Supramolecular PEGylated Dendritic Systems as pH/Redox Dual-Responsive Theranostic Nanoplatforms for Platinum Drug Delivery and NIR Imaging

Stable Porous Organic Cage Nanocapsules for pH-Responsive Anticancer Drug Delivery for Precise Tumor Therapy

The search for drug nanocarriers with stimuli-responsive properties and high payloads for targeted drug delivery and precision medicine is currently a focal point of biomedical research, but this endeavor still encounters various challenges. Herein, a porous organic cage (POC) is applied to paclitaxel (PTX) drug delivery for cancer therapy for the first time. Specifically, water-soluble, stable, and biocompatible POC-based nanocapsules (PTX@POC@RH40) with PTX encapsulation efficiency over 98% can be synthesized by simply grafting nonionic surfactant (Polyoxyl 40 hydrogenated castor oil, RH40) on the POC surface. These PTX@POC@RH40 nanocapsules demonstrate remarkable stability for more than a week without aggregation and exhibit pH-responsive behavior under acidic conditions (pH 5.5) and display sustained release behavior at both pH 7.4 and pH 5.5. Intravenous administration of PTX@POC@RH40 led to a 3.5-fold increase in PTX bioavailability compared with the free PTX group in rats. Moreover, in vivo mouse model experiments involving 4T1 subcutaneous breast cancer tumors revealed that PTX@POC@RH40 exhibited enhanced anticancer efficacy with minimal toxicity compared with free PTX. These findings underscore the potential of POCs as promising nanocarriers for stimuli-responsive drug delivery in therapeutic applications.

Reversible Cross-linked Thermoresponsive Polycaprolactone Micelles for Enhanced Stability and Controlled Release

Thermoresponsive amphiphilic poly(ε-caprolactone)s (PCL)s are excellent candidates for drug delivery due to their biodegradability, biocompatibility, and controlled release. However, the thermoresponsivity of modified PCL can often lead to premature drug release because their lower critical solution temperature (LCST) is close to physiological temperature conditions. To address this issue, we developed a novel approach that involves functionalizing redox-responsive lipoic acid to the hydrophobic block of PCL. Lipoic acid has disulfide bonds that undergo reversible cross-linking after encapsulating the drug. Herein, we synthesized an ether-linked propargyl-substituted PCL as the hydrophobic block of an amphiphilic copolymer along with unsubstituted PCL. The propargyl group was used to attach lipoic acid through a postpolymerization modification reaction. The hydrophilic block is composed of an ether-linked, thermoresponsive tri(ethylene glycol)-substituted PCL. Anticancer drug doxorubicin (DOX) was encapsulated within the core of the micelles and induced cross-linking in the presence of a reducing agent, dithiothreitol. The developed micelles are thermodynamically stable and demonstrated thermoresponsivity with an LCST value of 37.5 °C but shifted to 40.5 °C after cross-linking. The stability and release of both uncross-linked (LA-PCL) and cross-linked (CLA-PCL) micelles were studied at physiological temperatures. The results indicated that CLA-PCL was stable, and only 35% release was observed after 46 h at 37 °C while LA-PCL released more than 70% drug at the same condition. Furthermore, CLA-PCL was able to release a higher amount of DOX in the presence of glutathione and above the LCST condition (42 °C). Cytotoxicity experiments revealed that CLA-PCL micelles are more toxic toward MDA-MB-231 breast cancer cells at 42 °C than at 37 °C, which supported the thermoresponsive release of the drug. These results indicate that the use of reversible cross-linking is a great approach toward synthesizing stable thermoresponsive micelles with reduced premature drug leakage.

Theranostic chimeric antigen receptor (CAR)-T cells: Insight into recent trends and challenges in solid tumors

Cell therapy has reached significant milestones in various life-threatening diseases, including cancer. Cell therapy using fluorescent and radiolabeled chimeric antigen receptor (CAR)-T cell is a successful strategy for diagnosing or treating malignancies. Since cell therapy approaches have different results in cancers, the success of hematological cancers has yet to transfer to solid tumor therapy, leading to more casualties. Therefore, there are many areas for improvement in the cell therapy platform. Understanding the therapeutic barriers associated with solid cancers through cell tracking and molecular imaging may provide a platform for effectively delivering CAR-T cells into solid tumors. This review describes CAR-T cells' role in treating solid and non-solid tumors and recent advances. Furthermore, we discuss the main obstacles, mechanism of action, novel strategies and solutions to overcome the challenges from molecular imaging and cell tracking perspectives.

Stimuli-responsive nanocarrier delivery systems for Pt-based antitumor complexes: a review

Platinum-based anticancer drugs play a crucial role in the clinical treatment of various cancers. However, the application of platinum-based drugs is heavily restricted by their severe toxicity and drug resistance/cross resistance. Various drug delivery systems have been developed to overcome these limitations of platinum-based chemotherapy. Stimuli-responsive nanocarrier drug delivery systems as one of the most promising strategies attract more attention. And huge progress in stimuli-responsive nanocarrier delivery systems of platinum-based drugs has been made. In these systems, a variety of triggers including endogenous and extracorporeal stimuli have been employed. Endogenous stimuli mainly include pH-, thermo-, enzyme- and redox-responsive nanocarriers. Extracorporeal stimuli include light-, magnetic field- and ultrasound responsive nanocarriers. In this review, we present the recent advances in stimuli-responsive drug delivery systems with different nanocarriers for improving the efficacy and reducing the side effects of platinum-based anticancer drugs.

Platinum Drug-Incorporating Polymeric Nanosystems for Precise Cancer Therapy

Platinum (Pt) drugs are widely used in clinic for cancer therapy, but their therapeutic outcomes are significantly compromised by severe side effects and acquired drug resistance. With the emerging immunotherapy and imaging-guided cancer therapy, precise delivery and release of Pt drugs have drawn great attention these days. The targeting delivery of Pt drugs can greatly increase the accumulation at tumor sites, which ultimately enhances antitumor efficacy. Further, with the combination of Pt drugs and other theranostic agents into one nanosystem, it not only possesses excellent synergistic efficacy but also achieves real-time monitoring. In this review, after the introduction of Pt drugs and their characteristics, the recent progress of polymeric nanosystems for efficient delivery of Pt drugs is summarized with an emphasis on multi-modal synergistic therapy and imaging-guided Pt-based cancer treatment. In the end, the conclusions and future perspectives of Pt-encapsulated nanosystems are given.

