Polymeric nanoparticles responsive to intracellular ROS for anticancer drug delivery

Reactive oxygen species driven prodrug-based nanoscale carriers for transformative therapies

Reactive oxygen species (ROS) drive processes in various pathological conditions serving as an attractive target for therapeutic strategies. This review highlights the development and use of ROS-dependent prodrug-based nanoscale carriers that has transformed many biomedical applications. Incorporating prodrugs into nanoscale carriers not only improves their stability and solubility but also enables site-specific drug delivery ultimately enhancing the therapeutic effectiveness of the nanoscale carriers. We critically examine recent advances in ROS-responsive nanoparticulate platforms, encompassing liposomes, polymeric nanoparticles, and inorganic nanocarriers. These platforms facilitate precise control over drug release upon encountering elevated ROS levels at disease sites, thereby minimizing off-target effects and maximizing therapeutic efficiency. Furthermore, we investigate the potential of combination therapies in which ROS-activated prodrugs are combined with other therapeutic agents and underscore their synergistic potential for treating multifaceted diseases. This comprehensive review highlights the immense potential of ROS-dependent prodrug-based nanoparticulate systems in revolutionizing biomedical applications; such nanoparticulate systems can facilitate selective and controlled drug delivery, reduce toxicity, and improve therapeutic outcomes for ROS-associated diseases.

Polymeric nanoparticles delivery circumvents bacterial resistance to ciprofloxacin

OBJECTIVE

The efficient inhibition of bacteria and their by-products from infected root canals is hampered by the limitations of traditional root canal disinfection strategies, bacterial resistance to antibiotic drugs, and regenerative endodontics. Polymeric nanoparticles nanocarrier for controlling antibiotic drug delivery were used to overcome the limitations encountered in endodontics treatment.

BACKGROUND

Several polymeric nanoparticles have been used for the delivery of ciprofloxacin drug. The application of poly (ethylene glycol) methyl ether-block-poly(lactide-co-glycolide) (PEG-PLGA) nanoparticles has highlighted the clean and safe delivery of ciprofloxacin (CIP) hydrophilic drug for endodontics treatment. PEG/PLGA was prepared using the solid/oil/water method and the CIP was loaded into polymeric nanoparticles via an ion pairing agent.

RESULTS

The CIP-loaded PEG-PLGA nanoparticles have a spherical shape with a 120 ± 0.43 nm size, the CIP encapsulating efficiency was 63.26 ± 9.24% with a loading content of 7.75 ± 1.13%, and sustained release was achieved over 168 h which followed Higuchi model with a non-Fickian mechanism. Moreover, CIP-loaded PEG-PLGA had low cytotoxicity to the stem cells of the apical papilla.

CONCLUSION

The results conclude invigorating future perspectives of polymeric nanoparticles for a wide range of drug delivery for various disease treatments. It's anticipated that these polymeric nanoparticles may divert new expectations in the future for topical antibiotic drug delivery with discrete intracellular medicament, and a safe and clean environment.

Biomaterial strategies for regulating the neuroinflammatory response

Injury and disease in the central nervous system (CNS) can result in a dysregulated inflammatory environment that inhibits the repair of functional tissue. Biomaterials present a promising approach to tackle this complex inhibitory environment and modulate the mechanisms involved in neuroinflammation to halt the progression of secondary injury and promote the repair of functional tissue. In this review, we will cover recent advances in biomaterial strategies, including nanoparticles, hydrogels, implantable scaffolds, and neural probe coatings, that have been used to modulate the innate immune response to injury and disease within the CNS. The stages of inflammation following CNS injury and the main inflammatory contributors involved in common neurodegenerative diseases will be discussed, as understanding the inflammatory response to injury and disease is critical for identifying therapeutic targets and designing effective biomaterial-based treatment strategies. Biomaterials and novel composites will then be discussed with an emphasis on strategies that deliver immunomodulatory agents or utilize cell-material interactions to modulate inflammation and promote functional tissue repair. We will explore the application of these biomaterial-based strategies in the context of nanoparticle- and hydrogel-mediated delivery of small molecule drugs and therapeutic proteins to inflamed nervous tissue, implantation of hydrogels and scaffolds to modulate immune cell behavior and guide axon elongation, and neural probe coatings to mitigate glial scarring and enhance signaling at the tissue-device interface. Finally, we will present a future outlook on the growing role of biomaterial-based strategies for immunomodulation in regenerative medicine and neuroengineering applications in the CNS.

