NO prodrug-conjugated, self-assembled, pH-responsive and galactose receptor targeted nanoparticles for co-delivery of nitric oxide and doxorubicin

pH-responsive self-assembled nanoparticles for tumor-targeted drug delivery

Recent advances in the field of drug delivery have opened new avenues for the development of novel nanodrug delivery systems (NDDS) in cancer therapy. Self-assembled nanoparticles (SANPs) based on tumour microenvironment have great advantages in improving antitumor effect, and pH-responsive SANPs prepared by the combination of pH-responsive nanomaterials and self-assembly technology can effectively improve the efficacy and reduce the systemic toxicity of antitumor drugs. In this review, we describe the characteristics of self-assembly and its driving force, the mechanism of pH-responsive NDDS, and the nanomaterials for pH-responsive SANPs type. A series of pH-responsive SANPs for tumour-targeted drug delivery are discussed, with an emphasis on the relation between structural features and theranostic performance.

Sono-activated materials for enhancing focused ultrasound ablation: Design and application in biomedicine

The ablation effect of focused ultrasound (FUS) has played an increasingly important role in the biomedical field over the past decades, and its non-invasive features have great advantages, especially for clinical diseases where surgical treatment is not available or appropriate. Recently, rapid advances in the adjustable morphology, enzyme-mimetic activity, and biostability of sono-activated materials have significantly promoted the medical application of FUS ablation. However, a systematic review of sono-activated materials based on FUS ablation is not yet available. This progress review focuses on the recent design, fundamental principles, and applications of sono-activated materials in the FUS ablation biomedical field. First, the different ablation mechanisms and the key factors affecting ablation are carefully determined. Then, the design of sono-activated materials with high FUS ablation efficiencies is comprehensively discussed. Subsequently, the representative biological applications are summarized in detail. Finally, the primary challenges and future perspectives are also outlined. We believe this timely review will provide key information and insights for further exploration of focused ultrasound ablation and new inspiration for designing future sono-activated materials. STATEMENT OF SIGNIFICANCE: The ablation effect of focused ultrasound (FUS) has played an increasingly important role in the biomedical field over the past decades. However, there are also some challenges of FUS ablation, such as skin burns, tumour recurrence after thermal ablation, and difficulty in controlling cavitation ablation. The rapid advance in adjustable morphology, enzyme-mimetic activity, and biostability of sono-activated materials has significantly promoted the medical application of FUS ablation. However, the systematic review of sono-activated materials based on FUS ablation is not yet available. This progress review focuses on the recent design, fundamental principles, and applications in the FUS ablation biomedical field of sono-activated materials. We believe this timely review will provide key information and insights for further exploration of FUS ablation.

Functionalized MoS2-nanosheets with NIR-Triggered nitric oxide delivery and photothermal activities for synergistic antibacterial and regeneration-promoting therapy

Bacterial infection in skin and soft tissue has emerged as a critical concern. Overreliance on antibiotic therapy has led to numerous challenges, including the emergence of multidrug-resistant bacteria and adverse drug reactions. It is imperative to develop non-antibiotic treatment strategies that not only exhibit potent antibacterial properties but also promote rapid wound healing and demonstrate biocompatibility. Herein, a novel multimodal synergistic antibacterial system (SNO-CS@MoS2) was developed. This system employs easily surface-modified thin-layer MoS2 as photothermal agents and loaded with S-nitrosothiol-modified chitosan (SNO-CS) via electrostatic interactions, thus realizing the combination of NO gas therapy and photothermal therapy (PTT). Furthermore, this surface modification renders SNO-CS@MoS2 highly stable and capable of binding with bacteria. Through PTT's thermal energy, SNO-CS@MoS2 rapidly generates massive NO, collaborating with PTT to achieve antibacterial effects. This synergistic therapy can swiftly disrupt the bacterial membrane, causing protein leakage and ATP synthesis function damage, ultimately eliminating bacteria. Notably, after effectively eliminating all bacteria, the residual SNO-CS@MoS2 can create trace NO to promote fibroblast migration, proliferation, and vascular regeneration, thereby accelerating wound healing. This study concluded that SNO-CS@MoS2, a novel multifunctional nanomaterial with outstanding antibacterial characteristics and potential to promote wound healing, has promising applications in infected soft tissue wound treatment.

Smart Magnetic Nanocarriers for Codelivery of Nitric Oxide and Doxorubicin for Enhanced Apoptosis in Cancer Cells

Extremely short half-life therapeutic molecule nitric oxide (NO) plays significant roles in the functioning of various physiological and pathological processes in the human body, whereas doxorubicin hydrochloride (DOX) is a clinically important anticancer drug widely used in cancer chemotherapy. Thus, the intracellular delivery of these therapeutic molecules is tremendously important to achieve their full potential. Herein, we report a novel approach for the development of highly water-dispersible magnetic nanocarriers for codelivery of NO and DOX. Primarily, bifunctional magnetic nanoparticles enriched with carboxyl and thiol groups were prepared by introducing cysteine onto the surface of citrate-functionalized Fe3O4 nanoparticles. DOX was electrostatically conjugated onto the surface of bifunctional nanoparticles via carboxyl moieties, whereas the thiol group was further nitrosated to provide NO-releasing molecules. The developed magnetic nanocarrier exhibited good aqueous colloidal stability, protein resistance behavior, and high encapsulation efficacy for NO (65.5%) and DOX (85%), as well as sustained release characteristics. Moreover, they showed superior cytotoxicity toward cancer (A549 and MCF-7) cells via apoptosis induction over normal (WI26VA4) cells. Specifically, we have developed magnetic nanocarriers having the capability of dual delivery of NO and DOX, which holds great potential for combinatorial cancer treatment.

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.

Smart design of a therapeutic nanoplatform for mitochondria-targeted copper-depletion therapy combined with chemotherapy

Mitochondria-targeted copper-depletion is emerging as an attractive strategy to combat cancer. However, existing copper molecular chelators are non-specific, toxic and ineffective. Here, it is reported that multifunctional nanoparticles (MSN-TPP/BNA-DPA) can not only target mitochondria to deprive copper ions to trigger copper-depletion therapy, but also serve as nanocarriers to deliver anticancer drugs for chemotherapy, which are engineered by conjugating a fluorophore 4-bromo-1,8-naphthalicanhydride (BNA), a copper-depriving moiety dimethylpyridinamine (DPA) and a mitochondrial targeting ligand triphenylphosphonium (TPP) on the surface of mesoporous silica nanoparticles (MSN). BNA and the internal charge transfer of compound BNA-DPA endow MSN-TPP/BNA-DPA with green fluorescence emission upon UV excitation, which can be used to monitor the cellular uptake of nanoparticles. When copper ions bind to DPA, green fluorescence is quenched, providing visualization feedback of copper-depletion. Therapeutically, mitochondria-targeted copper-depletion effectively causes mitochondria damage, elevated oxidative stress and reduced ATP production to induce intensive cancer cell death. Moreover, the mesoporous structure enables MSN-TPP/BNA-DPA to deliver doxorubicin to mitochondria for chemotherapy and enhances copper-depletion therapy through H2O2 production. Together, the synergistic therapeutic effect of enhanced copper-depletion therapy and doxorubicin-mediated chemotherapy achieves a remarkable cancer cell-killing effect and significant tumor growth inhibition in 4T1 tumor-bearing mice. This work provides an efficacious strategy for copper-depletion based synergistic cancer therapy.

