Sustained Release of Nitric Oxide-Mediated Angiogenesis and Nerve Repair by Mussel-Inspired Adaptable Microreservoirs for Brain Traumatic Injury Therapy

Traumatic brain injury (TBI) triggers inflammatory response and glial scarring, thus substantially hindering brain tissue repair. This process is exacerbated by the accumulation of activated immunocytes at the injury site, which contributes to scar formation and impedes tissue repair. In this study, a mussel-inspired nitric oxide-release microreservoir (MINOR) that combines the features of reactive oxygen species (ROS) scavengers and sustained NO release to promote angiogenesis and neurogenesis is developed for TBI therapy. The injectable MINOR fabricated using a microfluidic device exhibits excellent monodispersity and gel-like self-healing properties, thus allowing the maintenance of its structural integrity and functionality upon injection. Furthermore, polydopamine in the MINOR enhances cell adhesion, significantly reduces ROS levels, and suppresses inflammation. Moreover, a nitric oxide (NO) donor embedded into the MINOR enables the sustained release of NO, thus facilitating angiogenesis and mitigating inflammatory responses. By harnessing these synergistic effects, the biocompatible MINOR demonstrates remarkable efficacy in enhancing recovery in mice. These findings benefit future therapeutic interventions for patients with TBI.

Recent Advancements in Polymeric N-Nitrosamine-Based Nitric Oxide (NO) Donors and their Therapeutic Applications

Nitric oxide (NO), a gasotransmitter, is known for its wide range of effects in vasodilation, cardiac relaxation, and angiogenesis. This diatomic free radical also plays a pivotal role in reducing the risk of platelet aggregation and thrombosis. Furthermore, NO demonstrates promising potential in cancer therapy as well as in antibacterial and antibiofilm activities at higher concentrations. To leverage their biomedical activities, numerous NO donors have been developed. Among these, N-nitrosamines are emerging as a notable class, capable of releasing NO under suitable photoirradiation and finding a broad range of therapeutic applications. This review discusses the design, synthesis, and biological applications of polymeric N-nitrosamines, highlighting their advantages over small molecular NO donors in terms of stability, NO payload, and target-specific delivery. Additionally, various small-molecule N-nitrosamines are explored to provide a comprehensive overview of this burgeoning field. We anticipate that this review will aid in developing next-generation polymeric N-nitrosamines with improved physicochemical properties.

Postpolymerization Modification of Poly(2-vinyl-4,4-dimethyl azlactone) as a Versatile Strategy for Drug Conjugation and Stimuli-Responsive Release

Postpolymerization modification of highly defined "scaffold" polymers is a promising approach for overcoming the existing limitations of controlled radical polymerization such as batch-to-batch inconsistencies, accessibility to different monomers, and compatibility with harsh synthesis conditions. Using multiple physicochemical characterization techniques, we demonstrate that poly(2-vinyl-4,4-dimethyl azlactone) (PVDMA) scaffolds can be efficiently modified with a coumarin derivative, doxorubicin, and camptothecin small molecule drugs. Subsequently, we show that coumarin-modified PVDMA has a high cellular biocompatibility and that coumarin derivatives are liberated from the polymer in the intracellular environment for cytosolic accumulation. In addition, we report the pharmacokinetics, biodistribution, and antitumor efficacy of a PVDMA-based polymer for the first time, demonstrating unique accumulation patterns based on the administration route (i.e., intravenous vs oral), efficient tumor uptake, and tumor growth inhibition in 4T1 orthotopic triple negative breast cancer (TNBC) xenografts. This work establishes the utility of PVDMA as a versatile chemical platform for producing polymer-drug conjugates with a tunable, stimuli-responsive delivery.

Advances in Nanoplatforms for Immunotherapy Applications Targeting the Tumor Microenvironment

Cancer immunotherapy is a treatment method that activates or enhances the autoimmune response of the body to fight tumor growth and metastasis, has fewer toxic side effects and a longer-lasting efficacy than radiotherapy and chemotherapy, and has become an important means for the clinical treatment of cancer. However, clinical results from immunotherapy have shown that most patients lack responsiveness to immunotherapy and cannot benefit from this treatment strategy. The tumor microenvironment (TME) plays a critical role in the response to immunotherapy. The TME typically prevents effective lymphocyte activation, reducing their infiltration, and inhibiting the infiltration of effector T cells. According to the characteristic differences between the TME and normal tissues, various nanoplatforms with TME targeting and regulation properties have been developed for more precise regulation of the TME and have the ability to codeliver a variety of active pharmaceutical ingredients, thereby reducing systemic toxicity and improving the therapeutic effect of antitumor. In addition, the precise structural design of the nanoplatform can integrate specific functional motifs, such as surface-targeted ligands, degradable backbones, and TME stimulus-responsive components, into nanomedicines, thereby reshaping the tumor microenvironment, improving the body's immunosuppressive state, and enhancing the permeability of drugs in tumor tissues, in order to achieve controlled and stimulus-triggered release of load cargo. In this review, the physiological characteristics of the TME and the latest research regarding the application of TME-regulated nanoplatforms in improving antitumor immunotherapy will be described. Furthermore, the existing problems and further applications perspectives of TME-regulated platforms for cancer immunotherapy will also be discussed.