Compartmentalization into Outer and Inner Shells of Hollow Nanospheres for Antibiosis Based on Chemistry and Physical Damages

There is a substantially ascending demand for nonantibiotic strategies to overcome the resistance of bacterial infections. Here, the discovery of a distinctive antibacterial structure is reported. The novel structure of nanoparticle strategy is proposed for appreciable bacteria killing by the smart design of the delayed addition of crosslinkers into the reaction mixture. [2-(methacryloyloxy)ethyl]trimethylammonium chloride solution (MTCl), a water-soluble ionic liquid (IL), has narrow-size material distribution, good whiteness, and high weather resistance. The quaternary ammonium salt is utilized to efficiently permeate cell membranes through electrostatic interaction, accordingly, boasting a beneficiary of antibacterial properties. More importantly, it allows bacteria to attach the nanomaterials easily, especially the double-shelled nanosphere. In light of the introduction of 9-amino(9-deoxy)ep-quinine (QNNH2) on its inner shell, it blocks the nucleic acid and glucose metabolism in bacteria, which is betterment of the antibacterial activity of double-shelled structure nanoparticle compared to other structure of nanomaterials. This physical/chemical/biological triple antibacterial process eliminates the need for traditional antibiotics, and the fabrication strategies and material properties described here provide insights into the design of antibacterial nanomaterials based on chemical and physical effects.

Biopolymer-based tumor microenvironment-responsive nanomedicine for targeted cancer therapy

Nanomedicine has opened up new avenues for cancer treatment by enhancing drug solubility, permeability and targeted delivery to cancer cells. Despite its numerous advantages over conventional therapies, nanomedicine may exhibit off-target drug distribution, harming nontarget regions. The increased permeation and retention effect of nanomedicine in tumor sites also has its limitations, as abnormal tumor vasculature, dense stroma structure and altered tumor microenvironment (TME) may result in limited intratumor distribution and therapeutic failure. However, TME-responsive nanomedicine has exhibited immense potential for efficient, safe and precise delivery of therapeutics utilizing stimuli specific to the TME. This review discusses the mechanistic aspects of various TME-responsive biopolymers and their application in developing various types of TME-responsive nanomedicine.

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.

Synthesis of Multifunctional Polymersomes Prepared by Polymerization-Induced Self-Assembly

Polymersomes are an exciting modality for drug delivery due to their structural similarity to biological cells and their ability to encapsulate both hydrophilic and hydrophobic drugs. In this regard, the current work aimed to develop multifunctional polymersomes, integrating dye (with hydrophobic Nile red and hydrophilic sulfo-cyanine5-NHS ester as model drugs) encapsulation, stimulus responsiveness, and surface-ligand modifications. Polymersomes constituting poly(N-2-hydroxypropylmethacrylamide)-b-poly(N-(2-(methylthio)ethyl)acrylamide) (PHPMAm-b-PMTEAM) are prepared by aqueous dispersion RAFT-mediated polymerization-induced self-assembly (PISA). The hydrophilic block lengths have an effect on the obtained morphologies, with short chain P(HPMAm)₁₆ affording spheres and long chain P(HPMAm)₄₃ yielding vesicles. This further induces different responses to H₂O₂, with spheres fragmenting and vesicles aggregating. Folic acid (FA) is successfully conjugated to the P(HPMAm)₄₃, which self-assembles into FA-functionalized P(HPMAm)₄₃-b-P(MTEAM)₃₀₀ polymersomes. The FA-functionalized P(HPMAm)₄₃-b-P(MTEAM)₃₀₀ polymersomes entrap both hydrophobic Nile red (NR) and hydrophilic Cy5 dye. The NR-loaded FA-linked polymersomes exhibit a controlled release of the encapsulated NR dye when exposed to 10 mM H₂O₂. All the polymersomes formed are stable in human plasma and well-tolerated in MCF-7 breast cancer cells. These preliminary results demonstrate that, with simple and scalable chemistry, PISA offers access to different shapes and opens up the possibility of the one-pot synthesis of multicompartmental and responsive polymersomes.

