Hierarchical Targeting Strategy for Enhanced Tumor Tissue Accumulation/Retention and Cellular Internalization

Glutathione-depleting polyprodrug nanoparticle for enhanced photodynamic therapy and cascaded locoregional chemotherapy

Nanomedicines that combine reactive oxygen species (ROS)-responsive polyprodrug and photodynamic therapy have shown great potential for improving treatment efficacy. However, the consumption of ROS by overexpressed glutathione in tumor cells is a major obstacle for achieving effective ROS amplification and prodrug activation. Herein, we report a polyprodrug-based nanoparticle that can realize ROS amplification and cascaded drug release. The nanoparticle can respond to the high level of hydrogen peroxide in tumor microenvironment, achieving self-destruction and release of quinone methide. The quinone methide depletes intracellular glutathione and thus decreases the antioxidant capacity of cancer cells. Under laser irradiation, a large amount of ROS will be generated to induce cell damage and prodrug activation. Therefore, the glutathione-depleting polyprodrug nanoparticles can efficiently inhibit tumor growth by enhanced photodynamic therapy and cascaded locoregional chemotherapy.

Nordihydroguaiaretic Acid-Cross-Linked Phenylboronic Acid-Functionalized Polyplex Micelles for Anti-angiogenic Gene Therapy of Orthotopic and Metastatic Tumors

Polyplexes are required to be equipped with multiple functionalities to accomplish adequate structure stability and gene transfection efficacy for gene therapy. Herein, a 4-carboxy-3-fluorophenylboronic acid (FPBA)-functionalized block copolymer of PEG-b-PAsp(DET/FBA) and PAsp(DET/FBA) (abbreviated as PB and HB) was synthesized and applied for engineering functional polyplex micelles (PMs) through ionic complexation with pDNA followed by strategic cross-linking with nordihydroguaiaretic acid (NDGA) in respect to the potential linkage of polyphenol and FPBA moieties. In relation to polyplex micelles void of cross-linking, the engineered multifunctional polyplex micelles (PBHBN-PMs) were determined to possess improved structural tolerability against the exchange reaction with charged species. Besides, the FPBA/NDGA cross-linking appeared to be selectively cleaved in the acidic endosomal compartments but not the neutral milieu. Furthermore, the PBHB-PMs with the optimal FPBA/NDGA cross-linking degree were identified to possess appreciable cellular uptake and endosomal escape activities, eliciting a significantly high level of gene expression relative to P-PMs and PB-PMs. Eventually, in vivo antitumor therapy by our proposed multifunctional PMs appeared to be capable of facilitating expression of the antiangiogenic genomic payloads (sFlt-1 pDNA) via systemic administration. The enriched antiangiogenic sFlt-1 in the tumors could silence the activities of angiogenic cytokines for the inhibited neo-vasculature and the suppressed growth of orthotopic 4T1 tumors. Of note, the persistent expression of the antiangiogenic sFlt-1 is also presumed to migrate into the blood circulation, thereby accounting for an overall antiangiogenic environment in preventing the potential pulmonary metastasis. Hence, our elaborated multifaceted PMs inspired fascinating potential as an intriguing gene delivery system for the treatment of clinical solid tumors and metastasis.

Imidazolyl Lipids Enhanced LNP Endosomal Escape for Ferroptosis RNAi Treatment of Cancer

Treatments for cancer that incorporate small interfering RNA (siRNA) to target iron-dependent ferroptosis are thought to be highly promising. However, creating a reliable and clinically feasible siRNA delivery system continues to be a major obstacle in the field of cancer treatment. Here, three imidazole-based ionizable lipid nanoparticles (LNPs) with pH-sensitive effects are rationally designed and synthesized for siRNA delivery. LNPs formulated with the top-performing lipid (O12-D3-I3) encapsulating FVII siRNA (FVII@O-LNP) elicited greater gene silencing than those with the benchmark Onpattro lipid DLin-MC3-DMA (MC3) due to its stronger endosomal escape. Moreover, Fc-siRNA@O-LNPs encapsulated with ferrocene (Fc) and SLC7A11/Nrf2-targeted siRNA is formulated. The outcomes demonstrate optimal safety profiles and a significant anti-tumor effect by inducing long-lasting and efficient ferroptosis through a synergistic action in vivo. In summary, this work shows that imidazolyl lipid-prepared LNPs are efficient delivery vehicles for cancer therapy and ferroptosis-targeting siRNA administration, both of which have extensive clinical application potential.

Single Atom Catalysts Remodel Tumor Microenvironment for Augmented Sonodynamic Immunotherapy

The immunosuppressive tumor microenvironment (TME) is a huge hurdle in immunotherapy. Sono-immunotherapy is a new treatment modality that can reverse immunosuppressive TME, but the sonodynamic effects are compromised by overexpressed glutathione (GSH) and hypoxia in the TME. Herein, this work reports a new sono-immunotherapy strategy using Pdδ+ single atom catalysts to enhance positive sonodynamic responses to the immunosuppressive and sono-suppressive TME. To demonstrate this technique, this work employs rich and reductive Ti vacancies in Ti3-xC2Ty nanosheets to construct the atomically dispersed Pd-C3 single atom catalysts (SAC) with Pd content up to 2.5 wt% (PdSA/Ti3-xC2Ty). Compared with Pd nanoparticle loaded Ti3-xC2Ty, PdSA/Ti3-xC2Ty single-atom enzyme showed augmented sonodynamic effects that are ascribed to SAC facilitated electron-hole separation, rapid depletion of overexpressed GSH by ultrasound (US) excited holes, and catalytic decomposition of endogenous H2O2 for relieving hypoxia. Importantly, the sono-immunotherapy strategy can boost abscopal antitumor immune responses by driving maturation of dendritic cells and polarization of tumor-associated macrophages into the antitumoral M1 phenotype. Bilateral tumor models demonstrate the complete eradication of localized tumors and enhance metastatic regression. Th strategy highlights the potential of single-atom catalysts for robust sono-immunotherapy by remodeling the tumor microenvironment.

Controlled In Situ Self-Assembly of Biotinylated Trans-Cyclooctene Nanoparticles for Orthogonal Dual-Pretargeted Near-Infrared Fluorescence and Magnetic Resonance Imaging

A pretargeted strategy that decouples targeting vectors from radionuclides has shown promise for nuclear imaging and/or therapy in vivo. However, the current pretargeted approach relies on the use of antibodies or nanoparticles as the targeting vectors, which may be compromised by poor tissue penetration and limited accumulation of targeting vectors in the tumor tissues. Herein, we present an orthogonal dual-pretargeted approach by combining stimuli-triggered in situ self-assembly strategy with fast inverse electron demand Diels-Alder (IEDDA) reaction and strong biotin-streptavidin (SA) interaction for near-infrared fluorescence (NIR FL) and magnetic resonance (MR) imaging of tumors. This approach uses a small-molecule probe (P-Cy-TCO&Bio) containing both biotin and trans-cyclooctene (TCO) as a tumor-targeting vector. P-Cy-TCO&Bio can efficiently penetrate subcutaneous HeLa tumors through biotin-assisted targeted delivery and undergo in situ self-assembly to form biotinylated TCO-bearing nanoparticles (Cy-TCO&Bio NPs) on tumor cell membranes. Cy-TCO&Bio NPs exhibited an "off-on" NIR FL and retained in the tumors, offering a high density of TCO and biotin groups for the concurrent capture of Gd-chelate-labeled tetrazine (Tz-Gd) and IR780-labeled SA (SA-780) via the orthogonal IEDDA reaction and SA-biotin interaction. Moreover, Cy-TCO&Bio NPs offered multiple-valent binding modes toward SA, which additionally regulated the cross-linking of Cy-Gd&Bio NPs into microparticles (Cy-Gd&Bio/SA MPs). This process could significantly (1) increase r1 relaxivity and (2) enhance the accumulation of Tz-Gd and SA-780 in the tumors, resulting in strong NIR FL, bright MR contrast, and an extended time window for the clear and precise imaging of HeLa tumors.