Nitric oxide releasing novel amino acid-derived polymeric nanotherapeutic with anti-inflammatory properties for rapid wound tissue regeneration

Endogenous gasotransmitter nitric oxide (NO) is a central signalling molecule that modulates wound healing by maintaining homeostasis, collagen formation, wound contraction, anti-microbial action and accelerating tissue regeneration. The optimum delivery of NO using nanoparticles (NPs) is clinically challenging; hence, it is drawing significant attention in wound healing. Herein, a novel polymeric nanoplatform loaded with sodium nitroprusside (SP) NPs was prepared and used for wound healing to obtain the sustained release of NO in therapeutic quantities. SP NPs-induced excellent proliferation (∼300%) of mouse fibroblast (L929) cells was observed. With an increase in the SP NPs dose at 200 μg mL-1 concentration, a 200% upsurge in proliferation was observed along with enhanced migration, and only 17.09 h were required to fill the 50% gap compared to 37.85 h required by the control group. Further, SP NPs showed an insignificant impact on the coagulation cascade, revealing safe wound-healing treatment when tested in isolated rat RBCs. Additionally, SP NPs exhibited excellent angiogenic activity at a 10 μg mL-1 dose. Moreover, the formulated SP nanoformulation is non-irritant, non-toxic, and does not produce any skin sensitivity reaction on the rat's skin. Further, an in vivo wound healing study revealed that within 11 days of treatment with SP nanoformulation, 99.2 ± 1.0% of the wound was closed, while in the control group, only 45.5 ± 3.8% was repaired. These results indicate that owing to sustained NO release, the SP NP and SP nanoformulations are paramount with enormous clinical potential for the regeneration of wound tissues.

Photostimulated Extended Nitric Oxide (NO) Release from Water-Soluble Block Copolymer to Enhance Antibacterial Activity

N-Nitrosamines are well established motifs to release nitric oxide (NO) under photoirradiation. Herein, a series of amphiphilic N-nitrosamine-based block copolymers (BCPx-NO) are developed to attain controlled NO release under photoirradiation (365 nm, 3.71 mW/cm2). The water-soluble BCPx-NO forms micellar architecture in aqueous medium and exhibits a sustained NO release of 92-160 μM within 11.5 h, which is 36.8-64.0% of the calculated value. To understand the NO release mechanism, a small molecular NO donor (NOD) resembling the NO releasing functional motif of BCPx-NO is synthesized, which displays a burst NO release in DMSO within 2.5 h. The radical nature of the released NO is confirmed by electron paramagnetic resonance (EPR) spectroscopy. The gradual NO release from micellar BCPx-NO enhances antibacterial activity over NOD and exhibits a superior bactericidal effect on Gram-positive Staphylococcus aureus. In relation to biomedical applications, this work offers a comprehensive insight into tuning light-triggered NO release to improve antibacterial activity.

Recent advance in self-assembled polymeric nanomedicines for gaseous signaling molecule delivery

Gaseous signaling molecules such as nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2 S) have recently been recognized as essential signal mediators that regulate diverse physiological and pathological processes in the human body. With the evolution of gaseous signaling molecule biology, their therapeutic applications have attracted growing attention. One of the challenges in translational research of gaseous signaling molecules is the lack of efficient and safe delivery systems. To tackle this issue, researchers developed a library of gas donors, which are low molecular weight compounds that can release gaseous signaling molecules upon decomposition under physiological conditions. Despite the significant efforts to control gaseous signaling molecule release from gas donors, the therapeutic potential of gaseous signaling molecules cannot be fully explored due to their unfavorable pharmacokinetics and toxic side effects. Recently, the use of nanoparticle-based gas donors, especially self-assembled polymeric gas donors, have emerged as a promising approach. In this review, we describe the development of conventional small gas donors and the challenges in their therapeutic applications. We then illustrate the concepts and critical aspects for designing self-assembled polymeric gas donors and discuss the advantages of this approach in gasotransmistter delivery. We also highlight recent efforts to develop the delivery systems for those molecules based on self-assembled polymeric nanostructures. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Biofilm heterogeneity-adaptive photoredox catalysis enables red light-triggered nitric oxide release for combating drug-resistant infections

The formation of biofilms is closely associated with persistent and chronic infections, and physiological heterogeneity such as pH and oxygen gradients renders biofilms highly resistant to conventional antibiotics. To date, effectively treating biofilm infections remains a significant challenge. Herein, we report the fabrication of micellar nanoparticles adapted to heterogeneous biofilm microenvironments, enabling nitric oxide (NO) release through two distinct photoredox catalysis mechanisms. The key design feature involves the use of tertiary amine (TA) moieties, which function as sacrificial agents to avoid the quenching of photocatalysts under normoxic and neutral pH conditions and proton acceptors at acidic pH to allow deep biofilm penetration. This biofilm-adaptive NO-releasing platform shows excellent antibiofilm activity against ciprofloxacin-resistant Pseudomonas aeruginosa (CRPA) biofilms both in vitro and in a mouse skin infection model, providing a strategy for combating biofilm heterogeneity and biofilm-related infections.

Mechanisms and Application of Gas-Based Anticancer Therapies

Cancer is still one of the major factors threatening public health, with morbidity and mortality rates at the forefront of the world. Clinical drawbacks, such as high toxicity and side effects of drug therapy, and easy recurrence after surgery affect its therapeutic effect. Gas signaling molecules are essential in maintaining biological homeostasis and physiological functions as specific chemical substances for biological information transfer. In recent years, the physiological regulatory functions of gas molecules in the cancer process have been gradually revealed and have shown broad application prospects in tumor therapy. In this paper, standard gas therapies are classified and introduced. Taking H2, CO2, NO, CO, H2S, and SO2 gases as examples, the research progress and application of gas therapies in malignant tumors are mainly introduced in terms of biological characteristics, anticancer mechanisms, and treatment strategies. Finally, the problems and prospects for developing gases as anticancer drugs are outlined.