Targeting active sites of inflammation using inherent properties of tissue-resident mast cells

Mast cells play a pivotal role in initiating and directing host's immune response. They reside in tissues that primarily interface with the external environment. Activated mast cells respond to environmental cues throughout acute and chronic inflammation through releasing immune mediators via rapid degranulation, or long-term de novo expression. Mast cell activation results in the rapid release of a variety of unique enzymes and reactive oxygen species. Furthermore, the increased density of mast cell unique receptors like mas related G protein-coupled receptor X2 also characterizes the inflamed tissues. The presence of these molecules (either released mediators or surface receptors) are particular to the sites of active inflammation, and are a result of mast cell activation. Herein, the molecular design principles for capitalizing on these novel mast cell properties is discussed with the goal of manipulating localized inflammation. STATEMENT OF SIGNIFICANCE: Mast cells are immune regulating cells that play a crucial role in both innate and adaptive immune responses. The activation of mast cells causes the release of multiple unique profiles of biomolecules, which are specific to both tissue and disease. These unique characteristics are tightly regulated and afford a localized stimulus for targeting inflammatory diseases. Herein, these important mast cell attributes are discussed in the frame of highlighting strategies for the design of bioresponsive functional materials to target regions of inflammations.

Exploring the Application of Micellar Drug Delivery Systems in Cancer Nanomedicine

Various formulations of polymeric micelles, tiny spherical structures made of polymeric materials, are currently being investigated in preclinical and clinical settings for their potential as nanomedicines. They target specific tissues and prolong circulation in the body, making them promising cancer treatment options. This review focuses on the different types of polymeric materials available to synthesize micelles, as well as the different ways that micelles can be tailored to be responsive to different stimuli. The selection of stimuli-sensitive polymers used in micelle preparation is based on the specific conditions found in the tumor microenvironment. Additionally, clinical trends in using micelles to treat cancer are presented, including what happens to micelles after they are administered. Finally, various cancer drug delivery applications involving micelles are discussed along with their regulatory aspects and future outlooks. As part of this discussion, we will examine current research and development in this field. The challenges and barriers they may have to overcome before they can be widely adopted in clinics will also be discussed.

Reactive oxygen species-responsive polymer drug delivery systems

Applying reactive polymer materials sensitive to biological stimuli has recently attracted extensive research interest. The special physiological effects of reactive oxygen species (ROS) on tumors or inflammation and the application of ROS-responsive polymers as drug-delivery systems in organisms have attracted much attention. ROS is a vital disease signal molecule, and the unique accumulation of ROS-responsive polymers in pathological sites may enable ROS-responsive polymers to deliver payload (such as drugs, ROS-responsive prodrugs, and gene therapy fragments) in a targeted fashion. In this paper, the research progress of ROS-responsive polymers and their application in recent years were summarized and analyzed. The research progress of ROS-responsive polymers was reviewed from the perspective of nanoparticle drug delivery systems, multi-responsive delivery systems, and ROS-responsive hydrogels. It is expected that our work will help understand the future development trends in this field.

Light-Activated Reactive Oxygen Species-Responsive Nanocarriers for Enhanced Photodynamic Immunotherapy of Cancer

Exploring polymeric nanoplatforms combined with reactive oxygen species (ROS) responsiveness with mitochondria targeting has emerged as an effective strategy for enhanced photodynamic therapy (PDT). Amphiphilic copolymers were synthesized by reacting acrylamide thioketal (TK) linkers with amino-terminated triphenylphosphonium-polyethylene glycol and dodecylamine for encapsulating chlorin e6 (Ce6) via self-assembly. Then, anionic cladding with tumor targeting deshelled in tumor acidic microenvironments was surface-anchored by electrostatic forces (BioPEGDMA@RM). After sequential targeting to the mitochondria of cancerous cells, BioPEGDMA@RM could be light-activated with Ce6 released upon ROS cleavage of TK linkages. It was found that Ce6-loaded BioPEGDMA@RM exhibited higher cytotoxicity on CT26 cells and performed stronger ability on the production of ROS than that without TK linkers. Moreover, a minimum illumination of 3 and 5 min could be required for achieving the maximum release of Ce6 and high in vitro cytotoxicity for Ce6-loaded BioPEGDMA@RM, respectively. Furthermore, Ce6-loaded BioPEGDMA@RM showed 1.29-fold and 1.21-fold higher tumor inhibition on BALB/c nude mice and Kunming mice and stimulated immunologic reactions with more generation of IFN-γ and TNF-α and activation of CD3⁺, CD4⁺, and CD8⁺ T-lymphocytes and DCs than that of Ce6-loaded nanoparticles without TK bonds. This work provided an academic reference for the development of ROS-responsive drug delivery systems for advanced PDT efficiency.

