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.

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.

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.

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.

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.

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.

Metformin, as a first-line drug in the treatment of type 2 diabetes, is widely used in clinic with definite efficacy and few adverse reactions. In recent years, other effects besides hypoglycemia have been found, such as a possible therapeutic effect on mental disorders (e.g., anxiety disorder, Alzheimer's disease), cancer, and cardiovascular disease. It also has regulatory effects on intestinal microbiota. The purpose of this review is to summarize the recent investigations of metformin on mental disorders, cardiovascular diseases, cancer, and intestinal microbiota.

The quality evaluation of compound Chinese medicines is an important but challenging issue in this research field, which has been paid much controversial due to the constrained association with clinical efficacy. Developing a methodology for quality evaluation of compound Chinese medicines related to clinical efficacy is an important measure in research on Chinese material medica quality to ensure clinical effectiveness and safety. Therefore, based on the research concept that "originating from clinic-testing in experiment-returning to clinic", and taking Xiaoke prescription as an example, the characteristic information of metabolome, proteome and microbiome are discussed from the clinical aspect, and the integrated markers associated with clinical efficacy constructed with artificial intelligence technology. Taking the integrated markers as the link and indication are connecting the clinical and basic, the main pharmacodynamic substances and key targets of Xiaoke prescription that are related to clinical efficacy are explained. Clinical samples are used for validation. Based on the main pharmacodynamic substances and key targets, methods and key technologies for chemical and biological evaluation of the quality of Xiaoke prescription are established, providing a methodology for quality evaluation of compound Chinese medicines, including clinical efficacy response indicators (related to clinic), main pharmacodynamic substances (chemical evaluation), and key targets (biological evaluation), to provide new ideas and methods for improving the quality evaluation of compound Chinese medicines.

Fifteen alkaloid compounds were isolated from the 70% aqueous alcohol extract of Stephania tetrandra S. Moore by silica gel, reversed phase silica gel, Sephadex LH-20 column chromatography and semi-preparative high performance liquid chromatography. They were identified as tetrandraside A (1), (Z)-N-formyl-nornuciferin (2), (E)-N-formyl-nornuciferin (3), salutaridine (4), salutaridine N-oxide (5), (E)-3-(4-hydroxy-3-methoxyphenyl)-N-[2-(4-hydroxy-3-methoxyphenyl)ethyl]-2 propenamide (6), dauriporphine (7), sinomenine (8), liriodenine (9), α-magnoflorine (10), (1S)-4'-β-glucosylcoclaurine (11), tetrandrine (12), fangchinoline (13), tetrandrine 2'-β-oxide (14), and tetrandrine 2'-α-oxide (15), respectively, by MS, NMR and single crystal diffraction. Among them, compound 1 is a new alkaloid glycoside. Compounds 2-11 were obtained from this plant for the first time. These compounds showed obvious cytotoxic activity against drug-resistant lung cancer cell line H1299, and compound 9 had the best activity, with an IC₅₀ of 5.38 μmol·L^-1.

Aconitum pendulum is a Tibetan medicine that is rich in bioactive compounds such as aconitine-type C₁₉-diterpenoid alkaloids. To investigate the key enzymes in the aconitine biosynthesis pathway, roots, leaves and flowers of Aconitum pendulum were subjected to a high-throughput transcriptomic sequencing analysis by Illumina HiSeq^TM2000. Trinity de novo assembly yielded 47 264 unigenes with an average length of 1 140 bp and N50 of 1 678 bp, of which 30 231 unigenes (63.96%) were annotated. In the KEGG database, 542 unigenes were implicated in 17 secondary metabolic pathways; the analysis showed that 44 genes encoded 20 key enzymes in the diterpene skeleton of aconitine biosynthesis and 12 BAHD acyltransferase genes were related to the acetylation modification, with differential expression among three organs. For example, ApTPS8 was the only committed enzyme in the upstream aconitine biosynthetic pathway. The high expression level of ApTPS8 in root indicated that it is the main tissue for the production of precursors of diterpene alkaloids. Consistent with the accumulation of aconitine, we propose that ApBAHD1/2/8 is involved in the biosynthesis of 2-hydroxyaconitine, dehydrated 14-benzoylaconitine, 8-O-methyl-14-benzoylaconine, benzoyldeoxyaconitine and benzoylaconitine, and ApBAHD10 is involved in the biosynthesis of acontine, lucidusculine, 14-O-acetylneoline and 14-O-acetylvirescenin. Comparative transcriptome analysis of A. pendulum and A. carmichaeli indicates significant gene loss in the family of diterpene synthases and acyltransferases in A. pendulum, which is in accordance with the significantly fewer type and quantity of aconitine compounds in this species. Therefore, A. pendulum has proved to be an ideal material for the study of the aconitine biosynthesis pathway. This work provides basic scientific data for further study of aconitine biosynthesis, the discussion of molecular mechanisms of toxicity, and the synthesis of genuine medicinal materials.