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.

New Weapons to Fight against Staphylococcus aureus Skin Infections

The treatment of Staphylococcus aureus skin and soft tissue infections faces several challenges, such as the increased incidence of antibiotic-resistant strains and the fact that the antibiotics available to treat methicillin-resistant S. aureus present low bioavailability, are not easily metabolized, and cause severe secondary effects. Moreover, besides the susceptibility pattern of the S. aureus isolates detected in vitro, during patient treatment, the antibiotics may never encounter the bacteria because S. aureus hides within biofilms or inside eukaryotic cells. In addition, vascular compromise as well as other comorbidities of the patient may impede proper arrival to the skin when the antibiotic is given parenterally. In this manuscript, we revise some of the more promising strategies to improve antibiotic sensitivity, bioavailability, and delivery, including the combination of antibiotics with bactericidal nanomaterials, chemical inhibitors, antisense oligonucleotides, and lytic enzymes, among others. In addition, alternative non-antibiotic-based experimental therapies, including the delivery of antimicrobial peptides, bioactive glass nanoparticles or nanocrystalline cellulose, phototherapies, and hyperthermia, are also reviewed.

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.

A Mini Review of S-Nitrosoglutathione Loaded Nano/Micro-Formulation Strategies

As a potential therapeutic agent, the clinical application of S-nitrosoglutathione (GSNO) is limited because of its instability. Therefore, different formulations have been developed to protect GSNO from degradation, delivery and the release of GSNO at a physiological concentration in the active position. Due to the high water-solubility and small molecular-size of GSNO, the biggest challenges in the encapsulation step are low encapsulation efficiency and burst release. This review summarizes the different nano/micro-formulation strategies of a GSNO related delivery system to provide references for subsequent researchers interested in GSNO encapsulation.

Hydrogen Peroxide-Activated Nitric Oxide-Releasing Vancomycin-Loaded Electrostatic Complexation for Efficient Elimination of Methicillin-Resistant Staphylococcus aureus Abscesses

The treatment of subcutaneous abscesses has been greatly hindered due to the spread of drug-resistant strains such as methicillin-resistant Staphylococcus aureus (MRSA). Thus, alternative strategies are highly desired to complement conventional antibiotic therapies and surgical intervention. As one of such strategies, applications of nitric oxide (NO) have shown great potential in the treatment of bacteria-induced subcutaneous abscesses by improving the efficacy of many therapeutic methods. However, it is extremely challenging to achieve precise delivery and controlled release because of its gaseous nature. In the present study, an effective strategy was reported in which on demand hydrogen peroxide (H₂O₂)-activated nitric oxide-releasing vancomycin (Van)-loaded electrostatic complexation (Lipo/Van@Arg) was fabricated. In this system, Van was encapsulated into a negative-charged DSPG/Chol liposome (Lipo/Van) and electrostatically bound with the positive-charged l-arginine (l-Arg). As expected, Lipo/Van@Arg exhibited superior bacterial binding and biofilm penetration abilities. After being in the interior of the biofilms, Lipo/Van@Arg could be triggered by the endogenous H₂O₂ and effectively release NO. The released NO could exhibit combined antibacterial and biofilm eradication effects with Van. Moreover, an in vivo evaluation using a BALB/c mouse model of subcutaneous abscesses indicated that the combination treatment of NO and Van based on Lipo/Van@Arg could effectively eliminate MRSA from the abscesses, thereby preventing abscess recurrence. In summary, the Lipo/Van@Arg system developed in this study realized controlled delivery and precise release of NO, which had significant clinical implications in the efficient treatment of abscesses.

Regulation of pleiotropic physiological roles of nitric oxide signaling

Nitric Oxide (NO) is a highly diffusible, ubiquitous signaling molecule and a free radical that is naturally synthesized by our body. The pleiotropic effects of NO in biological systems are due to its reactivity with different molecules, such as molecular oxygen (O₂), superoxide anion, DNA, lipids, and proteins. There are several contradictory findings in the literature pertaining to its role in oncology. NO is a Janus-faced molecule shown to have both tumor promoting and tumoricidal effects, which depend on its concentration, duration of exposure, and location. A high concentration is shown to have cytotoxic effects by triggering apoptosis, and at a low concentration, NO promotes angiogenesis, metastasis, and tumor progression. Upregulated NO synthesis has been implicated as a causal factor in several pathophysiological conditions including cancer. This dichotomous effect makes it highly challenging to discover its true potential in cancer biology. Understanding the mechanisms by which NO acts in different cancers helps to develop NO based therapeutic strategies for cancer treatment. This review addresses the physiological role of this molecule, with a focus on its bimodal action in various types of cancers.

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.