Innovative nanotheranostics: Smart nanoparticles based approach to overcome breast cancer stem cells mediated chemo- and radioresistances

The alarming increase in the number of breast cancer patients worldwide and the increasing death rate indicate that the traditional and current medicines are insufficient to fight against it. The onset of chemo- and radioresistances and cancer stem cell-based recurrence make this problem harder, and this hour needs a novel treatment approach. Competent nanoparticle-based accurate drug delivery and cancer nanotheranostics like photothermal therapy, photodynamic therapy, chemodynamic therapy, and sonodynamic therapy can be the key to solving this problem due to their unique characteristics. These innovative formulations can be a better cargo with fewer side effects than the standard chemotherapy and can eliminate the stability problems associated with cancer immunotherapy. The nanotheranostic systems can kill the tumor cells and the resistant breast cancer stem cells by novel mechanisms like local hyperthermia and reactive oxygen species and prevent tumor recurrence. These theranostic systems can also combine with chemotherapy or immunotherapy approaches. These combining approaches can be the future of anticancer therapy, especially to overcome the breast cancer stem cells mediated chemo- and radioresistances. This review paper discusses several novel theranostic systems and smart nanoparticles, their mechanism of action, and their modifications with time. It explains their relevance and market scope in the current era. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Poly(β-cyclodextrin)/platinum prodrug supramolecular nano system for enhanced cancer therapy: Synthesis and in vivo study

The use of cisplatin is restricted by systemic toxicity and drug resistance. Supramolecular nano-drug delivery systems involving drugs as building blocks circumvent these limitations promisingly. Herein, we describe a novel supramolecular system [Pt(IV)-SSNPs] based on poly(β-cyclodextrin), which was synthesized for efficient loading of adamantly-functionalized platinum(IV) prodrug [Pt(IV)-ADA₂] via the host-guest interaction between β-cyclodextrin and adamantyl. Pt(IV)-ADA₂ can be converted to active cisplatin in reducing environment in cancer cells, which further reduces systemic toxicity. The introduction of the adamantane group-tethered mPEG_2k endowed the Pt(IV)-SSNPs with a longer blood circulation time. In vitro assays exhibited that the Pt(IV)-SSNPs could be uptaken by CT26 cells, resulting in cell cycle arrest in the G2/M and S phases, together with apoptosis. Furthermore, the Pt(IV)-SSNPs showed effective tumor accumulation, better antitumor effect, and negligible cytotoxicity to major organs. These results indicate that supramolecular nanoparticles are a promising platform for efficient cisplatin delivery and cancer treatment.

Super-sensitive bifunctional nanoprobe: Self-assembly of peptide-driven nanoparticles demonstrating tumor fluorescence imaging and therapy

The development of nanomedicine has recently achieved several breakthroughs in the field of cancer treatment; however, biocompatibility and targeted penetration of these nanomaterials remain as limitations, which lead to serious side effects and significantly narrow the scope of their application. The self-assembly of intermediate filaments with arginine-glycine-aspartate (RGD) peptide (RGD-IFP) was triggered by the hydrophobic cationic molecule 7-amino actinomycin D (7-AAD) to synthesize a bifunctional nanoparticle that could serve as a fluorescent imaging probe to visualize tumor treatment. The designed RGD-IFP peptide possessed the ability to encapsulate 7-AAD molecules through the formation of hydrogen bonds and hydrophobic interactions by a one-step method. This fluorescent nanoprobe with RGD peptide could be targeted for delivery into tumor cells and released in acidic environments such as endosomes/lysosomes, ultimately inducing cytotoxicity by arresting tumor cell cycling with inserted DNA. It is noteworthy that the RGD-IFP/7-AAD nanoprobe tail-vein injection approach demonstrated not only high tumor-targeted imaging potential, but also potent antitumor therapeutic effects in vivo. The proposed strategy may be used in peptide-driven bifunctional nanoparticles for precise imaging and cancer therapy.

Are smart delivery systems the solution to overcome the lack of selectivity of current metallodrugs in cancer therapy?

Chemotherapeutic metallodrugs such as cisplatin and its derivatives are among the most widely applied anticancer treatments worldwide. Despite their clinical success, patients suffer from severe adverse effects while subjected to treatment due to platinum's low selectivity for tumour over healthy tissues. Additionally, intrinsic or acquired resistance to metallodrugs, as well as their inability to reach cancer metastases, often results in therapeutic failure. The evident need for highly efficient and specific treatments has driven the scientific community to research novel ways to surpass the stated limitations. Within this scenario, a rising number of smart drug delivery systems have been lately reported to target primary cancers or metastases, where the metallodrugs are released in a controlled and selective way triggered by specific tumour-related stimuli, thus suggesting a viable and attractive therapeutic approach. Herein, we discuss the main efforts undertaken in the past few years towards the smart delivery of metal-based drugs and drug candidates to tumour sites, particularly focusing on the pH- and/or redox-responsive targeted delivery of platinum and ruthenium anticancer complexes.

Fluorescent ABC-Triblock Polymer Nanocarrier for Cisplatin Delivery to Cancer Cells

Monitoring intracellular administration of non-luminescent anticancer drugs like cisplatin is a very challenging task in cancer research. Perylenebisimide (PBI) chromophore tagged fluorescent ABC-triblock polycaprolactone (PCL) nanoscaffold was engineered having carboxylic acid blocks for the chemical conjugation of cisplatin at the core and hydrophilic PEG blocks at the periphery. The amphiphilic ABC triblock Pt-prodrug was self-assembled into < 200 nm nanoparticles and exhibited excellent shielding against drug detoxification by the glutathione (GSH) species in the cytosol. In vitro drug release studies confirmed that the Pt-prodrug was stable at extracellular conditions and the PCL block exclusively underwent lysosomal-enzymatic biodegradation at the intracellular level to release the cisplatin drug in the active-form for accomplishing more than 90% cell growth inhibition. Confocal microscopic imaging of the red-fluorescence signals from the perylene chromophores established the simultaneous monitoring and delivery aspects of Pt-prodrug, and the proof-of-concept was successfully demonstrated in breast and cervical cancer cell lines.

