pH-Sensitive Molecular-Switch-Containing Polymer Nanoparticle for Breast Cancer Therapy with Ferritinophagy-Cascade Ferroptosis and Tumor Immune Activation.

Ferritin internalized into tumor cells is degraded and releases iron ions via ferritinophagy. Iron ions participate in Fenton reaction to produce reactive oxygen species for lipid peroxidation and ferroptosis. Inhibition of indoleamine-2,3-dioxygenase (IDO) decreases tryptophan elimination to induce T cells activation for tumor immunosuppression relief. The active tumor targeting nanoparticles containing ferritin and a pH-sensitive molecular-switch (FPBC@SN) are developed to utilize ferritinophagy-cascade ferroptosis and tumor immunity activation for cancer therapy. FPBC@SN disintegrates in acidic cytoplasm and releases sorafenib (SRF) and IDO inhibitor (NLG919). SRF upregulates nuclear receptor coactivator 4 (NCOA4) to induce ferritin and endogenous iron pool degradation by ferritinophagy, then obtained iron ions participate in the Fenton reaction to produce lipid peroxide (LPO). Meanwhile, SRF blocks glutathione synthesis to downregulate glutathione peroxidase 4 (GPX4) which can scavenge LPO as a different pathway from ferritinophagy to promote ferroptosis in tumor cells. NLG919 inhibits IDO to reduce tryptophan metabolism, so immunity in tumors is aroused to anti-tumor. In vitro and in vivo experiments prove FPBC@SN inhibits tumor cell growth and metastasis, indicating the potential of FPBC@SN for breast cancer therapy based on the combination of ferritinophagy-cascade ferroptosis and tumor immunity activation.

Coadministration of chemotherapy and PI3K/Akt pathway treatment with multistage acidity/CathB enzyme-responsive nanocarriers for inhibiting the metastasis of breast cancer.

As the principal reason for the inducement of high mortality, tumor metastasis is regulated by different pathways owing to its complexity and multistep process. In order to inhibit the proliferation and metastasis of human breast cancer simultaneously, controlling the codelivery of chemotherapeutics and pathway inhibitors precisely has been considered as a high-potential strategy to accurately eliminate tumor metastasis. In this study, polymer PLGA-p-PEI-DA was synthesised and automatically assembled into a cascade "trinity" response drug delivery system, i.e., PPP-DA/NPs (PLGA: poly(lactin-co-glycolic acid), PEI: polyethyleneimine, DA: 2,3-dimethylmaleic anhydride). In the tumor microenvironment, PPP-DA/NPs could remove the outer DA molecules via the pH-sensitive hydrolysis of ß-carboxylic amide bonded with DA and PEI. Then, PPP-DA/NPs were broken up owing to the enzymatically cleavable GFLGF (Gly-Phe-Leu-Gly-Phe) linker. The structure of the polymer and the properties of PPP-DA/NPs were evaluated in detail. Moreover, studies on the antitumor metastasis efficiency and antitumor mechanism of PPP-DA/NPs were carried out in detail. As demonstrated in this study, PPP-DA/NPs could reverse the potential in pH 6.8 PBS and showed elevated cellular uptake efficiency. Moreover, PPP-DA/NPs exhibited strong antitumor metastasis ability in vitro and in vivo. The tumor inhibiting rate (TIR) of PPP-DA/NPs (68.4%) was significantly higher than that of docetaxel (DTX) (5.9%). The antitumor mechanistic studies confirmed that PPP-DA/NPs could down-regulate the expressions of Akt, MMP-9 and pro-caspase-3/9 protein, as indicated by western blot analysis. This multifunctional drug delivery system (DDS) is highly selective and effective in inhibiting tumor metastasis, which shows a great potential in inventing smart nanocarriers for targeted tumor-metastasis therapy.

RGD(Arg-Gly-Asp) internalized docetaxel-loaded pH sensitive liposomes: Preparation, characterization and antitumor efficacy in vivo and in vitro.