Opportunities for Nitric Oxide in Potentiating Cancer Immunotherapy

Despite nearly 30 years of development and recent highlights of nitric oxide (NO) donors and NO delivery systems in anticancer therapy, the limited understanding of exogenous NO's effects on the immune system has prevented their advancement into clinical use. In particular, the effects of exogenously delivered NO differing from that of endogenous NO has obscured how the potential and functions of NO in anticancer therapy may be estimated and exploited despite the accumulating evidence of NO's cancer therapy-potentiating effects on the immune system. After introducing their fundamentals and characteristics, this review discusses the current mechanistic understanding of NO donors and delivery systems in modulating the immunogenicity of cancer cells as well as the differentiation and functions of innate and adaptive immune cells. Lastly, the potential for the complex modulatory effects of NO with the immune system to be leveraged for therapeutic applications is discussed in the context of recent advancements in the implementation of NO delivery systems for anticancer immunotherapy applications. SIGNIFICANCE STATEMENT: Despite a 30-year history and recent highlights of nitric oxide (NO) donors and delivery systems as anticancer therapeutics, their clinical translation has been limited. Increasing evidence of the complex interactions between NO and the immune system has revealed both the potential and hurdles in their clinical translation. This review summarizes the effects of exogenous NO on cancer and immune cells in vitro and elaborates these effects in the context of recent reports exploiting NO delivery systems in vivo in cancer therapy applications.

S-nitrosoglutathione functionalized polydopamine nanoparticles incorporated into chitosan/gelatin hydrogel films with NIR-controlled photothermal/NO-releasing therapy for enhanced wound healing

Nitric oxide (NO) has aroused wide interest in the treating infected wounds due to its characteristic functionalities. However, its utilization is limited due to its volatile properties, high reactivity, direct potential toxicity, and byproducts of NO donors limited its application. Herein, endogenously NO donor S-nitrosoglutathione (GSNO) was connected covalently to polydopamine nanoparticles (PDA-GSNO NPs) to minimize the loss of NO in aqueous medium. Meanwhile, near-infrared (NIR)-controlled NO release and photothermal therapy (PTT) was obtained through the photothermal conversion by PDA. Then chitosan (CS)/gelatin (GE) biocomposite hydrogel films with preferable biocompatibility, surface hydrophilicity, hydroabsorptivity, and mechanical adhesive properties were constructed. By embedding PDA-GSNO NPs into the films, a multifunctional wound dressing was fabricated. Under NIR light irradiation, the combination of PTT, NO-releasing, and CS antibacterial agents can strengthen the in vitro antimicrobial efficacy and in vivo wound healing activities. Meanwhile, the obtained wound dressing presented good biocompatibility. This work outlines an approach for combating bacterial infections and demonstrating the possibility for synergistic NO-releasing wound healing.

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.

Ultrasound-Mediated Release of Gaseous Signaling Molecules for Biomedical Applications

Although nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H₂ S) have been considered as notorious gas pollutants for decades, they are considered as endogenous gaseous signaling molecules (GSMs), which have been widely recognized for their important signaling functions and prominent medical applications in human physiology. To achieve local delivery of GSMs to optimize therapeutic efficacy and reduce systemic side effects, stimuli-responsive nanocarriers have been successfully developed. Among them, ultrasound is considered as an attractive theranostic modality that can be used to track drug carriers, trigger drug release, and improve drug deposition, etc. In this minireview, we summarize recent achievements in designing ultrasound-responsive nanocarriers for the controlled delivery of GSMs and their biomedical applications. This emerging research direction enables the controlled delivery of GSMs to deep tissues, and the combination of ultrasound imaging techniques offers many possibilities for the fabrication of new theranostic platforms. This article is protected by copyright. All rights reserved.

Versatile polymer-based strategies for antibacterial drug delivery systems and antibacterial coatings

Human health damage and economic losses due to bacterial infections are very serious worldwide. Excessive use of antibiotics has caused an increase in bacterial resistance. Fortunately, various non-antibiotic antibacterial materials...

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.

Macrophage Reprogramming and Cancer Therapeutics: Role of iNOS-Derived NO

Nitric oxide and its production by iNOS is an established mechanism critical to tumor promotion or suppression. Macrophages have important roles in immunity, development, and progression of cancer and have a controversial role in pro- and antitumoral effects. The tumor microenvironment consists of tumor-associated macrophages (TAM), among other cell types that influence the fate of the growing tumor. Depending on the microenvironment and various cues, macrophages polarize into a continuum represented by the M1-like pro-inflammatory phenotype or the anti-inflammatory M2-like phenotype; these two are predominant, while there are subsets and intermediates. Manipulating their plasticity through programming or reprogramming of M2-like to M1-like phenotypes presents the opportunity to maximize tumoricidal defenses. The dual role of iNOS-derived NO also influences TAM activity by repolarization to tumoricidal M1-type phenotype. Regulatory pathways and immunomodulation achieve this through miRNA that may inhibit the immunosuppressive tumor microenvironment. This review summarizes the classical physiology of macrophages and polarization, iNOS activities, and evidence towards TAM reprogramming with current information in glioblastoma and melanoma models, and the immunomodulatory and therapeutic options using iNOS or NO-dependent strategies.