Recent Progress in Bio-Responsive Drug Delivery Systems for Tumor Therapy

Spatially- and/or temporally-controlled drug release has always been the pursuit of drug delivery systems (DDSs) to achieve the ideal therapeutic effect. The abnormal pathophysiological characteristics of the tumor microenvironment, including acidosis, overexpression of special enzymes, hypoxia, and high levels of ROS, GSH, and ATP, offer the possibility for the design of stimulus-responsive DDSs for controlled drug release to realize more efficient drug delivery and anti-tumor activity. With the help of these stimulus signals, responsive DDSs can realize controlled drug release more precisely within the local tumor site and decrease the injected dose and systemic toxicity. This review first describes the major pathophysiological characteristics of the tumor microenvironment, and highlights the recent cutting-edge advances in DDSs responding to the tumor pathophysiological environment for cancer therapy. Finally, the challenges and future directions of bio-responsive DDSs are discussed.

Stimuli-Responsive Nanoparticles for Controlled Drug Delivery in Synergistic Cancer Immunotherapy

Cancer immunotherapy has achieved promising clinical progress over the recent years for its potential to treat metastatic tumors and inhibit their recurrences effectively. However, low patient response rates and dose-limiting toxicity remain as major dilemmas for immunotherapy. Stimuli-responsive nanoparticles (srNPs) combined with immunotherapy offer the possibility to amplify anti-tumor immune responses, where the weak acidity, high concentration of glutathione, overexpressions of enzymes, and reactive oxygen species, and external stimuli in tumors act as triggers for controlled drug release. This review highlights the design of srNPs based on tumor microenvironment and/or external stimuli to combine with different anti-tumor drugs, especially the immunoregulatory agents, which eventually realize synergistic immunotherapy of malignant primary or metastatic tumors and acquire a long-term immune memory to prevent tumor recurrence. The authors hope that this review can provide theoretical guidance for the construction and clinical transformation of smart srNPs for controlled drug delivery in synergistic cancer immunotherapy.

A versatile modular preparation strategy for targeted drug delivery systems against multidrug-resistant cancer cells

Nanotechnology is widely used in targeted drug delivery, but different drug delivery systems need to 're-determine' different synthesis schemes, which greatly limits the further expansion of targeted nanomedicine applications. In this study, we propose a facile and versatile modular stacking strategy to fabricate targeted drug delivery systems to enable tailored designs for patient-specific therapeutic responses. The systems were constructed by a pH-sensitive prodrug module and a mitochondrial targeting module via self-assembly. Using this modular strategy, we successfully prepared two targeting nano-drug delivery systems, TPP-DOX and PK-DOX, where the mitochondrial targeting molecules were triphenylphosphonium (TPP) and 1-(2-Chlorophenyl)-N-methyl-N-(1-methylpropyl)-3-isoquinolinecarboxamide (PK11195), respectively. Confocal laser microscopy and flow cytometry tests revealed that TPP-DOX and PK-DOX exhibited high mitochondria targeting capability and greatly improved the drug retention in drug-resistant cells. The antitumor activity tests showed that the IC50 values of TPP-DOX and PK-DOX in MCF-7/ADR cells were 2.5- and 8.2-fold lower than that of free DOX, respectively. These results indicated that PK was more effective than TPP. The studies on their therapeutic effects on human breast cancer resistant cells verified the feasibility of the modular approach, indicated that the two modular targeted drug delivery systems: (1) retain the drug toxicity and cell-killing effect of the prodrug module, (2) have precise targeting capabilities due to mitochondrial targeting module, (3) enhance drug uptake, reduce drug efflux and reverse the multidrug resistance effect to a certain extent. The results show that modular stacking is a practical, effective and versatile method for preparing targeting drugs with broad application prospects. This study provides an easy approach on preparing customizable targeted drug delivery systems to improve precision therapies.

