Polydopamine-modified ROS-responsive prodrug nanoplatform with enhanced stability for precise treatment of breast cancer

Smart Nanoplatforms Responding to the Tumor Microenvironment for Precise Drug Delivery in Cancer Therapy

The tumor microenvironment (TME) is a complex and dynamic entity, comprising stromal cells, immune cells, blood vessels and extracellular matrix, which is intimately associated with the occurrence and development of cancers, as well as their therapy. Utilizing the shared characteristics of tumors, such as an acidic environment, enzymes and hypoxia, researchers have developed a promising cancer therapy strategy known as responsive release of nano-loaded drugs, specifically targeted at tumor tissues or cells. In this comprehensive review, we provide an in-depth overview of the current fundamentals and state-of-the-art intelligent strategies of TME-responsive nanoplatforms, which include acidic pH, high GSH levels, high-level adenosine triphosphate, overexpressed enzymes, hypoxia and reductive environment. Additionally, we showcase the latest advancements in TME-responsive nanoparticles. In conclusion, we thoroughly examine the immediate challenges and prospects of TME-responsive nanopharmaceuticals, with the expectation that the progress of these targeted nanoformulations will enable the exploitation, overcoming or modulation of the TME, ultimately leading to significantly more effective cancer therapy.

Tumor Microenvironment-Responsive Polymer-Based RNA Delivery Systems for Cancer Treatment

Ribonucleic acid (RNA) therapeutics offer a broad prospect in cancer treatment. However, their successful application requires overcoming various physiological barriers to effectively deliver RNAs to the target sites. Currently, a number of RNA delivery systems based on polymeric nanoparticles are developed to overcome these barriers in RNA delivery. This work provides an overview of the existing RNA therapeutics for cancer gene therapy, and particularly summarizes those that are entering the clinical phase. This work then discusses the core features and latest research developments of tumor microenvironment-responsive polymer-based RNA delivery carriers which are designed based on the pathological characteristics of the tumor microenvironment. Finally, this work also proposes opportunities for the transformation of RNA therapies into cancer immunotherapy methods in clinical applications.

Taxanes prodrug-based nanomedicines for cancer therapy

Malignant tumor remains a huge threat to human health and chemotherapy still occupies an important place in clinical tumor treatment. As a kind of potent antimitotic agent, taxanes act as the first-line broad-spectrum cancer drug in clinical use. However, disadvantages such as prominent hydrophobicity, severe off-target toxicity or multidrug resistance lead to unsatisfactory therapeutic effects, which restricts its wider usage. The efficient delivery of taxanes is still quite a challenge despite the rapid developments in biomaterials and nanotechnology. Great progress has been made in prodrug-based nanomedicines (PNS) for cancer therapy due to their outstanding advantages such as high drug loading efficiency, low carrier induced immunogenicity, tumor stimuli-responsive drug release, combinational therapy and so on. Based on the numerous developments in this filed, this review summarized latest updates of taxanes prodrugs-based nanomedicines (TPNS), focusing on polymer-drug conjugate-based nanoformulations, small molecular prodrug-based self-assembled nanoparticles and prodrug-encapsulated nanosystems. In addition, the new trends of tumor stimuli-responsive TPNS were also discussed. Moreover, the future challenges of TPNS for clinical translation were highlighted. We here expect this review will inspire researchers to explore more practical taxanes prodrug-based nano-delivery systems for clinical use.

Two-Pronged Anti-Tumor Therapy by a New Polymer-Paclitaxel Conjugate Micelle with an Anti-Multidrug Resistance Effect

Introduction

Cancerous tumors are still a major disease that threatens human life, with tumor multidrug resistance (MDR) being one of the main reasons for the failure of chemotherapy. Thus, reversing tumor MDR has become a research focus of medical scientists.

Methods

Here, a reduction-sensitive polymer prodrug micelle, mPEG-DCA-SS-PTX (PDSP), was manufactured with a new polymer inhibitor of drug resistance as a carrier to overcome MDR and improve the anti-tumor effect of PTX.

Results

The PDSP micelles display good stability, double-responsive drug release, and excellent biocompatibility. The PDSP micelles reduced the cytotoxicity of PTX to normal HL-7702 cells and enhanced that to SMMC-7721 and MCF-7 cells in vitro. Improved sensitivity of A549/ADR to PDSP was also observed in vitro. Furthermore, in vivo experiments show reduced systemic toxicity and enhanced therapeutic efficacy of PTX to H22 subcutaneous tumor-bearing mice.

Conclusion

This work proves that the reduction-sensitive polymer prodrug micelles carried by the new polymer inhibitor can be used as an alternative delivery system to target tumors and reverse MDR for paclitaxel and other tumor-resistant drugs.

Carrier-free nanodrugs for safe and effective cancer treatment

Clinical applications of many anti-cancer drugs are restricted due to their hydrophobic nature, requiring use of harmful organic solvents for administration, and poor selectivity and pharmacokinetics resulting in off-target toxicity and inefficient therapies. A wide variety of carrier-based nanoparticles have been developed to tackle these issues, but such strategies often fail to encapsulate drug efficiently and require significant amounts of inorganic and/or organic nanocarriers which may cause toxicity problems in the long term. Preparation of nano-formulations for the delivery of water insoluble drugs without using carriers is thus desired, requiring elegantly designed strategies for products with high quality, stability and performance. These strategies include simple self-assembly or involving chemical modifications via coupling drugs together or conjugating them with various functional molecules such as lipids, carbohydrates and photosensitizers. During nanodrugs synthesis, insertion of redox-responsive linkers and tumor targeting ligands endows them with additional characteristics like on-target delivery, and conjugation with immunotherapeutic reagents enhances immune response alongside therapeutic efficacy. This review aims to summarize the methods of making carrier-free nanodrugs from hydrophobic drug molecules, evaluating their performance, and discussing the advantages, challenges, and future development of these strategies.