Enhanced cancer therapeutic efficiency of NO combined with siRNA by caspase-3 responsive polymers

The combination of nitric oxide (NO) and siRNA is highly desirable for cancer therapy. Here, the furoxans-grafted PEI polymer (FDP) with caspase-3 responsive cleavable DEVD linker was synthesized, and used to bind siRNAs via electrostatic interaction and self-assembled into FDP/siRNA nanoplexes by hydrophobic force. After cellular uptake and lysosomal escape, the FDP/siRNA nanoplexes could achieve GSH-triggered NO release, and then increase the activity of caspase-3. The activated caspase-3 could specifically cleave the DEVD peptide sequence and enhance cell apoptosis. With the cleavage of DEVD peptide sequence, the disassembly of FDP/siRNA nanoplexes was further promoted, thereby resulting in increased siRNAs of ~40% were released at 48 h compared with the caspase-3 non-responsive FDnP/siRNA nanoplexes. By this way, cell apoptosis promotion and cell proliferation inhibition was achieved by siRNA-based downregulation of EGFR protein and the upregulated activity of caspase-3, followed by the enhanced cascade release of NO from FDP/siRNA nanoplexes. Furthermore, in vivo results demonstrated the improved anti-cancer efficiency of FDP/siEGFR nanoplexes without any detectable side effects. Therefore, it is believed that the caspase-3 responsive cleavable furoxans-grafted PEI polymers could provide a potential and efficient enhancement for cancer therapeutic efficiency by the co-delivery of nitric oxide and siRNA.

Phenylalanine-based poly(ester urea)s composite films with nitric oxide-releasing capability for anti-biofilm and infected wound healing applications

Infected wounds show delayed and incomplete healing processes and even render patients at a high risk of death due to the formed bacterial biofilms in the wound site, which protect bacteria against antimicrobial treatments and immune response. Nitric oxide based therapy is considered a promising strategy for eliminating biofilms and enhancing wound healing, which encounters a significant challenge of controlling the NO release behavior at the wound site. Herein, a kind of phenylalanine based poly(ester urea)s with high thermal stability are synthesized and fabricated to electrospun films as NO loading vehicle for infected wound treatment. The resultant films can continuously and stably release nitric oxide for 360 h with a total concentration of 1.15 μmol L^-1, which presents obvious advantages in killing the bacteria and removing biofilms. The results exhibit the films have no cytotoxicity and may accelerate the wound repair without causing inflammation, hemolysis, or cytotoxic reactions as well as stimulate the proliferation of fibroblasts and increase the synthesis of collagen. Therefore, the films may be a suitable NO releasing dressing for removing biofilms and repairing infected wounds.

High-Density Three-Dimensional Network of Covalently Linked Nitric Oxide Donors to Achieve Antibacterial and Antibiofilm Surfaces

Bacterial colonization on biomedical devices often leads to biofilms that are recalcitrant to antibiotic treatment and the leading cause of hospital-acquired infections. We have invented a novel pretreatment chemistry for device surfaces to produce a high-density three-dimensional (3-D) network of covalently linked S-nitrosothiol (RSNO), which is a nitric oxide (NO) donor. Poly(polyethylene glycol-hydroxyl-terminated) (i.e., PPEG-OH) brushes were grafted from an ozone-pretreated polyurethane (PU) surface. The high-density hydroxyl groups on the dangling PPEG-OH brushes then underwent condensation with a mercapto-silane (i.e., MPS, mercaptopropyl trimethoxysilane) followed by S-nitrosylation to produce a 3-D network of NO-releasing RSNO to form the PU/PPEG-OH-MPS-NO coating. This 3-D coating produces NO flux of up to 7 nmol/(cm² min), which is nearly 3 orders of magnitude higher than the picomole/(cm² min) levels of other NO-releasing biomedical implants previously reported. The covalent immobilization of RSNO avoids donor leaching and reduces the risks of cytotoxicity arising from leachable RSNO. Our coated PU surfaces display good biocompatibility and exhibit excellent antibiofilm formation activity in vitro (up to 99.99%) against a broad spectrum of Gram-positive and Gram-negative bacteria. Further, the high-density RSNO achieves nearly 99% and 99.9% in vivo reduction of Pseudomonas aeruginosa (P. aeruginosa) and methicillin-resistant Staphylococcus aureus (MRSA) in a murine subcutaneous implantation infection model. Our surface chemistry to create high NO payload without NO-donor leaching can be applied to many biomedical devices.

3D printed nitric oxide-releasing poly(acrylic acid)/F127/cellulose nanocrystal hydrogels

Hydrogels have been used as matrices for the topical delivery of nitric oxide (NO) for achieving vasodilation, wound healing and analgesic actions. More recently, supramolecular hydrogels comprised of poly(acrylic acid) (PAA) and micellar Pluronic F127 (F127), prepared by thermal reaction, emerged as a suitable matrix for the incorporation of hydrophilic NO donors, such as S-nitrosoglutathione (GSNO). Herein, we describe an innovative method for the three-dimensional (3D) printing of cellulose nanocrystal (CNC)-containing and semi-interpenetrating PAA/F127 hydrogels by PAA photopolymerization via digital light processing (DLP), in the absence of organic solvents. Scanning electron microscopy showed that, differently from typical porous PAA-based hydrogels, the 3D printed PAA/F127/CNC hydrogels have dense morphology. By using transmission electron microscopy we confirmed for the first time the presence of F127 micelles in the printable resin, and their preservation after the photopolymerization process. The F127 micelles conferred compressive recoverability to the 3D printed PAA/F127/CNC hydrogels, widening their potential applications as soft biomaterials. PAA/F127/CNC hydrogels charged with GSNO are shown to release NO spontaneously upon hydration at initial rates that depend on the GSNO charge and are higher in the presence of CNC. As local NO release may exert cell proliferation action, 3D printed PAA/F127/CNC/GSNO hydrogels may serve as a versatile soft biomaterial for local NO delivery in regenerative medicine and other biomedical applications.