Immunosuppressive enzyme-responsive nanoparticles for enhanced accumulation in liver allograft to overcome acute rejection

Acute rejection is a life-threatening complication after liver transplantation. Immunosuppressants such as tacrolimus are used to inhibit acute rejection of liver grafts in clinic. However, inefficient intragraft accumulation may reduce the therapeutic outcomes of tacrolimus. Here, an enzyme-responsive nanoparticle is developed to selectively enhance the accumulation of tacrolimus in liver allograft through enzyme-induced aggregation to refine immunotherapeutic efficacy of tacrolimus. The nanoparticles are composed of amphiphilic tacrolimus prodrugs synthesized by covalently conjugating tacrolimus and matrix metalloproteinase 9 (MMP9)-cleavable peptide-containing methoxy poly (ethylene glycol) to poly (l-glutamic acid). Upon exposure to MMP9, which is overexpressed in rejected liver allografts, the nanoparticles undergo a morphological transition from spherical micellar nanoparticles to microscale aggregate-like scaffolds. Intravenous administration of MMP9-responsive nanoparticles into a rat model of acute liver graft rejection results in enhanced nanoparticle accumulation in allograft as compared to nonresponsive nanoparticles. Consequently, the MMP9-responsive nanoparticles significantly inhibit intragraft inflammatory cell infiltration and proliferation, maintain intragraft immunosuppressive environment, alleviate graft damage, improve liver allograft function, abate weight loss and prolong recipient survival. This work proves that morphology-switchable enzyme-responsive nanoparticles represent an innovative strategy for selectively enhancing intragraft accumulation of immunosuppressive agents to improve treatment of liver allograft rejection.

CD44 targeted-chondroitin sulfate nanoparticles: Fine-tuning hydrophobic groups to enhance in vitro pH-responsiveness and in vivo efficacy for advanced breast cancer treatment

The design of tumor-targeting nanoparticles with precisely controlled physical-biological properties may improve the delivery of chemotherapeutic agents. This study introduces pH-sensitive chondroitin sulfate-cholesterol (ChS-Chol) nano-assemblies for targeted intracellular doxorubicin (Dox) delivery in breast cancer treatment. Various ChS-Chol copolymers were synthesized, yielding self-assembling nanostructures with adjustable lipophilic content. In an aqueous environment, the ChS-Chol conjugates could form self-assembled nanostructures with a narrower size variation and a high negative potential. Moreover, the carriers would rapidly disassemble and release Dox in response to acidic pH. The in vitro cytotoxicity assay exhibited concentration-related anti-proliferation activity with Dox-loaded nanoparticles against 4T1, MCF-7, and MDA-MB-231 breast cancer cells. The nanoparticles demonstrated enhanced early apoptosis induction, efficient cellular uptake, and improved prevention of tumor cell proliferation compared to free Dox. In vivo results showcased significant tumor growth inhibition, underscoring the potential of these nanoparticle-based drug delivery systems for breast cancer therapy. The study emphasizes tailored nanocarrier design, leveraging pH-responsiveness and precise hydrophobic tuning to achieve targeted and potent therapeutic effects in the fight against breast cancer.

Microwave Encounters Ionic Liquid: Synergistic Mechanism, Synthesis and Emerging Applications

Progress in microwave (MW) energy application technology has stimulated remarkable advances in manufacturing and high-quality applications of ionic liquids (ILs) that are generally used as novel media in chemical engineering. This Review focuses on an emerging technology via the combination of MW energy and the usage of ILs, termed microwave-assisted ionic liquid (MAIL) technology. In comparison to conventional routes that rely on heat transfer through media, the contactless and unique MW heating exploits the electromagnetic wave-ions interactions to deliver energy to IL molecules, accelerating the process of material synthesis, catalytic reactions, and so on. In addition to the inherent advantages of ILs, including outstanding solubility, and well-tuned thermophysical properties, MAIL technology has exhibited great potential in process intensification to meet the requirement of efficient, economic chemical production. Here we start with an introduction to principles of MW heating, highlighting fundamental mechanisms of MW induced process intensification based on ILs. Next, the synergies of MW energy and ILs employed in materials synthesis, as well as their merits, are documented. The emerging applications of MAIL technologies are summarized in the next sections, involving tumor therapy, organic catalysis, separations, and bioconversions. Finally, the current challenges and future opportunities of this emerging technology are discussed.

Photothermal and Photocatalytic Glycol Chitosan and Polydopamine-Grafted Oxygen Vacancy Bismuth Oxyiodide (BiO1-x I) Nanoparticles for the Diagnosis and Targeted Therapy of Diabetic Wounds

Treatment of diabetic wounds is a significant clinical challenge due to the massive infections caused by bacteria. In this study, multifunctional glycol chitosan and polydopamine-coated BiO1-x I (GPBO) nanoparticles (NPs) with near-infrared (NIR) photothermal and photocatalytic abilities are prepared. When infection occurs, the local microenvironment becomes acidic, and the pH-switchable GPBO can target the bacteria of the wound site. The NIR-assisted GPBO treatment exhibits anti-bacterial effects with fast response, high efficiency, and long duration to Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. GPBO achieves excellent photothermal imaging and CT imaging of the mouse subcutaneous abscess model. With the assistance of NIR irradiation, the GPBO promotes the healing of the diabetic wound model with the effects of anti-bacteria, anti-inflammation, the M2 polarization promotion of macrophages, and angiogenesis. This is the first-time report of nano-sized BiO1-x I. The synthesis and selected application for the imaging and targeted therapy of diabetic wounds are presented. This study offers an example of the NP-assisted precise diagnosis and therapy of bacterial infection diseases.

Engineered cell membrane-coated nanoparticles based cancer therapy: A robust weapon against the lethal and challenging hepatocellular carcinoma

Hepatocellular carcinoma (HCC) has become an important public health problem, and there are still challenges to overcome in clinical treatment. The nanodrug delivery system (NDDS) has developed tremendously in recent years, and many researchers have explored NDDS for the treatment of HCC. Engineered cell membrane-coated nanoparticles (ECNPs) have emerged, combining the unique functions of cell membranes with the engineering versatility of synthetic nanoparticles (NPs) to effectively deliver therapeutic drugs. It is designed to have the capabilities: specific active targeting, immune evasion, prolonging the circulation blood time, controlled drug release delivery, and reducing drugs systematic toxicity. Thus, ECNPs are a promising bionic tool in the treatment of HCC and have operability to achieve combination and integrated therapy. This review focuses on the mechanism and strategy of ECNPs for the treatment of HCC and summarizes its research progress in the treatment of HCC in recent years.

