportunities of cancer nanomedicine, and presented a cutting-edge prospect on the rational design of nanomedicine and clinical trial strategies.

Vaccination is an effective way to reduce the morbidity and mortality of infectious diseases. As a needle-free transcutaneous immunization (NF-TCI) vaccination technology, microneedles (MNs), composed of multiple micro-needles orderly attached to a substrate, can overcome the problems of low immune efficiency, poor compliance and waste of resources that exists in the conventional vaccination by injection, thus becoming a research hotspot in biomedicine. The microneedle vaccine can directly break through the stratum corneum barrier of the skin without touching nerves and blood vessels in the dermis, and effectively delivers the vaccine to the immune cells in the skin tissue to initiate the immune response of the body, thus triggering strong humoral and cellular immune processes. Vaccine delivery via the MNs system possesses the advantages of high safety, satisfying immune effect and practical economy, and shows great prospect in the prevention and treatment of infectious diseases and antineoplastic therapy. This article reviews the development background of MNs in transcutaneous immunization, the types of vaccine delivery, the factors affecting the immune effect, the problems to be solved and development direction in the future.

Exosomes are one of the most important ways of cell-to-cell communication in living lives. They are involved in major physiological and pathological processes, including drug resistance, infection propagation, cancer development and cardiovascular diseases. The biological functions of exosomes made it possess characteristics of low immunogenicity, high delivery efficiency, ability to cross multiple biological barriers and targeting capacity, which also encourage people to try to use it as a drug carrier to overcome the disadvantages of poor stability, low solubility, low bioavailability and high toxicity of some drugs. In this paper, the latest progress of exosomes in the delivery of antitumor drugs, including small chemotherapeutic drugs, biological macromolecules and nucleic acid drugs, is reviewed. In addition, the isolation, drug loading, and modification method and the application prospect of exosomes are also discussed.

The neonatal Fc receptor (FcRn) was first found to be a membrane protein that maternal antibodies transmitted to fetuses and newborns, and also expressed in multiple organs and tissues for whole life in adults. It plays a significant role to central regulate the lifespan of immunoglobulin G and serum albumin, as well as its involvement in innate and adaptive immune responses. In modern biopharmaceuticals, FcRn is a great potential drug delivery target and a highlighted subject for current research. This paper briefly describes the basic biological properties and action mechanism of FcRn, as well as the commonly used drug carrier design strategies of FcRn, especially the functional applications of prolonging half-life, targeted drug delivery, transmembrane and antigen presentation and so on. We propose that these distribution in different tissues and the diverse biological activities may have significant implications of targeting FcRn for novel drug delivery systems and immunotherapy.

During fluorescence-guided cancer surgery, ultra-pH sensitive (UPS) fluorescent nanoprobes has multiple advantages such as real-time imaging procedures, ultra-high imaging sensitivity as well as broad tumor detection specificity. UPS nanoprobes stay at "OFF" state at higher pH and turn into "ON" state at lower pH with emission of strong fluorescence. Moreover, the transition pH points (transition pH point, pH_t) can be precisely controlled by structural-based strategy. One of the previously-reported UPS nanoprobes showed good imaging effect. However, it is still not clear about the effect of pH_t on cancer imaging efficiency of UPS nanoprobes and to further identify the optimal UPS. In this study, we synthesized a series of UPS nanoprobes with pH_t at 4.5, 6.2, 6.6, 7.8 by adjusting the hydrophobic blocks of UPS polymers. Each nanoprobe showed excellent stability in "OFF" state by dynamic light scattering and uniform morphology observed by transmission electron microscopy. In vitro imaging characterized the ultra-pH sensitive fluorescence transition of each probe. In vivo imaging results identified two UPS nanoprobes (NP-6.2 and NP-6.6) with superior tumor imaging effect. All animal experiments in this study were approved by the Animal Ethics Committee of Peking University Health Science Center and were strictly followed by the welfare regulations of laboratory animals of Peking University Health Science Center. Therefore, this study has explored the effect of pH_t on the cancer imaging efficiency of UPS nanoprobes and provides a new idea for design of the other cancer microenvironment-responsive polymers.

