The application of nitric oxide delivery in nanoparticle-based tumor targeting drug delivery and treatment

Piezoelectric Ba0.85 Sr0.15 TiO3 Nanosonosensitizer with Nitric Oxide Delivery for Boosting Cancer Therapy

The efficacy of sonodynamic therapy (SDT) mainly relies on the sonosensitizers, which generate reactive oxygen species (ROS) upon ultrasound (US) stimulation. However, the limited availability of high-efficiency sonosensitizers hampers the therapeutic effectiveness of SDT as a standalone modality. In this work, a robust sonodynamic and gas cancer therapeutic platform is constructed based on strontium (Sr) doped barium titanate (BST) piezoelectric nanoparticles functionalized with L-arginine (BST@LA). The doping of Sr into A site of the ABO3 piezoelectric nanocrystals not only introduces oxygen vacancies into the nanoparticles and enhance the intrinsic piezoelectricity, but also narrows the semiconductor band gap and enhances charge carrier migration, all of which facilitate the sonodynamic production of superoxide anion (•O2 - ) and hydroxyl radical (•OH). In addition, the generated ROS promotes the decomposition of the surface-tethered LA, enabling the controlled release of nitric oxide (NO) gas at the tumor site, thereby achieving a combination therapeutic effect. In vivo experiments exhibit remarkable tumor suppression rate (89.5%) in 4T1 tumor mice model, demonstrating the effectiveness of this strategy. The ion doping and oxygen vacancy engineering to improve sonosensitizers, along with the synergistic combination of sonodynamic and gas therapy, provides promising avenues for improving cancer therapy.

Nitric Oxide: Physiological Functions, Delivery, and Biomedical Applications

Nitric oxide (NO) is a gaseous molecule that has a central role in signaling pathways involved in numerous physiological processes (e.g., vasodilation, neurotransmission, inflammation, apoptosis, and tumor growth). Due to its gaseous form, NO has a short half-life, and its physiology role is concentration dependent, often restricting its function to a target site. Providing NO from an external source is beneficial in promoting cellular functions and treatment of different pathological conditions. Hence, the multifaceted role of NO in physiology and pathology has garnered massive interest in developing strategies to deliver exogenous NO for the treatment of various regenerative and biomedical complexities. NO-releasing platforms or donors capable of delivering NO in a controlled and sustained manner to target tissues or organs have advanced in the past few decades. This review article discusses in detail the generation of NO via the enzymatic functions of NO synthase as well as from NO donors and the multiple biological and pathological processes that NO modulates. The methods for incorporating of NO donors into diverse biomaterials including physical, chemical, or supramolecular techniques are summarized. Then, these NO-releasing platforms are highlighted in terms of advancing treatment strategies for various medical problems.

Nitric oxide-driven nanotherapeutics for cancer treatment

Nitric oxide (NO) is a gaseous molecule endowed with diverse biological functions, offering vast potential in the realm of cancer treatment. Considerable efforts have been dedicated to NO-based cancer therapy owing to its good biosafety and high antitumor activity, as well as its efficient synergistic therapy with other antitumor modalities. However, delivering this gaseous molecule effectively into tumor tissues poses a significant challenge. To this end, nano drug delivery systems (nano-DDSs) have emerged as promising platforms for in vivo efficient NO delivery, with remarkable achievements in recent years. This review aims to provide a summary of the emerging NO-driven antitumor nanotherapeutics. Firstly, the antitumor mechanism and related clinical trials of NO therapy are detailed. Secondly, the latest research developments in the stimulation of endogenous NO synthesis are presented, including the regulation of nitric oxide synthases (NOS) and activation of endogenous NO precursors. Moreover, the emerging nanotherapeutics that rely on tumor-specific delivery of NO donors are outlined. Additionally, NO-driven combined nanotherapeutics for multimodal cancer theranostics are discussed. Finally, the future directions, application prospects, and challenges of NO-driven nanotherapeutics in clinical translation are highlighted.

Passing of Nanocarriers across the Histohematic Barriers: Current Approaches for Tumor Theranostics

Over the past several decades, nanocarriers have demonstrated diagnostic and therapeutic (i.e., theranostic) potencies in translational oncology, and some agents have been further translated into clinical trials. However, the practical application of nanoparticle-based medicine in living organisms is limited by physiological barriers (blood-tissue barriers), which significantly hampers the transport of nanoparticles from the blood into the tumor tissue. This review focuses on several approaches that facilitate the translocation of nanoparticles across blood-tissue barriers (BTBs) to efficiently accumulate in the tumor. To overcome the challenge of BTBs, several methods have been proposed, including the functionalization of particle surfaces with cell-penetrating peptides (e.g., TAT, SynB1, penetratin, R8, RGD, angiopep-2), which increases the passing of particles across tissue barriers. Another promising strategy could be based either on the application of various chemical agents (e.g., efflux pump inhibitors, disruptors of tight junctions, etc.) or physical methods (e.g., magnetic field, electroporation, photoacoustic cavitation, etc.), which have been shown to further increase the permeability of barriers.

