pH and ROS sequentially responsive podophyllotoxin prodrug micelles with surface charge-switchable and self-amplification drug release for combating multidrug resistance cancer

Chemistry and Biology of Podophyllotoxins: An Update

Podophyllotoxin is an aryltetralin lignan lactone derived from different plants of Podophyllum. It consists of five rings with four chiral centers, one trans-lactone and one aryl tetrahydronaphthalene skeleton with multiple modification sites. Moreover, podophyllotoxin and its derivatives showed lots of bioactivities, including anticancer, anti-inflammatory, antiviral, and insecticidal properties. The demand for podophyllotoxin and its derivatives is rising as a result of their high efficacy. As a continuation of our previous review (Chem. Eur. J., 2017, 23, 4467-4526), herein, total synthesis, biotransformation, structural modifications, bioactivities, and structure-activity relationships of podophyllotoxin and its derivatives from 2017 to 2022 are summarized. Meanwhile, a piece of update information on the origin of new podophyllotoxin analogues from plants from 2014 to 2022 was compiled. We hope that this review will provide a reference for future high value-added applications of podophyllotoxin and its analogues in the pharmaceutical and agricultural fields.

Charge-Reversible Nanoparticles: Advanced Delivery Systems for Therapy and Diagnosis

The past two decades have witnessed a rapid progress in the development of surface charge-reversible nanoparticles (NPs) for drug delivery and diagnosis. These NPs are able to elegantly address the polycation dilemma. Converting their surface charge from negative/neutral to positive at the target site, they can substantially improve delivery of drugs and diagnostic agents. By specific stimuli like a shift in pH and redox potential, enzymes, or exogenous stimuli such as light or heat, charge reversal of NP surface can be achieved at the target site. The activated positive surface charge enhances the adhesion of NPs to target cells and facilitates cellular uptake, endosomal escape, and mitochondrial targeting. Because of these properties, the efficacy of incorporated drugs as well as the sensitivity of diagnostic agents can be essentially enhanced. Furthermore, charge-reversible NPs are shown to overcome the biofilm formed by pathogenic bacteria and to shuttle antibiotics directly to the cell membrane of these microorganisms. In this review, the up-to-date design of charge-reversible NPs and their emerging applications in drug delivery and diagnosis are highlighted.

Development and challenges of antimicrobial peptide delivery strategies in bacterial therapy: A review

The escalating global prevalence of antimicrobial resistance poses a critical threat, prompting concerns about its impact on public health. This predicament is exacerbated by the acute shortage of novel antimicrobial agents, a scarcity attributed to the rapid surge in bacterial resistance. This review delves into the realm of antimicrobial peptides, a diverse class of compounds ubiquitously present in plants and animals across various natural organisms. Renowned for their intrinsic antibacterial activity, these peptides provide a promising avenue to tackle the intricate challenge of bacterial resistance. However, the clinical utility of peptide-based drugs is hindered by limited bioavailability and susceptibility to rapid degradation, constraining efforts to enhance the efficacy of bacterial infection treatments. The emergence of nanocarriers marks a transformative approach poised to revolutionize peptide delivery strategies. This review elucidates a promising framework involving nanocarriers within the realm of antimicrobial peptides. This paradigm enables meticulous and controlled peptide release at infection sites by detecting dynamic shifts in microenvironmental factors, including pH, ROS, GSH, and reactive enzymes. Furthermore, a glimpse into the future reveals the potential of targeted delivery mechanisms, harnessing inflammatory responses and intricate signaling pathways, including adenosine triphosphate, macrophage receptors, and pathogenic nucleic acid entities. This approach holds promise in fortifying immunity, thereby amplifying the potency of peptide-based treatments. In summary, this review spotlights peptide nanosystems as prospective solutions for combating bacterial infections. By bridging antimicrobial peptides with advanced nanomedicine, a new therapeutic era emerges, poised to confront the formidable challenge of antimicrobial resistance head-on.

Diselenium-linked dimeric prodrug nanomedicine breaking the intracellular redox balance for triple-negative breast cancer targeted therapy

