Advances in aggregatable nanoparticles for tumor-targeted drug delivery

Aggregable gold nanoparticles for cancer photothermal therapy

Photothermal therapy (PTT) is an important non-invasive cancer treatment method. Enhancing the photothermal conversion efficiency (PCE) of photothermal agents (PTAs) and prolonging their tumor accumulation and retention are effective strategies to enhance the efficiency of cancer PTT. Recently, tremendous progress has been made in developing stimuli-responsive aggregable gold nanoparticles as effective PTAs for PTT. In this review, we discuss the chemical principles underlying gold nanoparticle aggregation and highlight the progress in gold nanoparticle aggregation triggered by different stimuli, especially tumor microenvironment-related factors, for cancer PTT. Covalent condensation reactions, click cycloaddition reactions, chelation reactions, and Au-S bonding, as well as non-covalent electrostatic interactions, hydrophobic interactions, hydrogen bonding, and van der Waals forces play key roles in the aggregation of gold nanoparticles. Enzymes, pH, reactive oxygen species, small molecules, salts, and light drive the occurrence of gold nanoparticle aggregation. Targeted aggregation of gold nanoparticles prolongs tumor accumulation and retention of PTAs and improves PCE, resulting in enhanced tumor PTT. Moreover, the major challenges of aggregable gold nanoparticles as PTAs are pointed out and the promising applications are also prospected at the end. With the deepening of research, we expect aggregable gold nanoparticles to become essential PTAs for tumor therapy.

Nanomedicines Targeting Ferroptosis to Treat Stress-Related Diseases

Ferroptosis, a unique form of regulated cell death driven by iron-dependent lethal lipid peroxidation, is implicated in various stress-related diseases like neurodegeneration, vasculopathy, and metabolic disturbance. Stress-related diseases encompass widespread medical disorders that are influenced or exacerbated by stress. These stressors can manifest in various organ or tissue systems and have significant implications for human overall health. Understanding ferroptosis in these diseases offers insights for therapeutic strategies targeting relevant pathways. This review explores ferroptosis mechanisms, its role in pathophysiology, its connection to stress-related diseases, and the potential of ferroptosis-targeted nanomedicines in treating conditions. This monograph also delves into the engineering of ferroptosis-targeted nanomedicines for tackling stress-related diseases, including cancer, cardia-cerebrovascular, neurodegenerative, metabolic and inflammatory diseases. Anyhow, nanotherapy targeting ferroptosis holds promise by both promoting and suppressing ferroptosis for managing stress-related diseases.

A natural compound-empowered podophyllotoxin prodrug nanoassembly magnifies efficacy-toxicity benefits in cancer chemotherapy

Small-molecule prodrug nanoassembly technology with a unique advantage in off-target toxicity reduction has been widely used for antitumor drug delivery. However, prodrug activation remains a rate-limiting step for exerting therapeutic actions, which requires to quickly reach the minimum valid concentrations of free drugs. Fortunately, we find that a natural compound (BL-193) selectively improves the chemotherapy sensitivity of breast cancer cells to podophyllotoxin (PPT) at ineffective dose concentrations. Based on this, we propose to combine prodrug nanoassembly with chemotherapy sensitization to fully unleash the chemotherapeutic potential of PPT. Specifically, a redox-sensitive prodrug (PSSF) of PPT is synthesized by coupling 9-fluorenyl-methanol (Fmoc-OH) with PPT linked via disulfide bond. Intriguingly, PSSF with a π-conjugated structure readily co-assembles with BL-193 into stable nanoassembly. Significantly, BL-193 serves as an excellent chemosensitizer that creates an ultra-low-dose chemotherapeutic window for PPT. Moreover, prodrug design and precise hybrid nanoassembly well manage off-target toxicity. As expected, such a BL-193-empowered prodrug nanoassembly elicits potent antitumor responses. This study offers a novel paradigm to magnify chemotherapy efficacy-toxicity benefits.

Organoid-Based Assessment of Metal-Organic Framework (MOF) Nanomedicines for Ex Vivo Cancer Therapy

Nanomaterials have been extensively exploited in tumor treatment, leading to numerous innovative strategies for cancer therapy. While nanomedicines present immense potential, their application in cancer therapy is characterized by significant complexity and unpredictability, especially regarding biocompatibility and anticancer efficiency. These considerations underscore the essential need for the development of ex vivo research models, which provide invaluable insights and understanding into the biosafety and efficacy of nanomedicines in oncology. Fortunately, the emergence of organoid technology offers a novel approach to the preclinical evaluation of the anticancer efficacy of nanomedicines in vitro. Hence, in this study, we constructed intestine and hepatocyte organoid models (Intestine-orgs and Hep-orgs) for assessing intestinal and hepatic toxicity at the microtissue level. We utilized three typical metal-organic frameworks (MOFs), ZIF-8, ZIF-67, and MIL-125, as nanomedicines to further detect their interactions with organoids. Subsequently, the MIL-125 with biocompatibility loaded methotrexate (MTX), forming the nanomedicine (MIL-125-PEG-MTX), indicated a high loading efficiency (82%) and a well-release capability in an acid microenvironment. More importantly, the anticancer effect of the nanomedicine was investigated using an in vitro patient-derived organoids (PDOs) model, achieving inhibition rates of 48% and 78% for PDO-1 and PDO-2, respectively, demonstrating that PDOs could predict clinical response and facilitate prospective therapeutic selection. These achievements presented great potential for organoid-based ex vivo models for nano theragnostic evaluation in biosafety and function.