Tumor Microenvironment Regulation and Cancer Targeting Therapy Based on Nanoparticles

Although we have made remarkable achievements in cancer awareness and medical technology, there are still tremendous increases in cancer incidence and mortality. However, most anti-tumor strategies, including immunotherapy, show low efficiency in clinical application. More and more evidence suggest that this low efficacy may be closely related to the immunosuppression of the tumor microenvironment (TME). The TME plays a significant role in tumorigenesis, development, and metastasis. Therefore, it is necessary to regulate the TME during antitumor therapy. Several strategies are developing to regulate the TME as inhibiting tumor angiogenesis, reversing tumor associated macrophage (TAM) phenotype, removing T cell immunosuppression, and so on. Among them, nanotechnology shows great potential for delivering regulators into TME, which further enhance the antitumor therapy efficacy. Properly designed nanomaterials can carry regulators and/or therapeutic agents to eligible locations or cells to trigger specific immune response and further kill tumor cells. Specifically, the designed nanoparticles could not only directly reverse the primary TME immunosuppression, but also induce effective systemic immune response, which would prevent niche formation before metastasis and inhibit tumor recurrence. In this review, we summarized the development of nanoparticles (NPs) for anti-cancer therapy, TME regulation, and tumor metastasis inhibition. We also discussed the prospect and potential of nanocarriers for cancer therapy.

Ultrasound-Triggered Piezocatalysis for Selectively Controlled NO Gas and Chemodrug Release to Enhance Drug Penetration in Pancreatic Cancer

Nitric oxide (NO) is drawing widespread attention in treating pancreatic ductal adenocarcinoma (PDAC) as a safe and therapeutically efficient technique through modulating the dense fibrotic stroma in the tumor microenvironment to enhance drug penetration. Considerable NO nanogenerators and NO releasing molecules have been developed to shield the systemic toxicity caused by free diffusion of NO gas. However, on-demand controlled release of NO and chemotherapy drugs at tumor sites remains a problem limited by the complex and dynamic tumor microenvironment. Herein, we present an ultrasound-responsive nanoprodrug of CPT-t-R-PEG₂₀₀₀@BaTiO₃ (CRB) which encapsulates piezoelectric nanomaterials barium titanate nanoparticle (BaTiO₃) with amphiphilic prodrug molecules that consisted of thioketal bond (t) linked chemotherapy drug camptothecin (CPT) and NO-donor l-arginine (R). Based on ultrasound-triggered piezocatalysis, BaTiO₃ can continuously generate ROS in the hypoxic tumor environment, which induces a cascade of reaction processes to break the thioketal bond to release CPT and oxidize R to release NO, simultaneously delivering CPT and NO to the tumor site. It is revealed that CRB shows a uniform size distribution, prolonged blood circulation time, and excellent tumor targeting ability. Moreover, controlled release of CPT and NO were observed both in vitro and in vivo under the stimulation of ultrasound, which is beneficial to the depletion of dense stroma and subsequently enhanced delivery and efficacy of CPT. Taken together, CRB significantly increased the antitumor efficacy against highly malignant Panc02 tumors in mice through inhibiting chemoresistance, representing a feasible approach for targeted therapies against Panc02 and other PDAC.

Historical Perspectives of the Role of NO/NO Donors in Anti-Tumor Activities: Acknowledging Dr. Keefer's Pioneering Research

The role of nitric oxide (NO) in cancer has been a continuous challenge and particularly the contradictory findings in the literature reporting NO with either anti-cancer properties or pro-cancer properties. This dilemma was largely resolved by the level of NO/inducible nitric oxide synthase in the tumor environment as well as other cancer-associated gene activations in different cancers. The initial findings on the role of NO as an anti-cancer agent was initiated in the late 1990's in Dr. Larry Keefer's laboratory, who had been studying and synthesizing many compounds with releasing NO under different conditions. Using an experimental model with selected NO compounds they demonstrated for the first time that NO can inhibit tumor cell proliferation and sensitizes drug-resistant cancer cells to chemotherapy-induced cytotoxicity. This initial finding was the backbone and the foundation of subsequent reports by the Keefer's laboratory and followed by many others to date on NO-mediated anti-cancer activities and the clinical translation of NO donors in cancer therapy. Our laboratory initiated studies on NO-mediated anti-cancer therapy and chemo-immuno-sensitization following Keefer's findings and used one of his synthesized NO donors, namely, (Z)-1-[N-(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate (DETANONOate), throughout most of our studies. Many of Keefer's collaborators and other investigators have reported on the selected compound, O2-(2,4-dinitrophenyl) 1-[(4-ethoxycarbonyl)piperazin-1-yl] diazen-1-ium-1,2-diolate (JS-K), and its therapeutic role in many tumor model systems. Several lines of evidence that investigated the treatment with NO donors in various cancer models revealed that a large number of gene products are modulated by NO, thus emphasizing the pleiotropic effects of NO on cancers and the identification of many targets of therapeutic significance. The present review reports historically of several examples reported in the literature that emanated on NO-mediated anti-cancer activities by the Keefer's laboratory and his collaborators and other investigators including my laboratory at the University of California at Los Angeles.