Triple-negative breast cancer (TNBC) has been regarded as the strongest malignancy in cases of breast cancer with a poor prognosis. The development of effective treatment strategies for TNBC has always been an urgent and unmet need. The intracellular redox balance is essential for maintaining TNBC cell malignancy. Disrupting intracellular redox balance by enlarging reactive oxygen species (ROS) generation and facilitating glutathione (GSH) depletion to amplify intracellular oxidative stress may be an alternative strategy to eliminate TNBC cells. However, inducing ROS generation and GSH depletion concurrently may be challenging. Herein, a diselenium linked-dimeric prodrug nanomedicine FA-SeSe-NPs was developed to break the intracellular redox homeostasis for TNBC targeted therapy. The dimeric prodrug was synthesized by conjugating two cucurbitacin B (CuB) molecules via one diselenium bond, which was subsequently assembled with FA-PEG-DSPE to form the final nanomedicine FA-SeSe-NPs. Using the active targeting potential of folic acid (FA), FA-SeSe-NPs could accumulate in tumor tissue with elevated levels and then be specifically internalized by cancer cells. In the high ROS and GSH conditions of TNBC cells, the diselenium bond can specifically respond to ROS to produce selenium free radicals to increase ROS and react with GSH to generate S-Se bond to deplete GSH. The released CuB further induced ROS production in TNBC cells. The diselenium bond and CuB functioned synergistically to amplify oxidative stress to kill the TNBC cells. Here, we provide a promising strategy to disrupt the intracellular redox balance of cancer cells for effective TNBC therapy.

Cobalt-doped hollow polydopamine for oxygen generation and GSH consumption enhanced chemo-PTT combined cancer therapy

Nanotechnology has revolutionized the field of therapeutics by introducing a plethora of nanomaterials capable of enhancing traditional drug efficacy or paving the way for innovative treatment methods. Within this domain, we propose a novel Cobalt-doped hollow polydopamine nanosphere system. This system, incorporating Doxorubicin loading and hyaluronic acid (HA) surface coating (CoHPDA@DOX-HA), is designed for combined tumor therapy. The overarching aim is to diminish the administration dosage, mitigate the cytotoxic side effects of chemotherapy drugs, augment chemosensitivity within neoplastic tissues, and attain superior results in tumor treatment via combined therapeutic strategies. The targeted molecule, hyaluronic acid (HA), amplifies the biocompatibility of CoHPDA@DOX-HA throughout circulation and fosters endocytosis of the nanoparticle system within cancer cells. This nanosphere system possesses pH sensitivity properties, allowing for a meticulous drug release within the acidic microenvironment of tumor cells. Concurrently, Polydopamine (PDA) facilitates proficient photothermal therapy upon exposure to 808 nm laser irradiation. This process further amplifies the Glutathione (GSH) depletion, and when coupled with the oxygen production capabilities of the Cobalt-doped hollow PDA, significantly enhances the chemo-photothermal therapeutic efficiency. Findings from the treatment of tumor-bearing mice substantiate that even at dosages equivalent to a singular DOX administration, the CoHPDA@DOX-HA can provide efficacious synergistic therapy. Therefore, it is anticipated that multifunctional nanomaterials with Photoacoustic Tomography (PAT) imaging capabilities, targeted delivery, and a controlled collaborative therapeutic framework may serve as promising alternatives for accurate diagnostics and efficacious treatment strategies.

Core-shell inorganic NP@MOF nanostructures for targeted drug delivery and multimodal imaging-guided combination tumor treatment

It is well known that metal-organic framework (MOF) nanostructures have unique characteristics such as high porosity, large surface areas and adjustable functionalities, so they are ideal candidates for developing drug delivery systems (DDSs) as well as theranostic platforms in cancer treatment. Despite the large number of MOF nanostructures that have been discovered, conventional MOF-derived nanosystems only have a single biofunctional MOF source with poor colloidal stability. Accordingly, developing core-shell MOF nanostructures with good colloidal stability is a useful method for generating efficient drug delivery, multimodal imaging and synergistic therapeutic systems. The preparation of core-shell MOF nanostructures has been done with a variety of materials, but inorganic nanoparticles (NPs) are highly effective for drug delivery and imaging-guided tumor treatment. Herein, we aimed to overview the synthesis of core-shell inorganic NP@MOF nanostructures followed by the application of core-shell MOFs derived from magnetic, quantum dots (QDs), gold (Au), and gadolinium (Gd) NPs in drug delivery and imaging-guided tumor treatment. Afterward, we surveyed different factors affecting prolonged drug delivery and cancer therapy, cellular uptake, biocompatibility, biodegradability, and enhanced permeation and retention (EPR) effect of core-shell MOFs. Last but not least, we discussed the challenges and the prospects of the field. We envision this article may hold great promise in providing valuable insights regarding the application of hybrid nanostructures as promising and potential candidates for multimodal imaging-guided combination cancer therapy.

A co-delivery system based on chlorin e6-loaded ROS-sensitive polymeric prodrug with self-amplified drug release to enhance the efficacy of combination therapy for breast tumor cells

Background: Recently, various combination therapies for tumors have garnered popularity because of their synergistic effects in improving therapeutic efficacy and reducing side effects. However, incomplete intracellular drug release and a single method of combining drugs are inadequate to achieve the desired therapeutic effect.

