Hypoxia-responsive nanoparticle based drug delivery systems in cancer therapy: An up-to-date review

Sonodynamic and sonomechanical effect on cellular stemness and extracellular physicochemical environment to potentiate chemotherapy

BACKGROUND

Hypoxia-activated prodrug (HAP) is a promising candidate for highly tumor-specific chemotherapy. However, the oxygenation heterogeneity and dense extracellular matrix (ECM) of tumor, as well as the potential resistance to chemotherapy, have severely impeded the resulting overall efficacy of HAP.

RESULTS

A HAP potentiating strategy is proposed based on ultrasound responsive nanodroplets (PTP@PLGA), which is composed of protoporphyrin (PpIX), perfluoropropane (PFP) and a typical HAP, tirapazamine (TPZ). The intense vaporization of PFP upon ultrasound irradiation can magnify the sonomechanical effect, which loosens the ECM to promote the penetration of TPZ into the deep hypoxic region. Meanwhile, the PpIX enabled sonodynamic effect can further reduce the oxygen level, thus activating the TPZ in the relatively normoxic region as well. Surprisingly, abovementioned ultrasound effect also results in the downregulation of the stemness of cancer cells, which is highly associated with drug-refractoriness.

CONCLUSIONS

This work manifests an ideal example of ultrasound-based nanotechnology for potentiating HAP and also reveals the potential acoustic effect of intervening cancer stem-like cells.

Stimuli-sensitive polymer prodrug nanocarriers by reversible-deactivation radical polymerization

Polymer prodrugs are based on the covalent linkage of therapeutic molecules to a polymer structure which avoids the problems and limitations commonly encountered with traditional drug-loaded nanocarriers in which drugs are just physically entrapped (e.g., burst release, poor drug loadings). In the past few years, reversible-deactivation radical polymerization (RDRP) techniques have been extensively used to design tailor-made polymer prodrug nanocarriers. This synthesis strategy has received a lot of attention due to the possibility of fine tuning their structural parameters (e.g., polymer nature and macromolecular characteristics, linker nature, physico-chemical properties, functionalization, etc.), to achieve optimized drug delivery and therapeutic efficacy. In particular, adjusting the nature of the drug-polymer linker has enabled the easy synthesis of stimuli-responsive polymer prodrugs for efficient spatiotemporal drug release. In this context, this review article will give an overview of the different stimuli-sensitive polymer prodrug structures designed by RDRP techniques, with a strong focus on the synthesis strategies, the macromolecular architectures and in particular the drug-polymer linker, which governs the drug release kinetics and eventually the therapeutic effect. Their biological evaluations will also be discussed.

Active Anchoring Stimuli-Responsive Nano-Craft to Relieve Pulmonary Vasoconstriction by Targeting Smooth Muscle Cell for Hypoxic Pulmonary Hypertension Treatment

Recently, nanotechnology-based drug delivery platforms in treating pulmonary arterial hypertension (PAH) have gradually emerged. However, large mechanical stress and shear stress in blood vessels greatly affect the retention of nanopreparative materials at lesion sites, severely limiting nanotechnology-based drug delivery. Herein, a stimuli-responsive nanocraft is rationally designed by actively anchoring E-selectin overexpressed on pulmonary arterial endothelial cells (PAECs), under hypoxic conditions, allowing effective accumulation and retention of the drug at the lesion site. Briefly, a nitrobenzene group is incorporated into the framework of a nanocarrier, and then it is simultaneously linked with chitosan. Additionally, the surface of the nanocarrier with sialic acid (SA) and encapsulated the clinically used drug ambrisentan (Am), which enables the anchoring of E-selectin and subsequent drug delivery is modifed. This system facilitates intercellular transport to pulmonary artery smooth muscle cells (PASMCs) when targeting PAECs and specifically responds to a reductive hypoxic microenvironment with elevated nitroreductase in PASMCs. Moreover, compared with free Am, nanoencapsulation and SA-PEG2000-NH2 prolong the blood circulation time, achieving better therapeutic outcomes in preventing vascular remodeling and reversing systolic dysfunction. The originality and contribution of this work reveal the promising value of this pulmonary arterial anchoring stimuli-responsive nanocraft as a novel therapeutic strategy for satisfactory PAH treatment.

Dual-targeted delivery of temozolomide by multi-responsive nanoplatform via tumor microenvironment modulation for overcoming drug resistance to treat glioblastoma

Glioblastoma (GBM) is the most aggressive primary brain tumor with low survival rate. Currently, temozolomide (TMZ) is the first-line drug for GBM treatment of which efficacy is unfortunately hindered by short circulation time and drug resistance associated to hypoxia and redox tumor microenvironment. Herein, a dual-targeted and multi-responsive nanoplatform is developed by loading TMZ in hollow manganese dioxide nanoparticles functionalized by polydopamine and targeting ligands RAP12 for photothermal and receptor-mediated dual-targeted delivery, respectively. After accumulated in GBM tumor site, the nanoplatform could respond to tumor microenvironment and simultaneously release manganese ion (Mn2+), oxygen (O2) and TMZ. The hypoxia alleviation via O2 production, the redox balance disruption via glutathione consumption and the reactive oxygen species generation, together would down-regulate the expression of O6-methylguanine-DNA methyltransferase under TMZ medication, which is considered as the key to drug resistance. These strategies could synergistically alleviate hypoxia microenvironment and overcome TMZ resistance, further enhancing the anti-tumor effect of chemotherapy/chemodynamic therapy against GBM. Additionally, the released Mn2+ could also be utilized as a magnetic resonance imaging contrast agent for monitoring treatment efficiency. Our study demonstrated that this nanoplatform provides an alternative approach to the challenges including low delivery efficiency and drug resistance of chemotherapeutics, which eventually appears to be a potential avenue in GBM treatment.

Hypoxia: Intriguing Feature in Cancer Cell Biology

Hypoxia, a key aspect of the tumor microenvironment, plays a vital role in cell proliferation, angiogenesis, metabolism, and the immune response within tumors. These factors collectively promote tumor advancement, aggressiveness, metastasis and result in a poor prognosis. Hypoxia inducible factor 1α (HIF-1α), activated under low oxygen conditions, mediates many of these effects by altering drug target expression, metabolic regulation, and oxygen consumption. These changes promote cancer cell growth and survival. Hypoxic tumor cells develop aggressive traits and resistance to chemotherapy and radiotherapy, leading to increased mortality. Targeting hypoxic tumor offers a potential solution to overcome the challenges posed by tumor heterogeneity and can be used in designing diagnostic and therapeutic nanocarriers for various solid cancers. This concept provides an overview of the intricate relationship between hypoxia and the tumor microenvironment, highlighting its potential as a promising tool for cancer therapies. The article explores the development of hypoxia in cancer cells and its role in cancer progression, along with the latest advancements in hypoxia-triggered cancer treatment.

A 700 nm LED Light Activated Ru(II) Complex Destroys Tumor Cytoskeleton via Photosensitization and Photocatalysis

Photoactivable chemotherapy (PACT) using metallic complexes provides spatiotemporal selectivity over drug activation for targeted anticancer therapy. However, the poor absorption in near-infrared (NIR) light region of most metallic complexes renders tissue penetration challenging. Herein, an NIR light triggered dinuclear photoactivable Ru(II) complex (Ru2) is presented and the antitumor mechanism is comprehensively investigated. The introduction of a donor-acceptor-donor (D-A-D) linker greatly enhances the intramolecular charge transition, resulting in a high molar extinction coefficient in the NIR region with an extended triplet excited state lifetime. Most importantly, when activated by 700 nm NIR light, Ru2 exhibits unique slow photodissociation kinetics that facilitates synergistic photosensitization and photocatalytic activity to destroy diverse intracellular biomolecules. In vitro and in vivo experiments show that when activated by 700 nm NIR light, Ru2 exhibits nanomolar photocytotoxicity toward 4T1 cancer cells via the induction of calcium overload and endoplasmic reticulum (ER) stress. These findings provide a robust foundation for the development of NIR-activated Ru(II) PACT complexes for phototherapeutic application.