Tumor extracellular matrix modulating strategies for enhanced antitumor therapy of nanomedicines

Nanomedicines have shown a promising strategy for cancer therapy because of their higher safety and efficiency relative to small-molecule drugs, while the dense extracellular matrix (ECM) in tumors often acts as a physical barrier to hamper the accumulation and diffusion of nanoparticles, thus compromising the anticancer efficacy. To address this issue, two major strategies including degrading ECM components and inhibiting ECM formation have been adopted to enhance the therapeutic efficacies of nanomedicines. In this review, we summarize the recent progresses of tumor ECM modulating strategies for enhanced antitumor therapy of nanomedicines. Through degrading ECM components or inhibiting ECM formation, the accumulation and diffusion of nanoparticles in tumors can be facilitated, leading to enhanced efficacies of chemotherapy and phototherapy. Moreover, the ECM degradation can improve the infiltration of immune cells into tumor tissues, thus achieving strong immune response to reject tumors. The adoptions of these two ECM modulating strategies to improve the efficacies of chemotherapy, phototherapy, and immunotherapy are discussed in detail. A conclusion, current challenges and outlook are then given.

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Extracellular matrix modulating strategies have been adopted to enhance the therapeutic efficacies of nanomedicines.

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Degrading extracellular matrix components or inhibiting extracellular matrix formation can improve the accumulation and diffusion of nanoparticles in tumors and the infiltration of immune cells into tumor tissues.

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The adoptions of two extracellular matrix modulating strategies to improve the efficacies of chemotherapy, phototherapy, and immunotherapy are summarized.

Nanoparticle-based delivery of nitric oxide for therapeutic applications

Nitric oxide (NO), a low molecular weight signaling molecule, plays critical roles in both cellular health and disease. There is continued interest in new modalities for the controlled therapeutic delivery of NO to cells and tissues. The physicochemical properties of NO (including its short half-life and on-demand synthesis at the point of function), however, pose considerable challenges for its specific and efficient delivery. Recently, a number of nanoparticle (NP)-based systems are described that address some of these issues by taking advantage of the unique attributes of the NP carrier to effect efficient NO delivery. This review highlights the progress that has been made over the past 5 years in the use of various constructs for the therapeutic delivery of NO.

Doxorubicin hydrochloride and L-arginine co-loaded nanovesicle for drug resistance reversal stimulated by near-infrared light

Drug resistance is accountable for the inadequate outcome of chemotherapy in clinics. The newly emerging role of nitric oxide (NO) to conquer drug resistance has been recognized as a potential strategy. However, it remains a great challenge to realize targeted delivery as well as accurate release of NO at desired sites. Herein, we developed a PEGylated indocyanine green (mPEG-ICG) integrated nanovesicle system (PIDA) to simultaneously load doxorubicin hydrochloride (DOX⋅HCl) and the NO donor L-arginine (L-Arg), which can produce NO triggered by NIR light irradiation and exert multimodal therapy to sensitize drug-resistant cancers. Upon 808 nm irradiation, the NO released from PIDA led to a decrease in mitochondrial membrane potential, an increase in ROS and significant ATP depletion in K562/ADR cells, thus inhibiting cell growth and resolving the problem of drug resistance. Consequently, the in vivo experiment on K562/ADR-bearing nude mice indicated that PIDA nanovesicles achieved significant anticancer efficacy with a tumor inhibition rate of 80.8%. Above all, PIDA nanovesicles offer guidance for designing nanoplatforms for drug-resistant cancer treatment.