Singlet Oxygen-Responsive Polymeric Nanomedicine for Light-Controlled Drug Release and Image-Guided Photodynamic-Chemo Combination Therapy

Coencapsulation of chemotherapeutic agents and photosensitizers into nanocarriers can help to achieve a combination of chemotherapy and photodynamic therapy for superior antitumor effects. However, precise on-demand drug release remains a major challenge. In addition, the loaded photosensitizers usually tend to aggregate, which can significantly weaken their fluorescent signals and photodynamic activities. To address these issues, herein, a smart nanocarrier termed as singlet oxygen-responsive nanoparticle (SOR-NP) was constructed by introducing singlet oxygen (¹O₂)-sensitive aminoacrylate linkers into amphiphilic mPEG-b-PCL copolymers. Boron dipyrromethene (BDP) and paclitaxel (PTX) as model therapeutic agents were coloaded into an ¹O₂-responsive nanocarrier for realizing light-controlled drug release and combination cancer treatment. This polymeric nanocarrier could substantially relieve the aggregation of encapsulated BDP due to the presence of a long hydrophobic chain. Therefore, the formed SOR-NP_BDP/PTX nanodrug could generate bright fluorescent signals and high levels of ¹O₂, which could mediate cell death via PDT and rupture aminoacrylate linker simultaneously, leading to collapse of SOR-NP_BDP/PTX and subsequent PTX release. The light-triggered drug release and combined anticancer effects of SOR-NP_BDP/PTX were validated in HepG2 and MCF-7 cancer cells and H22 tumor-bearing mice. This study provides a promising strategy for tumor-specific drug release and selective photodynamic-chemo combination treatment.

[Reactive oxygen species stimuli-responsive nanocarriers]

纳米载体一般是由天然高分子或人工合成高分子组成的、纳米级范畴的运输系统,具有减少药物毒性、提高药物的靶向性、增加药物有效性等优点。随着生物医学技术的进步,有研究表明,作为氧化代谢产物的活性氧(ROS)在疾病部位常常伴随着过表达的异常现象。基于此,近年来ROS刺激响应纳米载体获得了关注和发展,以不同响应机制的ROS响应基团为基础,发展了一系列的ROS响应纳米载体,实现了疾病部位ROS刺激下的药物特异性可控释放。该文聚焦于近年来常用于纳米载体的ROS响应基团,依据元素划分为两大类:硫族元素类响应基团(硫醚、缩硫酮、硒化物、二硒化物、碲化物)和其他元素类响应基团(芳香硼酸酯、过氧草酸酯、二茂铁);通过不同的设计理念将其引入纳米载体,根据ROS响应纳米载体的不同响应机制(疏水-亲水相变、断裂),探讨了载体各自的ROS响应情况、体外药物释放情况,以及在活体中的应用情况。

Reactive Oxygen Species Responsive Polymers for Drug Delivery Systems

Reactive oxygen species (ROS) play an essential role in regulating various physiological functions of living organisms; however, as the concentration of ROS increases in the area of a lesion, this may undermine cellular homeostasis, leading to a series of diseases. Using cell-product species as triggers for targeted regulation of polymer structures and activity represents a promising approach for the treatment. ROS-responsive polymer carriers allow the targeted delivery of drugs, reduce toxicity and side effects on normal cells, and control the release of drugs, which are all advantages compared with traditional small-molecule chemotherapy agents. These formulations have attracted great interest due to their potential applications in biomedicine. In this review, recent progresses on ROS responsive polymer carriers are summarized, with a focus on the chemical mechanism of ROS-responsive polymers and the design of molecular structures for targeted drug delivery and controlled drug release. Meanwhile, we discuss the challenges and future prospects of its applications.

Oral Codelivery of WR-1065 Using Curcumin-Linked ROS-Sensitive Nanoparticles for Synergistic Radioprotection