[Research Progress on the Influence of Tumor Extracellular Matrix Mechanic Properties on Nanodrug Delivery]

Nanodrugs are widely utilized in the biomedical fields, exhibiting immense potential in cancer therapy in particular. However, tumors exist in an extremely complicated microenvironment where substances like collagen are continuously deposited and remodeled, leading to significant alterations in the mechanical properties of the extracellular matrix (ECM) during tumor development. Previous research has primarily focused on the specific physicochemical properties of nanodrugs, such as particle size, electric charge, shape, surface chemistry, etc., and their effects on cellular uptake, cytotoxicity, and in vivo pharmacokinetics. Limited studies have been done to explore the impact of ECM mechanical properties on nanodrug delivery. In this review, we systematically summarized the relevant research findings on this topic from the perspective of the characteristics and testing methods of tumor ECM mechanics. Additionally, we made a thorough discussion of the potential mechanical and biological mechanisms involved in nanodrug delivery. We proposed several noteworthy research directions. Regarding the overall strategy, there is a need to emphasize targeted delivery that combines ECM mechanics and nanomechanics to achieve precise drug delivery. Regarding the spatial aspect, attention should be given to the nonlinear spatial mechanical heterogeneity within the interior of solid tumors and the construction of mechanic microenvironment-adaptive nanocarriers to improve the delivery efficiency. Regarding the temporal aspect, emphasis should be placed on the dynamic development and changes in the mechanical microenvironment during solid tumor growth and treatment processes. Based on the stromal mechanical characteristics of the tumor tissues of individual patients, personalized treatment strategies can be formulated, which will enhance treatment specificity and efficacy. In addition, issues such as mechanically targeted nanodrug delivery, degradation, and metabolism under dynamic ECM mechanical conditions warrant further investigation.

A Review on Gold Nanoclusters for Cancer Phototherapy

Cancer phototherapy, including photodynamic therapy (PDT) and photothermal therapy (PTT), has been extensively studied in recent years because of its noninvasive properties, high efficiency, improved selectivity, and reduced side effects. Gold nanoclusters (AuNCs) have the advantages of high biocompatibility, high biosafety, excellent photoresponse, and high tumor penetration ability. This review analyzes the use of AuNCs in tumor phototherapy in recent years from three aspects, namely, AuNCs in PDT, AuNCs in PTT, and AuNCs in combination therapy, and presents the high potential of AuNCs in cancer phototherapy. This review aims to provide readers with the unique advantages, diversified application approaches, and bright application prospects of AuNCs in phototherapy and to provide insights into strategies for applying AuNCs to tumor phototherapy.

Surface modification strategies in translocating nano-vesicles across different barriers and the role of bio-vesicles in improving anticancer therapy

Nanovesicles and bio-vesicles (BVs) have emerged as promising tools to achieve targeted cancer therapy due to their ability to overcome many of the key challenges currently being faced with conventional chemotherapy. These challenges include the diverse and often complex pathophysiology involving the progression of cancer, as well as the various biological barriers that circumvent therapeutic molecules reaching their target site in optimum concentration. The scientific evidence suggests that surface-functionalized nanovesicles and BVs camouflaged nano-carriers (NCs) both can bypass the established biological barriers and facilitate fourth-generation targeting for the improved regimen of treatment. In this review, we intend to emphasize the role of surface-functionalized nanovesicles and BVs camouflaged NCs through various approaches that lead to an improved internalization to achieve improved and targeted oncotherapy. We have explored various strategies that have been employed to surface-functionalize and biologically modify these vesicles, including the use of biomolecule functionalized target ligands such as peptides, antibodies, and aptamers, as well as the targeting of specific receptors on cancer cells. Further, the utility of BVs, which are made from the membranes of cells such as mesenchymal stem cells (MSCs), white blood cells (WBCs), red blood cells (RBCs), platelets (PLTs) as well as cancer cells also been investigated. Lastly, we have discussed the translational challenges and limitations that these NCs can encounter and still need to be overcome in order to fully realize the potential of nanovesicles and BVs for targeted cancer therapy. The fundamental challenges that currently prevent successful cancer therapy and the necessity of novel delivery systems are in the offing.

Modular Drug-Loaded Nanocapsules with Metal Dome Layers as a Platform for Obtaining Synergistic Therapeutic Biological Activities

Multifunctional drug-loaded polymer-metal nanocapsules have attracted increasing attention in drug delivery due to their multifunctional potential endowed by drug activity and response to physicochemical stimuli. Current chemical synthesis methods of polymer/metal capsules require specific optimization of the different components to produce particles with precise properties, being particularly complex for Janus structures combining polymers and ferromagnetic and highly reactive metals. With the aim to generate tunable synergistic nanotherapeutic actuation with enhanced drug effects, here we demonstrate a versatile hybrid chemical/physical fabrication strategy to incorporate different functional metals with tailored magnetic, optical, or chemical properties on solid drug-loaded polymer nanoparticles. As archetypical examples, we present poly(lactic-co-glycolic acid) (PLGA) nanoparticles (diameters 100-150 nm) loaded with paclitaxel, indocyanine green, or erythromycin that are half-capped by either Fe, Au, or Cu layers, respectively, with application in three biomedical models. The Fe coating on paclitaxel-loaded nanocapsules permitted efficient magnetic enhancement of the cancer spheroid assembly, with 40% reduction of the cross-section area after 24 h, as well as a higher paclitaxel effect. In addition, the Fe-PLGA nanocapsules enabled external contactless manipulation of multicellular cancer spheroids with a speed of 150 μm/s. The Au-coated and indocyanine green-loaded nanocapsules demonstrated theranostic potential and enhanced anticancer activity in vitro and in vivo due to noninvasive fluorescence imaging with long penetration near-infrared (NIR) light and simultaneous photothermal-photodynamic actuation, showing a 3.5-fold reduction in the tumor volume growth with only 5 min of NIR illumination. Finally, the Cu-coated erythromycin-loaded nanocapsules exhibited enhanced antibacterial activity with a 2.5-fold reduction in the MIC50 concentration with respect to the free or encapsulated drug. Altogether, this technology can extend a nearly unlimited combination of metals, polymers, and drugs, thus enabling the integration of magnetic, optical, and electrochemical properties in drug-loaded nanoparticles to externally control and improve a wide range of biomedical applications.

Intra-Operative Definition of Glioma Infiltrative Margins by Visualizing Immunosuppressive Tumor-Associated Macrophages

Accurate delineation of glioma infiltrative margins remains a challenge due to the low density of cancer cells in these regions. Here, a hierarchical imaging strategy to define glioma margins by locating the immunosuppressive tumor-associated macrophages (TAMs) is proposed. A pH ratiometric fluorescent probe CP2-M that targets immunosuppressive TAMs by binding to mannose receptor (CD206) is developed, and it subsequently senses the acidic phagosomal lumen, resulting in a remarkable fluorescence enhancement. With assistance of CP2-M, glioma xenografts in mouse models with a tumor-to-background ratio exceeding 3.0 for up to 6 h are successfully visualized. Furthermore, by intra-operatively mapping the pH distribution of exposed tissue after craniotomy, the glioma allograft in rat models is precisely excised. The overall survival of rat models significantly surpasses that achieved using clinically employed fluorescent probes. This work presents a novel strategy for locating glioma margins, thereby improving surgical outcomes for tumors with infiltrative characteristics.