Methods: A reactive oxygen species (ROS)-sensitive co-delivery micelle (Ce6@PTP/DP). It was a photosensitizer and a ROS-sensitive paclitaxel (PTX) prodrug for synergistic chemo-photodynamic therapy. Micelles size and surface potential were measured. In vitro drug release, cytotoxicity and apoptosis were investigated.

Results: Ce6@PTP/DP prodrug micelles exhibited good colloidal stability and biocompatibility, high PTX and Ce6 loading contents of 21.7% and 7.38%, respectively. Upon light irradiation, Ce6@PTP/DP micelles endocytosed by tumor cells can generate sufficient ROS, not only leading to photodynamic therapy and the inhibition of tumor cell proliferation, but also triggering locoregional PTX release by cleaving the thioketal (TK) bridged bond between PTX and methoxyl poly (ethylene glycol). Furthermore, compared with single drug-loaded micelles, the light-triggered Ce6@PTP/DP micelles exhibited self-amplified drug release and significantly greater inhibition of HeLa cell growth.

Conclusion: The results support that PTX and Ce6 in Ce6@PTP/DP micelles exhibited synergistic effects on cell-growth inhibition. Thus, Ce6@PTP/DP micelles represent an alternative for realizing synergistic chemo-photodynamic therapy.

Tumor microenvironment-regulating nanomedicine design to fight multi-drug resistant tumors

The tumor microenvironment (TME) is a very cunning system that enables tumor cells to escape death post-traditional antitumor treatments through the comprehensive effect of different factors, thereby leading to drug resistance. Deep insights into TME characteristics and tumor resistance encourage the construction of nanomedicines that can remodel the TME against drug resistance. Tremendous interest in combining TME-regulation measurement with traditional tumor treatment to fight multidrug-resistant tumors has been inspired by the increasing understanding of the role of TME reconstruction in improving the antitumor efficiency of drug-resistant tumor therapy. This review focuses on the underlying relationships between specific TME characteristics (such as hypoxia, acidity, immunity, microorganisms, and metabolism) and drug resistance in tumor treatments. The exciting antitumor activities strengthened by TME regulation are also discussed in-depth, providing solutions from the perspective of nanomedicine design. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

A deep tumor penetration nanoplatform for glycolysis inhibition and antimetastasis of breast cancer

The poor penetration into deep tumor tissues of nanomedicines could not inhibit the production of lactic acid by deep tumor glycolysis, which leads to the accumulation of lactic acid and promotes tumor metastasis. In order to increase tumor penetration, it remains challenging to avoid tumor metastasis by the direct degradation of the extracellular matrix (ECM). Herein, in order to increase tumor penetration, a nano-platform, which can reduce extracellular matrix (ECM) production, and inhibit the glycolysis of deep tumors by releasing ethylenediaminetetraacetic acid (EDTA) is reported. In this design, EDTA and indocyanine green (ICG) are encapsulated in the liposome by a thin-film hydration method, and folic acid (FA) and the polyethyleneimine polymer (FA-PEI) are applied to coat the surface of liposomes through electrostatic interactions, and the FA-EDTA/ICG-Lip nanoparticles are obtained. FA-EDTA/ICG-Lip NPs can release EDTA and ICG in lysosomes (pH 4.5) to reduce ECM production by down-regulating transforming growth factor β (TGF-β) and activating an immune response by inducing tumor cell immunogenic cell death (ICD), respectively. Simultaneously, EDTA inhibits glycolysis of deep tumors by chelating Mg²⁺. By avoiding tumor metastasis, the strategy of indirectly reducing ECM production is demonstrated to enhance tumor penetration and inhibit deep tumor glycolysis.

Preparation and application of pH-responsive drug delivery systems

Microenvironment-responsive drug delivery systems (DDSs) can achieve targeted drug delivery, reduce drug side effects and improve drug efficacies. Among them, pH-responsive DDSs have gained popularity since the pH in the diseased tissues such as cancer, bacterial infection and inflammation differs from a physiological pH of 7.4 and this difference could be harnessed for DDSs to release encapsulated drugs specifically to these diseased tissues. A variety of synthetic approaches have been developed to prepare pH-sensitive DDSs, including introduction of a variety of pH-sensitive chemical bonds or protonated/deprotonated chemical groups. A myriad of nano DDSs have been explored to be pH-responsive, including liposomes, micelles, hydrogels, dendritic macromolecules and organic-inorganic hybrid nanoparticles, and micron level microspheres. The prodrugs from drug-loaded pH-sensitive nano DDSs have been applied in research on anticancer therapy and diagnosis of cancer, inflammation, antibacterial infection, and neurological diseases. We have systematically summarized synthesis strategies of pH-stimulating DDSs, illustrated commonly used and recently developed nanocarriers for these DDSs and covered their potential in different biomedical applications, which may spark new ideas for the development and application of pH-sensitive nano DDSs.