Cancer Cell-Specific Fluorescent Prodrug Delivery Platforms

Targeting cancer cells with high specificity is one of the most essential yet challenging goals of tumor therapy. Because different surface receptors, transporters, and integrins are overexpressed specifically on tumor cells, using these tumor cell-specific properties to improve drug targeting efficacy holds particular promise. Targeted fluorescent prodrugs not only improve intracellular accumulation and bioavailability but also report their own localization and activation through real-time changes in fluorescence. In this review, efforts are highlighted to develop innovative targeted fluorescent prodrugs that efficiently accumulate in tumor cells in different organs, including lung cancer, liver cancer, cervical cancer, breast cancer, glioma, and colorectal cancer. The latest progress and advances in chemical design and synthetic considerations in fluorescence prodrug conjugates and how their therapeutic efficacy and fluorescence can be activated by tumor-specific stimuli are reviewed. Additionally, novel perspectives are provided on strategies behind engineered nanoparticle platforms self-assembled from targeted fluorescence prodrugs, and how fluorescence readouts can be used to monitor the position and action of the nanoparticle-mediated delivery of therapeutic agents in preclinical models. Finally, future opportunities for fluorescent prodrug-based strategies and solutions to the challenges of accelerating clinical translation for the treatment of organ-specific tumors are proposed.

Extracellular-Vesicle-Based Therapeutics in Neuro-Ophthalmic Disorders

Extracellular vesicles (EVs) have been recognized as promising candidates for developing novel therapeutics for a wide range of pathologies, including ocular disorders, due to their ability to deliver a diverse array of bioactive molecules, including proteins, lipids, and nucleic acids, to recipient cells. Recent studies have shown that EVs derived from various cell types, including mesenchymal stromal cells (MSCs), retinal pigment epithelium cells, and endothelial cells, have therapeutic potential in ocular disorders, such as corneal injury and diabetic retinopathy. EVs exert their effects through various mechanisms, including promoting cell survival, reducing inflammation, and inducing tissue regeneration. Furthermore, EVs have shown promise in promoting nerve regeneration in ocular diseases. In particular, EVs derived from MSCs have been demonstrated to promote axonal regeneration and functional recovery in various animal models of optic nerve injury and glaucoma. EVs contain various neurotrophic factors and cytokines that can enhance neuronal survival and regeneration, promote angiogenesis, and modulate inflammation in the retina and optic nerve. Additionally, in experimental models, the application of EVs as a delivery platform for therapeutic molecules has revealed great promise in the treatment of ocular disorders. However, the clinical translation of EV-based therapies faces several challenges, and further preclinical and clinical studies are needed to fully explore the therapeutic potential of EVs in ocular disorders and to address the challenges for their successful clinical translation. In this review, we will provide an overview of different types of EVs and their cargo, as well as the techniques used for their isolation and characterization. We will then review the preclinical and clinical studies that have explored the role of EVs in the treatment of ocular disorders, highlighting their therapeutic potential and the challenges that need to be addressed for their clinical translation. Finally, we will discuss the future directions of EV-based therapeutics in ocular disorders. Overall, this review aims to provide a comprehensive overview of the current state of the art of EV-based therapeutics in ophthalmic disorders, with a focus on their potential for nerve regeneration in ocular diseases.

Chronic exposure to nitric oxide sensitizes prostate cancer cells and improved ZnO/CisPt NPs cytotoxicity and selectivity

The co-therapy of common chemotherapeutics with nitric oxide (NO), an endogenous signaling molecule, is proposed as an alternative to sensitize cancer cells and enhance treatments' efficacy. Herein, we have synthesized cisplatin-releasing zinc oxide nanoparticles (ZnO/CisPt NPs), which promoted a sustained and pH targeted release, able to release a higher amount of CisPt at tumor microenvironment conditions. This material was combined with a chronic NO treatment, at low concentration, in prostate cancer cells (PC3). NO treatment enhanced the S-NO concentration in PC3 cells, suggesting the nitrosylation or transnitrosylation processes enhancement, which are directly related to S-NO binding to proteins, function alterations and cancer cells death. Indeed, these mechanisms directly impacted the cytotoxic effect of ZnO/CisPt NPs, inducing a 30 % higher viability reduction of PC3 cells after NO treatment, along with a higher selectivity index when compared to normal human fibroblasts (FN1).

Ultrasound-Induced Piezocatalysis Triggered NO Generation for Enhanced Hypoxic Tumor Therapy

Conventional NO gas generation based on l-arginine (l-Arg) is usually dependent on H₂O₂ and O₂, both of which are very limited within the tumor microenvironment, thus greatly limiting l-Arg's therapeutic effect. Herein, a novel nanoplatform for efficiently triggering NO production based on ultrasound-induced piezocatalysis was developed, which was fabricated by coating amphiphilic poly-l-arginine (DSPE-PEG₂₀₀₀-Arg, DPA) on the piezoelectric material of barium titanate (BTO). The resulting BTO@DPA nanoparticles can efficiently generate H₂O₂, ¹O₂, and O₂ via ultrasound-induced piezocatalysis based on BTO and oxidize the surface arginine to produce NO, which can even further interact with the reactive oxygen species (ROS) to produce more reactive peroxynitrite, thus inducing serious tumor cell apoptosis both in hypoxia and normoxia. After intravenous injection, BTO@DPA accumulated well at the tumor tissue at 4 h postinjection; later, ultrasound irradiation on the tumor not only achieved the best tumor inhibition rate of ∼70% but also completely inhibited tumor metastasis to the lungs via the alleviation of tumor hypoxia. Such a strategy was not dependent on the tumor microenvironment and can be well controlled by ultrasound irradiation, providing a simple and efficient therapy paradigm for hypoxic tumor.