Protecting the body from radiation damage is a huge medical challenge. Amifostine and curcumin are both effective radioprotectants, but their use has been greatly restricted due to various reasons including low bioavailability. Nanoscale drug delivery systems of poly(ethylene glycol)-poly(ε-caprolactone) copolymers can improve the bioavailability of drugs due to excellent biocompatibility, biodegradability, and long circulation characteristics. In this study, a new reactive oxygen species-sensitive nanocarrier fabricated by linking curcumin and thioketal to poly(ethylene glycol)-poly(ε-caprolactone) polymer was used for delivery of WR-1065 (the active ingredient of amifostine). The content of curcumin in this polymer was about 7.6%, and the drug loading of WR-1065 was 44%. The WR-1065-loaded nanoparticles (NPs) had an average size of 128.6 nm and uniform spherical morphology. These WR-1065-loaded NPs reduced the metabolism of curcumin and WR-1065 in the gastrointestinal tract and could be well absorbed by cells and distributed to multiple organs. Compared with a single drug, oral administration of WR-1065-loaded NPs demonstrated obvious radioprotective effects on the hematopoietic system and prevented intestinal injury. The 30-day survival rate after half-lethal dose (7.2 Gy) of total body irradiation was 100%. In general, WR-1065-loaded NPs improved the oral bioavailability of WR-1065 and curcumin. This multifunctional nanocarrier provides a possibility for combination therapy in treating ionizing radiation damage.

Blood circulation stable doxorubicin prodrug nanoparticles containing hydrazone and thioketal moieties for antitumor chemotherapy

Prodrug nanoparticles with cleavable moieties sensitive to intracellular stimuli have drawn great attention on cancer chemotherapy. Herein, a reactive oxygen species (ROS)-responsive doxorubicin prodrug mPEG-Phe-TK-Phe-hyd-DOX was synthesized, in which hydrophilic methoxy poly(ethylene glycol) (mPEG) and hydrophobic anticancer drug doxorubicin (DOX) were conjugated with hydrazone (hyd) and ROS-responsive thioketal (TK) moieties. The ROS-responsiveness of prodrug was confirmed by proton nuclear magnetic resonance (¹H NMR) and dynamic light scattering (DLS). Unexpectedly, the results of in vitro drug release indicated that the hydrazone bond of prodrug nanoparticles was insensitive to pH, which may be due to the strong hydrophobicity, π-π interactions and cation-π interactions jointly inhibited the hydrolysis of hydrazone bonds under acidic conditions. The cellular uptake and in vitro anticancer study showed that ROS-responsive prodrug nanoparticles exhibited faster cellular uptake and better anticancer efficacy. The in vivo experiments showed that the ROS-responsive prodrug nanoparticles had comparable antitumor efficacy with free anticancer drug DOX and reduced organ toxicity. Our results provide novel idea of successfully design multi-stimuli-responsive nano-drug carrier.

α-Tocopherol-loaded reactive oxygen species-scavenging ferrocene nanocapsules with high antioxidant efficacy for wound healing

The elevated production of reactive oxygen species (ROS) in wounded sites triggers a series of harmful effects, including cellular senescence, fibrotic scar formation, and inflammation. Therefore, alleviating oxidative stress in the microenvironment of wounded sites might promote regenerative wound healing. Generally, ROS-scavenging nanocapsules are effective for treating wounds owing to their anti-oxidative stress activity and targeted effects. In this study, a highly versatile ferrocene functional polymer was synthesized by one-pot radical polymerization, for formulating self-assembled ferrocene nanocapsules (FNCs), which could function as smart carriers of an antioxidant, α-tocopherol (TP), with high stability and loading efficiency. The FNCs showed ROS-sensitive properties, as demonstrated using dynamic light scattering, transmission electron microscopy, and the controlled release of a model drug in an ROS microenvironment. The antioxidant activity of TP-loaded FNCs, analyzed using 2,2-diphenyl-1-picrylhydrazyl assay, was significantly higher than that of unloaded TP. Furthermore, TP-loaded FNCs repressed oxidative damage to mouse NIH 3T3 fibroblasts and reduced intracellular ROS production according to an in vitro antioxidant assay. Most importantly, TP-loaded FNCs showed good biocompatibility and greatly facilitated the healing of infected wounds, as demonstrated using a scratch assay. Therefore, TP-loaded FNCs have potential as an ROS-mediated drug delivery system to treat various oxidative stress-associated diseases.