Metal-Coordinated Supramolecular Self-Assemblies for Cancer Theranostics

Metal-coordinated supramolecular nanoassemblies have recently attracted extensive attention as materials for cancer theranostics. Owing to their unique physicochemical properties, metal-coordinated supramolecular self-assemblies can bridge the boundary between traditional inorganic and organic materials. By tailoring the structural components of the metal ions and binding ligands, numerous multifunctional theranostic nanomedicines can be constructed. Metal-coordinated supramolecular nanoassemblies can modulate the tumor microenvironment (TME), thus facilitating the development of TME-responsive nanomedicines. More importantly, TME-responsive organic-inorganic hybrid nanomaterials can be constructed in vivo by exploiting the metal-coordinated self-assembly of a variety of functional ligands, which is a promising strategy for enhancing the tumor accumulation of theranostic molecules. In this review, recent advancements in the design and fabrication of metal-coordinated supramolecular nanomedicines for cancer theranostics are highlighted. These supramolecular compounds are classified according to the order in which the coordinated metal ions appear in the periodic table. Furthermore, the prospects and challenges of metal-coordinated supramolecular self-assemblies for both technical advances and clinical translation are discussed. In particular, the superiority of TME-responsive nanomedicines for in vivo coordinated self-assembly is elaborated, with an emphasis on strategies that enhance the accumulation of functional components in tumors for an ideal theranostic outcome.

Nano-therapeutic strategies to target coronavirus

The coronaviruses have caused severe acute respiratory syndrome (SARS), the Middle East respiratory syndrome (MERS), and the more recent coronavirus pneumonia (COVID-19). The global COVID-19 pandemic requires urgent action to develop anti-virals, new therapeutics, and vaccines. In this review, we discuss potential therapeutics including human recombinant ACE2 soluble, inflammatory cytokine inhibitors, and direct anti-viral agents such as remdesivir and favipiravir, to limit their fatality. We also discuss the structure of the SARS-CoV-2, which is crucial to the timely development of therapeutics, and previous attempts to generate vaccines against SARS-CoV and MERS-CoV. Finally, we provide an overview of the role of nanotechnology in the development of therapeutics as well as in the diagnosis of the infection. This information is key for computational modeling and nanomedicine-based new therapeutics by counteracting the variable proteins in the virus. Further, we also try to effectively share the latest information about many different aspects of COVID-19 vaccine developments and possible management to further scientific endeavors.

Engineered non-invasive functionalized dendrimer/dendron-entrapped/complexed gold nanoparticles as a novel class of theranostic (radio)pharmaceuticals in cancer therapy

Nanomedicine represents a very significant contribution in current cancer treatment; in addition to surgical intervention, radiation and chemotherapeutic agents that unfortunately also kill healthy cells, inducing highly deleterious and often life-threatening side effects in the patient. Of the numerous nanoparticles used against cancer, gold nanoparticles had been developed for therapeutic applications. Inter alia, a large variety of dendrimers, i.e. soft artificial macromolecules, have turned up as non-viral functional nanocarriers for entrapping drugs, imaging agents, and targeting molecules. This review will provide insights into the design, synthesis, functionalization, and development in biomedicine of engineered functionalized hybrid dendrimer-tangled gold nanoparticles in the domain of cancer theranostic. Several aspects are highlighted and discussed such as 1) dendrimer-entrapped gold(0) hybrid nanoparticles for the targeted imaging and treatment of cancer cells, 2) dendrimer encapsulating gold(0) nanoparticles (Au DENPs) for the delivery of genes, 3) Au DENPs for drug delivery applications, 4) dendrimer encapsulating gold radioactive nanoparticles for radiotherapy, and 5) dendrimer/dendron-complexed gold(III) nanoparticles as technologies to take down cancer cells.

Dendrimer Architectonics to Treat Cancer and Neurodegenerative Diseases with Implications in Theranostics and Personalized Medicine

Integration of diagnostic and therapeutic functions in a single platform namely theranostics has become a cornerstone for personalized medicine. Theranostics platform facilitates noninvasive detection and treatment while allowing the monitoring of disease progression and therapeutic efficacy in case of chronic conditions of cancer and Alzheimer's disease (AD). Theranostic tools function by themselves or with the aid of carrier, viz. liposomes, micelles, polymers, or dendrimers. The dendrimer architectures (DA) are well-characterized molecular nanoobjects with a large number of terminal functional groups to enhance solubility and offer multivalency and multifunctional properties. Various noninvasive diagnostic tools like magnetic resonance imaging (MRI), computed tomography (CT), gamma scintigraphy, and optical techniques have been accomplished utilizing DAs for simultaneous imaging and drug delivery. Obstacles in the formulation design, drug loading, payload delivery, biocompatibility, overcoming cellular membrane and blood-brain barrier (BBB), and systemic circulation remain a bottleneck in translational efforts. This review focuses on the diagnostic, therapeutic and theranostic potential of DA-based nanocarriers in treating cancer and neurodegenerative disorders like AD and Parkinson's disease (PD), among others. In view of the inverse relationship between cancer and AD, designing suitable DA-based theranostic nanodrug with high selectivity has tremendous implications in personalized medicine to treat cancer and neurodegenerative disorders.

Cryptobiosis-inspired assembly of "AND" logic gate platform for potential tumor-specific drug delivery

Developing tumor-specific drug delivery systems with minimized off-target cargo leakage remains an enduring challenge. In this study, inspired from the natural cryptobiosis explored by certain organisms and stimuli-responsive polyphenol‒metal coordination chemistry, doxorubicin (DOX)-conjugated gelatin nanoparticles with protective shells formed by complex of tannic acid and Fe^III (DG@TA-Fe^III NPs) were successfully developed as an “AND” logic gate platform for tumor-targeted DOX delivery. Moreover, benefiting from the well-reported photothermal conversion ability of TA-Fe^III complex, a synergistic tumor inhibition effect was confirmed by treating 4T1 tumor-bearing mice with DG@TA-Fe^III NPs and localized near-infrared (NIR) laser irradiation. As a proof of concept study, this work present a simple strategy for developing “AND” logic gate platforms by coating enzyme-degradable drug conjugates with detachable polyphenol‒metal shells.

A minireview on multiparameter-activated nanodevices for cancer imaging and therapy

Tumor microenvironment (TME)-responsive nanodevices are essential tools for cancer imaging and therapy. Exploiting the advantages of molecular engineering, nanodevices are emerging for biomedical applications. In order to reach targeted cancer areas, activated nanodevices first respond to the TME and then serve as an actuator for sensing, imaging and therapy. Most nanodevices depend on a single parameter as an input for their downstream activation, potentially leading to inaccurate diagnostic results and poor therapeutic outcomes. However, in the TME, some biomarkers are cross-linked, and such correlated biomarkers are potentially useful for cancer imaging and theranostic applications. Based on this phenomenon, researchers have developed approaches for the construction of multiparameter-activated nanodevices (MANs) to improve accuracy. This minireview summarizes the recent advances in the development of MANs for cancer imaging including fluorescence imaging, photoacoustic (PA) imaging, magnetic resonance imaging (MRI) and computed tomography (CT) imaging, as well as cancer therapy including radiotherapy, chemotherapy, photoinduced therapy and immunotherapy. We highlight different approaches for improving the specificity and precision of cancer imaging and therapy. In the future, MANs will show promise for clinical work in multimodal diagnosis and therapeutics.