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.

Mapping the intellectual structure and landscape of nano-drug delivery systems in colorectal cancer

Background: Colorectal cancer (CRC) is a prevalent malignancy affecting the digestive tract, and its incidence has been steadily rising over the years. Surgery remains the primary treatment modality for advanced colorectal cancer, complemented by chemotherapy. The development of drug resistance to chemotherapy is a significant contributor to treatment failure in colorectal cancer. Nanodrug delivery systems (NDDS) can significantly improve the delivery and efficacy of antitumor drugs in multiple ways. However, there is a lack of visualization of NDDS research structures and research hotspots in the field of colorectal cancer, and the elaboration of potential research areas remains to be discovered. Objective: To comprehensively explore the current research status and development trend of NDDS in CRC research. Methods: Bibliometric analysis of articles and reviews on NDDS for CRC published between 2002 and 2022 using tools including CiteSpace, VOSviewer, R-bibliometrix, and Microsoft Excel was performed. Results: A total of 1866 publications authored by 9,870 individuals affiliated with 6,126 institutions across 293 countries/regions were included in the analysis. These publications appeared in 456 journals. Abnous Khalil has the highest number of publications in this field. The most published journals are the International Journal of Nanomedicine, International Journal of Pharmaceutics, and Biomaterials. Notably, the Journal of Controlled Release has the highest citation count and the third-highest H-index. Thematic analysis identified "inflammatory bowel disease"," "oral drug delivery," and "ulcerative colitis" as areas requiring further development. Keyword analysis revealed that "ulcerative colitis," "exosomes," and "as1411"have emerged as keywords within the last 2 years. These emerging keywords may become the focal points of future research. Conclusion: Our findings reveal the current research landscape and intellectual structure of NDDS in CRC research which helps researchers understand the research trends and hot spots in this field.

Nanodelivery systems: An efficient and target-specific approach for drug-resistant cancers

BACKGROUND

Cancer treatment is still a global health challenge. Nowadays, chemotherapy is widely applied for treating cancer and reducing its burden. However, its application might be in accordance with various adverse effects by exposing the healthy tissues and multidrug resistance (MDR), leading to disease relapse or metastasis. In addition, due to tumor heterogeneity and the varied pharmacokinetic features of prescribed drugs, combination therapy has only shown modestly improved results in MDR malignancies. Nanotechnology has been explored as a potential tool for cancer treatment, due to the efficiency of nanoparticles to function as a vehicle for drug delivery.

METHODS

With this viewpoint, functionalized nanosystems have been investigated as a potential strategy to overcome drug resistance.

RESULTS

This approach aims to improve the efficacy of anticancer medicines while decreasing their associated side effects through a range of mechanisms, such as bypassing drug efflux, controlling drug release, and disrupting metabolism. This review discusses the MDR mechanisms contributing to therapeutic failure, the most cutting-edge approaches used in nanomedicine to create and assess nanocarriers, and designed nanomedicine to counteract MDR with emphasis on recent developments, their potential, and limitations.

CONCLUSIONS

Studies have shown that nanoparticle-mediated drug delivery confers distinct benefits over traditional pharmaceuticals, including improved biocompatibility, stability, permeability, retention effect, and targeting capabilities.

Self-Amplified Cascade Degradation and Oxidative Stress Via Rational pH Regulation of Oxidation-Responsive Poly(ferrocene) Aggregates

Precise activation of polymer nanoparticles at lesion sites is crucial to achieve favorable therapeutic efficacy. However, conventional endogenous stimuli-responsive polymer nanoparticles probably suffer from few triggers to stimulate the polymer degradation and subsequent functions. Here, we describe oxidation-responsive poly(ferrocene) amphiphiles containing phenylboronic acid ester and ferrocene as the repeating backbone units. Upon triggering by hydrogen peroxide inside the tumor cells, the phenylboronic acid ester bonds are broken and poly(ferrocene) units are degraded to afford free ferrocene and noticeable hydroxide ions. The released hydroxide ions can immediately improve the pH value within the poly(ferrocene) aggregates, and the degradation rate of the phenylboronic acid ester backbone is further promoted by the upregulated pH; thereupon, the accelerated degradation can release much more additional hydroxide ions to improve the pH, thus achieving a positive self-amplified cascade degradation of poly(ferrocene) aggregates accompanied by oxidative stress boosting and efficient cargo release. Specifically, the poly(ferrocene) aggregates can be degraded up to ∼90% within 12 h when triggered by H2O2, while ferrocene-free control nanoparticles are degraded by only 30% within 12 days. In addition, the maleimide moieties tethered in the hydrophilic corona can capture blood albumin to form an albumin-rich protein corona and significantly improve favorable tumor accumulation. The current oxidation-responsive poly(ferrocene) amphiphiles can efficiently inhibit tumors in vitro and in vivo. This work provides a proof-of-concept paradigm for self-amplified polymer degradation and concurrent oxidative stress, which is promising in actively regulated precision medicine.

Gas-assisted phototherapy for cancer treatment

Phototherapies, mainly including photodynamic and photothermal therapy, have made considerable strides in the field of cancer treatment. With the aid of phototherapeutic agents, reactive oxygen species (ROS) or heat are generated under light irradiation to selectively damage cancer cells. However, sole-modality phototherapy faces certain drawbacks, such as limited penetration of phototherapeutic agents into tumor tissues, inefficient ROS generation due to hypoxia, treatment-induced inflammation and resistance of tumor to treatment (e.g., high levels of antioxidants, expression of heat shock protein). Gas therapy, an emerging therapy approach that damages cancer cells by improving the level of certain gas at the tumor site, shows potential to overcome the challenges associated with phototherapies. In addition, with the rapid development of nanotechnology, gas-assisted phototherapy based on nanomedicines has emerged as a promising strategy to enhance the treatment efficacy. This review summarizes recent advances in gas-assisted phototherapy and discusses the prospects and challenges of this strategy in cancer phototherapy.

Activatable Graphene Quantum-Dot-Based Nanotransformers for Long-Period Tumor Imaging and Repeated Photodynamic Therapy

Photodynamic therapy (PDT) is considered as an emerging therapeutic modality against cancer with high spatiotemporal selectivity because the utilized photosensitizers (PSs) are only active and toxic upon light irradiation. To maximize its effectiveness, PDT is usually applied repetitively for ablating various tumors. However, the total overdose of PSs from repeated administrations causes severe side effects. Herein, acidity-activated graphene quantum dots-based nanotransformers (GQD NT) are developed as PS vehicles for long-period tumor imaging and repeated PDT. Under the guidance of Arg-Gly-Asp peptide, GQD NT targets to tumor tissues actively, and then loosens and enlarges in tumor acidity, thus promising long tumor retention. Afterwards, GQD NT transforms into small pieces for better penetration in tumor. Upon laser irradiation, GQD NT generates mild hyperthermia that enhances cell membrane permeability and further promotes the PSs uptake. Most intriguingly, the as-prepared GQD NT not only "turns-on" fluorescence/magnetic resonance signals, but also achieves efficient repeated PDT. Notably, the total PSs dose is reduced to 3.5 µmol kg^-1 , which is 10-30 times lower than that of other reported works. Overall, this study exploits a smart vehicle to enhance accumulation, retention, and release of PSs in tumors through programmed deformation, thus overcoming the overdose obstacle in repeated PDT.