Reactive oxygen species and glutathione dual responsive nanoparticles for enhanced prostate cancer therapy

Docetaxel (DTX)-based chemotherapy of prostate cancer is still confronted with significant challenges due to insufficient drug accumulation at the tumor sites and the systemic side effects on normal cells and organs. Tumor microenvironment-responsive nanosized drug delivery systems have shown enormous potential to improve the anticancer efficacy and minimize the systemic side effects of chemotherapeutics. However, most of the currently redox-responsive nanoparticles respond only to single stimuli, which compromise the treatment effect. Hence, inspired by the abundance of reactive oxygen species (ROS) and intracellular glutathione (GSH) in cancer cells, we proposed a unique ROS and GSH dual responsive nanocarrier (PCL-SS) for DTX delivery. The DTX-loaded PCL-SS nanoparticles (PCL-SS@DTX NPs) were not only stable in a normal physiological environment but also rapidly triggered DTX release in prostate cancer cells. In vitro experiments showed that PCL-SS@DTX NPs had robust prostate cancer cell cytotoxicity, induced cell apoptosis, inhibited cell migration and invasion and exhibited satisfactory biocompatibility. In mice bearing orthotopic prostate cancer, PCL-SS@DTX NPs could accumulate in orthotopic tumor sites and then significantly weaken tumor growth by inhibiting prostate cancer cell proliferation and inducing cell apoptosis, without obvious damages to major organs. Overall, this dual responsive nanosized drug delivery system may act as a promising therapeutic option for prostate cancer chemotherapy.

Redox-sensitive polymeric micelles with aggregation-induced emission for bioimaging and delivery of anticancer drugs

BACKGROUND

Nano-drug delivery systems show considerable promise for effective cancer therapy. Polymeric micelles have attracted extensive attention as practical nanocarriers for target drug delivery and controlled drug delivery system, however, the distribution of micelles and the release of the drug are difficult to trace in cancer cells. Therefore, the construction of a redox-sensitive multifunctional drug delivery system for intelligent release of anticancer drugs and simultaneous diagnostic imaging and therapy remains an attractive research subject.

RESULTS

To construct a smart drug delivery system for simultaneous imaging and cancer chemotherapy, mPEG-ss-Tripp was prepared and self-assembled into redox-sensitive polymeric micelles with a diameter of 105 nm that were easily detected within cells using confocal laser scanning microscopy based on aggregation-induced emission. Doxorubicin-loaded micelles rapidly released the drug intracellularly when GSH reduced the disulfide bond. The drug-loaded micelles inhibited tumor xenografts in mice, while this efficacy was lower without the GSH-responsive disulfide bridge. These results establish an innovative multi-functional polymeric micelle for intracellular imaging and redox-triggered drug deliver to cancer cells.

CONCLUSIONS

A novel redox-sensitive drug delivery system with AIE property was constructed for simultaneous cellular imaging and intelligent drug delivery and release. This smart drug delivery system opens up new possibilities for multifunctional drug delivery systems.

Recent progress of redox-responsive polymeric nanomaterials for controlled release

This perspective focuses on the development of redox-responsive polymeric nanomaterials for controlled payload release within the last four years.

Preparation of ROS-responsive core crosslinked polycarbonate micelles with thioketal linkage

Herein, we prepared novel reactive oxygen species (ROS) responsive core crosslinked (CCL/TK) polycarbonate micelles conveniently by click reaction between amphiphilic diblock copolymer poly(ethylene glycol)-poly(5-methyl-5-propargylxycar-bonyl-1,3-dioxane-2-one) (PEG-PMPC) with pendant alkynyl group and thioketal containing azide derivative bis (2-azidoethyl) 3, 3'- (propane-2, 2-diylbis (sulfanediyl)) dipropanoate (TK-N₃). The CCL/TK micelles were obtained with small size of 146.4 nm, showing excellent stability against dilution and high doxorubicin (DOX) loading. In vitro toxicity tests demonstrated that the obtained CCL/TK micelles have good biocompatibility and low toxicity with cell viability above 95 %. Furthermore, DOX-loaded CCL/TK micelles showed significantly superior toxicity with IC₅₀ values for HeLa and MCF-7 cells about 3.74 μg/mL and 3.91 μg/mL, respectively. Confocal laser scanning microscope (CLSM) and flow cytometry showed excellent internalization efficiency and intracellular drug release of DOX-loaded CCL/TK micelles. The obtained ROS-responsive CCL/TK micelles showed great potential for anticancer drug delivery.