Introducing urea into tirapazamine derivatives to enhance anticancer therapy

Tirapazamine (TPZ) has been approved for multiple clinical trials relying on its excellent anticancer potential. However, as a typical hypoxia-activated prodrug (HAP), TPZ did not exhibit survival advantages in Phase III clinical trials when used in combination therapy due to the insufficient hypoxia levels in patients' tumors. In this study, to improve the therapeutic effects of TPZ, we first introduced urea to synthesize a series of urea-containing derivatives of TPZ. All urea-containing TPZ derivatives showed increased hypoxic cytotoxicity (9.51-30.85-fold) compared with TPZ, while maintaining hypoxic selectivity. TPZP, one of these derivatives, showed 20-fold higher cytotoxicity than TPZ while maintaining a similar hypoxic cytotoxicity ratio. To highly efficiently deliver TPZP to the tumors and reduce its side effects on healthy tissues, we further prepared TPZP into a nanodrug with fibrin-targeting ability: FT11-TPZP-NPs. CA4-NPs, a vascular disrupting agent, was used to increase the fibrin level within tumors and exacerbate tumor hypoxia. By being combined with CA4-NPs, FT11-TPZP-NPs can accumulate in the hypoxia-aggravated tumors and activate sufficiently to kill tumor cells. After a single-dose treatment, FT11-TPZP-NPs + CA4-NPs showed a high inhibition rate of 98.1% against CT26 tumor models with an initial volume of ∼480 mm3 and four out of six tumors were completely eliminated; it thereby exerted a significant antitumor effect. This study provides a new strategy for improving the therapeutic effect of TPZ and other HAPs in anticancer therapy.

Theranostic Fluorescent Probes

The ability to gain spatiotemporal information, and in some cases achieve spatiotemporal control, in the context of drug delivery makes theranostic fluorescent probes an attractive and intensely investigated research topic. This interest is reflected in the steep rise in publications on the topic that have appeared over the past decade. Theranostic fluorescent probes, in their various incarnations, generally comprise a fluorophore linked to a masked drug, in which the drug is released as the result of certain stimuli, with both intrinsic and extrinsic stimuli being reported. This release is then signaled by the emergence of a fluorescent signal. Importantly, the use of appropriate fluorophores has enabled not only this emerging fluorescence as a spatiotemporal marker for drug delivery but also has provided modalities useful in photodynamic, photothermal, and sonodynamic therapeutic applications. In this review we highlight recent work on theranostic fluorescent probes with a particular focus on probes that are activated in tumor microenvironments. We also summarize efforts to develop probes for other applications, such as neurodegenerative diseases and antibacterials. This review celebrates the diversity of designs reported to date, from discrete small-molecule systems to nanomaterials. Our aim is to provide insights into the potential clinical impact of this still-emerging research direction.

Nanocatalysts for modulating antitumor immunity: fabrication, mechanisms and applications

Immunotherapy harnesses the inherent immune system in the body to generate systemic antitumor immunity, offering a promising modality for defending against cancer. However, tumor immunosuppression and evasion seriously restrict the immune response rates in clinical settings. Catalytic nanomedicines can transform tumoral substances/metabolites into therapeutic products in situ, offering unique advantages in antitumor immunotherapy. Through catalytic reactions, both tumor eradication and immune regulation can be simultaneously achieved, favoring the development of systemic antitumor immunity. In recent years, with advancements in catalytic chemistry and nanotechnology, catalytic nanomedicines based on nanozymes, photocatalysts, sonocatalysts, Fenton catalysts, electrocatalysts, piezocatalysts, thermocatalysts and radiocatalysts have been rapidly developed with vast applications in cancer immunotherapy. This review provides an introduction to the fabrication of catalytic nanomedicines with an emphasis on their structures and engineering strategies. Furthermore, the catalytic substrates and state-of-the-art applications of nanocatalysts in cancer immunotherapy have also been outlined and discussed. The relationships between nanostructures and immune regulating performance of catalytic nanomedicines are highlighted to provide a deep understanding of their working mechanisms in the tumor microenvironment. Finally, the challenges and development trends are revealed, aiming to provide new insights for the future development of nanocatalysts in catalytic immunotherapy.

Programmable intratumoral drug delivery to breast cancer using wireless bioelectronic device with electrochemical actuation

OBJECTIVE

Breast cancer is a global health concern that demands attention. In our contribution to addressing this disease, our study focuses on investigating a wireless micro-device for intratumoral drug delivery, utilizing electrochemical actuation. Microdevices have emerged as a promising approach in this field due to their ability to enable controlled injections in various applications.

METHODS

Our study is conducted within a computational framework, employing models that simulate the behavior of the microdevice and drug discharge based on the principles of the ideal gas law. Furthermore, the distribution of the drug within the tissue is simulated, considering both diffusion and convection mechanisms. To predict the therapeutic response, a pharmacodynamic model is utilized, considering the chemotherapeutic effects and cell proliferation.

RESULTS

The findings demonstrate that an effective current of 3 mA, along with an initial gas volume equal to the drug volume in the microdevice, optimizes drug delivery. Microdevices with multiple injection capabilities exhibit enhanced therapeutic efficacy, effectively suppressing cell proliferation. Additionally, tumors with lower microvascular density experience higher drug concentrations in the extracellular space, resulting in significant cell death in hypoxic regions.

CONCLUSIONS

Achieving an efficient therapeutic response involves considering both the characteristics of the tumor microenvironment and the frequency of injections within a specific time frame.

Current advances in modulating tumor hypoxia for enhanced therapeutic efficacy

Hypoxia is a common feature of most solid tumors, which promotes the proliferation, invasion, metastasis, and therapeutic resistance of tumors. Researchers have been developing advanced strategies and nanoplatforms to modulate tumor hypoxia to enhance therapeutic effects. A timely review of this rapidly developing research topic is therefore highly desirable. For this purpose, this review first introduces the impact of hypoxia on tumor development and therapeutic resistance in detail. Current developments in the construction of various nanoplatforms to enhance tumor treatment in response to hypoxia are also systematically summarized, including hypoxia-overcoming, hypoxia-exploiting, and hypoxia-disregarding strategies. We provide a detailed discussion of the rationale and research progress of these strategies. Through a review of current trends, it is hoped that this comprehensive overview can provide new prospects for clinical application in tumor treatment. STATEMENT OF SIGNIFICANCE: As a common feature of most solid tumors, hypoxia significantly promotes tumor progression. Advanced nanoplatforms have been developed to modulate tumor hypoxia to enhanced therapeutic effects. In this review, we first introduce the impact of hypoxia on tumor progression. Current developments in the construction of various nanoplatforms to enhance tumor treatment in response to hypoxia are systematically summarized, including hypoxia-overcoming, hypoxia-exploiting, and hypoxia-disregarding strategies. We discuss the rationale and research progress of the above strategies in detail, and finally introduce future challenges for treatment of hypoxic tumors. By reviewing the current trends, this comprehensive overview can provide new prospects for clinical translatable tumor therapy.

Adjuvant Novel Nanocarrier-Based Targeted Therapy for Lung Cancer

Lung cancer has the lowest survival rate due to its late-stage diagnosis, poor prognosis, and intra-tumoral heterogeneity. These factors decrease the effectiveness of treatment. They release chemokines and cytokines from the tumor microenvironment (TME). To improve the effectiveness of treatment, researchers emphasize personalized adjuvant therapies along with conventional ones. Targeted chemotherapeutic drug delivery systems and specific pathway-blocking agents using nanocarriers are a few of them. This study explored the nanocarrier roles and strategies to improve the treatment profile's effectiveness by striving for TME. A biofunctionalized nanocarrier stimulates biosystem interaction, cellular uptake, immune system escape, and vascular changes for penetration into the TME. Inorganic metal compounds scavenge reactive oxygen species (ROS) through their photothermal effect. Stroma, hypoxia, pH, and immunity-modulating agents conjugated or modified nanocarriers co-administered with pathway-blocking or condition-modulating agents can regulate extracellular matrix (ECM), Cancer-associated fibroblasts (CAF),Tyro3, Axl, and Mertk receptors (TAM) regulation, regulatory T-cell (Treg) inhibition, and myeloid-derived suppressor cells (MDSC) inhibition. Again, biomimetic conjugation or the surface modification of nanocarriers using ligands can enhance active targeting efficacy by bypassing the TME. A carrier system with biofunctionalized inorganic metal compounds and organic compound complex-loaded drugs is convenient for NSCLC-targeted therapy.