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.

BODIPY as a Multifunctional Theranostic Reagent in Biomedicine: Self-Assembly, Properties, and Applications

The use of boron dipyrromethene (BODIPY) in biomedicine is reviewed. To open, its synthesis and regulatory strategies are summarized, and inspiring cutting-edge work in post-functionalization strategies is highlighted. A brief overview of assembly model of BODIPY is then provided: BODIPY is introduced as a promising building block for the formation of single- and multicomponent self-assembled systems, including nanostructures suitable for aqueous environments, thereby showing the great development potential of supramolecular assembly in biomedicine applications. The frontier progress of BODIPY in biomedical application is thereafter described, supported by examples of the frontiers of biomedical applications of BODIPY-containing smart materials: it mainly involves the application of materials based on BODIPY building blocks and their assemblies in fluorescence bioimaging, photoacoustic imaging, disease treatment including photodynamic therapy, photothermal therapy, and immunotherapy. Lastly, not only the current status of the BODIPY family in the biomedical field but also the challenges worth considering are summarized. At the same time, insights into the future development prospects of biomedically applicable BODIPY are provided.

Design of Disintegrable Nanoassemblies to Release Multiple Small-Sized Nanoparticles

The therapeutic and diagnostic effects of nanoparticles depend on the efficiency of their delivery to targeted tissues, such as tumors. The size of nanoparticles, among other characteristics, plays a crucial role in determining their tissue penetration and retention. Small nanoparticles may penetrate deeper into tumor parenchyma but are poorly retained, whereas large ones are distributed around tumor blood vessels. Thus, compared to smaller individual nanoparticles, assemblies of such nanoparticles due to their larger size are favorable for prolonged blood circulation and enhanced tumor accumulation. Upon reaching the targeted tissues, nanoassemblies may dissociate at the target region and release the smaller nanoparticles, which is beneficial for their distribution at the target site and ultimate clearance. The recent emerging strategy that combines small nanoparticles into larger, biodegradable nanoassemblies has been demonstrated by several groups. This review summarizes a variety of chemical and structural designs for constructing stimuli-responsive disintegrable nanoassemblies as well as their different disassembly routes. These nanoassemblies have been applied as demonstrators in the fields of cancer therapy, antibacterial infection, ischemic stroke recovery, bioimaging, and diagnostics. Finally, we summarize stimuli-responsive mechanisms and their corresponding nanomedicine designing strategies, and discuss potential challenges and barriers towards clinical translation.

Smart Nanosystems for Overcoming Multiple Biological Barriers in Cancer Nanomedicines Transport: Design Principles, Progress, and Challenges

The development of smart nanosystems, which could overcome diverse biological barriers of nanomedicine transport, has received intense scientific interest in improving the therapeutic efficacies of traditional nanomedicines. However, the reported nanosystems generally hold disparate structures and functions, and the knowledge of involved biological barriers is usually scattered. There is an imperative need for a summary of biological barriers and how these smart nanosystems conquer biological barriers, to guide the rational design of the new-generation nanomedicines. This review starts from the discussion of major biological barriers existing in nanomedicine transport, including blood circulation, tumoral accumulation and penetration, cellular uptake, drug release, and response. Design principles and recent progress of smart nanosystems in overcoming the biological barriers are overviewed. The designated physicochemical properties of nanosystems can dictate their functions in biological environments, such as protein absorption inhibition, tumor accumulation, penetration, cellular internalization, endosomal escape, and controlled release, as well as modulation of tumor cells and their resident tumor microenvironment. The challenges facing smart nanosystems on the road heading to clinical approval are discussed, followed by the proposals that could further advance the nanomedicine field. It is expected that this review will provide guidelines for the rational design of the new-generation nanomedicines for clinical use.

Repolarization of macrophages to improve sorafenib sensitivity for combination cancer therapy

Sorafenib is the first line drug for hepatocellular carcinoma (HCC) therapy. However, HCC patients usually acquire resistance to sorafenib treatment within 6 months. Recent evidences have shown that anticancer drugs with antiangiogenesis effect (e.g., sorafenib) can aggravate the hypoxia microenvironment and promote the infiltration of more tumor-associated macrophages (TAMs) into the tumor tissues. Therefore, repolarization of TAMs phenotype could be expected to not only eliminate the influence of TAMs on sorafenib lethality to HCC cells, but also provide an additional anticancer effect to achieve combination therapy. However, immune side effects remain a great challenge due to the non-specific macrophage repolarization in normal tissues. We herein employed a tumor microenvironment (TME) pH-responsive nanoplatform to concurrently transport sorafenib and modified resiquimod (R848-C16). This nanoparticle (NP) platform is made with a TME pH-responsive methoxyl-poly(ethylene glycol)-b-poly(lactic-co-glycolic acid) copolymer. After intravenous administration, the co-delivery NPs could highly accumulate in the tumor tissues and then respond to the TME pH to detach their surface PEG chains. With this PEG detachment to enhance uptake by TAMs and HCC cells, the co-delivery NPs could combinatorially inhibit HCC tumor growth via sorafenib-mediated lethality to HCC cells and R848-mediated repolarization of TAMs into tumoricidal M1-like macrophages. STATEMENT OF SIGNIFICANCE: Anticancer drugs with antiangiogenesis effect (e.g., sorafenib) can aggravate the hypoxia microenvironment and promote the infiltration of more tumor-associated macrophages (TAMs) into the tumor tissues to restrict the anticancer effect. In this work, we designed and developed a tumor microenvironment (TME) pH-responsive nanoplatform for systemic co-delivery of sorafenib and resiquimod in hepatocellular carcinoma (HCC) therapy. These co-delivery NPs show high tumor accumulation and could respond to the TME pH to enhance uptake by TAMs and HCC cells. With the sorafenib-mediated lethality to HCC cells and R848-mediated repolarization of TAMs, the co-delivery NPs show a combinational inhibition of HCC tumor growth in both xenograft and orthotopic tumor models.

Self-Assembly-Based Nanoprobes for the Simultaneous Detection and Downregulation of HSP90α mRNA to Enhance Photothermal Therapy

Although photothermal therapy (PTT) has been widely applied for tumor treatment, tumor cells thermotolerance still limits PTT efficiency. Since the overexpressed HSP90α in tumor cells further enhances thermotolerance and protects them from PTT damage, a new nanoprobe that can specifically detect and downregulate HSP90α mRNA was developed to enhance the PTT effect. Based on the HSP90α mRNA sequence, the nanoprobe Au-DNA1/DNA2 can specifically bind to HSP90α mRNA for recovering its fluorescence and further inhibit the synthesis of HSP90α to reduce tumor heat tolerance. Moreover, another nanoprobe, Au-DNA3, can self-assemble with the Au-DNA1 nanoprobe after the detection to form Au aggregations to enhance PTT afterward for better efficiency. Simultaneously, such a design improves tissue penetration and tumor retention, thereby reducing the damage to the surrounding normal tissues. Both in vitro and in vivo experiments showed that the nanoprobes have excellent tumor diagnosis and cancer treatment capabilities, which is of great significance for clinical translational applications.