Metal-organic framework for biomimetic nitric oxide generation and anticancer drug delivery

The potential therapeutic implications of nitric oxide (NO) have drawn a great deal of interest for reversing multidrug resistance (MDR) in cancer; however, previous strategies utilized unstable or toxic NO donors often oxidized by the excessive addition of reactive oxygen species, leading to unexpected side effects. Therefore, this study proposed a metal-organic framework (MOF), Porous coordination network (PCN)-223-Fe, to be loaded with a biocompatible NO donor, L-arginine (L-arg; i.e., PCN-223-Fe/L-arg). This specific MOF possesses a ligand of Fe-porphyrin, a biomimetic catalyst. Thus, with PCN-223-Fe/L-arg, L-arg was released in a sustained manner, which generated NO by a catalytic reaction between L-arg and Fe-porphyrin in PCN-223-Fe. Through this biomimetic process, PCN-223-Fe/L-arg could generate sufficient NO to reverse MDR at the expense of hydrogen peroxide already present and highly expressed in cancer environments. For treatment of MDR cancer, this study also proposed PCN-223-Fe loaded with an anticancer drug, irinotecan (CPT-11; i.e., PCN-223-Fe/CPT-11), to be formulated together with PCN-223-Fe/L-arg. Owing to the synergistic effect of reversed MDR by NO generation and sustained release of CPT-11, this combined formulation exhibited a higher anticancer effect on MDR cancer cells (MCF-7/ADR). When intratumorally injected in vivo, coadministration of PCN-223-Fe/L-arg and PCN-223-Fe/CPT-11 greatly suppressed tumor growth in nude mice bearing MDR tumors.

Polymeric dual-modal imaging nanoprobe with two-photon aggregation-induced emission for fluorescence imaging and gadolinium-chelation for magnetic resonance imaging

Nanoprobes that offer both fluorescence imaging (FI) and magnetic resonance imaging (MRI) can provide supplementary information and hold synergistic advantages. However, synthesis of such dual-modality imaging probes that simultaneously exhibit tunability of functional groups, high stability, great biocompatibility and desired dual-modality imaging results remains challenging. In this study, we used an amphiphilic block polymer from (ethylene glycol) methyl ether methacrylate (OEGMA) and N-(2-hydroxypropyl) methacrylamide (HPMA) derivatives as a carrier to conjugate a MR contrast agent, Gd-DOTA, and a two-photon fluorophore with an aggregation-induced emission (AIE) effect, TPBP, to construct a MR/two-photon fluorescence dual-modality contrast agent, Gd-DOTA-TPBP. Incorporation of gadolinium in the hydrophilic chain segment of the OEGMA-based carrier resulted in a high r₁ value for Gd-DOTA-TPBP, revealing a great MR imaging resolution. The contrast agent specifically accumulated in the tumor region, allowing a long enhancement duration for vascular and tumor contrast-enhanced MR imaging. Meanwhile, coupling TPBP with AIE properties to the hydrophobic chain segment of the carrier not only improved its water solubility and reduced its cytotoxicity, but also significantly enhanced its imaging performance in an aqueous phase. Gd-DOTA-TPBP was also demonstrated to act as an excellent fluorescence probe for two-photon-excited bioimaging with higher resolution and greater sensitivity than MRI. Since high-resolution, complementary MRI/FI dual-modal images were acquired at both cellular and tissue levels in tumor-bearing mice after application of Gd-DOTA-TPBP, it has great potential in the early phase of disease diagnosis.

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A highly stable and biocompatibility MR/two-photon AIE fluorescent dual-modality imaging probe Gd-DOTA-TPBP is prepared.

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Gd-DOTA and TPBP are conjugated to the hydrophilic and hydrophobic chain of the amphiphilic block polymer, respectively.

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The different coupling sites of Gd-DOTA and TPBP promote dual-modality imaging effects of Gd-DOTA-TPBP after self-assembly.

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The dual-modality images with Gd-DOTA-TPBP have obtained complementary information at the cellular and tissue level in vivo.

A Comprehensive Review on Liver Targeting: Emphasis on Nanotechnology- based Molecular Targets and Receptors Mediated Approaches

BACKGROUND

The pathogenesis of hepatic diseases involves several cells, which complicates the delivery of pharmaceutical agents. Many severe liver diseases affecting the worldwide population cannot be effectively treated. Major hindrances or challenges are natural physiological barriers and non-specific targeting of drugs administered, leading to inefficient treatment. Hence, there is an earnest need to look for novel therapeutic strategies to overcome these hindrances. A kind of literature has reported that drug safety and efficacy are incredibly raised when a drug is incorporated inside or attached to a polymeric material of either hydrophilic or lipophilic nature. This has driven the dynamic investigation for developing novel biodegradable materials, drug delivery carriers, target-specific drug delivery systems, and many other novel approaches.

OBJECTIVE

Present review is devoted to summarizing receptor-based liver cell targeting using different modified novel synthetic drug delivery carriers. It also highlights recent progress in drug targeting to diseased liver mediated by various receptors, including asialoglycoprotein, mannose and galactose receptor, Fc receptor, low-density lipoprotein, glycyrrhetinic, and bile acid receptor. The essential consideration is given to treating liver cancer targeting using nanoparticulate systems, proteins, viral and non-viral vectors, homing peptides and gene delivery.

CONCLUSION

Receptors based targeting approach is one such approach that was explored by researchers to develop novel formulations which can ensure site-specific drug delivery. Several receptors are on the surfaces of liver cells, which are highly overexpressed in various disease conditions. They all are helpful for the treatment of liver cancer.

Therapeutic gas-releasing nanomedicines with controlled release: Advances and perspectives

Nanoparticle-based drug delivery has become one of the most popular approaches for maximising drug therapeutic potentials. With the notable improvements, a greater challenge hinges on the formulation of gasotransmitters with unique challenges that are not met in liquid and solid active ingredients. Gas molecules upon release from formulations for therapeutic purposes have not really been discussed extensively. Herein, we take a critical look at four key gasotransmitters, that is, carbon monoxide (CO), nitric oxide (NO), hydrogen sulphide (H2S) and sulphur dioxide (SO2), their possible modification into prodrugs known as gas-releasing molecules (GRMs), and their release from GRMs. Different nanosystems and their mediatory roles for efficient shuttling, targeting and release of these therapeutic gases are also reviewed extensively. This review thoroughly looks at the diverse ways in which these GRM prodrugs in delivery nanosystems are designed to respond to intrinsic and extrinsic stimuli for sustained release. In this review, we seek to provide a succinct summary for the development of therapeutic gases into potent prodrugs that can be adapted in nanomedicine for potential clinical use.

Emerging Strategies in Stimuli-Responsive Prodrug Nanosystems for Cancer Therapy

Prodrugs are chemically modified drug molecules that are inactive before administration. After administration, they are converted in situ to parent drugs and induce the mechanism of action. The development of prodrugs has upgraded conventional drug treatments in terms of bioavailability, targeting, and reduced side effects. Especially in cancer therapy, the application of prodrugs has achieved substantial therapeutic effects. From serendipitous discovery in the early stage to functional design with pertinence nowadays, the importance of prodrugs in drug design is self-evident. At present, studying stimuli-responsive activation mechanisms, regulating the stimuli intensity in vivo, and designing nanoscale prodrug formulations are the major strategies to promote the development of prodrugs. In this review, we provide an outlook of recent cutting-edge studies on stimuli-responsive prodrug nanosystems from these three aspects. We also discuss prospects and challenges in the future development of such prodrugs.