Construction of traceable cucurbit[7]uril-based virus-mimicking quaternary complexes with aggregation-induced emission for efficient gene transfection

Construction of an efficient cationic gene delivery system with low cytotoxicity, high transfection efficacy, as well as gene tracking function remains a major challenge in gene therapy. Fabrication of simple and reversible nanocomplexes based on host-guest interaction provides an opportunity to construct stimuli-responsive intelligent supramolecular systems. Inspired by the hierarchical structure of viruses, a novel virus-mimicking PG/CB/TPE/DNA gene delivery system is developed via a multistep noncovalent self-assembly process between pDNA and the preformed PG/CB/TPE complexes based on the host-guest interaction between cucurbit[7]uril (CB[7]) and the protonated diamine group in the poly(glycidyl methacrylate)s derivative (PG), as well as the electrostatic interaction between para-carboxyl functionalized tetraphenylethylene (TPE) and cationic PG. The developed efficient multifunctional gene delivery system exhibits stimuli responsive characteristics and aggregation-induced emission phenomena, thereby enabling gene delivery pH responsiveness and traceability. Moreover, the introduction of TPE and CB[7] endows the self-assembled PG/CB/TPE/DNA complexes with virus-mimicking architecture and properties such as low cytotoxicity, high stability, excellent endosomal escape, and efficient transfection, which are expected to be used as a promising gene delivery system.

Stimuli-Responsive Polymeric Nanocarriers for Drug Delivery, Imaging, and Theragnosis

In the past few decades, polymeric nanocarriers have been recognized as promising tools and have gained attention from researchers for their potential to efficiently deliver bioactive compounds, including drugs, proteins, genes, nucleic acids, etc., in pharmaceutical and biomedical applications. Remarkably, these polymeric nanocarriers could be further modified as stimuli-responsive systems based on the mechanism of triggered release, i.e., response to a specific stimulus, either endogenous (pH, enzymes, temperature, redox values, hypoxia, glucose levels) or exogenous (light, magnetism, ultrasound, electrical pulses) for the effective biodistribution and controlled release of drugs or genes at specific sites. Various nanoparticles (NPs) have been functionalized and used as templates for imaging systems in the form of metallic NPs, dendrimers, polymeric NPs, quantum dots, and liposomes. The use of polymeric nanocarriers for imaging and to deliver active compounds has attracted considerable interest in various cancer therapy fields. So-called smart nanopolymer systems are built to respond to certain stimuli such as temperature, pH, light intensity and wavelength, and electrical, magnetic and ultrasonic fields. Many imaging techniques have been explored including optical imaging, magnetic resonance imaging (MRI), nuclear imaging, ultrasound, photoacoustic imaging (PAI), single photon emission computed tomography (SPECT), and positron emission tomography (PET). This review reports on the most recent developments in imaging methods by analyzing examples of smart nanopolymers that can be imaged using one or more imaging techniques. Unique features, including nontoxicity, water solubility, biocompatibility, and the presence of multiple functional groups, designate polymeric nanocues as attractive nanomedicine candidates. In this context, we summarize various classes of multifunctional, polymeric, nano-sized formulations such as liposomes, micelles, nanogels, and dendrimers.

Reduction-sensitive platinum (IV)-prodrug nano-sensitizer with an ultra-high drug loading for efficient chemo-radiotherapy of Pt-resistant cervical cancer in vivo

Cisplatin is widely used in the chemoradiotherapy (CRT) of cervical cancers. However, despite the severe systemic side effects, the therapeutic efficacy of cisplatin is often compromised by the development of drug resistance, which is closely related to the elevated intracellular thiol-containing species (especially glutathione (GSH)) and the adenosine triphosphate (ATP)-dependent glutathione S-conjugate pumps. The construction of a safe and redox-sensitive nano-sensitizer with high disulfide density and high Pt(IV) prodrug loading capacity (up to 16.50% Pt and even higher), as described herein, is a promising way to overcome the cisplatin resistance and enhance the CRT efficacy. The optimized nanoparticles (NPs) (referred to as ^SSCV₅) with moderate Pt loading (7.62% Pt) and median size (c.a. 40 nm) was screened out and used for further biological evaluation. Compared with free cisplatin, more drugs could be transported and released inside the cisplatin resistant cells (Hela-CDDP) by ^SSCV₅ NPs. With the synergistic effect of GSH scavenging and mitochondrial damage, ^SSCV₅ NPs can easily reverse the cisplatin resistance. Moreover, the higher nucleus DNA binding Pt content of ^SSCV₅ NPs not only caused the DNA damage and apoptosis of Hela-CDDP cells but also sensitized these cells to X-Ray radiation. The in vivo safety and efficacy results showed that ^SSCV₅ NPs effectively accumulated inside tumor and inhibited the growth of cisplatin resistant xenograft models while alleviating the serious side effect associated with cisplatin (the maximum tolerated cisplatin equivalent of single injection is higher than 20 mg/kg body weight). The intervention of exogenous radiation further improved the anticancer efficacy of ^SSCV₅ NPs and caused the shrinkage of tumor volume, thus making this safe and facile nano-sensitizer a promising route for the neoadjuvant CRT of cervical cancers.

Targeted nanocarriers based on iodinated-cyanine dyes as immunomodulators for synergistic phototherapy

Photodynamic therapy (PDT), as one of the most powerful photo-therapeutic strategies for cancer treatment with minimum invasiveness, can effectively damage local tumor cells and significantly induce systemic antitumor immunity. However, current nanotechnology-assisted PDT-immunomodulators have either poor penetration for deep tumors or low singlet oxygen generation. Herein, we construct a novel theranostic nanocarrier (HA-PEG-CyI, HPC) by inducing the self-assembly of PEGylated CyI and attaching the ligand HA to its surface. The prepared HPC can be used as an ideal PDT-immunomodulator for synergistic cancer therapy. CyI is an iodinated-cyanine dye with enhanced singlet oxygen generation ability as well as excellent photo-to-photothermal and near-infrared fluorescence imaging properties. Under 808 nm laser irradiation, the prepared HPC can generate both reactive oxygen species (ROS) and elevate temperature which can subsequently result in apoptosis and necrosis at tumor sites. Moreover, the HPC-induced cell death can generate a series of acute inflammatory reactions, leading to systemic immunity induction and secondary death of tumor cells, which further results in reducing tumor recurrence. In vitro and in vivo results show that HPC can enhance the tumor targeting efficacy, generate ROS efficiently and exhibit a high temperature response under NIR irradiation, which working together can activate immune responses for synergistic phototherapy on tumor cells. Accordingly, the proposed multi-functional HPC nanocarriers represent an important advance in PDT and can be used as a superior cancer treatment strategy with great promise for clinical applications.