A tumor-targetable NIR probe with photoaffinity crosslinking characteristics for enhanced imaging-guided cancer phototherapy

Spatiotemporally manipulating the in situ immobilization of theranostic agents within cancer cells to improve their bioavailability is highly significant yet challenging in tumor diagnosis and treatment. Herein, as a proof-of concept, we for the first time report a tumor-targetable near-infrared (NIR) probe DACF with photoaffinity crosslinking characteristics for enhanced tumor imaging and therapeutic applications. This probe possesses great tumor-targeting capability, intensive NIR/photoacoustic (PA) signals, and a predominant photothermal effect, allowing for sensitive imaging and effective photothermal therapy (PTT) of tumors. Most notably, upon 405 nm laser illumination, DACF could be covalently immobilized within tumor cells through a photocrosslinking reaction between photolabile diazirine groups and surrounding biomolecules resulting in enhanced tumor accumulation and prolonged retention simultaneously, which significantly facilitates the imaging and PTT efficacy of tumor in vivo. We therefore believe that our current approach would provide a new insight for achieving precise cancer theranostics.

Oxidation Responsive PEGylated Polyamino Acid Bearing Thioether Pendants for Enhanced Anticancer Drug Delivery

Reactive oxygen species (ROS) in biological tissues are in a state of dynamic balance. However, many diseases such as cancer and inflammation, are accompanied by a long-term increase in ROS. This situation inspires researchers to use ROS-sensitive nanocarriers for a site-specific release of cargo in pathological areas. Polyamino acid materials with good biodegradability, biocompatibility, and regular secondary structure are widely used in the biomedical field. Herein, a new oxidation responsive PEGylated polyamino acid is synthesised for anticancer drug delivery by ring-opening polymerisation of N-carboxyanhydrides bearing thioether pendants. The obtained block copolymer mPEG-b-PMLG self-assembles into spherical nanoparticles (NPs) in water with diameter ≈68.3 nm. NMR measurement demonstrated that the hydrophobic thioether pendants in the NPs can be selectively oxidised to hydrophilic sulfoxide groups by H₂ O₂ , which will lead to the disassociation of NPs. In vitro drug release results indicated that the encapsulated Nile red is selectively released in the trigger of 10 mM H₂ O₂ in PBS. Finally, anticancer drug doxorubicin (DOX) is encapsulated to the NPs, and the obtained NPs/DOX exhibits an improved antitumor efficacy in 4T1 tumour-bearing mice and lower cardiotoxicity than free DOX. These results indicates that the mPEG-b-PMLG NPs are promising for anticancer drug delivery.

Radiation-assisted strategies provide new perspectives to improve the nanoparticle delivery to tumor

Nanoparticles (NPs), with advantages in tumor targeting, have been extensively developed for anticancer treatment. However, the delivery efficacy of NPs tends to be heterogeneous in clinical research. Surprisingly, a traditional cancer treatment, radiotherapy (radiation), has been observed with the potential to improve the delivery of NPs by influencing the features of the tumor microenvironment, which provides new perspectives to overcome the barriers in the NPs delivery. Since the effect of radiation can also be enhanced by versatile NPs, these findings of radiation-assisted NPs delivery suggest innovative strategies combining radiotherapy with nanotherapeutics. This review summarizes the research on the delivery and therapeutic efficacy of NPs that are improved by radiation, focusing on relative mechanisms and existing challenges and opportunities.

Engineered Macrophages: A Safe-by-Design Approach for the Tumor Targeting Delivery of Sub-5 nm Gold Nanoparticles

Ultrasmall nanoparticles (NPs) are a promising platform for the diagnosis and therapy of cancer, but the particles in sizes as small as several nanometers have an ability to translocate across biological barriers, which may bring unpredictable health risks. Therefore, it is essential to develop workable cell-based tools that can deliver ultrasmall NPs to the tumor in a safer manner. Here, this work uses macrophages as a shuttle to deliver sub-5 nm PEGylated gold (Au) NPs to tumors actively or passively, while reducing the accumulation of Au NPs in the brain. This work demonstrates that sub-5 nm Au NPs can be rapidly exocytosed from live macrophages, reaching 45.6% within 24 h, resulting in a labile Au NP-macrophage system that may release free Au NPs into the blood circulation in vivo. To overcome this shortcoming, two straightforward methods are used to engineer macrophages to obtain "half-dead" and "dead" macrophages. Although the efficiency of engineered macrophages for delivering sub-5 nm Au NPs to tumors is 2.2-3.8% lower than that of free Au NPs via the passive enhanced permeability and retention effect, this safe-by-design approach can dramatically reduce the accumulation of Au NPs in the brain by more than one order of magnitude. These promising approaches offer an opportunity to expand the immune cell- or stem cell-mediated delivery of ultrasmall NPs for the diagnosis and therapy of diseases in a safer way in the future.

An Integrated Polymeric mRNA Vaccine without Inflammation Side Effects for Cellular Immunity Mediated Cancer Therapy

Among the few available mRNA delivery vehicles, lipid nanoparticles (LNPs) are the most clinically advanced but they require cumbersome four components and suffer from inflammation-related side effects that should be minimized for safety. Yet, a certain level of proinflammatory responses and innate immune activation are required to evoke T-cell immunity for mRNA cancer vaccination. To address these issues and develop potent yet low-inflammatory mRNA cancer vaccine vectors, a series of alternating copolymers "PHTA" featured with ortho-hydroxy tertiary amine (HTA) repeating units for mRNA delivery is synthesized, which can play triple roles of condensing mRNA, enhancing the polymeric nanoparticle (PNP) stability, and prolonging circulation time. Unlike LNPs exhibiting high levels of inflammation, the PHTA-based PNPs show negligible inflammatory side effects in vivo. Importantly, the top candidate PHTA-C18 enables successful mRNA cancer vaccine delivery in vivo and leads to a robust CD8⁺ T cell mediated antitumor cellular immunity. Such PHTA-based integrated PNP provides a potential approach for establishing mRNA cancer vaccines with good inflammatory safety profiles.

Simple Multifunctional PTX@Ce6 Nanomedicine for Eradicating Tumor in the Combination of Photodynamic Therapy and Metronomic Chemotherapy

Photodynamic therapy (PDT) is an effective treatment modality for various cancer types. However, tumor recurrence and metastasis stemming from residual cancer cells after PDT pose serious problems. In this study, a simple multifunctional PTX@Ce6 nanomedicine is prepared using a two-step reprecipitation method. In this core-shell nanostructure, the toxic paclitaxel (PTX) core is embedded into a nontoxic Ce6 shell. An ultralow dose of PTX (1 mg/kg) stimulates the differentiation of marrow-derived suppressor cells (MDSCs) into mature dendritic cells (DCs), resulting in the restoration of functions of tumor-specific CD8⁺ T cells and promotion of antitumor immune responses in vivo. Hence, the tumors in mice are eradicated with 100% tumor inhibition rate via combination therapy. Tumor recurrence and metastasis are also effectively inhibited. In addition, the combination therapy with PDT and metronomic chemotherapy based on core-shell PTX@Ce6 nanostructures shows high biosafety in treated mice. This study can aid in developing new cancer treatment modalities for eradicating tumors, preventing tumor recurrence and metastasis, and reducing the systemic side effects of therapy.