Prussian blue nanoparticle-based pH-responsive self-assembly for enhanced photothermal and chemotherapy of tumors

In recent years, there has been growing interest in size-transformable nanoplatforms that exhibit active responses to acidic microenvironments, presenting promising prospects in the field of nanomedicine for tumor therapy. However, the design and fabrication of such size-adjustable nanotherapeutics pose significant challenges compared to size-fixed nanocomposites, primarily due to their distinct pH-responsive requirements. In this study, we developed pH-activated-aggregating nanosystems to integrate chemotherapy and photothermal therapy by creating size-transformable nanoparticles based on Prussian blue nanoparticles (PB NPs) anchored with acid-responsive polyoxometalates (POMs) quantum dots via electrostatic interactions (PPP NPs). Subsequently, we utilized doxorubicin (DOX) as a representative drug to formulate PPPD NPs. Notably, PPPD NPs exhibited a significant response to acidic conditions, resulting in changes in surface charge and rapid aggregation of PPP NPs. Furthermore, the aggregated PPP NPs demonstrated excellent photothermal properties under near-infrared laser irradiation. Importantly, PPPD NPs prolonged their retention time in tumor cells via a size-transformation approach. In vitro cellular assays revealed that the anticancer efficacy of PPPD NPs was significantly enhanced. The IC50 values for the PPPD NPs groupand the PPPD NPs + NIR group were 50.11 μg/mL and 30.9 μg/mL. Overall, this study introduces a novel strategy for cancer therapy by developing size-aggregating nano-drugs with stimuli-responsive properties, holding promise for improved therapeutic outcomes in future combination approaches involving photothermal therapy and chemotherapy.

pH-Triggered Transformable Peptide Nanocarriers Extend Drug Retention for Breast Cancer Combination Therapy

Increasing the penetration and accumulation of antitumor drugs at the tumor site are crucial in chemotherapy. Smaller drug-loaded nanoparticles (NPs) typically exhibit increased tumor penetration and more effective permeation through the nuclear membrane, whereas larger drug-loaded NPs show extended retention at the tumor site. In addition, cancer stem cells (CSCs) have unlimited proliferative potential and are crucial for the onset, progression, and metastasis of cancer. Therefore, a drug-loaded amphiphilic peptide, DDP- and ATRA-loaded Pep1 (DA/Pep1), is designed that self-assembles into spherical NPs upon the encapsulation of cis-diamminedichloroplatinum (DDP) and all-trans retinoic acid (ATRA). In an acidic environment, DA/Pep1 transforms into aggregates containing sheet-like structures, which significantly increases drug accumulation at the tumor site, thereby increasing antitumor effects and inhibiting metastasis. Moreover, although DDP treatment can increase the number of CSCs present, ATRA can induce the differentiation of CSCs in breast cancer to increase the therapeutic effect of DDP. In conclusion, this peptide nanodelivery system that transforms in response to the acidic tumor microenvironment is an extremely promising nanoplatform that suggests a new idea for the combined treatment of tumors.

Curvature-mediated rapid extravasation and penetration of nanoparticles against interstitial fluid pressure for improved drug delivery

Elevated interstitial fluid pressure (IFP) within pathological tissues (e.g., tumors, obstructed kidneys, and cirrhotic livers) creates a significant hindrance to the transport of nanomedicine, ultimately impairing the therapeutic efficiency. Among these tissues, solid tumors present the most challenging scenario. While several strategies through reducing tumor IFP have been devised to enhance nanoparticle delivery, few approaches focus on modulating the intrinsic properties of nanoparticles to effectively counteract IFP during extravasation and penetration, which are precisely the stages obstructed by elevated IFP. Herein, we propose an innovative solution by engineering nanoparticles with a fusiform shape of high curvature, enabling efficient surmounting of IFP barriers during extravasation and penetration within tumor tissues. Through experimental and theoretical analyses, we demonstrate that the elongated nanoparticles with the highest mean curvature outperform spherical and rod-shaped counterparts against elevated IFP, leading to superior intratumoral accumulation and antitumor efficacy. Super-resolution microscopy and molecular dynamics simulations uncover the underlying mechanisms in which the high curvature contributes to diminished drag force in surmounting high-pressure differentials during extravasation. Simultaneously, the facilitated rotational movement augments the hopping frequency during penetration. This study effectively addresses the limitations posed by high-pressure impediments, uncovers the mutual interactions between the physical properties of NPs and their environment, and presents a promising avenue for advancing cancer treatment through nanomedicine.

pH-responsive drug-loaded peptides enhance drug accumulation and promote apoptosis in tumor cells

The efficacy of chemotherapeutic drugs in tumor treatment is limited by their toxicity and side effects due to their inability to selectively accumulate in tumor tissue. In addition, chemotherapeutic agents are easily pumped out of tumor cells, resulting in their inadequate accumulation. To overcome these challenges, a drug delivery system utilizing the amphiphilic peptide Pep1 was designed. Pep1 can self-assemble into spherical nanoparticles (PL/Pep1) and encapsulate paclitaxel (PTX) and lapatinib (LAP). PL/Pep1 transformed into nanofibers in an acidic environment, resulting in longer drug retention and higher drug concentrations within tumor cells. Ultimately, PL/Pep1 inhibited tumor angiogenesis and enhanced tumor cell apoptosis. The use of shape-changing peptides as drug carriers to enhance cancer cell apoptosis is promising.