Tumor-Oriented Telomerase-Terminated Nanoplatform as Versatile Strategy for Multidrug Resistance Reversal in Cancer Treatment

Multidrug resistance is one of the major problems in chemotherapy, and exploiting impactful targets to reverse drug resistance of most tumors remains a difficult problem. In this study, the tumor-oriented nanoparticle, BIBR1532-loaded peptide dendrimeric prodrug nanoassembly (B-PDPN), is used to assist telomerase inhibition for multidrug resistance reversal. B-PDPN possesses the characteristics of an acid-activated histidine to promote cellular uptake, a redox-sensitive poly(ethylene glycol) (PEG) layer to actualize endosomal escape and telomerase inhibitor release, and an acid sensitive chemical bond to facilitate chemotherapeutic drug release. Telomerase termination weakens the protective effect of hTERT protein on mitochondria and enhances reactive oxygen species (ROS) production, which increases DNA damage and apoptosis. The tumor-oriented nanoparticle B-PDPN achieves a broad-spectrum telomerase inhibition to combat multidrug resistance. In vivo experiments support the evidence that B-PDPN accumulates in the tumor site and reduces the expression of hTERT in tumor tissues to inhibit drug resistant tumor growth. This work introduces an innovative strategy of utilizing features of tumor-activated nanoplatform to assist telomerase termination. The nanoplatform enhances intracellular drug concentration and nucleus delivery of doxorubicin (DOX), and promotes DNA damage to combat multidrug resistance.

Stimuli-responsive nanocarriers for drug delivery, tumor imaging, therapy and theranostics

In recent years, much progress has been motivated in stimuli-responsive nanocarriers, which could response to the intrinsic physicochemical and pathological factors in diseased regions to increase the specificity of drug delivery. Currently, numerous nanocarriers have been engineered with physicochemical changes in responding to external stimuli, such as ultrasound, thermal, light and magnetic field, as well as internal stimuli, including pH, redox potential, hypoxia and enzyme, etc. Nanocarriers could respond to stimuli in tumor microenvironments or inside cancer cells for on-demanded drug delivery and accumulation, controlled drug release, activation of bioactive compounds, probes and targeting ligands, as well as size, charge and conformation conversion, etc., leading to sensing and signaling, overcoming multidrug resistance, accurate diagnosis and precision therapy. This review has summarized the general strategies of developing stimuli-responsive nanocarriers and recent advances, presented their applications in drug delivery, tumor imaging, therapy and theranostics, illustrated the progress of clinical translation and made prospects.

Integration of Indocyanine Green Analogs as Near-Infrared Fluorescent Carrier for Precise Imaging-Guided Gene Delivery

Codelivery of diagnostic probes and therapeutic molecules often suffers from intrinsic complexity and premature leakage from or degradation of the nanocarrier. Inspired by the "Y" shape of indocyanine green (ICG), the dye is integrated in an amphiphilic lipopeptide (RNF). The hydrophilic segment is composed of arginine-rich dendritic peptides, while cyanine dyes are modified with two long carbon chains and employed as the hydrophobic moiety. They are linked through a disulfide linkage to improve the responsivity in the tumor microenvironment. After formulation with other lipopeptides at an optimized ratio, the theranostic system (RNS-2) forms lipid-based nanoparticles with slight positive zeta potential enabling efficient condensation of DNA. The RNS-2 displays glutathione responded gene release, activatable fluorescence recovery, and up to sevenfold higher in vitro transfection than Lipofectamine 2000. Compared with a Cy3 and Cy5 labeled fluorescence resonance energy transfer indicator for gene release, the "turn-on" indocyanine green analogs exhibit longer emission wavelength and better positive correlation with the dynamic processes of gene delivery. More importantly, the RNS-2 system enables efficient near infrared imaging guided gene transfer in tumor-bearing mice and thus provides more precise and accurate information on location of the cargo gene and synthesized carriers.

Glutathione-responsive disassembly of disulfide dicyanine for tumor imaging with reduction in background signal intensity

Near-infrared (NIR) fluorescence imaging has been proved as an effective modality in identifying the tumor border and distinguishing the tumor cells from healthy tissue during the oncological surgery. Developing NIR fluorescent probes with high tumor to background (T/B) signal is essential for the complete debulking of the tumor, which will prolong the survival rate of tumor patients. However, the nonspecific binding and "always-on" properties of the conventional fluorescent probes leads to high background signals and poor specificity. Method: To address this problem, glutathione (GSH)-responsive, two disulfide-bonded dicyanine dyes (ss-diCy5 and ss-diNH800CW) were synthesized. As synthesized dyes are quenched under normal physiological conditions, however, once reached to the tumor site, these dyes are capable of emitting strong fluorescence signals primarily because of the cleavage of the disulfide bond in the tumor microenvironment with high GSH concentration. Besides, the GSH-responsive behavior of these dyes was monitored using the UV-vis and fluorescence spectroscopy. The diagnostic accuracy of the aforementioned dyes was also tested both in tumor cells and 4T1-bearing mice. Results: The fluorescence signal intensity of disulfide dicyanine dyes was quenched up to 89% compared to the mono cyanine dyes, thus providing a very low fluorescence background. However, when the disulfide dicyanine dye reaches the tumor site, the dicyanine is cleaved by GSH into two mono-dyes with high fluorescence strength, thus producing strong fluorescent signals upon excitation. The fluorescent signal of the dicyanine was enhanced by up to 27-fold after interacting with the GSH solution. In vivo xenografts tumor studies further revealed that the fluorescence signals of aforementioned dyes can be quickly recovered in the solid tumor. Conclusion: In summary, the disulfide dicyanines dyes can provide a promising platform for specific tumor-activatable fluorescence imaging with improved T/B value.