Recent advances in diverse nanosystems for nitric oxide delivery in cancer therapy

Gas therapy has been proven to be a promising and advantageous treatment option for cancers. Studies have shown that nitric oxide (NO) is one of the smallest structurally significant gas molecules with great potential to suppress cancer. However, there is controversy and concern about its use as it exhibits the opposite physiological effects based on its levels in the tumor. Therefore, the anti-cancer mechanism of NO is the key to cancer treatment, and rationally designed NO delivery systems are crucial to the success of NO biomedical applications. This review summarizes the endogenous production of NO, its physiological mechanisms of action, the application of NO in cancer treatment, and nano-delivery systems for delivering NO donors. Moreover, it briefly reviews challenges in delivering NO from different nanoparticles and the issues associated with its combination treatment strategies. The advantages and challenges of various NO delivery platforms are recapitulated for possible transformation into clinical applications.

Enhancing the therapeutic efficacy of nanoparticles for cancer treatment using versatile targeted strategies

Poor targeting of therapeutics leading to severe adverse effects on normal tissues is considered one of the obstacles in cancer therapy. To help overcome this, nanoscale drug delivery systems have provided an alternative avenue for improving the therapeutic potential of various agents and bioactive molecules through the enhanced permeability and retention (EPR) effect. Nanosystems with cancer-targeted ligands can achieve effective delivery to the tumor cells utilizing cell surface-specific receptors, the tumor vasculature and antigens with high accuracy and affinity. Additionally, stimuli-responsive nanoplatforms have also been considered as a promising and effective targeting strategy against tumors, as these nanoplatforms maintain their stealth feature under normal conditions, but upon homing in on cancerous lesions or their microenvironment, are responsive and release their cargoes. In this review, we comprehensively summarize the field of active targeting drug delivery systems and a number of stimuli-responsive release studies in the context of emerging nanoplatform development, and also discuss how this knowledge can contribute to further improvements in clinical practice.

Cancer cell membrane targeting and red light-triggered carbon monoxide (CO) release for enhanced chemotherapy

Chemotherapy assisted by carbon monoxide (CO) gas therapy is an emerging powerful cancer therapeutic modality. However, the effective delivery and controlled release of CO in tumor cells remain a challenge. Herein, a cell membrane bionic nano delivery system (RBC-H@DOX/3-HF@MSN, termed as RHM) was designed to selectively accumulate in tumors and generate CO in situ upon red light irradiation for the combination of chemotherapy and gas therapy. CO significantly improves the therapeutic effect of DOX from 29.0% to 82.4%.

Ribonucleotide reductase: Implications of thiol S-nitrosylation and tyrosine nitration for different subunits

Ribonucleotide reductase (RNR) is a multi-subunit enzyme responsible for catalyzing the rate-limiting step in the production of deoxyribonucleotides essential for DNA synthesis and repair. The active RNR complex is composed of multimeric R1 and R2 subunits. The RNR catalysis involves the formation of tyrosyl radicals in R2 subunits and thiyl radicals in R1 subunits. Despite the quaternary structure and cofactor diversity, all the three classes of RNR have a conserved cysteine residue at the active site which is converted into a thiyl radical that initiates the substrate turnover, suggesting that the catalytic mechanism is somewhat similar for all three classes of the RNR enzyme. Increased RNR activity has been associated with malignant transformation, cancer cell growth, and tumorigenesis. Efforts concerning the understanding of RNR inhibition in designing potent RNR inhibitors/drugs as well as developing novel approaches for antibacterial, antiviral treatments, and cancer therapeutics with improved radiosensitization have been made in clinical research. This review highlights the precise and potent roles of NO in RNR inhibition by targeting both the subunits. Under nitrosative stress, the thiols of the R1 subunits have been found to be modified by S-nitrosylation and the tyrosyl radicals of the R2 subunits have been modified by nitration. In view of the recent advances and progresses in the field of nitrosative modifications and its fundamental role in signaling with implications in health and diseases, the present article focuses on the regulations of RNR activity by S-nitrosylation of thiols (R1 subunits) and nitration of tyrosyl residues (R2 subunits) which will further help in designing new drugs and therapies.

Nanotechnology-aided advancement in the combating of cancer metastasis

Cancer, especially when it has metastasized to different locations in the body, is notoriously difficult to treat. Metastatic cancer accounts for most cancer deaths and thus remains an enormous challenge. During the metastasis process, cancer cells negotiate a series of steps termed the “metastatic cascadeˮ that offer potential for developing anti-metastatic therapy strategies. Currently available conventional treatment and diagnostic methods addressing metastasis come with their own pitfalls and roadblocks. In this contribution, we comprehensively discuss the potential improvements that nanotechnology-aided approaches are able to bring, either alone or in combination with the existing conventional techniques, to the identification and treatment of metastatic disease. We tie specific nanotechnology-aided strategies to the complex biology of the different steps of the metastatic cascade in order to open up new avenues for fine-tuned targeting and development of anti-metastatic agents designed specifically to prevent or mitigate the metastatic outgrowth of cancer. We also present a viewpoint on the progress of translation of nanotechnology into cancer metastasis patient care.