Recent Advances in Nanomedicine for Ocular Fundus Neovascularization Disease Management

As an indispensable part of the human sensory system, visual acuity may be impaired and even develop into irreversible blindness due to various ocular pathologies. Among ocular diseases, fundus neovascularization diseases (FNDs) are prominent etiologies of visual impairment worldwide. Intravitreal injection of anti-vascular endothelial growth factor drugs remains the primary therapy but is hurdled by common complications and incomplete potency. To renovate the current therapeutic modalities, nanomedicine emerged as the times required, which is endowed with advanced capabilities, able to fulfill the effective ocular fundus drug delivery and achieve precise drug release control, thus further improving the therapeutic effect. This review provides a comprehensive summary of advances in nanomedicine for FND management from state-of-the-art studies. First, the current therapeutic modalities for FNDs are thoroughly introduced, focusing on the key challenges of ocular fundus drug delivery. Second, nanocarriers are comprehensively reviewed for ocular posterior drug delivery based on the nanostructures: polymer-based nanocarriers, lipid-based nanocarriers, and inorganic nanoparticles. Thirdly, the characteristics of the fundus microenvironment, their pathological changes during FNDs, and corresponding strategies for constructing smart nanocarriers are elaborated. Furthermore, the challenges and prospects of nanomedicine for FND management are thoroughly discussed.

Development of Novel Chimeric Endolysin Conjugated with Chitosan-Zn-Metal-Organic Framework Nanocomposites with Antibacterial Activity

Bacterial diseases have been considered the most crucial issue and are threatening human health all around the world. Also, resistance to antimicrobial drugs has become a big hurdle against efficient therapy. As a result, recombinant chimeric endolysin was produced in E. coli host to use as a potential antibacterial agent against bacteria resistance and replacement to conventional antibiotics in this study. Then, chitosan (C)-coated nanoscale metal-organic frameworks (CS-NMOFs) nanocomposite was synthesized as a novel nano delivery system to further improve the antibacterial activity of endolysin. After characterization of nanocomposite with analytical devices such as FT-IR, DLS, and TEM and determining the nanometric size of samples (30 nm to 90 nm), endolysin was covalently (endolysin-CS-NMOFs (C)) and non-covalently (endolysin-CS-NMOFs (NC)) conjugated to nanocomposite. Thereafter, the lytic ability, synergistic interaction, and biofilm reduction manner of endolysin-containing CS-NMOF nanocomposites were evaluated on E. coli, S. aureus, and P. aeruginosa strains. The results depicted an excellent lytic ability of nanocomposites after 24 h and 48 h of treatment, especially endolysin-CS-NMOFs (NC) on E. coli and P. aeruginosa strains. The synergistic interaction between nanocomposite and vancomycin did not attain for P. aeruginosa strain whereas the reverse was true for E. coli and S. aureus strains at 8 ng/mL concentration. Next, nanocomposites demonstrated potential biofilm reduction activities in various strains, especially in S. aureus and P. aeruginosa. Ultimately, our outputs demonstrate an efficient performance of the synthesized nanocomposite as an appropriate substitution for conventional antibiotics against bacteria.

Chitosan-Albumin Nanocomposite as a Promising Nanocarrier for Efficient Delivery of Fluconazole Against Vaginal Candidiasis

Currently, the high incidence of fungal infections among females has resulted in outstanding problems. Candida species is related with multidrug resistance and destitute clinical consequences. Chitosan-albumin derivatives with more stability exhibit innate antifungal and antibacterial effects that boost the activity of the drug without inflammatory impact. The stability and sustained release of Fluconazole in mucosal tissues can be ensured by encapsulating in protein/polysaccharide nanocomposites. Thus, we developed chitosan-albumin nanocomposite (CS-A) loaded with Fluconazole (Flu) antifungals against vaginal candidiasis. Various ratios of CS/Flu (1:1, 1:2, 2:1) were prepared. Thereafter, the CS-A-Flu nanocomposites were qualified and quantified using FT-IR, DLS, TEM, and SEM analytical devices, and the size range from 60 to 100 nm in diameter was attained for the synthesized nanocarriers. Afterward, the antifungal activity, biofilm reduction potency, and cell viability assay were performed for biomedical evaluation of formulations. The minimum inhibitory concentration) and minimum fungicidal concentration on Candida albicans were attained at 125 ng/μL and 150 ng/μL after treatment with a 1:2 (CS/Flu) ratio of CS-A-Flu. The biofilm reduction assay indicated that biofilm formation was between 0.05 and 0.1% for CS-A-Flu at all ratios. The MTT assay also exhibited excellent biocompatibility for samples, about 7 to 14% toxicity on human HGF normal cells. These data have indicated that CS-A-Flu would be a promising candidate against Candida albicans.

A pro-death autophagy-based nanoplatform for enhancing antitumour efficacy with improved immune responses

Due to the pro-survival effect of mild autophagy, the therapeutic effect of chemo-immunotherapy is unsatisfactory. In addition, the adverse tumour microenvironment (TME), including the lack of antigen presentation, the deficiency of oxygen supply and immunosuppressive cells, results in immune escape and metastasis. Herein, a novel nanoplatform (CS-3BP/PA@DOX) based on the autophagy cascade is proposed for the first time to deliver the chemotherapeutic doxorubicin (DOX) and respiration inhibitor 3-bromopyruvic acid (3BP) to overcome the above obstacles. CS-3BP/PA@DOX exerts a synergistic therapeutic effect to initiate pro-death autophagy and facilitate the antigen presentation process by combining DOX chemotherapy and starvation therapy with 3BP. Additionally, CS-3BP/PA@DOX remodelled the immunosuppressive TME by alleviating hypoxia, damaging dense ECM, and downregulating PD-L1 to enhance antitumour immunity. 3BP was found to promote GSH depletion by inhibiting respiration for the first time, which reduces the chemical resistance of cancer and increases the sensitivity of cells to ROS, providing a new therapeutic direction of 3BP for antitumour treatment. Collectively, this study offers an opportunity to magnify pro-death autophagy, augment antitumour efficacy, facilitate anti-metastatic effects, and boost immune responses.

Novel Chimeric Endolysin Conjugated Chitosan Nanocomplex as a Potential Inhibitor Against Gram-Positive and Gram-Negative Bacteria

Resistance to antimicrobial agents has created potential problems in finding efficient treatments against bacteria. Thus, using new therapeutics, such as recombinant chimeric endolysin, would be more beneficial for eliminating resistant bacteria. The treatment ability of these therapeutics can be further improved if they are used with biocompatible nanoparticles like chitosan (CS). In this work, covalently conjugated chimeric endolysin to CS nanoparticles (C) and non-covalently entrapped endolysin in CS nanoparticles (NC) were effectively developed and, consequently, qualified and quantified using analytical devices, including FT-IR, dynamic light scattering, and TEM. Eighty to 150 nm and 100 nm to 200 nm in diameter were measured for CS-endolysin (NC) and CS-endolysin (C) using a TEM, respectively. The lytic activity, synergistic interaction, and biofilm reduction potency of nano-complexes were investigated on Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and Pseudomonas aeruginosa (P. aeruginosa) strains. The outputs revealed a good lytic activity of nano-complexes after 24 h and 48 h of treatment, especially in P. aeruginosa (approximately 40% cell viability after 48 h of treatment with 8 ng/mL), and potential biofilm reduction performance was attained in E. coli strains (about 70% reduction after treatment with 8 ng/mL). The synergistic interaction between nano-complexes and vancomycin was exhibited in E. coli, P. aeruginosa, and S. aureus strains at 8 ng/mL concentrations, while the synergistic effects of pure endolysin and vancomycin were not remarkable in E. coli strains. These nano-complexes would be more beneficial in suppressing the bacteria with a high level of antibiotic resistance.