The goal of this research was to formulate dual-targeting liposomes (RGD/DTX-PSL) that can selectively release loaded contents in a low pH level environment and to actively target to the tumor using liposomes that had surface arginine-glycine-aspartic (RGD) tripeptides. We investigated whether RGD/DTX-PSL could serve as an effective tumor-targeted nanoparticle that is capable of suppressing tumor growth. The results suggest that DTX is released from liposomes faster at pH 5.0 than pH 7.4, demonstrating their pH sensitivity. RGD/DTX-PSL has a longer blood circulation than Duopafei(®) in rats. The RGD/DTX-PSL formulation displayed stronger antiproliferative effects than DTX alone and the strongest inhibition of tumor growth of the formulations tested, thus expanding therapeutic window of DTX. In conclusion, we established a novel, promising and easy-to-handle liposome formulation that has a considerable antitumor activity in vitro and in vivo. This study provides important prerequisite for the clinical application of dual-targeting liposomes in delivering therapies.

Smart linkers in polymer-drug conjugates for tumor-targeted delivery.

To achieve effective chemotherapy, many types of drug delivery systems have been developed for the specific environments in tumor tissues. Polymer-drug conjugates are increasingly used in tumor therapy due to several significant advantages over traditional delivery systems. In the fabrication of polymer-drug conjugates, a smart linker is an important component that joins two fragments or molecules together and can be cleared by a specific stimulus, which results in targeted drug delivery and controlled release. By regulating the conjugation between the drug and the nanocarriers, stimulus-sensitive systems based on smart linkers can offer high payloads, certified stability, controlled release and targeted delivery. In this review, we summarize the current state of smart linkers (e.g. disulfide, hydrazone, peptide, azo) used recently in various polymer-drug conjugate-based delivery systems with a primary focus on their sophisticated design principles and drug delivery mechanisms as well as in vivo processes.

RGD-modified pH-sensitive liposomes for docetaxel tumor targeting.

Phosphatidylethanolamine-based pH-sensitive liposomes of various compositions have been described as efficient systems for delivery of therapeutic molecules into tumor cells. The aim of this work was to develop a drug delivery system based on pH-sensitive liposomes (PLPs) that were modified with arginine-glycine-aspartic acid (RGD) peptide to enhance the effectiveness of docetaxel treatment. Docetaxel/coumarin-6 loaded PLPs were prepared by the thin-film dispersion method and characterized in detail, including by particle size, polydispersity, zeta potential and drug encapsulation efficiency. In vitro studies using MCF-7, HepG2and A549 cells were employed to investigate cytotoxicity and cellular uptake of the drug solution or docetaxel/coumarin-6 loaded PLPs. The accumulation of 7-nitro-2-1,3-benzoxadiazol-4-yl (NBD)-labeled liposomes in vivo was studied through tumor section imaging of xenograft mouse models of MCF-7 24h after intravenous administration. The particle size of the non-coated or RGD modified PLPs ranged between 146 and 129nm. Drug release in vitro was modestly prolonged and had good pH sensitivity. In the in vitro study, RGD-coated PLPs showed higher cytotoxicity and cellular uptake relative to non-coated ones. The results of the in vivo study showed that RGD-coated PLPs had higher fluorescence, which suggested a more efficient accumulation than normal PLPs in tumors. In conclusion, these results confirmed RGD-modified PLPs as a potential drug delivery system to achieve controlled release and tumor targeting.

Propranolol hydrochloride-loaded liposomal gel for transdermal delivery: Characterization and in vivo evaluation.

This study was to develop propranolol hydrochloride (PRO)-loaded liposomal gel as a topical drug delivery system. Scanning electron microscope (SEM) revealed that the liposomes were spherical and scattered in the surface of the gel. Pseudoplastic flows of PRO liposomal gel were showed after stored at three different temperatures. Besides, PRO liposomal gel showed non-irritating to the skin of rabbit. Skin deposition studies in vivo demonstrated that PRO liposomal gel can apparently increase drug content in skin compared with PRO gel. Histopathology examination showed that PRO liposomal gel could obviously weaken the barrier function of stratum corneum (SC) by comparison with PRO gel. What is more, the plasma pharmacokinetic showed the maximum concentration in plasma was 0.41 µg/mL and 1.17 µg/mL after topical and oral administration respectively. However, tissue distribution study showed PRO liposomal gel obviously changed drug distribution in tissues, significantly increased drug concentration in skin with about 74 folds compared with PRO gel. In conclusion, liposomes-based gel could be a promising vehicle as a transdermal delivery system of PRO.