SMA-BmobaSNO: an intelligent photoresponsive nitric oxide releasing polymer for drug nanoencapsulation and targeted delivery

Nitric oxide (NO) is an important biological signalling molecule that acts to vasodilate blood vessels and change the permeability of the blood vessel wall. Due to these cardiovascular actions, co-administering NO with a therapeutic could enhance drug uptake. However current NO donors are not suitable for targeted drug delivery as they systemically release NO. To overcome this limitation we report the development of a smart polymer, SMA-BmobaSNO, designed to release NO in response to a photostimulus. The polymer's NO releasing functionality is an S-nitrosothiol group that, at 10 mg ml^-1, is highly resistant to both thermal (t_1/216 d) and metabolic (t_1/232 h) decomposition, but rapidly brakes down under photoactivation (2700 W m^-2, halogen source) to release NO (t_1/225 min). Photoresponsive NO release from SMA-BmobaSNO was confirmed in a cardiovascular preparation, where irradiation resulted in a 12-fold decrease in vasorelaxation EC₅₀(from 5.2μM to 420 nM). To demonstrate the polymer's utility for drug delivery we then used SMA-BmobaSNO to fabricate a nanoparticle containing the probe Nile Red (NR). The resulting SMA-BmobaSNO-NR nanoparticle exhibited spherical morphology (180 nm diameter) and sustained NR release (≈20% over 5 d). Targeted delivery was characterised in an abdominal preparation, where photoactivation (450 W m^-2) caused localized increases in vasodilation and blood vessel permeability, resulting in a 3-fold increase in NR uptake into photoactivated tissue. Nanoparticles fabricated from SMA-BmobaSNO therefore display highly photoresponsive NO release and can apply the Trojan Horse paradigm by using endogenous NO signalling pathways to smuggle a therapeutic cargo into target tissue.

Endogenous NO-releasing Carbon Nanodots for Tumor-specific Gas Therapy

Carbon nanodots based on L-arginine (L-Arg) were developed for enhanced nitric oxide (NO) gas therapy for cancer. The L-Arg-based carbon nanodots (Arg-dots) produced high levels of NO in the tumor environment rich in endogenous H₂O₂. In vitro cell experiments revealed that the Arg-dots could kill tumor cells (including human breast cancer cell line MCF-7, female gastric cancer cell line BGC-823, male lung cancer cell line A549, and female leukemic cell line K562) but did not affect the activity of normal cells (human normal lung epithelial cell line BEAS-2B). The Arg-dots produced twice the amount of NO for an equivalent amount of L-Arg. Theoretical calculations showed that the carbonization structure of the Arg-dots promoted significantly more electrons toward the guanidinium groups of L-Arg and boosted the adsorption of H₂O₂ molecules. In vitro and in vivo investigations confirmed that the Arg-dots reduced the multidrug resistance (MDR) effect of the tumor cells (MCF-7/ADR cells) and produced a combined antitumor efficacy with traditional chemotherapeutic drugs (adriamycin [ADR]). The fluorescence property (quantum yield, 6.88%) allows the Arg-dots to be used as a suitable fluorescent probe for fluorescence imaging of tumor cells. The ultra-small size of the Arg-dots (diameter: ca. 2.5 nm) enables them not only to penetrate deep tumors and provide enhanced antitumor activity but also to be removed through kidney filtration and have a renal clearance property. STATEMENT OF SIGNIFICANCE: Nitric oxide (NO), which serves as a biological messenger, can be used in gas therapy for cancer. The development of a safe and efficient NO cancer therapy is, however, challenging because of the low NO release amount and poor tumor specificity of most NO donors. Many efforts have been made to overcome these drawbacks, but solving both these limitations through a single approach has been seldom achieved. In the present work, carbon nanodots (Arg-dots) from L-arginine were used for gas therapy of cancer. The Arg-dots produced NO in the H₂O₂-rich tumor environment. Theoretical calculations were consistent with the mechanism of enhanced NO release amount. The Arg-dots also reduced the multidrug resistance effect in cancer chemotherapy. In vivo and in vitro toxicity assessments confirmed that the Arg-dots have excellent biosafety.

Engineering macromolecular nanocarriers for local delivery of gaseous signaling molecules

In addition to being notorious air pollutants, nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H₂S) have also been known as endogenous gaseous signaling molecules (GSMs). These GSMs play critical roles in maintaining the homeostasis of living organisms. Importantly, the occurrence and development of many diseases such as inflammation and cancer are highly associated with the concentration changes of GSMs. As such, GSMs could also be used as new therapeutic agents, showing great potential in the treatment of many formidable diseases. Although clinically it is possible to directly inhale GSMs, the precise control of the dose and concentration for local delivery of GSMs remains a substantial challenge. The development of gaseous signaling molecule-releasing molecules provides a great tool for the safe and convenient delivery of GSMs. In this review article, we primarily focus on the recent development of macromolecular nanocarriers for the local delivery of various GSMs. Learning from the chemistry of small molecule-based donors, the integration of these gaseous signaling molecule-releasing molecules into polymeric matrices through physical encapsulation, post-modification, or direct polymerization approach renders it possible to fabricate numerous macromolecular nanocarriers with optimized pharmacokinetics and pharmacodynamics, revealing improved therapeutic performance than the small molecule analogs. The development of GSMs represents a new means for many disease treatments with unique therapeutic outcomes.

Stimuli Responsive Nitric Oxide-Based Nanomedicine for Synergistic Therapy

Gas therapy has received widespread attention from the medical community as an emerging and promising therapeutic approach to cancer treatment. Among all gas molecules, nitric oxide (NO) was the first one to be applied in the biomedical field for its intriguing properties and unique anti-tumor mechanisms which have become a research hotspot in recent years. Despite the great progress of NO in cancer therapy, the non-specific distribution of NO in vivo and its side effects on normal tissue at high concentrations have impaired its clinical application. Therefore, it is important to develop facile NO-based nanomedicines to achieve the on-demand release of NO in tumor tissue while avoiding the leakage of NO in normal tissue, which could enhance therapeutic efficacy and reduce side effects at the same time. In recent years, numerous studies have reported the design and development of NO-based nanomedicines which were triggered by exogenous stimulus (light, ultrasound, X-ray) or tumor endogenous signals (glutathione, weak acid, glucose). In this review, we summarized the design principles and release behaviors of NO-based nanomedicines upon various stimuli and their applications in synergistic cancer therapy. We also discuss the anti-tumor mechanisms of NO-based nanomedicines in vivo for enhanced cancer therapy. Moreover, we discuss the existing challenges and further perspectives in this field in the aim of furthering its development.

pH-Sensitive Dextran-Based Micelles from Copper-Free Click Reaction for Antitumor Drug Delivery