Nanomaterials-based precision sonodynamic therapy enhancing immune checkpoint blockade: A promising strategy targeting solid tumor

Burgeoning is an evolution from conventional photodynamic therapy (PDT). Thus, sonodynamic therapy (SDT) regulated by nanoparticles (NPs) possesses multiple advantages, including stronger penetration ability, better biological safety, and not reactive oxygen species (ROS)-dependent tumor-killing effect. However, the limitation to tumor inhibition instead of shrinkage and the incapability of eliminating metastatic tumors hinder the clinical potential for SDT. Fortunately, immune checkpoint blockade (ICB) can revive immunological function and induce a long-term immune memory against tumor rechallenges. Hence, synergizing NPs-based SDT with ICB can provide a promising therapeutic outcome for solid tumors. Herein, we briefly reviewed the progress in NPs-based SDT and ICB therapy. We highlighted the synergistic anti-tumor mechanisms and summarized the representative preclinical trials on SDT-assisted immunotherapy. Compared to other reviews, we provided comprehensive and unique perspectives on the innovative sonosensitizers in each trial. Moreover, we also discussed the current challenges and future corresponding solutions.

Improvement of the effectiveness of sonodynamic therapy: by optimizing components and combination with other treatments

Sonodynamic therapy (SDT) is an emerging treatment method. In comparison with photodynamic therapy (PDT), SDT exhibits deep penetration, high cell membrane permeability, and free exposure to light capacity. Unfortunately, owing to inappropriate ultrasound parameter selection, poor targeting of sonosensitizers, and the complex tumor environment, SDT is frequently ineffective. In this review, we describe the approaches for selecting ultrasound parameters and how to develop sonosensitizers to increase targeting and improve adverse tumor microenvironments. Furthermore, the potential of combining SDT with other treatment methods, such as chemotherapy, chemodynamic therapy, photodynamic therapy, photothermal therapy, and immunotherapy, is discussed to further increase the treatment efficiency of SDT.

Camptothecin-based prodrug nanomedicines for cancer therapy

Camptothecin (CPT) is a cytotoxic alkaloid that attenuates the replication of cancer cells via blocking DNA topoisomerase 1. Despite its encouraging and wide-spectrum antitumour activity, its application is significantly restricted owing to its instability, low solubility, significant toxicity, and acquired tumour cell resistance. This has resulted in the development of many CPT-based therapeutic agents, especially CPT-based nanomedicines, with improved pharmacokinetic and pharmacodynamic profiles. Specifically, smart CPT-based prodrug nanomedicines with stimuli-responsive release capacity have been extensively explored owing to the advantages such as high drug loading, improved stability, and decreased potential toxicity caused by the carrier materials in comparison with normal nanodrugs and traditional delivery systems. In this review, the potential strategies and applications of CPT-based nanoprodrugs for enhanced CPT delivery toward cancer cells are summarized. We appraise in detail the chemical structures and release mechanisms of these nanoprodrugs and guide materials chemists to develop more powerful nanomedicines that have real clinical therapeutic capacities.

An update review of smart nanotherapeutics and liver cancer: opportunities and challenges

Hepatocellular carcinoma (HCC) is the most common form of primary liver cancer, typically diagnosed in advanced stages. Chemotherapy is necessary for treating advanced liver cancer; however, several challenges affect its effectiveness. These challenges include low specificity, high dosage requirements, high systemic toxicity and severe side effects, which significantly limit the efficacy of chemotherapy. These limitations can hinder the treatment of HCC. This review focuses on the prevalence of HCC, different types of liver cancer and the staging of the disease, along with available treatment methods. Additionally, explores recent and relevant studies on smart drug- and gene-delivery systems specifically designed for HCC. These systems include targeted endogenous and exogenous stimuli-responsive platforms.

Inorganic Sonosensitizers for Sonodynamic Therapy in Cancer Treatment

The rapid development of nanomedicine and nanobiotechnology has allowed the emergence of various therapeutic modalities with excellent therapeutic efficiency and biosafety, among which, the sonodynamic therapy (SDT), a combination of low-intensity ultrasound and sonosensitizers, is emerging as a promising noninvasive treatment modality for cancer treatment due to its deeper penetration, good patient compliance, and minimal damage to normal tissue. The sonosensitizers are indispensable components in the SDT process because their structure and physicochemical properties are decisive for therapeutic efficacy. Compared to the conventional and mostly studied organic sonosensitizers, inorganic sonosensitizers (noble metal-based, transition metal-based, carbon-based, and silicon-based sonosensitizers) display excellent stability, controllable morphology, and multifunctionality, which greatly expand their application in SDT. In this review, the possible mechanisms of SDT including the cavitation effect and reactive oxygen species generation are briefly discussed. Then, the recent advances in inorganic sonosensitizers are systematically summarized and their formulations and antitumor effects, particularly highlighting the strategies for optimizing the therapeutic efficiency, are outlined. The challenges and future perspectives for developing state-of-the-art sonosensitizers are also discussed. It is expected that this review will shed some light on future screening of decent inorganic sonosensitizers for SDT.

Evaluation of exogenous therapeutic protein activity under confinement and crowding effects

Dysfunction of intracellular proteins is frequently associated with various diseases, such as cancer. The exogenous proteins in cells are usually assembled with specific configurations due to physiological confinement/crowding to exhibit novel features in the protein structure, folding or conformational stability, distinguished with their behaviors in buffer solutions. Here, we synthesized exogenous proteins under confined/crowded conditions, to explore protein activity within cells. The findings suggested that the confinement and crowding effects on protein activity are heterogeneous; they showed an inhibitory effect on HRP by decreasing Km from ∼9.5- and ∼21.7-fold and Vmax from ∼6.8- and ∼20.2-fold lower than that of dilute solutions. Interestingly, the effects on Cyt C seem to be more complicated, and crowding exerts a positive effect by increasing Km ∼ 3.6-fold and Vmax ∼ 1.5-fold higher than that of dilute solutions; however, confinement exhibits a negative effect by decreasing Km ∼2.0 and Vmax ∼8.3 times. Additionally, in contrast to traditional nanoparticle-based confinement models, we synthesized a biodegradable nanoparticle to mimic the confined space, and the biggest advantage of this novel model is that the particles can be degraded and thus it can provide more intuitive observations of the properties of the target proteins under confinement and after release. Furthermore, we also evaluated protein activity in different cellular environments, indicating that the exogenous protein activity was closely related to the crowdedness of cellular environments, and the inhibition of protein activity in MDA-MB-231 cancer cells was more obvious than in HEK293 normal cells. Finally, SAXS analysis revealed the correlation between the protein conformation and the different environments. Our work will provide a unique method for precisely assessing whether the target cellular environments are native matrix in which specific exogenous protein drugs are delivered to function or whether they display a therapeutic role, which is of great significance for screening and development of new drugs.

Recent Advances in Nanoplatform Construction Strategy for Alleviating Tumor Hypoxia

Hypoxia is a typical feature of most solid tumors and has important effects on tumor cells' proliferation, invasion, and metastasis. This is the key factor that leads to poor efficacy of different kinds of therapy including chemotherapy, radiotherapy, photodynamic therapy, etc. In recent years, the construction of hypoxia-relieving functional nanoplatforms through nanotechnology has become a new strategy to reverse the current situation of tumor microenvironment hypoxia and improve the effectiveness of tumor treatment. Here, the main strategies and recent progress in constructing nanoplatforms are focused on to directly carry oxygen, generate oxygen in situ, inhibit mitochondrial respiration, and enhance blood perfusion to alleviate tumor hypoxia. The advantages and disadvantages of these nanoplatforms are compared. Meanwhile, nanoplatforms based on organic and inorganic substances are also summarized and classified. Through the comprehensive overview, it is hoped that the summary of these nanoplatforms for alleviating hypoxia could provide new enlightenment and prospects for the construction of nanomaterials in this field.