Blocking immune checkpoint programmed cell death receptor 1 (PD-1) or programmed death receptor-ligand 1 (PD-L1) can enhance anti-tumor activity of effector T cells. However, the lack of response in many patients to PD-1/PD-L1 therapy remains a question. Improving the immunosuppressive tumor microenvironment (TME) to enhance the efficacy of immune checkpoint inhibitors has become a promising cancer treatment strategy. We constructed a liposome system (PD-L1/siCXCL12-Lp) of CXCL12 siRNA and anti-PD-L1 peptide with matrix metalloproteinases (MMPs) responsiveness, which combined the TME regulation of siCXCL12 and the immune regulation of anti-PD-L1 peptide. All animal experiments were approved by the Biomedical Ethics Committee of Peking University. The authors found that PD-L1/siCXCL12-Lp directly down-regulated the expression of CXCL12 in vitro (33.8%) and in vivo (15.5%). It also effectively increased the ratio of CD8⁺/Treg by 20.0%, which helped the anti-PD-L1 peptide to better exert its immune effect. The combination therapy significantly inhibited tumor growth (52.08%) with great safety, which explored a new idea for cancer immunotherapy.

The non-specific accumulation and release of drugs are the main factors affecting the therapeutic effect as well as causing toxic side effects of chemotherapeutic drugs. Nowadays, the application of nanotechnology and responsive drug release is an important strategy to improve the tumor-specific accumulation of drugs and reduce their side effects. In this study, an α-enolase targeted peptide (ETP)-modified polyethylene glycol poly-lysine block copolymer loaded with oxaliplatin prodrug was synthesized first, and then, polymer-coating Fe₃O₄ nanoparticles were prepared by phase transfer dialysis method to improve the blood circulation stability and tumor targeting of oxaliplatin. At the same time, the physicochemical properties, reductant-responsive drug release, cellular uptake, tumor targeting and other biological functions of ETP modified oxaliplatin-loaded Fe₃O₄ nanoparticles were studied in vitro and in vivo. First, the results of reductant-triggered drug release study showed that the drug-loaded nanoparticles could achieve rapid release of more than 80% of the prototype oxaliplatin within 3 h under the reduction conditions simulating the tumor cytoplasmic microenvironment. Secondly, the results of flow cytometry showed that the modification of ETP could increase the ratio of cellular uptake of drug-loaded nanoparticles in tumor cells, and the way that drug-loaded nanoparticles endocytosed by tumor cells were mainly through the energy-dependent and receptor protein and fossin-mediated endocytosis pathway. The animal procedures were approved by the Institutional Animal Care and Use Committee of School of Pharmacy of Fudan University. Moreover, the results of pharmacokinetic experiment showed that the area under the curve (AUC_0-∞) of oxaliplatin could be significantly increased by nano-formulation which was about 5 times than that of free oxaliplatin. Besides, the pharmacokinetic results also showed that the drug-loaded Fe₃O₄ nanoparticles constructed by covalent linkage and chelation had good overall stability in vivo. Finally, the in vivo imaging results showed that ETP modification could increase tumor accumulation of drug-loaded nanoparticles, which would be conducive to the efficacy of oxaliplatin in tumor lesions. In summary, the oxaliplatin-loaded Fe₃O₄ nanoparticles with the capability of reductant-responsive drug release have good drug release characteristics, blood circulation stability and tumor targeting ability, and have the potential to improve the anti-tumor therapeutic effect of oxaliplatin.