Nanoparticle-based Cell Trackers for Biomedical Applications

The continuous or real-time tracking of biological processes using biocompatible contrast agents over a certain period of time is vital for precise diagnosis and treatment, such as monitoring tissue regeneration after stem cell transplantation, understanding the genesis, development, invasion and metastasis of cancer and so on. The rationally designed nanoparticles, including aggregation-induced emission (AIE) dots, inorganic quantum dots (QDs), nanodiamonds, superparamagnetic iron oxide nanoparticles (SPIONs), and semiconducting polymer nanoparticles (SPNs), have been explored to meet this urgent need. In this review, the development and application of these nanoparticle-based cell trackers for a variety of imaging technologies, including fluorescence imaging, photoacoustic imaging, magnetic resonance imaging, magnetic particle imaging, positron emission tomography and single photon emission computing tomography are discussed in detail. Moreover, the further therapeutic treatments using multi-functional trackers endowed with photodynamic and photothermal modalities are also introduced to provide a comprehensive perspective in this promising research field.

Multi-stimuli responsive polymeric prodrug micelles for combined chemotherapy and photodynamic therapy

The strategy of novel multi-stimuli response and synergistic chemo–photodynamic therapy nanoplatform will be helpful for exploiting intelligent cancer therapy.

Redox-sensitive dimeric camptothecin phosphatidylcholines-based liposomes for improved anticancer efficacy

Aim: A redox-triggered camptothecin (CPT) liposomal system was developed for an improved clinical potential in tumor therapy. Materials & methods: CPT–phosphorylcholine conjugates (CPT–SS–GPCs: CPT–SS–3–GPC and CPT–SS–11–GPC) were synthesized by conjugating CPT to glycerylphosphorylcholine via disulfide bond linker. CPT–SS–GPCs could be assembled into liposomes. Different in vitro and in vivo analyses were used to evaluate the anticancer activities of CPT–SS–GPCs. Results: CPT–SS–GPCs liposomes exhibited extremely high drug loading and uniform size of 150–200 nm. Moreover, the rapid release of parent CPT in reductive condition and high cellular uptake of CPT–SS–GPCs liposomes were observed. At last, in vitro and in vivo anticancer assay showed the enhanced efficacy of CPT–SS–GPCs liposomes. Conclusion: Redox-triggered CPT–SS–GPC liposomes have great potential in tumor therapy.

Cascade-Reaction-Based Nanodrug for Combined Chemo/Starvation/Chemodynamic Therapy against Multidrug-Resistant Tumors

We report a chemo/starvation/chemodynamic trimodal combination therapy to combat multidrug-resistant (MDR) tumors by developing a ferrocene-containing nanovesicle (FcNV), which encapsulates glucose oxidase (GOx) in the hydrophilic core and coordinates cisplatin (Pt) in the hydrophobic layer (GOx&Pt@FcNV). Contrasting with other reported multimodal combination therapies, the new nanodrug (GOx&Pt@FcNV) relies on cascade reactions to drastically increase the overall effectiveness against MDR tumors. Specifically, Pt blocks deoxyribonucleic acid replication and activates hydrogen peroxide (H₂O₂) generation for chemotherapy; GOx consumes glucose to produce H₂O₂ and gluconic acid for starvation therapy; and all H₂O₂ products are catalyzed by ferrous ions decomposed from ferrocene to generate the highly toxic hydroxyl radicals (^•OH) for chemodynamic therapy. The in vitro studies reveal that GOx&Pt@FcNV exhibits a highly efficient killing effect against various MDR tumor cells. The in vivo studies of double-tumor-bearing nude mice demonstrate that the tumor inhibitory rates (TIRs) of GOx&Pt@FcNV against cisplatin-resistant A549/DDP are 8.1 times and 3.3 times higher than those of Pt and Pt@FcNV, respectively; they are also 8.6 times and 4.3 times higher than Pt and Pt@FcNV against adriamycin-resistant MCF-7/ADR, respectively. This nanodrug with endogenous stimuli-activated cascade reactions offers a reference for the design of effective trimodal combination therapies to combat MDR tumors.

Recent advances in metallopolymer-based drug delivery systems

Metallopolymers (MPs) or metal-containing polymers have shown great potential as new drug delivery systems (DDSs) due to their unique properties, including universal architectures, composition, properties and surface chemistry. Over the past few decades, the exponential growth of many new classes of MPs that deal with these issues has been demonstrated. This review presents and assesses the recent advances and challenges associated with using MPs as DDSs. Among the most widely used MPs for these purposes, metal complexes based on synthetic and natural polymers, coordination polymers, metal-organic frameworks, and metallodendrimers are distinguished. Particular attention is paid to the stimulus- and multistimuli-responsive metallopolymer-based DDSs. Of considerable interest is the use of MPs for combination therapy and multimodal systems. Finally, the problems and future prospects of using metallopolymer-based DDSs are outlined. The bibliography includes articles published over the past five years.

Intracellular tracking of drug release from pH-sensitive polymeric nanoparticles via FRET for synergistic chemo-photodynamic therapy

BACKGROUND

Synergistic therapy of tumor is a promising way in curing cancer and in order to achieve effective tumor therapy with real-time drug release monitoring, dynamic cellular imaging and antitumor activity.

RESULTS

In this work, a polymeric nanoparticle with Forster resonance energy transfer (FRET) effect and chemo-photodynamic properties was fabricated as the drug vehicle. An amphiphilic polymer of cyclo(RGDfCSH) (cRGD)-poly(ethylene glycol) (PEG)-Poly(L-histidine) (PH)-poly(ε-caprolactone) (PCL)-Protoporphyrin (Por)-acting as both a photosensitizer for photodynamic therapy (PDT) and absorption of acceptor in FRET was synthesized and self-assembled into polymeric nanoparticles with epirubicin (EPI)-acting as an antitumor drug for chemotherapy and fluorescence of donor in FRET. Spherical EPI-loaded nanoparticles with the average size of 150 ± 2.4 nm was procured with negatively charged surface, pH sensitivity and high drug loading content (14.9 ± 1.5%). The cellular uptake of EPI-loaded cRGD-PEG-PH-PCL-Por was monitored in real time by the FRET effect between EPI and cRGD-PEG-PH-PCL-Por. The polymeric nanoparticles combined PDT and chemotherapy showed significant anticancer activity both in vitro (IC50 = 0.47 μg/mL) and better therapeutic efficacy than that of free EPI in vivo.