Tumor Therapy Strategies Based on Microenvironment-Specific Responsive Nanomaterials

The tumor microenvironment (TME) is a complex and variable region characterized by hypoxia, low pH, high redox status, overexpression of enzymes, and high-adenosine triphosphate concentrations. In recent years, with the continuous in-depth study of nanomaterials, more and more TME-specific response nanomaterials are used for tumor treatment. However, the complexity of the TME causes different types of responses with various strategies and mechanisms of action. Aiming to systematically demonstrate the recent advances in research on TME-responsive nanomaterials, this work summarizes the characteristics of TME and outlines the strategies of different TME responses. Representative reaction types are illustrated and their merits and demerits are analyzed. Finally, forward-looking views on TME-response strategies for nanomaterials are presented. It is envisaged that such emerging strategies for the treatment of cancer are expected to exhibit dramatic trans-clinical capabilities, demonstrating the extensive potential for the diagnosis and therapy of cancer.

Lysyl oxidase-responsive anchoring nanoparticles for modulation of the tumor immune microenvironment

In the tumor microenvironment, lysyl oxidase (LOX) is known to play a key role in stabilizing the tumor extracellular matrix. Here, we designed LOX-responsive nanoparticles to interact with the collagen matrix of the tumor microenvironment. Collagen-coated and imiquimod-loaded polydopamine nanoparticles (CPN/IQ) could form crosslinked structures with the collagen matrix via LOX. In vitro, anchoring of CPN/IQ nanoparticles was observed with LOX-secreting CT26 cells, but this was blocked by a LOX inhibitor. In CT26 tumor-bearing mice, co-administration of nanoparticles plus the LOX inhibitor did not significantly alter the antitumor efficacy among nanoparticles. In the absence of the LOX inhibitor, however, a single administration of CPN/IQ could provide sustained responsiveness to near-infrared irradiation and ablation of primary tumors. In the primary tumor microenvironment, CPN/IQ lowered the Treg cell population but increased the cytotoxic CD3+CD8+ T cell population. In splenic dendritic cells, CPN/IQ treatment significantly increased the CD11c+CD86+ and CD11c+CD80+ cell populations. In a CT26 distant tumor-rechallenge model, CPN/IQ treatment increased the cytotoxic CD3+CD8+ T cell population and provided 100% survival of mice until 64 days. This study indicates the feasibility of tumor immune microenvironment modulation using LOX-responsive size-transforming nanoparticles. Although we tested the concept in a CT26 cell-derived tumor model, the concept of LOX-responsive collagen matrix- anchoring nanoparticles may be broadly applied to other tumor tissues with LOX-rich tumor microenvironments.

Oxygen-Generating Organic/Inorganic Self-Assembled Nanocolloids for Tumor-Activated Dual-Model Imaging-Guided Photodynamic Therapy

Tumor phototheranostics is usually compromised by the hypoxic tumor microenvironment and poor theranostic efficiency. The interplay between organic polymers and inorganic nanoparticles in novel nanocomposites has proven to be advantageous, overcoming previous limitations and harnessing their full potential through activation via the tumor microenvironment. This study successfully fabricated hypoxia-activated nanocolloids called HOISNDs through a process of self-assembly involving superparamagnetic iron oxide nanoparticles (SPIONs) and an organic polymer ligand called tetrakis(4-carboxyphenyl) porphyrin (TCPP)-engineered organic polymer ligand [methoxy poly(ethyleneglycol)-block-poly(dopamine-ethylenediamine-conjugated-4-nitrobenzyl chloroformate)-l-glutamate, mPEG-b-P(Dopa-EDA-co-NBCF)LG-TCPP)]. The SPIONs act as an oxygen generator to overcome the challenges posed by hypoxic tumors and enable the use of hypoxic-activatable MR/fluorescence dual-modal imaging-guided photodynamic therapy (PDT). The colloid stability of these HOISNDs proved to be exceptional in diverse biomimetic environments. Furthermore, they not only augment T₂-weighted contrast capability as an MRI contrast agent but also function as an oxygen-producing device to amplify the generation and release of reactive oxygen species (ROS). The HOISNDs can significantly target to tumor sites through the enhanced permeability and retention (EPR) effect with prolonged blood circulation time and subsequently are effectively endocytosed into a hypoxic intracellular environment that "turn on" the imaging function and photodynamic activity. Moreover, HOISNDs possess the ability to effectively decompose naturally occurring H₂O₂ into oxygen (O₂) within the tumor utilizing the Fenton reaction. This method can mitigate the impact of hypoxia on oxygen-dependent PDT. The outcomes of in vivo diagnostic and therapeutic evaluations indicated that HOISNDs are a highly promising tool for dual-model imaging-guided cancer theranosis by ameliorating hypoxic conditions and augmenting PDT efficiency.

Advances of medical nanorobots for future cancer treatments

Early detection and diagnosis of many cancers is very challenging. Late stage detection of a cancer always leads to high mortality rates. It is imperative to develop novel and more sensitive and effective diagnosis and therapeutic methods for cancer treatments. The development of new cancer treatments has become a crucial aspect of medical advancements. Nanobots, as one of the most promising applications of nanomedicines, are at the forefront of multidisciplinary research. With the progress of nanotechnology, nanobots enable the assembly and deployment of functional molecular/nanosized machines and are increasingly being utilized in cancer diagnosis and therapeutic treatment. In recent years, various practical applications of nanobots for cancer treatments have transitioned from theory to practice, from in vitro experiments to in vivo applications. In this paper, we review and analyze the recent advancements of nanobots in cancer treatments, with a particular emphasis on their key fundamental features and their applications in drug delivery, tumor sensing and diagnosis, targeted therapy, minimally invasive surgery, and other comprehensive treatments. At the same time, we discuss the challenges and the potential research opportunities for nanobots in revolutionizing cancer treatments. In the future, medical nanobots are expected to become more sophisticated and capable of performing multiple medical functions and tasks, ultimately becoming true nanosubmarines in the bloodstream.

Enhanced brain delivery of hypoxia-sensitive liposomes by hydroxyurea for rescue therapy of hyperacute ischemic stroke

Ischemic stroke is characterized by high morbidity, disability, and mortality. Unfortunately, the only FDA-approved pharmacological thrombolytic, alteplase, has a narrow therapeutic window of only 4.5 h. Other drugs like neuroprotective agents have not been clinically used because of their low efficacy. To improve the efficacy of neuroprotective agents and the effectiveness of rescue therapies for hyperacute ischemic stroke, we investigated and verified the variation trends of the blood-brain barrier (BBB) permeability and regional cerebral blood flow over 24 h in rats that had ischemic strokes. Hypoperfusion and the biphasic increase of BBB permeability are still the main limiting factors for lesion-specific drug distribution and drug brain penetration. Herein, the nitric oxide donor hydroxyurea (HYD) was reported to downregulate the expression of tight junction proteins and upregulate intracellular nitric oxide content in the brain microvascular endothelial cells subjected to oxygen-glucose deprivation, which was shown to facilitate the transport of liposomes across  brain endothelial monolayer in an in vitro model. HYD also increased the BBB permeability and promoted microcirculation in the hyperacute phase of stroke. The neutrophil-like cell-membrane-fusogenic hypoxia-sensitive liposomes exhibited excellent performance in targeting the inflamed brain microvascular endothelial cells, enhancing cell association, and promoting rapid hypoxic-responsive release in the hypoxic microenvironment. Overall, the combined HYD and hypoxia-sensitive liposome dosing regimen effectively decreased the cerebral infarction volume and relieved neurological dysfunction in rats that had ischemic strokes; these therapies were involved in the anti-oxidative stress effect and the neurotrophic effect mediated by macrophage migration inhibitory factor.