Tryptophan-Modulated Nanoscale Metal-Organic Framework for Coordinated Loading of Biomolecules for Cascade Production of Reactive Oxygen and Nitrogen Species

Owing to the high surface area and porosity, metal-organic frameworks (MOFs) could be utilized as both nanocarriers of biopharmaceuticals and nanoreactors to organize cascade biological reactions with great potential in cancer treatment. However, nanoscale MOFs suitable for biomedical applications rely on harsh preparation conditions. Here, we utilized tryptophan to modulate the morphology and optical properties of zeolitic imidazolate framework-8 (ZIF-8) as nanocarrier to efficiently encapsulate the enzyme and mRNA. Under room temperature in an aqueous solution, tryptophan would coordinate with zinc ions to form ZIF-8:Trp with a decreased size from the μm range to sub-200 nm. In addition, cargo release could be monitored in real time via fluorescence red-shift effects. Besides being used as nanocarriers of biomolecules, ZIF-8:Trp could also be utilized as nanoreactors to induce cascade reactions to produce reactive oxygen and nitrogen species. Overall, this nanosized ZIF-8:Trp could provide a new strategy for preparation of cascade bioreactions and provide new insight for gas therapy.

Enhanced tumor penetration for efficient chemotherapy by a magnetothermally sensitive micelle combined with magnetic targeting and magnetic hyperthermia

The high accumulation and poor penetration of nanocarriers in tumor is a contradiction of nanomedicine, which reduces the efficacy of chemotherapy. Due to the positive effect of hyperthermia on in vivo drug diffusion, we designed a magnetothermally sensitive micelle (MTM) by integrating magnetic targeting (MT), magnetic hyperthermia (MH), and magnetothermally responsive drug release to facilitate simultaneous drug accumulation and penetration in tumor. Accordingly, we synthesized a cyanine7-modified thermosensitive polymer with phase transition at 42.3°C, and utilized it to prepare drug-loaded MTMs by encapsulating superparamagnetic MnFe2O4 nanoparticles and doxorubicin (DOX). The obtained DOX–MTM had not only high contents of DOX (9.1%) and MnFe2O4 (38.7%), but also some advantages such as superparamagnetism, high saturation magnetization, excellent magnetocaloric effect, and magnetothermal-dependent drug release. Therefore, DOX–MTM improved in vitro DOX cytotoxicity by enhancing DOX endocytosis under the assistance of MH. Furthermore, MT and MH enhanced in vivo DOX–MTM accumulation and DOX penetration in tumor, respectively, substantially inhibiting tumor growth (84%) with excellent biosafety. These results indicate the development of an optimized drug delivery system with MH and MH-dependent drug release, introducing a feasible strategy to enhance the application of nanomedicines in tumor chemotherapy.

Activatable self-assembled organic nanotheranostics: Aspartyl aminopeptidase triggered NIR fluorescence imaging-guided photothermal/photodynamic synergistic therapy

Phototherapy has developed as a powerful method for remedial modalities. The conventional photosensitizers are "always on" state and lack tumor targeting, which contributed to poor therapeutic effect and high toxicity. Therefore, we developed an aspartyl aminopeptidase (DNPEP) activated self-assembled organic nanoparticles (NRh-Asp NPs) with sensitive external irradiation-induced photothermal therapy and photodynamic therapy (PTT/PDT). NRh-Asp NPs can be activated to NRh-NH₂ NPs by DNPEP, demonstrating strong near-infrared (NIR) fluorescence, and efficiently generating heat and singlet oxygen under the near-infrared laser. NRh-Asp NPs was successfully used for visualizing DNPEP in vitro and in vivo in NIR region, and demonstrated good synergistic anti-cancer efficacy of PDT and PTT. These results suggest that DNPEP-mediated NRh-Asp NPs are promising candidates for image-guided phototherapeutic of tumor.

Stimuli-responsive image-guided nanocarriers as smart drug delivery platforms

INTRODUCTION

In recent years, to improve the precision of drug delivery and reduce toxicity associated from the uncontrolled drug release at off-target locations, extensive efforts have been paid to develop stimuli-responsive nanocarriers, which enable precise control over on-demand drug release due to internal stimuli like pH, redox, enzyme and external stimuli like light, magnetic field, and ultrasound. Moreover, some stimuli-responsive nanocarriers have been strategically incorporated with imaging probes for simultaneous monitoring of the drug delivery process and region of interest for treatment optimization.

AREAS COVERED

In this review, the state-of-art progress in developing stimuli-responsive image-guided nanocarriers are summarized, including their designed strategies, synergistic mechanism, and biomedical applications in cancer therapy, and the current challenges and new perspectives are discussed.

EXPERT OPINION

The stimuli-responsive nanocarriers provide assurance for precise release of drugs and imaging probes, and the molecular imaging techniques can monitor the pharmacokinetics, biodistribution and bioavailability of drugs in vivo, and feedback the drug delivery profile. Therefore, stimuli-responsive image-guided nanocarriers can integrate diagnosis and therapy in one nanoplatform and facilitate optimal therapeutic efficacy.

Preparation of Triptolide Nano Drug Delivery System and Its Antitumor Activity In-Vitro

Triptolide (as an effective antitumor drug) is limited in clinical application because of its poor solubility and absorption in-vivo. Herein, we prepared folic acid modified polymer micelles to encapsulate triptolide and enhance its biologicalavailability coupled with antitumor effect. We prepared nano-micelles of triptolide through thin lipid film hydrational method. Physical properties and in vitro release characterization of Fol-Plla-cl-Peg-Plla-cl-Tmicelles were evaluated, while bioavailability of the formulation in rats was investigated. Tumor targeting potential of micelles was determined by observing the uptake of A549 cells. In-Vitro antitumor activity of micelles and free triptolide (API) was investigated with MTT assay. The prepared polymer material exhibited no cytotoxicity. The particle size distribution of Fol-Plla-cl-Peg-Plla-cl-T micelles was uniform and small, with good stability and high efficiency of entrapment. Triptolide In-Vitro release from micelles demonstrated slow and continuous released for 24 h. Compared with API, the half-life of micelles was prolonged, whilst its bioavailability in-vivo was increased by about 6.35 times. More importantly, Fol-Plla-cl-Peg-Plla-cl-T micelles significantly improved the antitumor activity of triptolide and showed good tumor targeting potential. Fol-Plla-cl-Peg-Plla-cl-T micelles could improve the bioavailability and antitumor activity of triptolide, amid demonstration of good tumor targeting and high safety.

The role of imaging in targeted delivery of nanomedicine for cancer therapy

Nanomedicines overcome the pharmacokinetic limitations of traditional drug formulations and have promising prospect in cancer treatment. However, nanomedicine delivery in vivo is still facing challenges from the complex physiological environment. For the purpose of effective tumor therapy, they should be designed to guarantee the five features principle, including long blood circulation, efficient tumor accumulation, deep matrix penetration, enhanced cell internalization and accurate drug release. To ensure the excellent performance of the designed nanomedicine, it would be better to monitor the drug delivery process as well as the therapeutic effects by real-time imaging. In this review, we summarize strategies in developing nanomedicines for efficiently meeting the five features of drug delivery, and the role of several imaging modalities (fluorescent imaging (FL), magnetic resonance imaging (MRI), computed tomography (CT), photoacoustic imaging (PAI), positron emission tomography (PET), and electron microscopy) in tracing drug delivery and therapeutic effect in vivo based on five features principle.