CONCLUSIONS

This work provided a versatile strategy to fabricate nanoassemblies for intracellular tracking of drug release and synergistic chemo-photodynamic therapy.

Iodinated Cyanine Dyes for Fast Near-Infrared-Guided Deep Tissue Synergistic Phototherapy

Phototheranostics, which combines deep tissue imaging and phototherapy [photodynamic therapy (PDT) and/or photothermal therapy (PTT)] via light irradiation, is a promising strategy to treat tumors. Near-infrared (NIR) cyanine dyes are researched as potential phototheranostics reagents for their excellent photophysical properties. However, the low singlet oxygen generation efficiency of cyanine dyes often leads to inadequate therapeutic efficacy for tumors. Herein, we modified an indocyanine green derivative Cy7 with heavy atom iodine to form a novel NIR dye CyI to improve the reactive oxygen species (ROS) production and heat generation while, at the same time, maintain their fluorescence characteristics for in vivo noninvasive imaging. More importantly, in vitro and in vivo therapeutic results illustrated that CyI could quickly and simultaneously generate enhanced ROS and heat to induce more cancer cell apoptosis and higher inhibition rates in deep HepG2 tumors than other noniodinated NIR dyes upon NIR irradiation. Besides, low toxicity of the resulted iodinated NIR dyes was confirmed by in vivo biodistribution and acute toxicity. Results indicate that this low toxic NIR dye could be an ideal phototheranostics agent for deep tumor treatments. Our study presents a novel approach to achieve the fast-synergistic PDT/PTT treatment in deep tissues.

Supramolecular Nanotheranostics

This supramolecular nanotheranostics special issue collected a total of 17 review articles and 3 research articles broadly covering the current and emerging supramolecular nanotheranostics.

Host-Guest Chemistry in Supramolecular Theranostics

Macrocyclic hosts, such as cyclodextrins, calixarenes, cucurbiturils, and pillararenes, exhibit unparalleled advantages in disease diagnosis and therapy over the past years by fully taking advantage of their host-guest molecular recognitions. The dynamic nature of the non-covalent interactions and selective host-guest complexation endow the resultant nanomaterials with intriguing properties, holding promising potentials in theranostic fields. Interestingly, the differences in microenvironment between the abnormal and normal cells/tissues can be employed as the stimuli to modulate the host-guest interactions, realizing the purpose of precise diagnosis and specific delivery of drugs to lesion sites. In this review, we summarize the progress of supramolecular theranostics on the basis of host-guest chemistry benefiting from their fantastic topological structures and outstanding supramolecular chemistry. These state-of-the-art examples provide new methodologies to overcome the obstacles faced by the traditional theranostic systems, promoting their clinical translations.

Nano-Based Systems and Biomacromolecules as Carriers for Metallodrugs in Anticancer Therapy

Since the discovery of cisplatin and its potency in anticancer therapy, the development of metallodrugs has been an active area of research. The large choice of transition metals, oxidation states, coordinating ligands, and different geometries, allows for the design of metal-based agents with unique mechanisms of action. Many metallodrugs, such as titanium, ruthenium, gallium, tin, gold, and copper-based complexes have been found to have anticancer activities. However, biological application of these agents necessitates aqueous solubility and low systemic toxicity. This minireview highlights the emerging strategies to facilitate the in vivo application of metallodrugs, aimed at enhancing their solubility and bioavailability, as well as improving their delivery to tumor tissues. The focus is on encapsulating the metal-based complexes into nanocarriers or coupling to biomacromolecules, generating efficacious anticancer therapies. The delivery systems for complexes of platinum, ruthenium, copper, and iron are discussed with most recent examples.

Hypoxia-activated prodrugs and redox-responsive nanocarriers

Hypoxia is one of the marked features of malignant tumors, which is associated with several adaptation changes in the microenvironment of tumor cells. Therefore, targeting tumor hypoxia is a research hotspot for cancer therapy. In this review, we summarize the developing chemotherapeutic drugs for targeting hypoxia, including quinones, nitroaromatic/nitroimidazole, N-oxides, and transition metal complexes. In addition, redox-responsive bonds, such as nitroimidazole groups, azogroups, and disulfide bonds, are frequently used in drug delivery systems for targeting the redox environment of tumors. Both hypoxia-activated prodrugs and redox-responsive drug delivery nanocarriers have significant effects on targeting tumor hypoxia for cancer therapy. Hypoxia-activated prodrugs are commonly used in clinical trials with favorable prospects, while redox-responsive nanocarriers are currently at the experimental stage.

Stimuli-Responsive Therapeutic Metallodrugs

The success of platinum-based anticancer agents has motivated the exploration of novel metal-based drugs for several decades, whereas problems such as drug-resistance and systemic toxicity hampered their clinical applications and efficacy. Stimuli-responsiveness of some metal complexes offers a good opportunity for designing site-specific prodrugs to maximize the therapeutic efficacy and minimize the side effect of metallodrugs. This review presents a comprehensive and up-to-date overview on the therapeutic stimuli-responsive metallodrugs that have appeared in the past two decades, where stimuli such as redox, pH, enzyme, light, temperature, and so forth were involved. The compounds are classified into three major categories based on the nature of stimuli, that is, endo-stimuli-responsive metallodrugs, exo-stimuli-responsive metallodrugs, and dual-stimuli-responsive metallodrugs. Representative examples of each type are discussed in terms of structure, response mechanism, and potential medical applications. In the end, future opportunities and challenges in this field are tentatively proposed. With diverse metal complexes being introduced, the foci of this review are pointed to platinum and ruthenium complexes.

Rational design of multimodal therapeutic nanosystems for effective inhibition of tumor growth and metastasis

Simultaneous inhibition of both tumor growth and metastasis is the key to treating metastatic cancer, yet the development of effective drug delivery systems represents a great challenge since multimodal therapeutic agents must be rationally combined to overcome the biological mechanisms underpinning tumor cell proliferation and invasion. In this context, we report a hybrid therapeutic nanoscale platform that incorporates an anti-proliferative drug, doxorubicin (DOX), and an anti-NF-κB agent, p65-shRNA, for effective treatment of metastatic breast cancer. In our design, we first conjugated DOX via an acid-labile linker onto gold nanorods that were pre-modified with the tumor targeting peptide RGD and a positively charged, disulfide cross-linked short polyethylenimines (DSPEI), and then incorporated shRNA through electrostatic complexation with DSPEI. We show that this "all in one" nanotherapeutic system (RDG/shRNA@DOX) can be effectively internalized through RGD-mediated endocytosis, followed by stimuli-responsive intracellular co-release of DOX and shRNA. Our in vitro experiments suggest that this multimodal system can significantly inhibit cell proliferation, angiogenesis, and invasion of metastatic MDA-MB-435 cancer cells. Systemic administration of RDG/shRNA@DOX into a metastatic mouse model led to enhanced tumor accumulation, and, most importantly, significant inhibition of in situ tumor growth and almost complete suppression of tumor metastasis. We believe this hybrid multimodal nanotherapeutic system provides important insight into the rational design of therapeutic systems for the effective treatment of metastatic carcinoma.