Doxifluridine-based pharmacosomes delivering miR-122 as tumor microenvironments-activated nanoplatforms for synergistic treatment of hepatocellular carcinoma

A novel kind of anti-cancer pharmacosome (named NPC-D) derived from Doxifluridine (5'-DFUR) was described, which could be activated by tumor microenvironments (TMEs). The NPC-D with H₂O₂-sensitive linker was dispersed well in water and simultaneously interacted with nucleic acids including plasmids encoding miR-122 (p122) and EpCAM-targeted aptamer (ap1) via charge interaction and hydrogen bonding. The integrated nanosystem (p122-ap1@NPC-D) was found to unleash by programmed TMEs (high level of H₂O₂ and low pH) to efficiently transfect miR-122 into MHCC-LM3 cells, followed by the releases of 5-FU. Besides, p122-ap1@NPC-D significantly countered the chemotherapy resistance and played a synergistic effect. These unique nanoparticles dramatically enhanced the anti-proliferation, and modulated the cellular apoptosis by the down-regulation of various signal pathways which imparted a bright application prospect in HCC treatment.

Oxidation-strengthened disulfide-bridged prodrug nanoplatforms with cascade facilitated drug release for synergetic photochemotherapy

One of the major barriers in utilizing prodrug nanocarriers for cancer therapy is the slow release of parent drug in tumors. Tumor cells generally display the higher oxidative level than normal cells, and also displayed the heterogeneity in terms of redox homeostasis level. We previously found that the disulfide bond-linkage demonstrates surprising oxidation-sensitivity to form the hydrophilic sulfoxide and sulphone groups. Herein, we develop oxidation-strengthened prodrug nanosystem loaded with pyropheophorbide a (PPa) to achieve light-activatable cascade drug release and enhance therapeutic efficacy. The disulfide bond-driven prodrug nanosystems not only respond to the redox-heterogeneity in tumor, but also respond to the exogenous oxidant (singlet oxygen) elicited by photosensitizers. Once the prodrug nanoparticles (NPs) are activated under irradiation, they would undergo an oxidative self-strengthened process, resulting in a facilitated drug cascade release. The IC50 value of the PPa@PTX-S-S NPs without irradiation was 2-fold higher than those of NPs plus irradiation. In vivo, the PPa@PTX prodrug NPs display prolonged systemic circulation and increased accumulation in tumor site. The PPa@PTX-S-S NPs showed much higher efficiency than free PTX or the PPa@PTX-C-C NPs to suppress the growth of 4T1 tumors. Therefore, this novel oxidation-strengthened disulfide-bridged prodrug-nanosystem has a great potential in the enhanced efficacy of cancer synergetic photochemotherapy.

Tumor microenvironment responsive drug delivery systems

Conventional tumor-targeted drug delivery systems (DDSs) face challenges, such as unsatisfied systemic circulation, low targeting efficiency, poor tumoral penetration, and uncontrolled drug release. Recently, tumor cellular molecules-triggered DDSs have aroused great interests in addressing such dilemmas. With the introduction of several additional functionalities, the properties of these smart DDSs including size, surface charge and ligand exposure can response to different tumor microenvironments for a more efficient tumor targeting, and eventually achieve desired drug release for an optimized therapeutic efficiency. This review highlights the recent research progresses on smart tumor environment responsive drug delivery systems for targeted drug delivery. Dynamic targeting strategies and functional moieties sensitive to a variety of tumor cellular stimuli, including pH, glutathione, adenosine-triphosphate, reactive oxygen species, enzyme and inflammatory factors are summarized. Special emphasis of this review is placed on their responsive mechanisms, drug loading models, drawbacks and merits. Several typical multi-stimuli responsive DDSs are listed. And the main challenges and potential future development are discussed.

Therapeutic polymeric nanomedicine: GSH-responsive release promotes drug release for cancer synergistic chemotherapy

To obtain an efficient dual-drug release and enhance therapeutic efficiency for combination chemotherapy, a glutathione (GSH)-responsive therapeutic amphiphilic polyprodrug copolymer (mPEG-b-PCPT) is synthesized to load doxorubicin (DOX) via hydrophobic and π–π stacking interaction. In this nanomedicine system (mPEG-b-PCPT/DOX), the ratio of the two drugs can be easily modulated by changing the loading content of DOX. The in vitro drug release curves and laser confocal images suggested that the release of CPT and DOX is induced through a “release promotes release strategy”: after internalization into tumor cells, the disulfide bonds in the nanomedicine are cleaved by glutathione (GSH) in the cytoplasm and then lead to the release of CPT. Meanwhile, the disassembly of nanomedicine immediately promotes the co-release of DOX. The optimum dose ratio of CPT and DOX is evaluated via the combination index (CI) value using HepG-2 cells. The results of cell apoptosis and cell viability prove the better synergistic efficiency of the nanomedicine than free drugs at the optimum dose ratio of 1. Consequently, this stimuli-responsive synergistic chemotherapy system provides a direction for the fabrication of nanomedicines possessing promising potential in clinical trials.

In the GSH-responsive doxorubicin loading camptothecin prodrug nanomedicine, easy modulation of the dose ratio and controlled co-release were achieved, and the synergistic effect was significantly improved.