Approaches for reducing chemo/radiation-induced cardiotoxicity by nanoparticles

Nanoparticles are fascinating and encouraging carriers for cancer treatment due to their extraordinary properties and potential applications in targeted drug delivery, treatment, and diagnosis. Experimental studies including in vitro and in vivo examinations show that nanoparticles can cause a revolution in different aspects of cancer therapy. Normal tissue toxicity and early and late consequences are the major limitations of cancer therapy by radiotherapy and chemotherapy. However, the delivery of drugs into tumors or reducing the accumulation of drugs in normal tissues can permit a more satisfactory response of malignancies to therapy with more inferior side effects. Cardiac toxicity is one of the major problems for chemotherapy and radiotherapy. Therefore, several experimental studies have been performed to minimize the degenerative impacts of cancer treatment on the heart and also enhance the influences of radiotherapy and chemotherapy agents in cancers. This review article emphasizes the benefits of nanoparticle-based drug delivery techniques, including minimizing the exposure of the heart to anticancer drugs, enhancing the accumulation of drugs in cancers, and expanding the effectiveness of radiotherapy. The article also discusses the challenges and problems accompanied with nanoparticle-based drug delivery techniques such as toxicity, which need to be addressed through further research. Moreover, the article emphasizes the importance of developing safe and effective nanoparticle-based therapies that can be translated into clinical practice.

Codelivery of CuS and DOX into Deep Tumors with Size and Charge-Switchable PAMAM Dendrimers for Chemo-photothermal Therapy

Accurate targeting of therapeutic agents to specific tumor tissues, especially via deep tumor penetration, has been an effective strategy in cancer treatments. Here, we described a flexible nanoplatform, pH-responsive zwitterionic acylsulfonamide betaine-functionalized fourth-generation PAMAM dendrimers (G4-AB), which presented multiple advantages for chemo-photothermal therapy, including template synthesis of ultrasmall copper sulfide (CuS) nanoparticles and further encapsulation of doxorubicin (DOX) (G4-AB-DOX/CuS), long-circulating performance by a relatively large size and zwitterionic surface in a physiological environment, combined size shrinkage, and charge conversions via pH-responsive behavior in an acidic tumor microenvironment (TME). Accordingly, high tumor penetration and positive cell uptake for CuS and DOX have been determined, which triggered an excellent combination treatment under near-infrared irradiation in comparison to the monochemotherapy system and irresponsive chemo-photothermal system. Our study represented great promise in constructing multifunctional carriers for the effective delivery of photothermal nanoparticles and drugs in chemo-photothermal therapy.

Tumor Abnormality-Oriented Nanomedicine Design

Anticancer nanomedicines have been proven effective in mitigating the side effects of chemotherapeutic drugs. However, challenges remain in augmenting their therapeutic efficacy. Nanomedicines responsive to the pathological abnormalities in the tumor microenvironment (TME) are expected to overcome the biological limitations of conventional nanomedicines, enhance the therapeutic efficacies, and further reduce the side effects. This Review aims to quantitate the various pathological abnormalities in the TME, which may serve as unique endogenous stimuli for the design of stimuli-responsive nanomedicines, and to provide a broad and objective perspective on the current understanding of stimuli-responsive nanomedicines for cancer treatment. We dissect the typical transport process and barriers of cancer drug delivery, highlight the key design principles of stimuli-responsive nanomedicines designed to tackle the series of barriers in the typical drug delivery process, and discuss the "all-into-one" and "one-for-all" strategies for integrating the needed properties for nanomedicines. Ultimately, we provide insight into the challenges and future perspectives toward the clinical translation of stimuli-responsive nanomedicines.

A multifunctional integrated biomimetic spore nanoplatform for successively overcoming oral biological barriers

The biological barriers have seriously restricted the efficacious responses of oral delivery system in diseases treatment. Utilizing a carrier based on the single construction means is hard to overcome these obstacles simultaneously because the complex gastrointestinal tract environment requires carrier to have different or even contradictory properties. Interestingly, spore capsid (SC) integrates many unique biological characteristics, such as high resistance, good stability etc. This fact offers a boundless source of inspiration for the construction of multi-functional oral nanoplatform based on SC without further modification. Herein, we develop a type of biomimetic spore nanoplatform (SC@DS NPs) to successively overcome oral biological barriers. Firstly, doxorubicin (DOX) and sorafenib (SOR) are self-assembled to form carrier-free nanoparticles (DS NPs). Subsequently, SC is effectively separated from probiotic spores and served as a functional vehicle for delivering DS NPs. As expect, SC@DS NPs can efficaciously pass through the rugged stomach environment after oral administration and further be transported to the intestine. Surprisingly, we find that SC@DS NPs exhibit a significant improvement in the aspects of mucus penetration and transepithelial transport, which is related to the protein species of SC. This study demonstrates that SC@DS NPs can efficiently overcome multiple biological barriers and improve the therapeutic effect.

Recent development of polymer nanomicelles in the treatment of eye diseases

The eye, being one of the most intricate organs in the human body, hosts numerous anatomical barriers and clearance mechanisms. This highlights the importance of devising a secure and efficacious ocular medication delivery system. Over the past several decades, advancements have been made in the development of a nano-delivery platform based on polymeric micelles. These advancements encompass diverse innovations such as poloxamer, chitosan, hydrogel-encapsulated micelles, and contact lenses embedded with micelles. Such technological evolutions allow for sustained medication retention and facilitate enhanced permeation within the eye, thereby standing as the avant-garde in ocular medication technology. This review provides a comprehensive consolidation of ocular medications predicated on polymer nanomicelles from 2014 to 2023. Additionally, it explores the challenges they pose in clinical applications, a discussion intended to aid the design of future clinical research concerning ocular medication delivery formulations.