Recent Advances in Stimuli-Sensitive Amphiphilic Polymer-Paclitaxel Prodrugs

Paclitaxel (PTX) is a broad-spectrum chemotherapy drug employed in the treatment of a variety of tumors. However, the clinical applications of PTX are limited by its poor water solubility. Adjuvants are widely used to overcome this issue. However, these adjuvants often have side effects and poor biodistribution. The smart drug delivery system is a promising strategy for the improvement of solubility, permeability, and stability of drugs, and can promote sustained controlled release, increasing therapeutic efficacy and reducing side effects. Polymeric prodrugs show great advantages for drug delivery due to their high drug loading and stability. There has been some groundbreaking work in the development of PTX-based stimulus-sensitive polymeric prodrug micelles, which is summarized in this study. We consider these in terms of the four main types of stimulus (pH, reduction, enzyme, and reactive oxygen species (ROS)). The design, synthesis, and biomedical applications of stimulus-responsive polymeric prodrugs of PTX are reviewed, and the current research results and future directions of the field are summarized.

Reactive Oxygen Species-Responsive Nanococktail With Self-Amplificated Drug Release for Efficient Co-Delivery of Paclitaxel/Cucurbitacin B and Synergistic Treatment of Gastric Cancer

Application of drug combinations is a powerful strategy for the therapy of advanced gastric cancer. However, the clinical use of such combinations is greatly limited by the occurrence of severe systemic toxicity. Although polymeric-prodrug-based nanococktails can significantly reduce toxicity of drugs, they have been shown to have low intracellular drug release. To balance between efficacy and safety during application of polymeric-prodrug-based nanococktails, a reactive oxygen species (ROS)-responsive nanococktail (PCM) with self-amplification drug release was developed in this study. In summary, PCM micelles were co-assembled from ROS-sensitive cucurbitacin B (CuB) and paclitaxel (PTX) polymeric prodrug, which were fabricated by covalently grafting PTX and CuB to dextran via an ROS-sensitive linkage. To minimize the side effects of the PCM micelles, a polymeric-prodrug strategy was employed to prevent premature leakage. Once it entered cancer cells, PCM released CuB and PTX in response to ROS. Moreover, the released CuB further promoted ROS generation, which in turn enhanced drug release for better therapeutic effects. In vivo antitumor experiments showed that the PCM-treated group had lower tumor burden (tumor weight was reduced by 92%), but bodyweight loss was not significant. These results indicate that the developed polymeric prodrug, with a self-amplification drug release nanococktail strategy, can be an effective and safe strategy for cancer management.

Design of Smart Size-, Surface-, and Shape-Switching Nanoparticles to Improve Therapeutic Efficacy

Multiple biological barriers must be considered in the design of nanomedicines, including prolonged blood circulation, efficient accumulation at the target site, effective penetration into the target tissue, selective uptake of the nanoparticles into target cells, and successful endosomal escape. However, different particle sizes, surface chemistries, and sometimes shapes are required to achieve the desired transport properties at each step of the delivery process. In response, this review highlights recent developments in the design of switchable nanoparticles whose size, surface chemistry, shape, or a combination thereof can be altered as a function of time, a disease-specific microenvironment, and/or via an externally applied stimulus to enable improved optimization of nanoparticle properties in each step of the delivery process. The practical use of such nanoparticles in chemotherapy, bioimaging, photothermal therapy, and other applications is also discussed.

Charge reversal nano-systems for tumor therapy

Surface charge of biological and medical nanocarriers has been demonstrated to play an important role in cellular uptake. Owing to the unique physicochemical properties, charge-reversal delivery strategy has rapidly developed as a promising approach for drug delivery application, especially for cancer treatment. Charge-reversal nanocarriers are neutral/negatively charged at physiological conditions while could be triggered to positively charged by specific stimuli (i.e., pH, redox, ROS, enzyme, light or temperature) to achieve the prolonged blood circulation and enhanced tumor cellular uptake, thus to potentiate the antitumor effects of delivered therapeutic agents. In this review, we comprehensively summarized the recent advances of charge-reversal nanocarriers, including: (i) the effect of surface charge on cellular uptake; (ii) charge-conversion mechanisms responding to several specific stimuli; (iii) relation between the chemical structure and charge reversal activity; and (iv) polymeric materials that are commonly applied in the charge-reversal delivery systems.