Hybrids of carbonic anhydrase and cyclooxygenase inhibitors attenuate cardiac hypoxic inflammatory injuries

Cardiac inflammation is easily accompanied by hypoxia, while hypoxia-induced injury and microenvironmental variations limit the efficacy of common anti-inflammatory drugs. In order to effectively attenuate myocardial injury caused by hypoxic and inflammatory injury, we designed and synthesized a kind of anti-inflammatory compounds by coupling cyclooxygenase (COX) and carbonic anhydrase (CA) inhibitors, and evaluated the activity and their mechanism in vitro and in vivo. It was found that these compounds were structurally stable and had two enzymatic inhibition activities. By inhibiting the activity of overexpressed CA under hypoxia, the acidic microenvironment can be regulated to inhibit the hypoxic injury, in which the pH-dependent primary drug resistance can be overcome to improve the anti-inflammatory effect of the COX inhibitor. Consequently, this study provides a new strategy for the treatment of cardiac inflammation accompanied by hypoxia.

Degradable Fe3O4-based nanocomposite for cascade reaction-enhanced anti-tumor therapy

Cascade catalytic therapy has been recognized as a promising cancer treatment strategy, which is due in part to the induced tumor apoptosis when converting intratumoral hydrogen peroxide (H₂O₂) into highly toxic hydroxyl radicals (˙OH) based on the Fenton or Fenton-like reactions. Moreover this is driven by the efficient catalysis of glucose oxidization associated with starving therapy. The natural glucose oxidase (GO _x ), recognized as a "star" enzyme catalyst involved in cancer treatment, can specially and efficiently catalyze the glucose oxidization into gluconic acid and H₂O₂. Herein, pH-responsive biodegradable cascade therapeutic nanocomposites (Fe₃O₄/GO _x -PLGA) with dual enzymatic catalytic features were designed to respond to the tumor microenvironment (TME) and to catalyze the cascade reaction (glucose oxidation and Fenton-like reaction) for inducing oxidase stress. The GO _x -motivated oxidation reaction could effectively consume intratumoral glucose to produce H₂O₂ for starvation therapy and the enriched H₂O₂ was subsequently converted into highly toxic ˙OH by a Fe₃O₄-mediated Fenton-like reaction for chemodynamic therapy (CDT). In addition, the acidity amplification owing to the generation of gluconic acid will in turn accelerate the degradation of the nanocomposite and initiate the Fe₃O₄-H₂O₂ reaction for enhancing CDT. The resultant cooperative cancer therapy was proven to provide highly efficient tumor inhibition on HeLa cells with minimal systemic toxicity. This cascade catalytic Fenton nanocomposite might provide a promising strategy for efficient cancer therapy.

Development of stimuli responsive polymeric nanomedicines modulating tumor microenvironment for improved cancer therapy

The complexity of the tumor microenvironment (TME) severely hinders the therapeutic effects of various cancer treatment modalities. The TME differs from normal tissues owing to the presence of hypoxia, low pH, and immune-suppressive characteristics. Modulation of the TME to reverse tumor growth equilibrium is considered an effective way to treat tumors. Recently, polymeric nanomedicines have been widely used in cancer therapy, because their synthesis can be controlled and they are highly modifiable, and have demonstrated great potential to remodel the TME. In this review, we outline the application of various stimuli responsive polymeric nanomedicines to modulate the TME, aiming to provide insights for the design of the next generation of polymeric nanomedicines and promote the development of polymeric nanomedicines for cancer therapy.

Hypoxia-Triggered Bioreduction of Poly(N-oxide)-Drug Conjugates Enhances Tumor Penetration and Antitumor Efficacy

PEGylation prolongs the blood circulation time of drugs; however, it simultaneously reduces the tumor penetration of drugs due to the nonfouling function and bulky hydrodynamic volume of PEG, leading to unsatisfactory outcomes in the treatment of solid tumors. Herein, we report the in situ growth of a bioreducible polymer of poly(N-oxide) from an important protein drug of interferon alpha (IFN) to generate site-specific IFN-poly(N-oxide) conjugates with higher bioactivity than a clinically used PEGylated IFN of PEGASYS. An IFN-poly(N-oxide) conjugate is screened out to have a circulating half-life as long as 51 h, which is similar to that of PEGASYS but 96-fold greater than that of IFN. However, the conjugate greatly outperforms PEGASYS and IFN in tumor penetration and antitumor efficacy in mice bearing melanoma. This enhanced tumor penetration is ascribed to the adsorption-mediated transcytosis of the conjugate whose poly(N-oxide) is biologically reduced into poly(tertiary amine), under hypoxia, which can be further protonated in the acidic tumor microenvironment. These novel findings demonstrate that poly(N-oxide)s are not only long-circulating but also bioreducible under hypoxia and are of great promise as next-generation carriers to deliver drugs into the interior of solid tumors to enhance their antitumor efficacy.

Use of stimulatory responsive soft nanoparticles for intracellular drug delivery

Drug delivery has made tremendous advances in the last decade. Targeted therapies are increasingly common, with intracellular delivery highly impactful and sought after. Intracellular drug delivery systems have limitations due to imprecise and non-targeted release profiles. One way this can be addressed is through using stimuli-responsive soft nanoparticles, which contain materials with an organic backbone such as lipids and polymers. The choice of biomaterial is essential for soft nanoparticles to be responsive to internal or external stimuli. The nanoparticle must retain its integrity and payload in non-targeted physiological conditions while responding to particular intracellular environments where payload release is desired. Multiple internal and external factors could stimulate the intracellular release of drugs from nanoparticles. Internal stimuli include pH, oxidation, and enzymes, while external stimuli include ultrasound, light, electricity, and magnetic fields. Stimulatory responsive soft nanoparticulate systems specifically utilized to modulate intracellular delivery of drugs are explored in this review.

Research progress of potential factors influencing photodynamic therapy for gastrointestinal cancer

Gastrointestinal cancer is a malignant tumor of the gastrointestinal tract and its associated digestive organs, including esophageal cancer, gastric cancer, carcinoma of the ampulla, pancreas, bile duct, intestines and rectal cancer. They account for about 30% of global cancer-related incidence and about 40% of mortality. Photodynamic therapy (PDT), as a treatment mode, has been applied to the treatment of gastrointestinal cancer due to potential advantages targeting and potentially lower toxic side effects. However, In the course of clinical treatment, we have found that different patients have various responsiveness to PDT, and even the same patients may have different clinical effects after receiving treatment in different time periods. For influencing factors, traditionally, we only focus on adjusting the dose of photosensitizer and the intensity and time of irradiation,while minimizing other potential factors.Therefore, this paper looks for factors that affect PDT from the patient's own conditions, tumor characteristics and tumor microenvironment(including:tumor acidic microenvironment,tumor hypoxic microenvironment, multi-drug resistance, different tumor characteristics and the immune status of patients) and summarizes how to potentially improve the curative effect of PDT.

Drug-independent NADPH-consuming micelles collaborate with ROS-generator for cascade ferroptosis amplification by impairing redox homeostasis

Ferroptosis as promising antitumor therapy strategy could be comprised by intracellular antioxidants, especially GSH and thioredoxin (Trx). They are both cofactors of Gpx4, the enzyme catalyzing the production of lipid peroxides to relieve oxidative stress, which drives the acquired ferroptosis resistance in tumors. Herein, the NADPH-consuming micelles are specially designed, which could collaborate with the ROS generating photodynamics therapy (PDT) by depleting intracellular GSH and Trx under hypoxia condition, resulting in ruined redox homeostasis and the final cascade amplified ferroptosis. The tailored micelle was briefly prepared by conjugating hypoxia-sensitive segment p-nitrobenzyl chloroformate (PNZ-Cl) to the hydrophilic chitosan (CS), the resulting micelle was further modified with photosensitizer Ce6 via PEG linkage. When receiving laser irradiation, the photosensitizer would generate ROS and consume oxygen in the meanwhile. The resulting anabatic hypoxia in turns promote the NTR-catalyzed electron-accepting response of micelles, with evidently enhanced NADPH consumption and ultimately ruined redox homeostasis, contributing to cascade amplified ferroptosis with robust ROS. Most importantly, the accompanied immunogenic cell death (ICD) and releasing danger-associated molecular patterns (DAMPs) could boost dendritic cells (DCs) maturation and the subsequent T-cell-mediated profound immune response. Collectively, the work excavates the other biochemical reaction during the hypoxia-sensitive process of C-N-Ce6 by diminishing intracellular GSH and Trx, providing a candidate of ferroptosis inducers against solid tumors.