Nanochemistry Modulates Intracellular Decomposition Routes of S-Nitrosothiol Modified Silica-Based Nanoparticles

Cellular delivery of nitric oxide (NO) using NO donor moieties such as S-nitrosothiol (SNO) is of great interest for various applications. However, understandings of the intracellular decomposition routes of SNO toward either NO or ammonia (NH₃ ) production are surprisingly scarce. Herein, the first report of SNO modified mesoporous organosilica nanoparticles with tetrasulfide bonds for enhanced intracellular NO delivery, ≈10 times higher than a commercial NO donor, is presented. The tetrasulfide chemistry modulates the SNO decomposition by shifting from NH₃ to NO production in glutathione rich cancer cells. This study provides a new strategy to control the NO level in biological systems.

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.

More than skin deep: using polymers to facilitate topical delivery of nitric oxide

Skin, the largest organ in the human body, provides several important functions, including providing protection from mechanical impacts, micro-organisms, radiation and chemicals; regulation of body temperature; the sensations of touch and temperature; and the synthesis of several substances including vitamin D, melanin, and keratin. Common dermatological disorders (CDDs) include inflammatory or immune-mediated skin diseases, skin infection, skin cancer, and wounds. In the treatment of skin disorders, topical administration has advantages over other routes of administration, and polymers are widely used as vehicles to facilitate the delivery of topical therapeutic agents, serving as matrices to keep therapeutic agents in contact with the skin. Nitric oxide (NO), a cellular signalling molecule, has attracted significant interest in treating a broad spectrum of diseases, including various skin disorders. However, there are a number of challenges in effectively delivering NO. It must be delivered in a controlled manner at sufficient concentrations to be efficacious and the delivery system must be stable during storage. The use of polymer-based systems to deliver NO topically can be an effective strategy to overcome these challenges. There are three main approaches for incorporating NO with polymers in topical delivery systems: (i) physical incorporation of NO donors into polymer bases; (ii) covalent attachment of NO donors to polymers; and (iii) encapsulation of NO donors in polymer-based particles. The latter two approaches provide the greatest control over NO release and have been used by numerous researchers in treating CDDs, including chronic wounds and skin cancer.

NO release regulated by doxorubicin as the green light-harvesting antenna

We report for the first time a NO photodonor (NOPD) operating with the widely used chemotherapeutic agent doxorubicin (DOX) as the light-harvesting antenna. This permits NO uncaging from an N-nitroso appendage upon selective excitation of DOX with highly biocompatible green light, without precluding its typical red emission. This NOPD effectively binds DNA and photodelivers NO nearby, representing an intriguing candidate for potential multimodal therapeutic applications based on the combination of DOX and NO.

Theranostic Activity of Nitric Oxide-Releasing Carbon Quantum Dots

The synthesis and anticancer cell activity of nitric oxide (NO)-releasing carbon quantum dots (CQDs) are described as potential theranostics. A series of secondary amine-modified CQDs were prepared using a hydrothermal method to modify β-cyclodextrin with hydroxyl and primary amine terminal functional groups. Subsequent reaction of the CQDs with NO gas under alkaline conditions yielded N-diazeniumdiolate NO donor-modified CQDs with adjustable NO payloads (0.2-1.1 μmol/mg) and release kinetics (half-lives from 29 to 79 min) depending on the level of secondary amines and surface functional groups. The anticancer activity of the NO-releasing CQDs against Pa14c, A549, and SW480 cancer cell lines proved to be dependent on both NO payloads and surface functionalizations. Primary amine-modified CQDs with NO payloads ∼1.11 μmol/mg exhibited the greatest anticancer action. A fluorescence microscopy study demonstrated the utility of these NO-releasing CQDs as dual NO-releasing and bioimaging probes.

Advances in inorganic-based colloidal nanovehicles functionalized for nitric oxide delivery

Nitric oxide (NO) is an important pharmaceutical agent of considerable therapeutic interest ascribed to its vasodilative, tumoricidal and antibacterial effects. Rapid development of functional nanomaterials has provided opportunities for us to achieve controllable exogenous delivery of NO. In the current review, a variety of functionalized colloidal nanovehicles that have been developed to date for nitric oxide delivery are reported. Specifically, we focus on inorganic nanomaterials such as semiconductor quantum dots, silica nanoparticles, upconversion nanomaterials, carbon/graphene nanodots, gold nanoparticles, iron oxide nanoparticles as the functional or/and supporting materials to carry NO donors. N-diazeniumdiolates, S-nitrosothiols, nitrosyl metal complexes and organic nitrates as main types of NO donors have their own unique properties and molecular structures. Conjugating the NO donors of different forms with appropriate nanomaterials results in NO delivery nanovehicles capable of releasing NO in a dose-controllable or/and on-demand manner. We also consider the therapeutic applications of those NO delivery nanovehicles, especially their applications for cancer therapy. In the end, we discuss possible future directions for developing exogenous NO delivery systems with more desired structure and improved performance. This review aims to offer the readers an overall view of the advances in functionalized colloidal nanovehicles for NO delivery. It will be attractive to scientists and researchers in the areas of material science, nanotechnology, biomedical engineering, chemical biology, etc.