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

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

Targeting Ca2+ signaling: A new arsenal against cancer

The drug resistance of cancer cells is a major concern in medical oncology, resulting in the failure of chemotherapy. Ca²⁺ plays a pivotal role in inducing multidrug resistance in cancer cells. Calcium signaling is a critical regulator of many cancer hallmarks, such as angiogenesis, invasiveness, and migration. In this review, we describe the involvement of Ca²⁺ signaling and associated proteins in cancer progression and in the development of multidrug resistance in cancer cells. We also highlight the possibilities and challenges of targeting the Ca²⁺ channels, transporters, and pumps involved in Ca²⁺ signaling in cancer cells through structure-based drug design. This work will open a new therapeutic window to be used against cancer in upcoming years.

Tumor vasculature-targeting nanomedicines

Uncontrolled tumor growth and subsequent distant metastasis are highly dependent on an adequate nutrient supply from tumor blood vessels, which have relatively different pathophysiological characteristics from those of normal vasculature. Obviously, strategies targeting tumor vasculature, such as anti-angiogenic drugs and vascular disrupting agents, are attractive methods for cancer therapy. However, the off-target effects and high dose administration of these drug regimens critically restrict their clinical applications. In recent years, nanomedicines focused on tumor vasculature have been shown to be superior to traditional therapeutic methods and do not induce side effects. This review will first highlight the recent development of tumor vasculature-targeting nanomedicines from the following four aspects: 1) angiogenesis-inhibiting nanomedicines (AINs); 2) vasculature-disrupting nanomedicines (VDNs); 3) vasculature infarction nanomedicines (VINs); and 4) vasculature-regulating nanomedicines (VRNs). Furthermore, the design principles, limitations, and future directions are also discussed. STATEMENT OF SIGNIFICANCE: Based on the essential roles of tumor blood vessels, the therapeutic strategies targeting tumor vasculature have exhibited good clinical therapeutic outcomes. However, poor patient adherence to free drug administration limits their clinical usage. Nanomedicines have great potential to overcome the abovementioned obstacle. This review summarizes the tumor-vasculature targeting nanomedicines from four aspects: 1) angiogenesis-inhibiting nanomedicines (AINs); 2) vasculature-disrupting nanomedicines (VDNs); 3) vasculature infarction nanomedicines (VINs); and 4) vasculature regulating nanomedicines (VRNs). In addition, this review provides perspectives on this research field.

Bio- and Hemo-Compatible Silk Fibroin PEGylated Nanocarriers for 5-Fluorouracil Chemotherapy in Colorectal Cancer: In Vitro Studies

5-fluorouracil (5-FU) remains the gold standard of treatment for colorectal cancer, but its poor bioavailability and high systemic toxicity highlight the urgent need for the development of novel delivery strategies to increase the efficacy of 5-FU treatment. The present study is aimed to design and validate a PEGylated Silk Fibroin Nanocarrier (SF/PEG nanoparticles (NPs)) as an efficient 5-FU delivery system for potential intravenous administration. Using the human adenocarcinoma HT–29 cell line as an in vitro model for colorectal cancer, the cytotoxicity screening of the SF/PEG NPs showed that pristine nanocarriers were highly biocompatible, while the addition of 5-FU triggers a dramatic reduction in tumor cell viability, proliferation potential and mitochondrial integrity as well as a significant increase in nitric oxide production. Despite their high in vitro cytotoxicity, the 5-FU SF/PEG NPs were found hemocompatible as no impact on red blood cells hemolysis or the phagocytic activity of the granulocytes was observed. Exposure of HT–29 tumor cells and blood samples to 5-FU SF/PEG NPs augmented the tumor necrosis factor-α levels. Moreover, 5-FU SF/PEG NPs showed an impact on tumor cell migration and invasive potential as both of these processes were inhibited by the NP treatment.

Damaging Tumor Vessels with an Ultrasound-Triggered NO Release Nanosystem to Enhance Drug Accumulation and T Cells Infiltration

INTRODUCTION

Limited by tumor vascular barriers, restricted intratumoural T cell infiltration and nanoparticles accumulation remain major bottlenecks for anticancer therapy. Platelets are now known to maintain tumor vascular integrity. Therefore, inhibition of tumor-associated platelets may be an effective method to increase T cell infiltration and drug accumulation at tumor sites. Herein, we designed an ultrasound-responsive nitric oxide (NO) release nanosystem, SNO-HSA-PTX, which can release NO in response to ultrasound (US) irradiation, thereby inhibiting platelet function and opening the tumor vascular barrier, promoting drug accumulation and T cell infiltration.