Supramolecular nanomedicines based on host-guest interactions of cyclodextrins

In the biomedical and pharmaceutical fields, cyclodextrin (CD) is undoubtedly one of the most frequently used macrocyclic compounds as the host molecule because it has good biocompatibility and can increase the solubility, bioavailability, and stability of hydrophobic drug guests. In this review, we generalized the unique properties of CDs, CD-related supramolecular nanocarriers, supramolecular controlled release systems, and targeting systems based on CDs, and introduced the paradigms of these nanomedicines. In addition, we also discussed the prospects and challenges of CD-based supramolecular nanomedicines to facilitate the development and clinical translation of these nanomedicines.

Recent Research Progress of RGD Peptide–Modified Nanodrug Delivery Systems in Tumor Therapy

There have been great advancements in targeted nanodrug delivery systems for tumor therapy. Liposomes, polymeric nanoparticles, and inorganic nanoparticles are commonly employed as nanocarriers for drug delivery, and it has been found that arginine glycine aspartic acid (RGD) peptides and their derivatives can be used as ligands of integrin receptors to enhance the direct targeting ability. In this paper, we review the recent applications of RGD-modified liposomes, polymeric nanoparticles, and inorganic nanocarriers in cancer diagnosis and treatment, discuss the current challenges and prospects, and examine the progress made by the latest research on RGD peptide–modified nano delivery systems in cancer therapy. In recent years, RGD peptide–modified nanodrug delivery systems have been proven to have great potential in tumor therapy. Finally, we provide an overview of the current limitations and future directions of RGD peptide–modified nano-drug delivery systems for cancer therapy. This review aims to elucidate the contribution of RGD peptide–modified nanodrug delivery systems in the field of tumor therapy.

Reduction-Responsive Stearyl Alcohol-Cabazitaxel Prodrug Nanoassemblies for Cancer Chemotherapy

Cabazitaxel (CTX) has distinct therapeutic merits for advanced and metastatic cancer. However, the present clinical formulation (Jevtana®) has several defects, especially for undesirable tumor-targeting and serious side effects, greatly limiting the therapeutic efficacy. Small-molecule prodrug-based nanoassemblies integrate the advantages of both prodrug strategy and nanotechnology, emerging as a promising treatment modality. Herein, disulfide bonds with different lengths were employed as linkages to elaborately synthesize three redox-sensitive stearyl alcohol (SAT)-CTX prodrug-based nanoassemblies (SAC NPs, SBC NPs and SGC NPs) for seeking optimal chemotherapeutical treatment. All the prodrug-based nanoassemblies exhibited impressive drug-loading efficiency, superior self-assembly capability and excellent colloidal stability. Interestingly, the drug release behaviors of three prodrug-nanoassemblies in the same reductive environment were different owing to tiny changes in the carbon chain length of disulfide bonds, resulting in disparate cytotoxicity effects, pharmacokinetic outcomes and in vivo antitumor efficacies. Among them, SAC NPs displayed rapid drug release, excellent cytotoxicity, long blood circulation and enhanced tumor accumulation, thus showing strong tumor inhibition in the 4T1-bearing mouse model. Our study shed light on the vital role of connecting bonds in designing high-efficiency, low-toxicity prodrug nanoassemblies.

Molecularly engineering a dual-drug nanoassembly for self-sensitized photodynamic therapy via thioredoxin impairment and glutathione depletion

Photodynamic therapy (PDT) has been extensively investigated as a spatiotemporally noninvasive and controllable modality for cancer treatment. However, the intracellular antioxidant systems mainly consisting of thioredoxin (Trx) and glutathione (GSH) significantly counteract and prevent reactive oxygen species (ROS) accumulation, resulting in a serious loss of PDT efficiency. To address this challenge, we propose that PDT can be improved by precisely blocking antioxidant systems. After molecular engineering and synergistic cytotoxic optimization, a DSPE-PEG2K-modified dual-drug nanoassembly (PPa@GA/DSPE-PEG2K NPs) of pyropheophorbide a (PPa) and gambogic acid (GA) is successfully constructed. Interestingly, GA can effectively destroy intracellular antioxidant systems by simultaneously inhibiting Trx and GSH. Under laser irradiation, the cell-killing effects of PPa is significantly enhanced by GA-induced inhibition of the antioxidant systems. As expected, PPa@GA/DSPE-PEG2K nanoparticles demonstrate potent antitumor activity in a 4T1 breast tumor-bearing BALB/c mouse xenograft model. Such a carrier-free self-sensitized nanotherapeutic offers a novel co-delivery strategy for effective PDT.

Nanocarriers for Active Ingredients of Chinese Medicine (AIFCM) Used in Gastrointestinal Cancer Therapy

Active ingredients of Chinese medicine (AIFCM) are pharmacological substances taken from traditional Chinese medicine that show promise in treating gastrointestinal cancer. Compared with traditional chemotherapeutic drugs, AIFCM have advantages such as multi-target and multi-level treatment of gastrointestinal cancer. Nanocarriers have the following advantages, better bioavailability, passive or active targeting of tumor sites and responsive release of drugs. The use of nanocarriers for delivery of AIFCM in treatment of gastrointestinal cancer, can overcome the disadvantages of some AIFCM, such as insolubility and low bioavailability. In this review, we first outline the background on gastrointestinal cancer, main curative factors and conventional therapeutic approaches. Then, the mechanisms for AIFCM in gastrointestinal cancer therapy are presented in the following four aspects: gene regulation, immune modulation, cellular pathway transduction, and alteration of intestinal flora. Thirdly, preparation of various nanocarriers and results when combining AIFCM in gastrointestinal cancer are presented. Fourth, application of novel targeted nanocarriers and responsive nanocarriers in gastrointestinal tumors is further introduced. Finally, the application of AIFCM in the treatment of gastrointestinal cancer is summarized and prospected, hoping to shed some light on the nanocarrier-bound AIFCM in the treatment of gastrointestinal cancer.