There remains a need to develop new strategies to fabricate dextran-based biocompatible drug delivery systems for safe and effective chemotherapy. Herein, a copper-free azide-propiolate ester click reaction was introduced for dextran modification to fabricate a pH-sensitive dextran-based drug delivery system. A pH-sensitive dextran-based micelle system, self-assembled from amphiphilic dextran-graft-poly(2-(diisopropylamino)ethyl methacrylate-co-2-(2',3',5'-triiodobenzoyl)ethyl methacrylate) or dextran-g-P(DPA-co-TIBMA), is reported for effective chemotherapy. The amphiphilic dextran-g-P(DPA-co-TIBMA) was prepared via reversible addition-fragmentation chain-transfer (RAFT) polymerization and copper-free azide-propiolate ester click reaction. Doxorubicin (DOX)-loaded dextran-g-P(DPA-co-TIBMA) micelles were prepared through self-assembly of DOX and dextran-g-P(DPA-co-TIBMA) in aqueous solution, and had a mean diameter of 154 nm and a drug loading content of 9.7 wt %. The release of DOX from DOX-loaded dextran-g-P(PDPA-co-TIBMA) micelles was slow at pH 7.4, but was greatly accelerated under acidic conditions (pH 6 and 5). Confocal laser scanning microscopy and flow cytometry experiments showed that the dextran-g-P(DPA-co-TIBMA) micelles could effectively deliver and release DOX in human breast cancer cell line (MCF-7 cells). MTT assay showed that dextran-g-P(DPA-co-TIBMA) exhibited excellent biocompatibility while DOX-loaded dextran-g-P(DPA-co-TIBMA) micelles have good antitumor efficacy in vitro. The in vivo therapeutic studies indicated that the DOX-loaded dextran-g-P(PDPA-co-TIBMA) micelles could effectively reduce the growth of tumor with little body weight reduction.

Synergistic Therapy Using Doxorubicin-Loading and Nitric Oxide-Generating Hollow Prussian Blue Nanoparticles with Photoacoustic Imaging Potential Against Breast Cancer

Introduction

Traditional antitumor chemotherapy faces great challenges, such as multi-drug resistance (MDR) and poor penetration into tumor tissues. The newly emerging nitric oxide (NO)-based gas therapy has been recognized to reduce MDR and has improved permeation into tumor tissue.

Methods

In this study, NO-generating prodrug sodium nitroprusside (SNP) was doped to hollow mesoporous Prussian blue (PB) nanoparticles to fabricate NO-generating nanoparticles (NO-PB), which was further loaded with doxorubicin (DOX).

Results

DOX loaded NO-PB (DOX-NO-PB) was released quicker at pH 6 compared with neutral pH, suggesting NO-PB may facilitate the release of loaded drug in acidic tumor tissue. The capacity of NO production by NO-PB was measured, and the results showed the presence of NO in the culture medium from 4T1 cells incubated with NO-PB and inside the cells. NP-PB could be detected by photoacoustic imaging (PAI) in tumor tissue in 4T1 tumor bearing mice, suggesting this nanoparticle may serve as contrast agent for the noninvasive diagnosis of tumor tissues. NO-PB suppressed the growth of tissues in 4T1 tumor bearing mice. DOX-NO-PB showed more potent anti-tumor effects in 4T1 cells and tumor bearing mice compared with free DOX and NO-PB alone, indicating that the combination of DOX and NO-PB exhibited synergistic effects on tumor suppression.

Conclusion

This study provides a novel nanocarrier for gas therapy with additional PAI imaging capacity. This nanocarrier can be utilized for combination therapy of NO and chemotherapeutics which may serve as theranostic agents.

Cascaded amplification of intracellular oxidative stress and reversion of multidrug resistance by nitric oxide prodrug based-supramolecular hydrogel for synergistic cancer chemotherapy

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Supramolecular hydrogel was facilely developed by self-assembly of NO prodrug conjugated hydrogelator sequence.

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The locoregionally sustained NO release from the hydrogel could be triggered by intracellular over-expressed GSH/GST.

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NO could effectively reverse the P-gp mediated MDR effect and facilitate the intracellular accumulation of DOX.

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This type of stimuli-sensitive NO delivery platform holds great potential for combating drug-resistance cancer.

Photogenerated Holes Mediated Nitric Oxide Production for Hypoxic Tumor Treatment

Nitric oxide (NO) is a gaseous signal molecule with multiple physiological functions, and it also plays a key role in cancer therapy. However, the production of NO which depends on O₂ or H₂ O₂ is limited within the tumor microenvironment, leading to unsatisfactory anticancer effect. Herein, we report a NO-based phototherapeutic strategy mediated by photogenerated holes for hypoxic tumors, which is achieved by irradiation of the poly-L-arginine modified carbon-dots-doped graphitic carbon nitride nanomaterial (ArgCCN). Upon red light irradiation, the photogenerated holes on ArgCCN oxidized water into H₂ O₂ which subsequently oxidized the arginine residues to produce NO. In vitro and in vivo experiments showed that the high concentration of NO produced by ArgCCN could induce cancer cell apoptosis. The presented phototherapeutic strategy is based on microenvironment-independent photogenerated holes mediated oxidation reaction, paving the way for the development of NO therapeutic strategy.

Advanced nitric oxide donors: chemical structure of NO drugs, NO nanomedicines and biomedical applications

Nitric oxide (NO), as an endogenous diatomic molecule, plays a key regulatory role in many physiological and pathological processes. This diatomic free radical has been shown to affect different physiological and cellular functions and participates in many regulatory functions ranging from changing the cardiovascular system to regulating neuronal functions. Thus, NO gas therapy as an emerging and promising treatment method has attracted increasing attention in the treatment of various pathological diseases. As is known, the physiological and pathological regulation of NO depends mainly on its location, exposure time and released dosage. However, NO gas lacks effective accumulation and controlled long-term gas releasing capacity at specific sites, resulting in limited therapeutic efficacy and potential side effects. Thus, researchers have developed various NO donors, but eventually found that it is still difficult to control the long-term release of NO. Inspired by the self-assembly properties of nanomaterials, researchers have realized that nanomaterials can be used to support NO donors to form nanomedicine to achieve spatial and temporal controlled release of NO. In this review, according to the history of the medicinal development of NO, we first summarize the chemical design of NO donors, NO prodrugs, and NO-conjugated drugs. Then, NO nanomedicines formed by various nanomaterials and NO donors depending on nanotechnology are highlighted. Finally, the biomedical applications of NO nanomedicine with optimized properties are summarized.

Nitric Oxide Nano-Delivery Systems for Cancer Therapeutics: Advances and Challenges

Nitric oxide (NO) plays important roles in various physiological and pathological functions and processes in the human body. Therapeutic application of NO molecules has been investigated in various diseases, including cardiovascular disease, cancer, and infections. However, the extremely short half-life of NO, which limits its clinical use considerably, along with non-specific distribution, has resulted in a low therapeutic index and undesired adverse effects. To overcome the drawbacks of using this gaseous signaling molecule, researchers in the last several decades have focused on innovative medical technologies, specifically nanoparticle-based drug delivery systems (DDSs), because these systems alter the biodistribution of the therapeutic agent through controlled release at the target tissues, resulting in a significant therapeutic drug effect. Thus, the application of nano-systems for NO delivery in the field of biomedicine, particularly in the development of new drugs for cancer treatment, has been increasing worldwide. In this review, we discuss NO delivery nanoparticle systems, with the aim of improving drug delivery development for conventional chemotherapies and controlling multidrug resistance in cancer treatments.