METHODS

We evaluated the ability of SNO-HSA-PTX to release NO in response to US irradiation. We also tested the effect of SNO-HSA-PTX on platelet function. Plenty of studies including cytotoxicity, pharmacokinetics study, biodistribution, blood perfusion, T cell infiltration, in vivo antitumor efficacy and safety assessment were conducted to investigate the antitumor effect of SNO-HSA-PTX.

RESULTS

SNO-HSA-PTX with US irradiation inhibited tumor-associated platelets activation and induced openings in the tumor vascular barriers, which promoted the accumulation of SNO-HSA-PTX nanoparticles to the tumor sites. Meanwhile, the damaged vascular barriers allowed oxygen-carrying hemoglobin to infiltrate tumor regions, alleviating hypoxia of the tumor microenvironment. In addition, the intratumoral T cell infiltration was augmented, together with chemotherapy and NO therapy, which greatly inhibited tumor growth.

DISCUSSION

Our research designed a simple strategy to open the vascular barrier by inhibiting the tumor-associated platelets, which provide new ideas for anti-tumor treatment.

Engineering nanoparticles to tackle tumor barriers

Engineering nanoparticles (NPs) as delivery systems of anticancer therapeutics has attracted tremendous attention in recent decades, and some nanoscale drug formulations have been approved for clinical use. However, their therapeutic efficacies are still limited by the presence of a series of biological barriers during the delivery process. Among these obstacles, tumor barriers are generally recognized as the bottleneck, because they dominate the NP extravasation from the tumor vasculature and penetration into the tumor parenchyma. Therefore, this review first discussed tumor barriers from two aspects: tumor vascular barriers and tumor stromal barriers. Pathological features of the two sets of barriers as well as their influence on the delivery efficacy were described. Then, we outlined strategies for engineering NPs to overcome these challenges: increasing extravasation through physical property optimization and tumor vascular targeting; and facilitating deep penetration through particle size manipulation, modulation of the tumor extracellular matrix, and some new mechanisms. This review will provide a critical perspective on engineering strategies for more efficient nanomedicine in oncology.

Main nitric oxide (NO) hallmarks to relieve arsenic stress in higher plants

Arsenic (As) is a toxic metalloid that adversely affects plant growth, and poses severe risks to human health. It induces disturbance to many physiological and metabolic pathways such as nutrient, water and redox imbalance, abnormal photosynthesis and ATP synthesis and loss of membrane integrity. Nitric oxide (NO) is a free radical molecule endogenously generated in plant cells which has signalling properties. Under As-stress, the endogenous NO metabolism is significantly affected in a clear connection with the metabolism of reactive oxygen species (ROS) triggering nitro-oxidative stress. However, the exogenous NO application provides beneficial effects under As-stress conditions which can relieve oxidative damages by stimulating the antioxidant systems, regulation of the expression of the transporter and other defence-related genes, modification of root cell wall composition or the biosynthesis of enriched sulfur compounds such phytochelatins (PCs). This review aims to provide up-to-date information on the key NO hallmarks to relieve As-stress in higher plants. Furthermore, it will be analyzed the diverse genetic engineering techniques to increase the endogenous NO content which could open new biotechnological applications, especially in crops under arsenic stress.

Tetrazine-mediated bioorthogonal removal of 3-isocyanopropyl groups enables the controlled release of nitric oxide in vivo

Bond cleavage bioorthogonal chemistry has been widely employed to restore or activate proteins or prodrugs. Nitric oxide (NO), as a free radical molecule, has joined the clinical arena of cancer therapy, since high levels of NO could produce a cancer cell growth inhibitory effect. However, the spatiotemporal controlled release of NO remains a great challenge, and bioorthogonal chemistry may open a new window. Herein, we described a class of O2-3-isocyanopropyl diazeniumdiolates 3a-f as new bioorthogonal NO precursors, which can be effectively uncaged via tetrazine-mediated bond cleavage reactions to liberate NO and acrolein in living cancer cells, exhibiting potent antiproliferative activity. Furthermore, 3a and tetrazine BTZ were respectively encapsulated into two liposomes. It was found that simultaneous administrations of the two liposomes could specifically release large amounts of NO in the implanted cancer cells in zebrafish, thus generating potent tumor suppression activity in vivo. Our findings indicate that the TZ-labile NO precursors could serve to expand the NO-based smart therapeutics and the scope of bioorthogonal chemistry utility in vivo in the near future.