STATEMENT OF SIGNIFICANCE

The key to successfully treat metastatic cancer is the simultaneous inhibition of both tumor growth and metastasis. This represents a great challenge for the design of drug delivery systems since multimodal therapeutic agents must be rationally combined to overcome the respective biological mechanisms underpinning tumor cell proliferation and invasion. Toward this end, we developed a hybrid nanomedicine platform that incorporates an anti-proliferative drug, doxorubicin (DOX), and an anti-NF-κB agent, p65-shRNA, for effective treatment of metastatic breast cancer. We showed that this multimodal system (RDG/shRNA@DOX) enhanced tumor accumulation, led to prolonged circulation, and most importantly, significant inhibition of in situ tumor growth and almost complete suppression of tumor metastasis. We believe this hybrid multimodal nanotherapeutic system provides significant insight into the rational design of therapeutic systems for the effective treatment of metastatic cancer.

Glutathione-Scavenging Poly(disulfide amide) Nanoparticles for the Effective Delivery of Pt(IV) Prodrugs and Reversal of Cisplatin Resistance

Despite the broad antitumor spectrum of cisplatin, its therapeutic efficacy in cancer treatment is compromised by the development of drug resistance in tumor cells and systemic side effects. A close correlation has been drawn between cisplatin resistance in tumor cells and increased levels of intracellular thiol-containing species, especially glutathione (GSH). The construction of a unique nanoparticle (NP) platform composed of poly(disulfide amide) polymers with a high disulfide density for the effective delivery of Pt(IV) prodrugs capable of reversing cisplatin resistance through the disulfide-group-based GSH-scavenging process, as described herein, is a promising route by which to overcome limitations associated with tumor resistance. Following systematic screening, the optimized NPs (referred to as CP5 NPs) showed a small particle size (76.2 nm), high loading of Pt(IV) prodrugs (15.50% Pt), a sharp response to GSH, the rapid release of platinum (Pt) ions, and notable apoptosis of cisplatin-resistant A2780cis cells. CP5 NPs also exhibited long blood circulation and high tumor accumulation after intravenous injection. Moreover, in vivo efficacy and safety results showed that CP5 NPs effectively inhibited the growth of cisplatin-resistant xenograft tumors with an inhibition rate of 83.32% while alleviating serious side effects associated with cisplatin. The GSH-scavenging nanoplatform is therefore a promising route by which to enhance the therapeutic index of Pt drugs used currently in cancer treatment.

A triple modality BSA-coated dendritic nanoplatform for NIR imaging, enhanced tumor penetration and anticancer therapy

Functional theranostic systems for drug delivery capable of concurrent near-infrared (NIR) fluorescence imaging, active tumor targeting and anticancer therapies are desired for concise cancer diagnosis and treatment. Dendrimers with controllable size and surface functionalities are good candidates for such platforms. However, integration of active targeting ligands and imaging agents separately on the surface or encapsulation of the imaging agents in the inner core of the dendrimers will result in a more complex composition or reduced drug loading efficiency. Herein, we reported a PAMAM-based theranostic system, with a simple integrin-specific imaging ligand prepared from two motifs. One motif is a NIR carbocyanine fluorescent dye (Cyp) for precise in vivo monitoring of the system and identification of tumor or cancer cells, and the other is a novel tumor-penetrating cyclic peptide (CRGDKGPDC, abbreviated iRGD). BSA was non-covalently bonded with Cyp to reduce NIR agent fluorescence-quenching aggregates and enhance imaging signals. The chemotherapy effect of these dendritic systems was achieved by encapsulating paclitaxel into the hydrophobic interior of the dendrimers. In vitro and in vivo targeting and penetrating studies revealed that a significantly high amount of the dendritic systems was endocytosed by HepG2 cells and enhanced accumulation and penetration at tumor sites. Our safety evaluation showed that masking of cationic-end groups of PAMAM to neutral or anionic groups has resulted in decreased or even zero-toxicity. The preliminary antitumor efficacy of the dendritic system was evaluated. In vitro and in vivo studies confirmed that paclitaxel-encapsulated functionalized PAMAM can efficiently kill HepG2 cancer cells. In conclusion, our functionalized theranostic dendritic system could be a promising nanocarrier to effectively deliver drugs to deep tumor regions for anticancer therapy.

Doxorubicin-loaded redox-responsive micelles based on dextran and indomethacin for resistant breast cancer

Multidrug resistance (MDR) against chemotherapeutic agents has become one of the major obstacles to successful cancer therapy and MDR-associated proteins (MRPs)-mediated drug efflux is the key factor for MDR. In this study, a redox-responsive polymer based on dextran (DEX) and indomethacin (IND), which could reduce MRPs-mediated efflux of chemotherapeutics, was synthesized, and the obtained polymer could spontaneously form stable micelles with well-defined core-shell structure and a uniform size distribution with an average diameter of 50 nm and effectively encapsulate doxorubicin (DOX); the micelles contain a disulfide bridge (cystamine, SS) between IND and DEX (DEX-SS-IND). In vitro drug release results indicated that DEX-SS-IND/DOX micelles could maintain good stability in a stimulated normal physiological environment and promptly depolymerized and released DOX in a reducing environment. After incubating DEX-SS-IND/DOX micelles with drug-resistant tumor (MCF-7/ADR) cells, the intracellular accumulation and retention of DOX were significantly increased under the synergistic effects of redox-responsive delivery and the inhibitory effect of IND on MRPs. In vitro cytotoxicity showed that DEX-SS-IND/DOX micelles exhibited higher cytotoxicity against MCF-7/ADR cells. Moreover, DEX-SS-IND/DOX micelles showed significantly enhanced inhibition of tumor in BALB/c nude mice bearing MCF-7/ADR tumors and reduced systemic toxicity. Overall, the cumulative evidence indicates that DEX-SS-IND/DOX micelles hold significant promise for overcoming MDR for cancer therapy.