Enhancement of Skin Wound Healing by rhEGF-Loaded Carboxymethyl Chitosan Nanoparticles

The self-assembly of hydrophobically modified polymers has become a research hotspot due to its wide application in the biomedical field. Recombinant human epidermal growth factors (rhEGFs) are molecules that are able to enhance wound healing; however, they have a short half-life and require sustained action to enhance their mitogenic effect on epithelial cells. Here, we proposed a new delivery system to avoid the inhibition of rhEGF by various enzymes, thus improving its bioavailability and sustained release. The amphiphilic polymer was composed of conjugated linoleic acid (CLA) and carboxymethyl chitosan (CMCS), which were further characterized by fourier transformed infrared spectroscopy (FTIR) and 1H nuclear magnetic resonance (1H NMR). Then, the self-assembly behavior of CLA-CMCS (CC) polymer in water was observed in which the particle size of CC decreased from 196 to 155 nm with the degree of CLA substitution increasing. The nanoparticles were loaded with rhEGF and the maximum rhEGF loading efficiency (LE) of CC3 nanoparticles was 82.43 ± 3.14%. Furthermore, CC nanoparticles (NPs) exhibited no cytotoxicity for L929 cells, and cell proliferation activity was well preserved after rhEGF loading to CC-NPs and was comparable to that of free rhEGF. Topically applied rhEGF:CC-NPs significantly accelerated the wound-closure rate in full thickness, which was most probably due to its sustained release and enhanced skin permeation. In conclusion, carboxymethyl chitosan-based nanoparticles were constructed and showed good cytocompatibility. Moreover, these findings also demonstrated the therapeutic potential of rhEGF:CC-NPs as a topical wound-healing drug carrier.

Strategies for engineering advanced nanomedicines for gas therapy of cancer

As an emerging and promising treatment method, gas therapy has attracted more and more attention for treatment of inflammation-related diseases, especially cancer. However, therapeutic/therapy-assisted gases (NO, CO, H₂S, H₂, O₂, SO₂ and CO₂) and most of their prodrugs lack the abilities of active intratumoral accumulation and controlled gas release, resulting in limited cancer therapy efficacy and potential side effects. Therefore, development of nanomedicines to realize tumor-targeted and controlled release of therapeutic/therapy-assisted gases is greatly desired, and also the combination of other therapeutic modes with gas therapy by multifunctional nanocarrier platforms can augment cancer therapy efficacy and also reduce their side effects. The design of nanomedicines with these functions is vitally important, but challenging. In this review, we summarize a series of engineering strategies for construction of advanced gas-releasing nanomedicines from four aspects: (1) stimuli-responsive strategies for controlled gas release; (2) catalytic strategies for controlled gas release; (3) tumor-targeted gas delivery strategies; (4) multi-model combination strategies based on gas therapy. Moreover, we highlight current issues and gaps in knowledge, and envisage current trends and future prospects of advanced nanomedicines for gas therapy of cancer. This review aims to inspire and guide the engineering of advanced gas-releasing nanomedicines.

ROS and GSH-responsive S-nitrosoglutathione functionalized polymeric nanoparticles to overcome multidrug resistance in cancer

Multidrug resistance of cancer cells is one of the major obstacle for chemotherapeutic efficiency. Nitric oxide (NO) has raised the potential to overcome multidrug resistance (MDR) with low side effects. Herein, we report a reactive oxygen species (ROS) and glutathione (GSH) responsive nanoparticle for the delivery of NO prodrug such as S-nitrosoglutathione (GSNO), which was chemically conjugated to an amphiphilic block copolymer. The GSNO functionalized nanoparticles show high NO loading capacity, good stability and sustained NO release with specific GSH activated NO-releasing kinetics. Such GSNO functionalized nanoparticles delivered doxorubicin (DOX) in a ROS triggered manner and increased the intracellular accumulation of DOX. However, in normal healthy cells, showing physiological concentrations of ROS, these nanoparticles presented good biocompatibility. The present work indicated that these multifunctional nanoparticles can serve as effective co-delivery platforms of NO and DOX to selectively kill chemo-resistant cancer cells through increasing chemo-sensitivity. STATEMENT OF SIGNIFICANCE: In this work, we constructed nitric oxide donor (S-nitrosoglutathione, GSNO) functionalized amphiphilic copolymer (PEG-PPS-GSNO) to deliver doxorubicin (DOX). The developed PEG-PPS-GSNO@DOX nanoparticles presented high NO capacity, ROS triggered DOX release and GSH triggered NO release. Thus NO reversed the chemo-resistance in HepG2/ADR cells increasing intrcellular accumulation of DOX. Furthermore, these PEG-PPS-GSNO@DOX nanoparticles exhibited biocompatibility to healthy cells and toxicity to cancer cells, due to elevated ROS.

Photo-degradable micelles for co-delivery of nitric oxide and doxorubicin

Photo-degradable triblock copolymers enable the co-delivery of nitric oxide and doxorubicin exerting an improved therapeutic effect.

Nanomedicine-Enabled Photonic Thermogaseous Cancer Therapy

Local photothermal hyperthermia for tumor ablation and specific stimuliresponsive gas therapy feature the merits of remote operation, noninvasive intervention, and in situ tumor-specific activation in cancer-therapeutic biomedicine. Inspired by synergistic/sequential therapeutic modality, herein a novel therapeutic modality is reported based on the construction of two-dimensional (2D) core/shell-structured Nb2C-MSNs-SNO composite nanosheets for photonic thermogaseous therapy. A phototriggered thermogas-generating nanoreactor is designed via mesoporous silica layer coating on the surface of Nb2C MXene nanosheets, where the mesopores provide the reservoirs for NO donor (S-nitrosothiol (RSNO)), and the core of Nb2C produces heat shock upon second near-infrared biowindow (NIR-II) laser irradiation. The Nb2C-MSNs-SNO-enabled photonic thermogaseous therapy undergoes a sequential process of phototriggered heat production from the core of Nb2C and thermotriggered NO generation, together with photoacoustic-imaging (PAI) guidance and monitoring. The constructed Nb2C-MSNs-SNO nanoreactors exhibit high-NIR-induced photothermal effect, intense NIR-controlled NO release, and desirable PAI performance. Based on these unique theranostic properties of Nb2C-MSNs-SNO nanocomposites, sequential photonic thermogaseous therapy with limited systematic toxicity on efficiently suppressing tumor growth is achieved by PAI-guided NIR-controlled NO release as well as heat generation. Such a thermogaseous approach representes a stimuli-selective strategy for synergistic/sequential cancer treatment.