Multifunctional hybrid nanoplatform based on Fe3O4@Ag NPs for nitric oxide delivery: development, characterization, therapeutic efficacy, and hemocompatibility

The combination of Fe₃O₄@Ag superparamagnetic hybrid nanoparticles and nitric oxide (NO) represents an innovative strategy for a localized NO delivery with a simultaneous antibacterial and antitumoral actions. Here, we report the design of Fe₃O₄@Ag hybrid nanoparticles, coated with a modified and nitrosated chitosan polymer, able to release NO in a biological medium. After their synthesis, physicochemical characterization confirmed the obtention of small NO-functionalized superparamagnetic Fe₃O₄@Ag NPs. Antibacterial assays demonstrated enhanced effects compared to control. Bacteriostatic effect against Gram-positive strains and bactericidal effect against E. coli were demonstrated. Moreover, NO-functionalized Fe₃O₄@Ag NPs demonstrated improved ability to reduce cancer cells viability and less cytotoxicity against non-tumoral cells compared to Fe₃O₄@Ag NPs. These effects were associated to the ability of these NPs act simultaneous as cytotoxic (necrosis inductors) and cytostatic compounds inducing S-phase cell cycle arrest. NPs also demonstrated low hemolysis ratio (<10%) at ideal work range, evidencing their potential for biomedical applications. Targeted and hemocompatible nitric oxide-releasing multi-functional hybrid nanoparticles for antitumor and antimicrobial applications.

Overcoming Biological Barriers With Block Copolymers-Based Self-Assembled Nanocarriers. Recent Advances in Delivery of Anticancer Therapeutics

Cancer is one of the most common life-threatening illness and it is the world's second largest cause of death. Chemotherapeutic anticancer drugs have many disadvantages, which led to the need to develop novel strategies to overcome these shortcomings. Moreover, tumors are heterogenous in nature and there are various biological barriers that assist in treatment reisistance. In this sense, nanotechnology has provided new strategies for delivery of anticancer therapeutics. Recently, delivery platforms for overcoming biological barriers raised by tumor cells and tumor-bearing hosts have been reported. Among them, amphiphilic block copolymers (ABC)-based self-assembled nanocarriers have attracted researchers worldwide owing to their unique properties. In this work, we addressed different biological barriers for effective cancer treatment along with several strategies to overcome them by using ABC-based self-assembled nanostructures, with special emphasis in those that have the ability to act as responsive nanocarriers to internal or external environmental clues to trigger release of the payload. These nanocarriers have shown promising properties to revolutionize cancer treatment and diagnosis, but there are still challenges for their successful translation to clinical applications.

The progress and perspective of nanoparticle-enabled tumor metastasis treatment

As one of the most serious threats to human being, cancer is hard to be treated when metastasis happens. What's worse, there are few identified targets of metastasis for drug development. Therefore, it is important to develop strategies to prevent metastasis or treat existed metastasis. This review focuses on the procedure of metastasis, and first summarizes the targeting delivery strategies, including primary tumor targeting drug delivery, tumor metastasis targeting drug delivery and hijacking circulation cells. Then, as a promising treatment, the application of immunotherapy in tumor metastasis treatment is introduced, and strategies that stimulating immune response are reviewed, including chemotherapy, photothermal therapy, photodynamic therapy, ferroptosis, sonodynamic therapy, and nanovaccines. Finally, the challenges and perspective about nanoparticle-enabled tumor metastasis treatment are discussed.

Hydrogen Sulfide: From a Toxic Molecule to a Key Molecule of Cell Life

Hydrogen sulfide (H2S) has always been considered toxic, but a huge number of articles published more recently showed the beneficial biochemical properties of its endogenous production throughout all regna. In this review, the participation of H2S in many physiological and pathological processes in animals is described, and its importance as a signaling molecule in plant systems is underlined from an evolutionary point of view. H2S quantification methods are summarized and persulfidation is described as the underlying mechanism of action in plants, animals and bacteria. This review aims to highlight the importance of its crosstalk with other signaling molecules and its fine regulation for the proper function of the cell and its survival.

Nitric Oxide (NO) and NO Synthases (NOS)-Based Targeted Therapy for Colon Cancer

Colorectal cancer (CRC) is one of the most lethal malignancies worldwide and CRC therapy remains unsatisfactory. In recent decades, nitric oxide (NO)-a free-radical gas-plus its endogenous producer NO synthases (NOS), have attracted considerable attention. NO exerts dual effects (pro- and anti-tumor) in cancers. Endogenous levels of NO promote colon neoplasms, whereas exogenously sustained doses lead to cytotoxic functions. Importantly, NO has been implicated as an essential mediator in many signaling pathways in CRC, such as the Wnt/β-catenin and extracellular-signal-regulated kinase (ERK) pathways, which are closely associated with cancer initiation, metastasis, inflammation, and chemo-/radio-resistance. Therefore, NO/NOS have been proposed as promising targets in the regulation of CRC carcinogenesis. Clinically relevant NO-donating agents have been developed for CRC therapy to deliver a high level of NO to tumor sites. Notably, inducible NOS (iNOS) is ubiquitously over-expressed in inflammatory-associated colon cancer. The development of iNOS inhibitors contributes to targeted therapies for CRC with clinical benefits. In this review, we summarize the multifaceted mechanisms of NO-mediated networks in several hallmarks of CRC. We review the clinical manifestation and limitations of NO donors and NOS inhibitors in clinical trials. We also discuss the possible directions of NO/NOS therapies in the immediate future.