Sonodynamic therapy-derived multimodal synergistic cancer therapy

Sonodynamic therapy (SDT) represents a promising modality that provides the possibility of non-invasively eliminating solid tumors in a site-directed manner. In light of the complexity and heterogeneity of tumors, more and more studies are attempting to combine SDT with other therapeutic methods so as to achieve better tumor treatment effect, which sheds new light on the potential of SDT-based synergistic therapeutics. Herein, the representative studies of SDT-instructed multimodal synergistic cancer therapy are comprehensively presented, such as sono-chemotherapy, sono-radiotherapy, sono-immunotherapy, and sono-chemodynamic therapy, etc., and their incorporate mechanisms are discussed in detail. The current challenges and future prospects to promote the advanced development of SDT-based nanomedicines in this burgeoning research field are highlighted. It is believed that such an emerging synergistic therapeutic modality based on SDT will play a more significant role in the field of tumor precision treatment medicine.

Challenging development of storable particles for oral delivery of a physiological nitric oxide donor

Nitric oxide (NO) deficiency is often associated with several acute and chronic diseases. NO donors and especially S-nitrosothiols such as S-nitrosoglutathione (GSNO) have been identified as promising therapeutic agents. Although their permeability through the intestinal barrier have recently be proved, suitable drug delivery systems have to be designed for their oral administration. This is especially challenging due to the physico-chemical features of these drugs: high hydrophilicity and high lability. In this paper, three types of particles were prepared with an Eudragit® polymer: nanoparticles and microparticles obtained with a water-in-oil-in-water emulsion/evaporation process versus microparticles obtained with a solid-in-oil-in-water emulsion/evaporation process. They had a similar encapsulation efficiency (around 30%), and could be freeze-dried then be stored at least one month without modification of their critical attributes (size and GSNO content). However, microparticles had a slightly slower in vitro release of GSNO than nanoparticles, and were able to boost by a factor of two the drug intestinal permeability (Caco-2 model). Altogether, this study brings new data about GSNO intestinal permeability and three ready-to-use formulations suitable for further preclinical studies with oral administration.

Modulation of Tumor Hypoxia by pH-Responsive Liposomes to Inhibit Mitochondrial Respiration for Enhancing Sonodynamic Therapy

Background and Purpose

Sonodynamic therapy (SDT) has been widely used for the noninvasive treatment of solid tumors, but the hypoxic tumor microenvironment limits its therapeutic effect. The current methods of reoxygenation to enhance SDT have limitations, prompting reconsideration of the design of therapeutic approaches. Here, we developed a tumor microenvironment-responsive nanoplatform by reducing oxygen consumption to overcome hypoxia-induced resistance to cancer therapy.

Methods

A pH-responsive drug-loaded liposome (MI-PEOz-lip) was prepared and used to reduce oxygen consumption, attenuating hypoxia-induced resistance to SDT and thereby improving therapeutic efficiency. Photoacoustic imaging (PAI) and fluorescence imaging (FI) of MI-PEOz-lip were evaluated in vitro and in breast xenograft tumor models. The pH-sensitive functionality of MI-PEOz-lip was applied for pH-triggered cargo release, and its capacity was evaluated. The MI-PEOz-lip-mediated SDT effect was compared with other treatments in vivo.

Results

MI-PEOz-lip was demonstrated to specifically accumulate in tumors. Metformin molecules in liposomes selectively accumulate in tumors by pH-responsive drug release to inhibit the mitochondrial respiratory chain while releasing IR780 to the tumor area. These pH-responsive liposomes demonstrated PAI and FI imaging capabilities in vitro and in vivo, providing potential for treatment guidance and monitoring. In particular, the prepared MI-PEOz-lip combined with ultrasound irradiation effectively inhibited breast tumors by producing toxic reactive singlet oxygen species (ROS), while the introduction of metformin inhibited mitochondrial respiration and reduced tumor oxygen consumption, resulting in excellent sonodynamic therapy performance compared with other treatments.

Conclusion

In this study, we present a novel strategy to achieve high therapeutic efficacy of SDT by the rational design of multifunctional nanoplatforms. This work provides a new strategy that can solve the current problems of inefficient oxygen delivery strategies and weaken resistance to various oxygen-dependent therapies.

Nitric Oxide-Releasing S-Nitrosoglutathione-Conjugated Poly(Lactic-Co-Glycolic Acid) Nanoparticles for the Treatment of MRSA-Infected Cutaneous Wounds

S-nitrosoglutathione (GSNO) has emerged as a potent agent for the treatment of infected cutaneous wounds. However, fabrication of GSNO-containing nanoparticles has been challenging due to its high hydrophilicity and degradability. The present study aimed to fabricate nanoparticles using newly synthesized GSNO-conjugated poly(lactic-co-glycolic acid) (PLGA) (GSNO-PLGA; GPNPs). Since hydrophilic GSNO was covalently bound to hydrophobic PLGA, loss of GSNO during the nanoparticle fabrication process was minimized, resulting in sufficient loading efficiency (2.32% of GSNO, 0.07 μmol/mg of NO). Real-time NO release analysis revealed biphasic NO release by GPNPs, including initial burst release within 3 min and continuous controlled release for up to 11.27 h, due to the differential degradation rates of the –SNO groups located at the surface and inside of GPNPs. Since GPNPs could deliver NO more efficiently than GSNO in response to increased interaction with bacteria, the former showed enhanced antibacterial effects against methicillin-resistant Staphylococcus aureus (MRSA) at the same equivalent concentrations of NO. Finally, the facilitating effects of GPNPs on infected wound healing were demonstrated in MRSA-challenged full-thickness wound mouse model. Collectively, the results suggested GPNPs as an ideal nanoparticle formulation for the treatment of MRSA-infected cutaneous wounds.