Functional Biodegradable Nitric Oxide Donor-Containing Polycarbonate-Based Micelles for Reduction-Triggered Drug Release and Overcoming Multidrug Resistance

Nitric oxide (NO), as a bioeffector to improve chemosensitivity by reversing multidrug resistance (MDR), is highly attractive for developing combinational delivery systems to deal with MDR tumors, while it is highly challenged by the stability and controlled release of NO during the pathway. Here we design and synthesize a cyclic nitrate trimethylene carbonate monomer (NTC), followed by ring-opening polymerization to prepare amphiphilic biodegradable polycarbonate-based copolymers as polymeric NO donors with tailored contents. The copolymer with desirable molecular weight is readily self-assembled to biodegradable micelles (NO-M) with a uniform size of 130 nm for highly stabilizing NO donors at the physiological conditions, while triggered NO release from micelles is performed at the intracellular reduction conditions. More importantly, NO-M shows superior inhibition of P-gP expression to enhance the chemosensitivity of multidrug-resistant MCF7 cells (MCF7/DOX^R). DOX-loaded NO-M (NO-M@DOX) realizes fast DOX release at the intracellular conditions, resulting in more intracellular DOX accumulation and higher antitumor activity mediated by the reduction-triggered NO/DOX release and NO-induced MDR reversal. Furthermore, the in vivo results show that NO-M@DOX effectively suppresses the MCF7/DOX^R tumor growth by a combination of directly NO-induced therapy and NO-mediated enhanced chemotherapy; meanwhile, the treatment with NO-M systems have much fewer side effects.

Near-infrared light switching nitric oxide nanoemitter for triple-combination therapy of multidrug resistant cancer

The multidrug resistance (MDR) of tumor cells often leads to the failure of chemotherapy against cancer. It is urgently needed to develop a safe and effective strategy of overcoming MDR for enhancing chemotherapy efficiency. In this work, one type of new folic acid-polyethylene glycol (FA-PEG) modified polydopamine nanoparticles (FAPPs) was synthesized for gas/chemo/photothermal triple-combination therapy of multidrug resistant cancer. The nanoparticles loaded nitric oxide (NO) donor act as a NO nanoemitter to generate NO via a NIR light irradiation switch, which has a great capacity of reversing MDR via inhibiting the overexpression of P-glycoprotein (P-gp) and cell respiration with the reduction of both the adenosine triphosphate (ATP) content and mitochondrial membrane potential (ΔΨ_m) in MDR tumor cells. Moreover, the amount of generated NO can be regulated by changing the action time of the nanoparticles. After that, the nanoparticles loaded chemotherapeutic agent (DOX) act as a photothermal-chemotherapy nanomedicine, which can release DOX with a high concentration in tumor cell for chemotherapy and simultaneously produce a large amount of heat for photothermal therapy under NIR irradiation. Finally, the gas/chemo/photothermal triple-combination therapy with the nanomedicines displays an excellent therapeutic efficacy in nude mice bearing MDR tumors. STATEMENT OF SIGNIFICANCE: The multidrug resistance (MDR) of tumor cells frequently leads to the failure of chemotherapy against cancer. It is urgently needed to develop a safe and effective strategy of overcoming MDR for enhancing chemotherapy efficiency. In this paper, a NIR light switching nitric oxide nanoemitter is successfully developed for gas/chemo/photothermal triple-combination therapy of multidrug resistant cancer. The controllably generated NO under NIR irradiation can effectively reverse multidrug resistance by inhibiting the overexpression of P-gp and cell respiration, significantly enhancing the chemotherapeutic agent concentration in tumor cells, and simultaneously a large amount of heat is produced for photothermal therapy.

Recent progress in drug delivery

Drug delivery systems (DDS) are defined as methods by which drugs are delivered to desired tissues, organs, cells and subcellular organs for drug release and absorption through a variety of drug carriers. Its usual purpose to improve the pharmacological activities of therapeutic drugs and to overcome problems such as limited solubility, drug aggregation, low bioavailability, poor biodistribution, lack of selectivity, or to reduce the side effects of therapeutic drugs. During 2015-2018, significant progress in the research on drug delivery systems has been achieved along with advances in related fields, such as pharmaceutical sciences, material sciences and biomedical sciences. This review provides a concise overview of current progress in this research area through its focus on the delivery strategies, construction techniques and specific examples. It is a valuable reference for pharmaceutical scientists who want to learn more about the design of drug delivery systems.

NIR-Responsive Polypeptide Nanocomposite Generates NO Gas, Mild Photothermia, and Chemotherapy to Reverse Multidrug-Resistant Cancer

Multidrug resistance (MDR) of cancers that results from overexpression of a P-glycoprotein (P-gp) transporter mainly causes chemotherapy (CT) failure and hinders clinical transitions of current polypeptide nanomedicines. Herein, a novel polypeptide nanocomposite PNOC-PDA that integrates heat-sensitive NO gas delivery and photothermal conversion attributes can overcome MDR and maximize CT; meanwhile the optimized CT and intracellular high-concentration NO gas can assist a mild photothermal therapy (PTT) to eradicate cancer cells. The triple therapies produced a superior and synergistic effect on MDR-reversal and killing MCF-7/ADR in vitro, and the P-gp expression level was downregulated to 46%, as confirmed by means of MTT, Western blot, flow cytometry, and confocal laser scanning microscopy. Significantly, by using one intravenous injection of PNOC-PDA/DOX and a single near-infrared irradiation, the triple therapies of mild PTT, NO gas therapy, and CT achieved complete MCF-7/ADR tumor ablation without skin damage, scarring, and tumor recurrence within 30 days. This work provides a versatile method for the fabrication of NIR-responsive polypeptide nanocomposite with intrinsic photothermal conversion and NO-releasing attributes, opening up a new avenue for reversing MDR in tumors.

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

Nitric oxide (NO) shows great role in tumor biology. Recent years, more and more researches utilized NO donor in tumor targeting drug delivery and treatment. In this review, we summarized the NO donors by their endogenous and exogenous stimuli. Then the application of NO donors, which was the main aim of the review, was discussed in detailed according to their functions, including inducing tumor cell apoptosis, reversing tumor multidrug resistance, inhibiting tumor metastasis and improving drug delivery.

Functional N-Substituted N-Thiocarboxyanhydrides as Modular Tools for Constructing H2S Donor Conjugates

We report a synthetic route toward a family of functional COS/H₂S-releasing N-substituted N-thiocarboxyanhydrides (NTAs) with functionalities to accommodate popular conjugation reactions, including olefin cross metathesis, thiol-ene, and copper-catalyzed azide-alkyne cycloaddition. The N-substituted NTAs were attached to small molecules, polymers, and a protein to synthesize novel H₂S donors convergently. All conjugates showed sustained H₂S release kinetics.