Targeted PEGylated Chitosan Nano-complex for Delivery of Sodium Butyrate to Prostate Cancer: An In Vitro Study

Introduction: Cancer remains a challenging issue against human health throughout the world; As a result, introducing novel approaches would be beneficial for cancer treatment. In this research, sodium butyrate (Sb) is one of the effective anti-cancer therapeutics (also a potent survival factor for normal cells) that was used for prostate cancer suppression in the platform of modified chitosan (CS) nano-complex (polyethylene glycol (PEG)-folic acid (FA)-Sb-CS). Methods: Different analytical devices including Fourier transform infrared, dynamic light scattering, high-performance liquid chromatography, scanning electron microscopy, and transmission electron microscopy were applied for the characterization of synthetics. On the other hand, biomedical tests including cell viability assay, molecular and functional assay of apoptosis/autophagy pathways, and cell cycle arrest analysis were potentially implemented on human PC3 (folate receptor-negative prostate cancer) and DU145 (folate receptor-positive prostate cancer) and HFF-1 normal cell lines. Results: The quality of the syntheses was effectively verified, and the size range from 140 to 170 nm was determined for the PEG-CS-FA-Sb sample. Also, 75  ±  5% of drug entrapment efficiency with controlled drug release manner (Sb release of 54.21% and 74.04% for pHs 7.4 and 5.0) were determined for nano-complex. Based on MTT results, PEG-CS-FA-Sb has indicated 72.07% and 33.53% cell viability after 24 h of treatment with 9 mM on PC3 and DU145 cell lines, respectively, which is desirable anti-cancer performance. The apoptotic and autophagy genes overexpression was 15-fold (caspase9), 2.5-fold (BAX), 11-fold (ATG5), 2-fold (BECLIN1), and 3-fold (mTORC1) genes in DU145 cancer cells. More than 50% of cell cycle arrest and 45.05% of apoptosis were obtained for DU145 cancer cells after treatment with nano-complex. Conclusion: Hence, the synthesized Sb-loaded nano-complex could specifically suppress prostate cancer cell growth and induce apoptosis and autophagy in the molecular and cellular phases.

In vitro blood brain barrier models: Molecular aspects and therapeutic strategies in glioma management

Glioma management is the most challenging task in clinical oncology due to numerous reasons. One of the major hurdles in glioma therapy is the presence of blood brain barrier which resists the entry of most of the drugs into the brain. However, in case of tumors, blood brain barrier integrity is compromised, which in turn can be advantageous in delivering the drugs, if the therapeutic module is strategically modified. For such improvised therapeutic strategy, it is necessary to understand the molecular composition and profiling of blood brain barrier and blood brain tumor barrier. This review mainly focuses on the composition, markers expressed on the blood brain barrier which will help the readers to understand its basic environment. It also gives a detailed account of the various in vitro models that are used to study the nature of the blood brain barrier and describes various strategies in improvising the drug delivery in glioma management.

Prospects for hypoxia-based drug delivery platforms for the elimination of advanced metastatic tumors: From 3D modeling to clinical concepts

Hypoxia is a unique characteristic of the solid tumor microenvironment. Hypoxia contributes to multi-drug resistance, metastasis and cancer relapse through numerous molecular pathways, but at the same time provides an opportunity for the development of novel drugs or modalities specifically targeting hypoxic tumor regions. Given the high significance of tumor hypoxia in therapeutic results, we here discuss a variety of hypoxia-adopted strategies, and their potential and utility in the treatment of deep-seated hypoxic tumor cells. We discuss the merits and demerits of these approaches, as well as their combination with other approaches such as photodynamic therapy. We also survey the currently available 3D hypoxia modeling systems, in particular organoid-based microfluidics. Finally, we discuss the potential and the current status of preclinical tumor hypoxia approaches in clinical trials for advanced cancer. We believe that multi-modal imaging and therapeutic hypoxia adopted drug delivery platforms could provide better efficacy and safety profiles, and more importantly personalized therapy. Determining the hypoxia status of tumors could offer a second chance for the clinical translation of hypoxia-based agents, such as hypoxia activated prodrugs (HAPs) from bench to bedside.

Breaking the niche: multidimensional nanotherapeutics for tumor microenvironment modulation

Most of the current antitumor therapeutics were developed targeting the cancer cells only. Unfortunately, in the majority of tumors, this single-dimensional therapy is found to be ineffective. Advanced research has shown that cancer is a multicellular disorder. The tumor microenvironment (TME), which is made by a complex network of the bulk tumor cells and other supporting cells, plays a crucial role in tumor progression. Understanding the importance of the TME in tumor growth, different treatment modalities have been developed targeting these supporting cells. Recent clinical results suggest that simultaneously targeting multiple components of the tumor ecosystem with drug combinations can be highly effective. This type of "multidimensional" therapy has a high potential for cancer treatment. However, tumor-specific delivery of such multi-drug combinations remains a challenge. Nanomedicine could be utilized for the tumor-targeted delivery of such multidimensional therapeutics. In this review, we first give a brief overview of the major components of TME. We then highlight the latest developments in nanoparticle-based combination therapies, where one drug targets cancer cells and other drug targets tumor-supporting components in the TME for a synergistic effect. We include the latest preclinical and clinical studies and discuss innovative nanoparticle-mediated targeting strategies.

Harnessing bioactive nanomaterials in modulating tumor glycolysis-associated metabolism

Glycolytic reprogramming is emerging as a hallmark of various cancers and a promising therapeutic target. Nanotechnology is revolutionizing the anti-tumor therapeutic approaches associated with glycolysis. Finely controlled chemical composition and nanostructure provide nanomaterials unique advantages, enabling an excellent platform for integrated drug delivery, biochemical modulation and combination therapy. Recent studies have shown promising potential of nanotherapeutic strategies in modulating tumor glycolytic metabolism alone or in combination with other treatments such as chemotherapy, radiotherapy and immunotherapy. To foster more innovation in this cutting-edge and interdisciplinary field, this review summarizes recent understandings of the origin and development of tumor glycolysis, then provides the latest advances in how nanomaterials modulate tumor glycolysis-related metabolism. The interplay of nanochemistry, metabolism and immunity is highlighted. Ultimately, the challenges and opportunities are presented.

Synergy between pH- and hypoxia-responsiveness in antibiotic-loaded micelles for eradicating mature, infectious biofilms

Antibiotic-loaded PEG/PAE-based micelles are frequently considered for eradicating infectious biofilms. At physiological pH, PEG facilitates transport through blood. Near an acidic infection-site, PAE becomes protonated causing micellar targeting to a biofilm. However, micellar penetration and accumulation is confined to the surface region of a biofilm. Especially matured biofilms also possess hypoxic regions. We here designed dual-responsive PEG/PAE-b-P(Lys-NBCF) micelles, responding to both acidity and low oxygen-saturation level in matured biofilms. Dual, pH- and hypoxia-responsive micelles targeted and accumulated evenly over the depth of 7- to 14-days old biofilms. Delineation demonstrated that pH-responsiveness was responsible for targeting of the infection-site and accumulation of micelles in the surface region of the biofilm. Hypoxia-responsiveness caused deep penetration in the biofilm. Dual, pH- and hypoxia-responsive micelles loaded with ciprofloxacin yielded more effective, synergistic eradication of 10-days old, matured Staphylococcus aureus biofilms underneath an abdominal imaging-window in living mice than achieved by ciprofloxacin in solution or single, pH- or hypoxia responsive micelles loaded with ciprofloxacin. Also, wound-healing after removal of window and its frame proceeded fastest after tail-vein injection of ciprofloxacin-loaded, dual, pH- and hypoxia-responsive micelles. Concluding, pH- and hypoxia-responsiveness are both required for eradicating mature biofilms and advancing responsive antibiotic nanocarriers to clinical application. STATEMENT OF SIGNIFICANCE: pH-responsive antibiotic nanocarriers have emerged as a possible new strategy to prevent antimicrobial-resistant bacterial infections from becoming the leading cause of death. In this paper, we show that commonly studied, pH-responsive micellar nanocarriers merely allow self-targeting to an infectious biofilm, but do not penetrate deeply into the biofilm. The dual-responsive (acidic pH- and hypoxia) antibiotic-loaded micelles designed here not only self-target to an infectious biofilm, but also penetrate deeply. The in vitro and in vivo advantages of dual-responsive nanocarriers are most obvious when studied in infectious biofilms grown for 10 viz a viz the 2 days, usually applied in the literature. Significantly, clinical treatment of bacterial infection usually starts more than 2 days after appearance of the first symptoms.