Sensitizing activities of nitric oxide donors for cancer resistance to anticancer therapeutic drugs

Cancer is not a single disease but it constitutes a large variety of different types that are also different from each other phenotypically and molecularly. Although the standard treatments have resulted in clinical responses in a subset of patients, though, many patients relapse and no longer respond to further treatments. Hence, both the innate and adaptive resistance to treatments are the main challenges in today's treatment strategies. Noteworthy, several novel treatment strategies, particularly immunotherapies, used alone or in combination, have been developed and that have significantly improved the therapeutic response of many unresponsive cancer patients. Nevertheless, even with the latest new developments of therapeutics that were effective in a larger subset of patients, there is still an urgent need to treat the remaining unresponsive subset of patients. This requires the development of new targeting agents of superior antitumor activities that will lead to overcoming the unaffected resistance by current treatments. There has been accumulating evidence suggesting nitric oxide donors as such targeting agents and considering their pleiotropic antitumor activities, including both the reversal of chemo and immuno-resistance of various unresponsive resistant cancers. The in vitro and in vivo preclinical findings corroborate the sensitizing antitumor activities of nitric oxide donors. In addition, a few clinical findings with NO donors that have been applied in patients have corroborated their antitumor and sensitizing activities in combination with standard therapies. In this review, the role and underlying mechanisms by which nitric oxide donors sensitize cancer resistant cells to both chemotherapy and immunotherapy are briefly described.

Low-Temperature Trigger Nitric Oxide Nanogenerators for Enhanced Mild Photothermal Therapy

Surmounting the restriction issues of nitric oxide (NO) delivery to realize their precious on-demand release is highly beneficial for the widespread deployment of gas therapy for application in biomedicine. Herein, by employing core-shell structure Au@SiO₂ nanomaterials with high photothermal performance, a novel strategy was proposed by integrating photothermal conversion nanomaterials and heat-triggered NO donors (RSNO) into a nanoplatform, which achieved photothermal therapy (PTT)-enhanced NO gas therapy under near-infrared (NIR) radiation. Specifically, 2-phenylethynesulfonamide (PES), an inhibitor of heat shock protein 70 (HSP-70), was loaded into the NO nanogenerators to realize effective low-temperature (∼45 °C) PTT. The obtained results showed that the near-infrared radiation (NIR) mediated mild PTT and gas therapy by releasing NO showed a substantially improved synergistic effect based on in vitro and in vivo results in breast cancer (MCF-7) models. Our study points out a strategy to realize mild photothermal therapy by inhibiting the expression of HSP-70 and simultaneously providing an avenue to achieve controllable release of NO. More important, this research highlights the great potential of multifunctional therapeutic agents in the synergistic treatment of cancer.

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.

Chitosan derivatives co-delivering nitric oxide and methicillin for the effective therapy to the methicillin-resistant S. aureus infection

We developed a co-delivery system of nitric oxide (NO) and antibiotic for the antibiotic-resistant bacterial infection therapy. The NO could disperse the bacterial biofilms and convert the bacteria into an antibiotic-susceptible planktonic form. Using the chitosan-graft-poly(amidoamine) dendrimer (CS-PAMAM) as the co-delivery system, methicillin (MET) and NO were conjugated successively to form CS-PAMAM-MET/NONOate. The positive CS-PAMAM could efficiently capture the negatively charged bacteria and PAMAM provide abundant reaction points for high payloads of NO and MET. The CS-PAMAM-MET/NONOate displayed effective and combined antibacterial activity to the E. coli and S. aureus. Particularly, for the MET-resistant S. aureus (MRSA), the CS-PAMAM-MET/NONOate displayed the synergistic antibacterial activity. In vivo wound healing assays also confirmed that CS-PAMAM-MET/NONOate could heal the infection formed by MRSA and then accelerate the wound healing effectively. Moreover, CS-PAMAM-MET/NONOate showed no toxicity towards 3T3 cells in vitro and rats in vivo, providing a readily but high-efficient strategy to drug-resistant bacterial infection therapy.

Multiple Functions Integrated inside a Single Molecule for Amplification of Photodynamic Therapy Activity

Nitric oxide (NO) can play both prosurvival and prodeath roles in photodynamic therapy (PDT). The generation efficiency of peroxynitrite anions (ONOO^-), by NO and superoxide anions (O₂^•-), significantly influenced the outcome. Reports indicated that such efficiency is closely related to the distance between NO and O₂^•-. Thus, in this manuscript, l-arginine (Arg) ethyl ester-modified zinc phthalocyanine (Arg-ZnPc) was designed and synthesized as a photosensitizer (PS) and NO donor. Post light irradiation, the guanido of Arg-ZnPc can be effectively oxidized by the generated reactive oxygen species (ROS) in the PDT process to release NO. Such a strategy could ensure O₂^•- and NO generation in the same place at the same time to guarantee effective ONOO^- formation. In addition, NO has other multiple synergistic cancer treatment functions, including tumor tissue vasodilatation for drug extravasation promotion, P-glycoprotein (P-gp) downregulation for drug efflux inhibition, and glutathione depletion for cancer cell endogenous antioxidant defense destruction. In vitro and in vivo results indicated that the effective ONOO^- formation and multiple functions of Arg-ZnPc could synergistically enhance its PDT activity and ensure satisfactory cancer treatment outcome.