ROS triggered cleavage of thioketal moiety to dissociate prodrug nanoparticles for chemotherapy

With the utilization of high concentration reactive oxygen species (ROS) in tumor microenvironment, PEG-doxorubicin (PEG-DOX) prodrug was synthesized via a thioketal moiety as the linker, which was ROS cleavable to trigger DOX release from the self-assembled prodrug nanoparticles. The in vitro ROS sensitivity of prodrug nanoparticles (NPs) was investigated in Fenton agent and H₂O₂, and the disassembly of NPs was more sensitive to Fenton reagent. After internalized in HepG2 cells via endocytosis, the cellular ROS consuming test revealed intracellular DOX release. The pharmacokinetics and biodistribution study demonstrated that the in vivo elimination of NPs was significantly improved and the NPs were passively targeted to tumor tissues via EPR effect. The ROS-responsive prodrug NPs exhibited excellent antitumor activity in HepG2 tumor-bearing nude mice, remarkably induced tumor cells apoptosis and reduced the systemic toxicity of DOX. Our study revealed the ROS responsive prodrug nanoparticle is an effective strategy to fabricate nanomedicine for cancer chemotherapy.

Bioactivatable reactive oxygen species-sensitive nanoparticulate system for chemo-photodynamic therapy

Bioactivatable polymer nanoparticles (NPs) have attracted considerable attention as a prospective cancer therapy. Herein, we describe bioactivatable reactive oxygen species (ROS)-sensitive prodrug NPs designed to elicit spatiotemporally controlled, phototriggered chemo-photodynamic therapy. First, an effective anticancer agent, doxorubicin (DOX), was conjugated to poly(ethylene glycol) (PEG) via an ROS-responsive degradable thioketal (TK) linker. The resulting amphiphilic PEG-DOX conjugate (PEG-TK-DOX) self-assembled into a bioactivatable ROS-responsive NP system could efficiently encapsulate a hydrophobic photodynamic therapy (PDT) agent, pheophorbide A (PhA), with good colloidal stability and unimodal size distribution. Second, after the selective retention of NPs in the tumor, the site-specific release of DOX and PhA was spatiotemporally controlled, initially by endogenous ROS and subsequently by exogenous ROS produced during PDT. The locoregional treatment not only photoactivates PhA molecules to generate cytotoxic ROS but also triggers an ROS cascade, which accelerates the release of DOX and PhA via the ROS-mediated structural destruction of NPs, resulting in an enhanced anticancer therapeutic effect. This prodrug-NP system may function as an effective nanomedicine platform, working synergistically to maximize the efficacy of the combination of chemotherapy and photodynamic therapy with a remote-controlled release mechanism. STATEMENT OF SIGNIFICANCE: Photodynamic therapy (PDT) is a noninvasive therapy involving local ROS generation through the activation of photosensitizer (PS) molecules induced via external irradiation with near-infrared (NIR) light. Combinational therapies with PDT could synergistically enhance the therapeutic efficacy and overcome the limitations of monotherapy. In this study, we describe bioactivatable reactive oxygen species (ROS)-sensitive prodrug nanoparticles designed to elicit spatiotemporally controlled, photo triggered chemo-photodynamic therapy. Upon accumulation in tumor by enhanced permeation and retention (EPR) effect, the nanoparticles exhibited target-specific release of chemo-drug and photosensitizer in a spatiotemporally controlled cascade manner by endogenous ROS in the initial stage and the excessive production of exogenous ROS during PDT, leading to a further ROS cascade that accelerates the release of therapeutic cargo.

Polymer-Drug Conjugate, a Potential Therapeutic to Combat Breast and Lung Cancer

Cancer is a chronic disease that is responsible for the high death rate, globally. The administration of anticancer drugs is one crucial approach that is employed for the treatment of cancer, although its therapeutic status is not presently satisfactory. The anticancer drugs are limited pharmacologically, resulting from the serious side effects, which could be life-threatening. Polymer drug conjugates, nano-based drug delivery systems can be utilized to protect normal body tissues from the adverse side effects of anticancer drugs and also to overcome drug resistance. They transport therapeutic agents to the target cell/tissue. This review article is based on the therapeutic outcomes of polymer-drug conjugates against breast and lung cancer.

Reactive oxygen species (ROS)-responsive ferrocene-polymer-based nanoparticles for controlled release of drugs

Ferrocene-containing nanoparticles show reversible redox activity that could trigger drug release mediated by reactive oxygen species (ROS).