Polyoxometalate-based nanocomposites for antitumor and antibacterial applications

Polyoxometalates (POMs), as emerging inorganic metal oxides, have been shown to have significant biological activity and great medicinal value. Nowadays, biologically active POM-based organic-inorganic hybrid materials have become the next generation of antibacterial and anticancer drugs because of their customizable molecular structures related to their highly enhanced antitumor activity and reduced toxicity to healthy cells. In this review, the current developed strategies with POM-based materials for the purpose of antibacterial and anticancer activities from different action principles inducing cell death and hyperpolarization, cell plasma membrane destruction, interference with bacterial respiratory chain and inhibiting bacterial growth are overviewed. Moreover, specific interactions between POM-based materials and biomolecules are highlighted for a better understanding of their antibacterial and anticancer mechanisms. POMs have great promise as next-generation antibacterial and anticancer drugs, and this review will provide a valuable systematic reference for the further development of POM-based nanomaterials.

Molecularly Self-Engineered Nanoamplifier for Boosting Photodynamic Therapy via Cascade Oxygen Elevation and Lipid ROS Accumulation

Photodynamic therapy (PDT) has been extensively explored as a noninvasive cancer treatment modality. However, the dilemma of tumor hypoxia and short half-life of singlet oxygen (¹O₂) severely restrict the therapeutic efficacy of PDT. Herein, we develop a facile three-in-one PDT nanoamplifier (AA@PPa/Hemin NPs) assembled by pyropheophorbide a (PPa), hemin, and arachidonic acid (AA). Interestingly, AA not only acts as an enabler to facilitate the assembly of PPa and hemin in the construction of ternary hybrid nanoassemblies but also acts as a lipid reactive oxygen species (ROS) amplifier for robust PDT. In tumor cells, hemin plays the role of a catalase-like catalyst that accelerates the production of oxygen (O₂) from hydrogen peroxide (H₂O₂), significantly alleviating tumor hypoxia. Under laser irradiation, vast amounts of ¹O₂ generated by PPa trigger the peroxidation of AA to produce large amounts of cytotoxic lipid ROS, immensely amplifying the efficiency of PDT by promptly eliciting cellular oxidative stress. As expected, AA@PPa/Hemin NPs exert potent antitumor activity in a 4T1 breast-tumor-bearing BALB/c mice xenograft model. Such a cascade nanohybrid amplifier provides a novel codelivery platform for accurate and effective PDT of cancer.

Lipid Membrane-Wrapped Zeolitic Imidazolate Framework-8 for Synergistic Chemotherapy and Photothermal Therapy to Target Prostate Cancer

Endocrine therapy is often used for advanced prostate cancer. However, with cancer progress, prostate cancer gradually resistant to hormone which lead to serious threatens to life of patients. Herein, a multifunctional synergistic core–shell nanoplatform is reported for improving the therapeutic effect of chemotherapy for advanced or metastatic prostate cancer, and reducing the risk of leakage of chemotherapy drugs. Particularly, Zeolitic imidazolate framework-8 (ZIF-8) is chosen as inner core to load doxorubicin, and the of liposomes which are embedded with IR780 iodide are used as outer shell, and further modified with target ligand that binds to luteinizing hormone releasing hormone receptor. The prepared nanocarrier exhibit satisfactory photothermal effect under near infrared laser irradiation, and the temperature increases to 60.8 °C within 6 min. Meanwhile, the elevated temperature accelerates the degradation of lipid shell, releasing ZIF-8 core to acidic microenvironment of tumor, and resulting in the release of doxorubicin. Moreover, in vivo and in vitro studies have shown the ZIF-D@ALIP core–shell nanoparticles can achieve targeted drug delivery, pH and NIR dual stimuli-responsive drug release, as well as chemotherapy and photothermal therapy synergistically on the tumor site. In addition, the problem of premature leakage and changes in the physicochemical properties of anticancer drugs are avoided under the protection of the outer shell structure. Therefore, the core–shell nanostructure proposes a new lipid membrane coating strategy to promote the effective targeting of prostate cancer cells or tissues and provides some insights in clinical treatment for advanced prostate cancer.

The in vivo fate of polymeric micelles

This review aims to provide a systemic analysis of the in vivo, as well as subcellular, fate of polymeric micelles (PMs), starting from the entry of PMs into the body. Few PMs are able to cross the biological barriers intact and reach the circulation. In the blood, PMs demonstrate fairly good stability mainly owing to formation of protein corona despite controversial results reported by different groups. Although the exterior hydrophilic shells render PMs "long-circulating", the biodistribution of PMs into the mononuclear phagocyte systems (MPS) is dominant as compared with non-MPS organs and tissues. Evidence emerges to support that the copolymer poly(ethylene glycol)-poly(lactic acid) (PEG-PLA) is first broken down into pieces of PEG and PLA and then remnants to be eliminated from the body finally. At the cellular level, PMs tend to be internalized via endocytosis due to their particulate nature and disassembled and degraded within the cell. Recent findings on the effect of particle size, surface characteristics and shape are also reviewed. It is envisaged that unraveling the in vivo and subcellular fate sheds light on the performing mechanisms and gears up the clinical translation of PMs.