Modification of nitric oxide donors onto a monoclonal antibody boosts accumulation in solid tumors

Although monoclonal antibodies (mAbs) have revolutionized cancer treatment, their accumulation in solid tumors is limited and requires improvement to enhance therapeutic efficacy. Here we developed a strategy to modify mAb with a donor of nitric oxide (NO) because NO functions to vasodilate as well as to enhance the permeability of vascular endothelium, which will contribute to enhancing the tumor accumulation of mAb. We selected S-nitrosothiol as a NO donor and established the procedure to modify S-nitrosothiol group on mAb under ambient conditions. The modified mAb (Ab-SNO) thus obtained released NO in a preferable speed and maintained its original properties such as binding affinity to a target antigen and efficacy to induce antibody-dependent cellular cytotoxicity. We demonstrated that Ab-SNO enhanced the tumor accumulation of co-administered proteins such as antibody and serum albumin.

S-nitrosothiols loaded mini-sized Au@silica nanorod elicits collagen depletion and mitochondrial damage in solid tumor treatment

To a large extent, the dense extracellular matrix (ECM), which tightly connects tumor cells to arm the tumor into an intractable fortress, significantly decreases the nanoparticles delivery efficacy and overall performance in cancer treatments. Therefore, it is necessary to transform the dense stroma of solid tumors to loose state, which could realize deep penetration of nanomedicine and enhance cancer treatment effects. Here, we fabricated a protein-free collagen nanosweeper, triphenylphosphonium bromide (TPP) coated and S-nitrosothiols loaded mini-sized Au@silica nanorod (Au@SiO2-SNO/PEG/TPP, GSNP-TPP), to clear the transport barriers of nanoparticles as well as elevate enhanced permeability and retention (EPR) effect, thus alleviating the diffusion resistance and realizing further penetration of nanoparticles. Methods: By modifying the Au@silica with thermo-sensitive S-nitrosothiols, the carrier could release the nitric oxide (NO) due to the surface overheat as well as perform photothermal therapy (PTT) under near-infrared (NIR) laser irradiation. The level of collagen depletion was observed via western blotting and immunofluorescent staining. In addition, the dual-imaging and antitumor efficiency of GSNP-TPPs were evaluated with the HeLa tumor-bearing mouse model. Results: On one hand, the released NO could deplete collagen by activating matrix metalloproteinases (MMPs) to break collagen fibers, thus loosening the dense ECM to enhance the cellular internalization. On the other hand, with the mitochondrial-targeted effect of TPP, the diffusible NO in tumor might rapidly interact with superoxide anion (O2Ÿ-) to produce highly toxic and powerful reactive nitrogen species (RNS) -- peroxynitrite (ONOO-), which resulted in mitochondrial damage to induce cell apoptosis. With the unique properties of mini-sized gold nanorods, the formulated nanoparticles exhibited good computed tomography (CT) and multi-spectral optoacoustic tomography (MSOT) imaging effects in precisely locating and monitoring tumor. Moreover, the antitumor efficacy of GSNP-TPPs + laser group was further confirmed by ex-vivo histological analysis of tumor tissue. Conclusion: This work points out a strategy to overcome the obstacle standing in nanoparticles penetration, and opens the door of further exploitation of NO-related theranostic systems.

Overcoming the biological barriers in the tumor microenvironment for improving drug delivery and efficacy

The delivery of drugs to tumors by nanoparticles is a rapidly growing field. However, the complex tumor microenvironment (TME) barriers greatly hinder drug delivery to tumors. In this study, we first summarized the barriers in TME, including anomalous vasculature, rigid extracellular matrix, hypoxia, acidic pH, irregular enzyme level, altered metabolism pathway and immunosuppressive conditions. To overcome these barriers, many strategies have been developed, such as modulating TME, active targeting by ligand modification and biomimetic strategies, and TME-responsive drug delivery strategies to improve nanoparticle penetration, cellular uptake and drug release. Although extensive progress has been achieved, there are still many challenges, which are discussed in the last section. Overall, we carefully discuss the landscape of TME, development for improving drug delivery, and challenges that need to be further addressed.