Enhancing Membrane-Disruptive Activity via Hydrophobic Phenylalanine and Lysine Tethered to Poly(aspartic acid)

Amphiphilic polymers with pH-responsive abilities have been widely used as carriers for intracellular delivery of bioactive substances, while their membrane-disruptive activity exerted on cells is a critical characteristic that determines delivery efficiency. Herein, we present a novel method to prepare amphiphilic and pH-responsive polymers by chemically tethering l-phenylalanine methyl ester and followed by N_ε-carbobenzyloxy-l-lysine benzyl ester to the side carboxylic acid groups of poly(aspartic acid). The obtained phenylalanine- and lysine-grafted polymer (PAsp- g-Phe)- g-Lys demonstrated enhanced membrane-disruptive activity at pH 7.4 in comparison with that of PAsp- g-Phe. Moreover, the pH-responsive behavior of the grafted polymers caused by the significantly intensified hydrophobicity could be modulated by the tethered amount of hydrophobic amino acids with phenyl groups. The prepared amphiphilic (PAsp- g-Phe)- g-Lys could facilitate entry of calcein into NIH/3T3 and HeLa cells at physiological pH values, possibly due to local chemical destabilization of cell membranes by the interaction between the polymer and membrane bilayers. Therefore, we have provided a feasible approach to prepare pH-responsive polymers with enhanced membrane-disruptive activity, and the phenylalanine- and lysine-grafted polymers could be a potential candidate for intracellular delivery of bioactive molecules in biomedical applications.

A switchable NO-releasing nanomedicine for enhanced cancer therapy and inhibition of metastasis

Clinical chemotherapy for cancer is limited by the physiological barrier of tumors, resulting in low drug delivery to tumors, poor efficacy of drugs and inability to block tumor metastasis. Here we developed an intelligent switchable nitric oxide (NO)-releasing nanoparticle, IPH-NO, which loads a photosensitizer (IR780) and the chemotherapy drug paclitaxel (PTX) into NO donor-S-nitrosated human serum albumin (HSA-NO). NO exhibits two effects based on its concentration: enhancement of chemotherapy by increasing the enhanced permeability and retention (EPR) effect at low concentrations and direct killing of cancer cells at high concentrations. IPH-NO can slowly release NO in the presence of glutathione to boost tumor vascular permeability and improve drug accumulation. Near-infrared light irradiation was utilized to induce a quick release of NO that can directly kill cancer cells at high concentrations. This combination of phototherapy and NO gas therapy activated by NIR together with chemotherapy showed significant effects in tumor inhibition. Furthermore, IPH-NO blocked tumor metastasis by inhibiting epithelial mesenchymal transition. PH-NO provides a novel strategy to control NO release at tumor site for drug accumulation and combination therapies, consequently potentiating the anticancer efficacy and inhibiting tumor metastasis.

A dual pH-sensitive liposomal system with charge-reversal and NO generation for overcoming multidrug resistance in cancer

In cancer therapy, chemotherapeutic drugs frequently encounter multidrug resistance (MDR) induced by the overexpression of drug transporters such as P-glycoprotein (P-gp). Herein, in order to overcome MDR and improve the effectiveness of chemotherapy, we developed a novel pH-sensitive charge-reversal and NO generation liposomal system by modifying a pH-sensitive polymer (PEG-PLL-DMA) on the surface of cationic liposomes for delivering a NO donor (DETA NONOate) and a chemotherapy drug (paclitaxel, PTX) into MDR cells. The proposed liposomal system (PTX/NO/DMA-L) exhibited a distinctive charge-reversal capacity, which was negatively charged under physiological conditions (pH 7.4) but could reverse to positive charge in a tumor microenvironment (pH 6.5) due to the cleavable amide linkages formed between PEG-PLL and DMA, leading to the improvement of cell uptake. Once arrived in the endosomes and lysosomes (pH 5.0), DETA NONOate was triggered to decompose and release NO, which further promoted the quick release of PTX and inhibited the P-gp mediated efflux. The charge-reversal, NO generation and NO-triggered rapid release of drugs could significantly increase the accumulation of PTX in tumors and eventually improve the antitumor efficacy. These results indicate that this dual pH-sensitive liposomal system is a highly promising approach for chemotherapy and may pave a new avenue for overcoming MDR in cancer.

A multi-component Cu2O@FePO4 core-cage structure to jointly promote fast electron transfer toward the highly sensitive in situ detection of nitric oxide

Electrochemical sensors actually involve an electrocatalytic process in efficient and selective energy conversion. In this work, we use different components to innovatively produce a core@cage material, in which the outer cage, iron phosphate, offers a high electrocatalytic ability to electrochemically oxidize NO, while the inner material, cuprous oxide, could absorb the intermediary HO- ions to kinetically promote NO oxidation for fast electron transfer, resulting in a strong synergistic effect. The unique core@cage structure also increases the active surface area and provides plenty of channels via the porous cage for significantly enhanced mass transport. The as-prepared core@cage NO sensor shows a high sensitivity of 326.09 μA cm-2 μM-1, which is the highest among the reported non-noble metal-based NO biosensors based on the electrooxidation scheme. A free-standing flexible NO sensor was further fabricated with the material for the in situ detection of NO released from cancer cells, demonstrating a low detection limit (0.45 nM) and a fast response time (0.8 s). This work holds great promise for its practical applications in the diagnosis or research of complicated biological processes, especially in real-time in situ detection approaches.

Lung cancer therapy using doxorubicin and curcumin combination: Targeted prodrug based, pH sensitive nanomedicine

Lung cancer is the leading cause of cancer death worldwide. To overcome the toxic side effects and multidrug resistance (MDR) during doxorubicin (DOX) chemotherapy, a urokinase plasminogen activator receptor (uPAR) targeting U11 peptide decorated, pH-sensitive, dual drugs co-encapsulated nanoparticles (NPs) system is employed in this study. A U11 peptide conjugated, pH-sensitive DOX prodrug (U11-DOX) was synthesized and used as materials to produce NPs. A curcumin (CUR) and U11-DOX co-encapsulated NPs system (U11-DOX/CUR NPs) was constructed to treat lung cancer. After the characterization of biophysical properties of this NPs system, synergistic chemotherapeutic efficacy was evaluated in both cultured cancer cells and tumor-bearing animal model. U11-DOX/CUR NPs had a uniformly spherical shape with a core-shell structure. The mean particle size and zeta potential of the U11-DOX/CUR NPs was 121.3 nm and -33.5 mV, with a DOX and CUR EE of 81.7 and 90.5%, respectively. The DOX release from U11-DOX/CUR NPs was 83.5, 55.2, and 32.8% correspondence to the pH of 5.0, 6.0 and 7.4. Cellular uptake efficiency of U11-DOX/CUR NPs was significantly higher than non U11 peptide decorated DOX/CUR NPs. U11-DOX/CUR NPs displayed a pronounced synergy effects in vitro and an obvious tumor tissue accumulation efficiency in vivo. In vivo antitumor experiment showed that U11-DOX/CUR NPs could inhibit the tumor growth to a level of 85%.In vitro and in vivo studies demonstrated that U11-DOX/CUR NPs is a sustained released, pH responsive, synergistic antitumor system. This study suggests that the U11-DOX/CUR NPs have promising potential for combination treatment of lung cancer.