Strategies of engineering nanomedicines for tumor retention

The retention of therapeutic agents in solid tumors at sufficient concentration and duration is crucial for their antitumor effects. Given the important contribution of nanomedicines to oncology, we herein summarized two major strategies of nanomedicines for tumor retention, such as transformation- and interactions-mediated strategies. The transformation-mediated retention strategy was achieved by enlarging particle size of nanomedicines or modulating the morphology into fibrous structures, while the interactions-mediated retention strategy was accomplished by modulating nanomedicines to promote their interactions with versatile cells or components in tumors. Moreover, we provide some considerations and perspectives of tumor-retaining nanomedicines for effective cancer therapy.

Enhanced Glioblastoma Selectivity of Harmine via the Albumin Carrier

Glioblastoma, the most common tumor in the brain, has witnessed very little clinical progress over the last decades. Exploring and discovering new therapeutic strategies for glioblastoma has become a critical problem. Harmine (HM), belonging to the beta-carboline alkaloid, is a natural product and isolated from the seeds of Peganum harmala L., which own notable antitumor activity in vitro. However, the poor water solubility and less selectivity of HM severely limit its clinical use. For enhancing its selective ability to tumor cells, we fabricated a kind of protein nanoparticles (BSA-HM NPs), composed of the modified bovine serum albumin (BSA) and HM. It was substantiated through in vitro and in vivo experiment that BSA-HM NPs could predominantly accumulate in tumor tissues and exhibited remarkably enhanced antitumor efficacy. This study provides a promising strategy to improve the bioavailability and avoid side effects of HM as antitumor agents by choosing BSA as carriers.

When imaging meets size-transformable nanosystems

Imaging techniques, including magnetic, optical, acoustic and nuclear imaging, are gaining popularity as a research tool and clinical diagnostics. The advent of imaging agents-incorporated nanosystems (NSs), with sufficient contrast and high resolution, facilitates better monitoring of disease progression, targeted delivery and therapeutic process. Of note, the size of NSs remarkably affects imaging performance, while both large and small NSs enjoy respective features and superiority for imaging aspect, including penetration depth, signal-to-background ratio and spatiotemporal resolution. In this review, after a systematic summary of the basic knowledge of imaging techniques and its relation with size-tunable strategies, we further provide insights into the opportunities and challenges facing size-transformable NSs of the future for bio-imaging application and clinical translation.

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

Introduction

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

Methods

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

Results

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

Conclusion

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

Acid-Responsive Aggregated Gold Nanoparticles for Radiosensitization and Synergistic Chemoradiotherapy in the Treatment of Esophageal Cancer

Radiotherapy and chemotherapy are limited by insufficient therapeutic efficacy of low-dose radiation and nonspecific drug biodistribution. Herein, an acid-responsive aggregated nanosystem (AuNPs-D-P-DA) loaded with doxorubicin (DOX) is designed for radiosensitization and synergistic chemoradiotherapy. In response to the acid microenvironment of esophageal cancer (EC), small-sized AuNPs-D-P-DA forms large-sized gold nanoparticle (AuNPs) aggregates in tumor tissues to hinder the backflow of AuNPs to the circulation, resulting in enhanced tumor accumulation and retention. Simultaneously, the AuNPs-based radiosensitization is significantly improved because of the high concentration and large size of intratumoral AuNPs, while DOX are delivered and released specifically into tumor cells triggered by the acid microenvironment for chemo-radio synergistic therapy. Acid-responsive AuNPs exacerbate radiation-induced DNA damage, cell apoptosis, cell cycle arrest, and low colony formation ability in vitro and enhance anti-tumor efficacy in vivo compared to un-responsive control. When combined with acid-responsive DOX, the therapeutic efficacy of the formulation is further improved by their synergistic effect. After the treatment of acid-responsive AuNPs plus radiotherapy, fatty acid metabolism is reprogrammed in xenograft models, which provides potential targets for further improvement of radiosensitization. In summary, the acid-responsive AuNPs-D-P-DA nanosystem leverages the radio- and chemotherapeutic synergies of AuNPs-sensitized X-ray irradiation and acid-responsive DOX in the treatment of EC.

Elaborately Engineering of a Dual-Drug Co-Assembled Nanomedicine for Boosting Immunogenic Cell Death and Enhancing Triple Negative Breast Cancer Treatment

Pure drug-assembled nanosystem provides a facile and promising solution for simple manufacturing of nanodrugs, whereas a lack of understanding of the underlying assembly mechanism and the inefficient and uncontrollable drug release still limits the development and application of this technology. Here, a simple and practical nanoassembly of DOX and DiR is constructed on basis of their co-assembly characteristics. Multiple interaction forces are found to drive the co-assembly process. Moreover, DOX release from the nanoassembly can be well controlled by the acidic tumor microenvironment and laser irradiation, resulting in favorable delivery efficiency of DiR and DOX in vitro and in vivo. As expected, the nanoassembly with high therapeutic safety completely eradicated the mice triple negative breast cancer cells (4T1) on BALB/c mice, owing to synergistic chemo-photothermal therapy. More interestingly, DiR and DOX synergistically induce immunogenic cell death (ICD) of tumor cells after treatment, enabling the mice to acquire immune memory against tumor growth and recurrence. Such a facile nanoassembly technique provides a novel multimodal cancer treatment platform of chemotherapy/phototherapy/immunotherapy.