Chemoimmunotherapy has attracted much attention as an emerging therapy pattern for the treatment of cancers. Exploring effective drug combination schemes and reasonable delivery methods remained the key issue in current research. Herein, we designed sorafenib (SF) and anti-Tim-3 monoclonal antibody (Tim-3 mAb) co-loaded MMP2-responsive mesoporous silica nanoparticles (ST-MSNs) for combined chemoimmunotherapy of hepatocellular carcinoma (HCC). The shell of ST-MSNs was fabricated by Tim-3 mAb through matrix metalloproteinase 2 (MMP2) sensitive peptides as "gatekeepers" to prevent drug release during the blood circulation. In tumor microenvironment, the high levels of MMP2 caused the responsive shedding of Tim-3 mAb, leading to the triggerred release of SF and Tim-3 mAb. Then, SF could be delivered to tumor cells and Tim-3 mAb could be delivered to T cells, respectively. In vivo tumor inhibition study results demonstrated that ST-MSNs can significantly enhance synergistic antitumor activity compared with sequential administration of free SF solution and Tim-3 mAb solution. Meanwhile, the expression of antitumor cytokines IFN-γ, IL-12 and the percentage of CD3⁺CD4⁺ cells, CD3⁺CD8⁺ cells in tumors were upregulated after the administration of ST-MSNs, demonstrating good immunomodulatory ability. In addition, within the dosage range, the ST-MSNs had low cytotoxicity and hemolysis, and no obvious tissue toxicity was observed. All animal experiments were performed in line with national regulations and approved by the Animal Experiments Ethical Committee of Shandong University. In conclusion, this study provided a promising drug combination of chemoimmunotherapy with good application prospects for clinical HCC treatment, and exhibited a potential drug carrier for clinical chemoimmunotherapy.

Photothermal therapy (PTT) is a highly effective anti-tumor method. However, when laser radiation was used to ablate tumors, it usually triggers a series of inflammatory reactions, promoting the further development of tumors and affecting the effect of anti-tumor therapy. Therefore, it is an effective method to improve the anti-tumor effect by suppressing the inflammatory response through the precise targeted delivery of anti-inflammatory drug while realizing the photothermal treatment of tumors. To this end, the redox-responsive linker 3, 3'-dithiodipropionic acid was used to bond the classic hydrophobic anti-inflammatory drug 18β-glycyrrhetinic acid (18β-GA) and the hydrophilic fragment methoxy-polyethylene glycol (mPEG-NH₂) to obtain redox-responsive amphiphilic polymer PEG-DA-GA in this study. Then, photothermal agent IR-780 was encapsulated to prepare redox-responsive polymer micelle PDG/IR-780 NPs. The PDG/IR-780 NPs exhibited uniform particle size of 80.2±5.3 nm and the polydispersity index (PDI) was 0.215±0.079. All animal experiments followed the ethical requirements formulated by the Ethics Committee of Sichuan University. The results showed that PDG/IR-780 NPs could respond to the abundant glutathione (GSH) in tumor cells to promote the disintegration of nanoparticle and the release of 18β-GA, thus significantly improved the killing efficiency on 4T1 cells, when compared with the non-redox-responsive control PSG/IR-780 NPs. When the concentration of 18β-GA was 50 μg·mL^-1, the cell viability of 4T1 cells in the PDG/IR-780 NPs group was only (19.29±1.80)%, which was significantly lower than the result of in PSG/IR-780 NPs group (29.30±1.37)%. The results of frozen sections of tumor tissues showed that the designed PDG NPs can promote the tumor-targeted distribution of drugs compared with the free drug group. Eventually, PDG/IR-780 NPs achieved wonderful anti-tumor efficacy on 4T1 triple-negative breast cancer model, revealing the new possibility of the combined therapy strategy of photothermal and anti-inflammatory therapy.

The dense extracellular matrix (ECM) of the tumor severely limits the deep penetration of nanomedicine and weakens its anti-tumor effect. Based on this, the yeast vesicle biomimetic nanomedicine with active deep penetration ability of tumor tissue was designed and developed for enhanced tumor therapy. Results of characterization showed that the yeast cell vesicles (YCV) displayed a spherical morphology with diameter of around 100 nm and was well dispersed. Then the chemotherapeutic drug doxorubicin (DOX) was selected as a model drug, and DOX was loaded into YCV to obtain YCV/DOX through electrostatic interaction, the encapsulation efficiencies of DOX were calculated as 82.5%. The drug release profile of YCV/DOX implied that DOX release showed a manner of pH-dependent, it may be that pH has affected the electrostatic effect of YCV and DOX. Compared with liposomes (Lipo), in vitro cell experiments showed that YCV from natural sources had stronger permeability in three-dimensional multicellular spheres. It is speculated that the mechanism may be good deformation capacity of YCV. A 4T1 xenograft tumor model was established to evaluate the therapeutic efficacy of YCV/DOX. The results suggested that YCV/DOX has stronger tumor tissue penetration ability and could effectively inhibit the tumor growth. All animal experiments were performed in line with national regulations and approved by the Animal Experiments Ethical Committee of Zhengzhou University. This study brings new ideas for the development of biomimetic nanomedicine to overcome the ECM of solid tumors.