"Targeting Design" of Nanoparticles in Tumor Therapy

Tumor-targeted therapy based on nanoparticles is a popular research direction in the biomedical field. After decades of research and development, both the passive targeting ability of the inherent properties of NPs and the active targeting based on ligand receptor interaction have gained deeper understanding. Unfortunately, most targeted delivery strategies are still in the preclinical trial stage, so it is necessary to further study the biological fate of particles in vivo and the interaction mechanism with tumors. This article reviews different targeted delivery strategies based on NPs, and focuses on the physical and chemical properties of NPs (size, morphology, surface and intrinsic properties), ligands (binding number/force, activity and species) and receptors (endocytosis, distribution and recycling) and other factors that affect particle targeting. The limitations and solutions of these factors are further discussed, and a variety of new targeting schemes are introduced, hoping to provide guidance for future targeting design and achieve the purpose of rapid transformation of targeted particles into clinical application.

Precision Nanomedicines: Targeting Hot Mitochondria in Cancer Cells

Mitochondrion is a multifunctional organelle in a cell, and it is one of the important targets of antitumor therapy. Conventional mitochondrial targeting strategies can hardly distinguish the mitochondria in cancer cells from those in normal cells, which might raise a concern about the biosafety. Recent studies suggest that a relatively high temperature of mitochondria exists in cancer cells. We named it tumor intrinsic mitochondrial overheating (TIMO). By taking advantage of the difference in mitochondrial temperatures between cancer cells and normal cells, therapeutic agents can be specifically delivered to the mitochondria in cancer cells. Here we will briefly overview the mitochondria-targeted delivery strategies. In addition, the recent discovery of hot mitochondria in cancer cells and the development of mitochondrial temperature-responsive delivery systems for antitumor therapy will be reviewed.

Strategies to enhance drug delivery to solid tumors by harnessing the EPR effects and alternative targeting mechanisms

The Enhanced Permeability and Retention (EPR) effect has been recognized as the central paradigm in tumor-targeted delivery in the last decades. In the wake of this concept, nanotechnologies have reached phenomenal levels in research. However, clinical tumors display a poor manifestation of EPR effect. Factors including tumor heterogeneity, complicating tumor microenvironment, and discrepancies between laboratory models and human tumors largely contribute to poor efficiency in tumor-targeted delivery and therapeutic failure in clinical translation. In this article, approaches for evaluation of EPR effect in human tumor were overviewed as guidance to employ EPR effect for cancer treatment. Strategies to augment EPR-mediated tumoral delivery are discussed in different dimensions including enhancement of vascular permeability, depletion of tumor extracellular matrix and optimization of nanoparticle design. Besides, the recent development in alternative tumor-targeted delivery mechanisms are highlighted including transendothelial pathway, endogenous cell carriers and non-immunogenic bacteria-mediated delivery. In addition, the emerging preclinical models better reflect human tumors are introduced. Finally, more rational applications of EPR effect in other disease and field are proposed. This article elaborates on fundamental reasons for the gaps between theoretical expectation and clinical outcomes, attempting to provide some perspective directions for future development of cancer nanomedicines in this still evolving landscape.

Spatial specific delivery of combinational chemotherapeutics to combat intratumoral heterogeneity

Hypoxia-induced intratumoral heterogeneity poses a major challenge in tumor therapy due to the varying susceptibility to chemotherapy. Moreover, the spatial distribution patterns of hypoxic and normoxic tissues makes conventional combination therapy less effective. In this study, a tumor-acidity and bioorthogonal chemistry mediated in situ size transformable nanocarrier (NP@DOX_DBCO plus iCPPA_N3) was developed to spatially deliver two combinational chemotherapeutic drugs (doxorubicin (DOX) and PR104A) to combat hypoxia-induced intratumoral heterogeneity. DOX is highly toxic to tumor cells in normoxia state but less toxic in hypoxia state due to the hypoxia-induced chemoresistance. Meanwhile, PR104A is a hypoxia-activated prodrug has less toxic in normoxia state. Two nanocarriers, NP@DOX_DBCO and iCPPA_N3, can cross-link near the blood vessel extravasation sites through tumor acidity responsive bioorthogonal click chemistry to enhance the retention of DOX in tumor normoxia. Moreover, PR104A conjugated to the small-sized dendritic polyamidoamine (PAMAM) released under tumor acidity can penetrate deep tumor tissues for hypoxic tumor cell killing. Our study has demonstrated that this site-specific combination chemotherapy is better than the traditional combination chemotherapy. Therefore, spatial specific delivery of combinational therapeutics via in situ size transformable nanocarrier addresses the challenges of hypoxia induced intratumoral heterogeneity and provides insights into the combination therapy.

Enzyme-mediated intratumoral self-assembly of nanotheranostics for enhanced imaging and tumor therapy

Enzyme-mediated intratumoral self-assembled (EMISA) nanotheranostics represent a new class of smart agents for combined imaging and therapy of cancer. Cancer cells overexpress various enzymes that are essential for high metabolism, fast proliferation, and tissue invasion and metastasis. By conjugating small molecules that contain an enzyme-specific cleavage site to appropriate chemical linkers, it is possible to induce self-assembly of nanostructures in tumor cells having the target enzyme. This approach of injecting small theranostic molecules that eventually become larger nanotheranostics in situ avoids some of the major limitations that are encountered when injecting larger, pre-assembled nanotheranostics. The advantage of EMISA nanotheranostics include the avoidance of nonspecific uptake and rapid clearance by phagocytic cells, increased cellular accumulation, reduced drug efflux and prolonged cellular exposure time, all of which lead to an amplified imaging signal and therapeutic efficacy. We review here the different approaches that can be used for preparing EMISA-based organic, inorganic, or organic/inorganic hybrid nanotheranostics based on noncovalent interactions and/or covalent bonding. Imaging examples are shown for fluorescence imaging, nuclear imaging, photoacoustic imaging, Raman imaging, computed tomography imaging, bioluminescent imaging, and magnetic resonance imaging. This article is categorized under: Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Biology-Inspired Nanomaterials > Peptide-Based Structures.

Peptide-based supramolecular assembly drugs toward cancer theranostics

INTRODUCTION

: Peptide-based supramolecular self-assembly has been demonstrated to be a flexible approach for the fabrication of programmable de novo nanodrugs by employing synergistic or reciprocal intermolecular non-covalent interactions; this class of nanomaterials holds significant promise for clinical translation, especially as cancer theranostics.

AREAS COVERED

: In this review, we describe the concept of cancer theranostic drug assembly by employing non-covalent interactions. That is, molecular drugs are formulated into nanoscale and even microscale architectures by peptide-modulated self-assembly. A series of peptide-based supramolecular assembly drugs are discussed, with an emphasis on the relation between structural feature and theranostic performance.

EXPERT OPINION

: Molecular design, manipulation of non-covalent interactions and elucidation of structure-function relationships not only facilitate the implementation of supramolecular self-assembly principles in drug development, but also provide a new means for advancing anticancer nanostructured drugs toward clinical application.