Tumor-specific nitric oxide generator to amplify peroxynitrite based on highly penetrable nanoparticles for metastasis inhibition and enhanced cancer therapy

Multiple biological barriers and tumor metastasis severely impede the tumor therapy. To address these adversities, an acid-activated poly (ethylene glycol)-poly-l-lysine-2,3-dimethylmaleic anhydride/poly (ε-caprolactone)-poly(l-arginine)/β-lapachone nanoparticles (mPEG-PLL-DMA/PCL-P(L-arg)/β-Lap, PLM/PPA/β-Lap NPs) were constructed with charge-reversal and size-reduction for β-Lap delivery with a cascade reaction of reactive oxygen species (ROS) and nitric oxide (NO) production. The nanosystem exhibited highly penetrable, superior cellular uptake and desirable endo-lysosomal escape thanks to size-reduction, charge-reversal and proton sponge, respectively. The vast bulk of ROS, which rapidly generated from β-Lap under high concentration quinone oxidoreductase 1 (NQO1), catalyzed guanidine groups to produce NO and generated highly toxic peroxynitrite (ONOO^-). ONOO^- would activate pro-matrix metalloproteinases (pro-MMPs) to generate MMPs, degrade the dense extracellular matrix (ECM) to augment the penetration capability, and aggravate DNA damage. NO and ONOO^- influenced mitochondrial function by decreasing mitochondrial membrane potential and prevented the production of adenosine triphosphate (ATP), which inhibited the ATP-dependent tumor-derived microvesicles (TMVs) and restrained tumor metastasis. NO was defined as an epithelial mesenchymal transition (EMT) inhibitor to restrain tumor metastasis. All consequences demonstrated that PLM/PPA/β-lap NPs exhibited efficient penetration capability, outstanding anti-metastasis activity and favorable antitumor efficacy. Those novel acid-activated NPs are intended to provide further inspiration for multifunctional NO gas therapy.

Tumor microenvironment-responsive size-switchable drug delivery nanosystems

INTRODUCTION

Compared with ordinary chemotherapeutic drugs, the variable-size nanoparticles (NPs) have better therapeutic effects and fewer side effects.

AREAS COVERED

This review mainly summarizes the strategies used to construct smart, size-tunable nanocarriers based on characteristic factors of tumor microenvironment (TME) to dramatically increase the penetration and retention of drugs within tumors.

EXPERT OPINION

Nanosystems with changeable sizes based on the TME have been extensively studied in the past decade, and their permeability and retention have been greatly improved, making them a very promising treatment for tumors.

Carrier-free nanodrugs with efficient drug delivery and release for cancer therapy: From intrinsic physicochemical properties to external modification

The considerable development of carrier-free nanodrugs has been achieved due to their high drug-loading capability, simple preparation method, and offering "all-in-one" functional platform features. However, the native defects of carrier-free nanodrugs limit their delivery and release behavior throughout the in vivo journey, which significantly compromise the therapeutic efficacy and hinder their further development in cancer treatment. In this review, we summarized and discussed the recent strategies to enhance drug delivery and release of carrier-free nanodrugs for improved cancer therapy, including optimizing the intrinsic physicochemical properties and external modification. Finally, the corresponding challenges that carrier-free nanodrugs faced are discussed and the future perspectives for its application are presented. We hope this review will provide constructive information for the rational design of more effective carrier-free nanodrugs to advance therapeutic treatment.

Emerging nanomedicines of paclitaxel for cancer treatment

Malignant tumor is still a leading threat to human health. Despite the rapid development of targeted therapeutic strategies, any treatment specifically acting on single target would inevitably suffer from tumor resistance, largely due to the genetic instability and variability of tumor cells. Thus, traditional therapies such as broad-spectrum chemotherapy would certainly occupy an important position in clinical cancer therapy. Nevertheless, most chemotherapeutic drugs have long been criticized for unsatisfactory therapeutic efficacy with severe off-target toxicity. Although several chemotherapeutic nanomedicines with improved therapeutic safety have been applied in clinics, the therapeutic outcomes still do not fulfill expectation. To address this challenge, enormous efforts have been devoted to developing novel nano-formulations for efficient delivery of chemotherapeutic drugs. Herein, we aim to outline the latest progression in the emerging nanomedicines of paclitaxel (PTX), with special attention to the functional nanocarriers, self-delivering prodrug-nanoassemblies and combination nanotherapeutics of PTX. Finally, the challenges and opportunities of these functional PTX nanomedicines in clinical translation are spotlighted.

A pH-sensitive supramolecular nanosystem with chlorin e6 and triptolide co-delivery for chemo-photodynamic combination therapy

The combination of Ce6, an acknowledged photosensitizer, and TPL, a natural anticancer agent, has been demonstrated as a useful strategy to reinforce the tumor growth suppression, as well as decrease the systemic side effects compared with their monotherapy. However, in view of the optimal chemo-photodynamic combination efficiency, there is still short of the feasible nanovehicle to steadily co-deliver Ce6 and TPL, and stimuli-responsively burst release drugs in tumor site. Herein, we described the synergistic antitumor performance of a pH-sensitive supramolecular nanosystem, mediated by the host–guest complexing between β-CD and acid pH-responsive amphiphilic co-polymer mPEG-PBAE-mPEG, showing the shell–core structural micelles with the tight β-CD layer coating. Both Ce6 and TPL were facilely co-loaded into the spherical supramolecular NPs (TPL+Ce6/NPs) by one-step nanoprecipitation method, with an ideal particle size (156.0 nm), acid pH-responsive drug release profile, and enhanced cellular internalization capacity. In view of the combination benefit of photodynamic therapy and chemotherapy, as well as co-encapsulation in the fabricated pH-sensitive supramolecular NPs, TPL+Ce6/NPs exhibited significant efficacy to suppress cellular proliferation, boost ROS level, lower MMP, and promote cellular apoptosis in vitro. Particularly, fluorescence imaging revealed that TPL+Ce6/NPs preferentially accumulated in the tumor tissue area, with higher intensity than that of free Ce6. As expected, upon 650-nm laser irradiation, TPL+Ce6/NPs exhibited a cascade of amplified synergistic chemo-photodynamic therapeutic benefits to suppress tumor progression in both hepatoma H22 tumor-bearing mice and B16 tumor-bearing mice. More importantly, lower systemic toxicity was found in the tumor-bearing mice treated with TPL+Ce6/NPs. Overall, the designed supramolecular TPL+Ce6/NPs provided a promising alternative approach for chemo-photodynamic therapy in tumor treatment.