This paper aims to develop folic acid-modified paclitaxel nanocrystals (PTX NC@FA) with good stability, high drug loading and tumor cell targeting for endoscopic injection for preoperative local chemotherapy of gastric cancer. PTX NC@FA was prepared by the "bottom-up" followed by ultrasonic to study its morphology, particle size, ζ-potential, drug loading, folic acid-modified phospholipid (FA-DSPE-PEG₂₀₀₀) content, crystalline characteristics, stability, in vitro release, cytotoxicity against human gastric cancer cell line SGC-7901, and anti-tumor effect in two different tumor sizes (tumor volume 100 mm³ or 300 mm³) after single peri-tumor injection in a murine subcutaneous SGC-7901 tumor model. Animal experiments were approved by the Experimental Animal Ethics Committee of the School of Pharmacy, Fudan University. The resulting PTX NC@FA was of short rod-like shape, average particle size 175.3±2.5 nm (PDI 0.17±0.02), ζ-potential -2.5±0.2 mV, PTX loading (28.23±0.74)% (w/w) and FA-DSPE-PEG₂₀₀₀ content (4.40±0.60)% (w/w). The size of the PTX NC@FA remained unchanged for 4 days in phosphate buffer with or without serum. Cellular growth inhibition effect on SGC-7901 showed the superiority of PTX NC@FA over nanocrystals without FA modification. PTX NC@FA inhibited tumor growth more efficiently than both nanocrystals without FA modification and commercially available paclitaxel injection (Taxol) 12 days after peri-tumor injection. For model tumor with the volume of 100 mm³, tumors of all animals in the PTX NC@FA group disappeared completely. For model tumor with the volume of 300 mm³, tumors of 3 animals in the PTX NC@FA group completely disappeared and tumors of the rest 4 animals also became significantly smaller with a tumor volume inhibition rate of 90%. PTX NC@FA showed good potential for preoperative chemotherapy of increase the chances of function preserving gastrectomy and improve the quality of life of patients.

There are two serious obstacles to tumor immunotherapy. Firstly, the immune response of the tumor is seriously reduced due to immunosuppressive tumor microenvironment (ITM) and low immunogenicity of tumor. The second obstacle is the dense and complex heterogeneous structures, which seriously prevent the nanoparticles (NPs) from penetrating deeper into tumor tissue. Immunogenic cell death (ICD) induced by doxorubicin (DOX) is an effective method to enhance tumor immune activity. However, interferon-γ (IFN-γ) secreted by cytotoxic T lymphocytes (CTL) after ICD induction would increase the expression of indoleamine 2, 3-dioxygenase 1 (IDO1) and enhance ITM. IDO1 siRNA would reduce the expression of IDO1 protein, regulate the tumor immunosuppressive microenvironment and regulate ITM, so as to enhance the ICD effect of DOX. In this paper, a novel charge conversional, particle size reduction and highly penetrable NPs based on a pH sensitive copolymer poly(ethylene glycol)-poly-L-lysine-2, 3-dimethylmaleic anhydride (mPEG-PLL-DMA, PLD) and polyamidoamine (PAMAM) dendrimers to achieve deep delivery of tumor tissue. DOX and IDO1 siRNA were encapsulated to achieve efficient tumor immunotherapy. Preparation and cell level experiments showed that PLD material had significant pH sensitivity. Results of 3D tumor penetrable experiment in vitro showed that adding the pH sensitive material PLD significantly improved the permeability of the preparation. In addition, 4T1 tumor model was established for BALB/c mice and all animal experiments were displayed in according with the requirements of the Animal Experiment Ethics Committee of Shenyang Pharmaceutical University. The results of in vivo efficacy experiments and tissue experiments evaluated that IDO1 siRNA significantly improved the ICD effect owing to DOX, so as to significantly inhibit tumor growth.