Chitosan-coated Zn-metal-organic framework nanocomposites for effective targeted delivery of LNA-antisense miR-224 to colon tumor: in vitro studies

Nowadays, nano-compartments are considered as an effective drug delivery system (DDS) for cancer therapy. Targeted delivery of therapeutic agents is an advantageous approach by which cancer cells can be targeted without harming normal cells, and eliminates the negative effects of conventional therapies such as chemotherapy. In this research, a novel zinc-based nanoscale metal-organic framework (Zn-NMOF) coated with folic acid (FA) functionalized chitosan (CS) has been constructed and applied as efficient delivery of LNA (locked nucleic acid)-antisense miR-224 to colon cancer cell lines. LNA-antisense miR-224 as a therapeutic sequence was able to considerably block highly expressed miR-224 and downregulated cancer cell growth. The prepared nano-complex was characterized by analytical devices such as FT-IR, UV-Vis spectrophotometry, DLS, TEM, and XRD. The size range of NMOF-CS-FA-LNA-antisense miR-224 (MCFL224) nano-complex was obtained nearly at 200 nm. The entrapment efficiency of LNA-antisense miR-224 was calculated 72 ± 5% and a significant release profile of LNA-antisense miR-224 was observed at first 6 h (about 50%). Then, in vitro assays were implemented on HCT116 (folic acid receptor-positive colon cancer cell line) and CRL1831 (normal colon cell line) to evaluate the therapeutic efficiency of the MCFL224 nano-complex. In these investigations, decreased cell viability (14.22 ± 0.3% after 72 h treatment), increased apoptotic and autophagy-related genes expression level (BECLIN1: 34-folds, BAX: 36-folds, mTORC1: 10-folds, and Caspase-9: 9-folds more than control), higher cell cycle arrest in sub-G1 phase (19.53% of cells in sub-G1 phase), and more apoptosis analyses (late apoptosis: 67.7%) were evaluated in colon cancer cells treated with MCFL224 nano-complex. Results remarkably indicate the inhibited growth of colon cancer cells and induced cell apoptosis which suggests MCFL224 as a promising nanocomposite for colon cancer therapy.

Recent progress in nitric oxide-generating nanomedicine for cancer therapy

Nitric oxide (NO) is an endogenous, multipotent biological signaling molecule that participates in several physiological processes. Recently, exogenous supplementation of tumor tissues with NO has emerged as a potential anticancer therapy. In particular, it induces synergistic effects with other conventional therapies (such as chemo-, radio-, and photodynamic therapies) by regulating the activity of P-glycoprotein, acting as a vascular relaxant to relieve tumor hypoxia, and participating in the metabolism of reactive oxygen species. However, NO is highly reactive, and its half-life is relatively short after generation. Meanwhile, NO-induced anticancer activity is dose-dependent. Therefore, the targeted delivery of NO to the tumor is required for better therapeutic effects. In the past decade, NO-generating nanomedicines (NONs), which enable sustained and specific NO release in tumor tissues, have been developed for enhanced cancer therapy. This review describes the recent efforts and preclinical achievements in the development of NON-based cancer therapies. The chemical structures employed in the fabrication of NONs are summarized, and the strategies involved in NON-based cancer therapies are elaborated.

Lanthanide-based MOFs: synthesis approaches and applications in cancer diagnosis and therapy

Metal-organic frameworks (MOFs) have attracted considerable attention as emerging nanomaterials. Based on their tunable size, high porosity, and large specific surface area, MOFs have a wide range of applications in the fields of chemistry, energy, and biomedicine. However, the MOF materials obtained from lanthanides with a unique electronic configuration as inorganic building units have unique properties such as optics, magnetism, and radioactivity. In this study, various synthetic methods for preparing MOF materials using lanthanides as inorganic building units are described. Combined with the characteristics of lanthanides, their application prospects of lanthanide-based MOFs in tumor diagnosis and treatment are emphasized. The authors hope to provide methodological reference for the construction of MOF materials of rare-earth elements, and to provide ideas and inspiration for their practical applications in the field of biomedicine.

Tumor Microenvironment-Based Stimuli-Responsive Nanoparticles for Controlled Release of Drugs in Cancer Therapy

With the development of nanomedicine technology, stimuli-responsive nanocarriers play an increasingly important role in antitumor therapy. Compared with the normal physiological environment, the tumor microenvironment (TME) possesses several unique properties, including acidity, high glutathione (GSH) concentration, hypoxia, over-expressed enzymes and excessive reactive oxygen species (ROS), which are closely related to the occurrence and development of tumors. However, on the other hand, these properties could also be harnessed for smart drug delivery systems to release drugs specifically in tumor tissues. Stimuli-responsive nanoparticles (srNPs) can maintain stability at physiological conditions, while they could be triggered rapidly to release drugs by specific stimuli to prolong blood circulation and enhance cancer cellular uptake, thus achieving excellent therapeutic performance and improved biosafety. This review focuses on the design of srNPs based on several stimuli in the TME for the delivery of antitumor drugs. In addition, the challenges and prospects for the development of srNPs are discussed, which can possibly inspire researchers to develop srNPs for clinical applications in the future.

Redox-Responsive Drug Delivery Systems: A Chemical Perspective

With the widespread global impact of cancer on humans and the extensive side effects associated with current cancer treatments, a novel, effective, and safe treatment is needed. Redox-responsive drug delivery systems (DDSs) have emerged as a potential cancer treatment with minimal side effects and enhanced site-specific targeted delivery. This paper explores the physiological and biochemical nature of tumors that allow for redox-responsive drug delivery systems and reviews recent advances in the chemical composition and design of such systems. The five main redox-responsive chemical entities that are the focus of this paper are disulfide bonds, diselenide bonds, succinimide-thioether linkages, tetrasulfide bonds, and platin conjugates. Moreover, as disulfide bonds are the most commonly used entities, the review explored disulfide-containing liposomes, polymeric micelles, and nanogels. While various systems have been devised, further research is needed to advance redox-responsive drug delivery systems for cancer treatment clinical applications.

Research progress on tumor hypoxia-associative nanomedicine

Hypoxia at the solid tumor site is generally related to the unrestricted proliferation and metabolism of cancerous cells, which can cause tumor metastasis and aggravate tumor progression. Besides, hypoxia plays a substantial role in tumor treatment, and it is one of the main reasons that malignant tumors are difficult to cure and have a poor prognosis. On account of the tumor specific hypoxic environment, many hypoxia-associative nanomedicine have been proposed for tumor treatment. Considering the enhanced targeting effect, designing hypoxia-associative nanomedicine can not only minimize the adverse effects of drugs on normal tissues, but also achieve targeted therapy at the lesion site. Mostly, there can be three strategies for the treatment of hypoxic tumor, including improvement of hypoxic environment, hypoxia responsive drug release and hypoxia activated prodrug. The review describes the design principle and applications of tumor hypoxia-associative nanomedicine in recent years, and also explores its development trends in solid tumor treatment. Moreover, this review presents the current limitations of tumor hypoxia-associative nanomedicine in chemotherapy, radiotherapy, photodynamic therapy, sonodynamic therapy and immunotherapy, which may provide a reference for clinic translation of tumor hypoxia-associative nanomedicine.