Tumor-Microenvironment-Responsive Nanomedicine for Enhanced Cancer Immunotherapy

The past decades have witnessed great progress in cancer immunotherapy, which has profoundly revolutionized oncology, whereas low patient response rates and potential immune-related adverse events remain major clinical challenges. With the advantages of controlled delivery and modular flexibility, cancer nanomedicine has offered opportunities to strengthen antitumor immune responses and to sensitize tumor to immunotherapy. Furthermore, tumor-microenvironment (TME)-responsive nanomedicine has been demonstrated to achieve specific and localized amplification of the immune response in tumor tissue in a safe and effective manner, increasing patient response rates to immunotherapy and reducing the immune-related side effects simultaneously. Here, the recent progress of TME-responsive nanomedicine for cancer immunotherapy is summarized, which responds to the signals in the TME, such as weak acidity, reductive environment, high-level reactive oxygen species, hypoxia, overexpressed enzymes, and high-level adenosine triphosphate. Moreover, the potential to combine nanomedicine-based therapy and immunotherapeutic strategies to overcome each step of the cancer-immunity cycle and to enhance antitumor effects is discussed. Finally, existing challenges and further perspectives in this rising field with the hope for improved development of clinical applications are discussed.

Synergistic Size and Charge Conversions of Functionalized PAMAM Dendrimers under Acidic Tumor Microenvironment

Developing nanomedicine with highly adaptive behaviors has presented great effectiveness in cancer treatment. However, the multi-functional integration of nano-therapeutic system inevitably leads to the complexity in structure and impairs the...

Rational construction of polycystine-based nanoparticles for biomedical applications

Polypeptide-based nanoparticles are one of the promising excipients of nanomedicines due to their excellent biosafety and flexible modification. Among all the types of polypeptide nanoparticles, polycystine (PCys2)-based ones draw increasing...

Towards principled design of cancer nanomedicine to accelerate clinical translation

Nanotechnology in medical applications, especially in oncology as drug delivery systems, has recently shown promising results. However, although these advances have been promising in the pre-clinical stages, the clinical translation of this technology is challenging. To create drug delivery systems with increased treatment efficacy for clinical translation, the physicochemical characteristics of nanoparticles such as size, shape, elasticity (flexibility/rigidity), surface chemistry, and surface charge can be specified to optimize efficiency for a given application. Consequently, interdisciplinary researchers have focused on producing biocompatible materials, production technologies, or new formulations for efficient loading, and high stability. The effects of design parameters can be studied in vitro, in vivo, or using computational models, with the goal of understanding how they affect nanoparticle biophysics and their interactions with cells. The present review summarizes the advances and technologies in the production and design of cancer nanomedicines to achieve clinical translation and commercialization. We also highlight existing challenges and opportunities in the field.

Nanocatalyst-Mediated Chemodynamic Tumor Therapy

Traditional tumor treatments, including chemotherapy, radiotherapy, photodynamic therapy, and photothermal therapy, are developed and used to treat different types of cancer. Recently, chemodynamic therapy (CDT) has been emerged as a novel cancer therapeutic strategy. CDT utilizes Fenton or Fenton-like reaction to generate highly cytotoxic hydroxyl radicals (•OH) from endogenous hydrogen peroxide (H₂ O₂ ) to kill cancer cells, which displays promising therapeutic potentials for tumor treatment. However, the low catalytic efficiency and off-target side effects of Fenton reaction limit the biomedical application of CDT. In this regard, various strategies are implemented to potentiate CDT against tumor, including retrofitting the tumor microenvironment (e.g., increasing H₂ O₂ level, decreasing reductive substances, and reducing pH), enhancing the catalytic efficiency of nanocatalysts, and other strategies. This review aims to summarize the development of CDT and summarize these recent progresses of nanocatalyst-mediated CDT for antitumor application. The future development trend and challenges of CDT are also discussed.

Ovotransferrin Antibacterial Peptide Coupling Mesoporous Silica Nanoparticle as an Effective Antibiotic Delivery System for Treating Bacterial Infection In Vivo

Antibiotic-resistant pathogens are a serious threat to global public health. The emergence of drug-resistant pathogens is due to the improper use of antibiotics, making the treatment of bacterial infections very challenging. Here, we reported an efficient antibiotic delivery nanoparticle to minimize antibiotic resistance. The nanoparticle was designed to target the bacterial membrane using mesoporous silica nanoparticles (MSNs) modified with an ovotransferrin-derived antimicrobial peptide (OVTp12), enabling the antibiotic to be delivered to the vicinity of the pathogenic bacteria. Moreover, we observed that OVTp12-modified nanoparticles effectively inhibited the growth of Escherichia coli in vitro and in vivo. The nanoparticle with high biosafety could significantly downregulate the expression of inflammation-related cytokines in infected tissues. Thus, this novel bacterial targeted nanoparticle provides advantages in minimizing bacterial drug resistance and treating bacterial infection.