Nanoparticle (Star Polymer) Delivery of Nitric Oxide Effectively Negates Pseudomonas aeruginosa Biofilm Formation

Hybrid thermosensitive hydrogel/amniotic membrane structure incorporating S-nitrosothiol microparticles: potential uses for controlled nitric oxide delivery

Insufficient levels of nitric oxide may lead to chronic and acute wounds. Additionally, it is crucial that nitric oxide is prepared in a controlled-release manner due to its gaseous nature and short half-life. To address this issue, utilizing nitric oxide donors, particularly S-nitrosothiols such as S-nitrosoglutathione (GSNO), could efficiently overcome instability and aid in biomedical applications. Decellularized human amniotic membranes are also best known for their anti-inflammatory, angiogenic, and antimicrobial properties to promote wound epithelization. In this study, a novel nitric oxide-generated wound dressing based on an amniotic membrane was investigated. This construct consisted of a chitosan/β-glycerophosphate thermosensitive hydrogel covered with a decellularized human amniotic layer embedded with GSNO-loaded polylactic acid microparticles. The structure of GSNO was confirmed by spectrometric, elemental, and chemical analyses. The GSNO-loaded microparticles had a diameter of 40.66 ± 6.92 µm, and an encapsulation efficiency of 45.6 ± 6.74%. The hybrid construct and GSNO-loaded microparticles enhanced the long-term stable release of GSNO compared to free GSNO. The construct released nitric oxide ranging from 24 to 68 nM/mg during 7 days. The thermosensitive hydrogel was formed at 32.7 ± 1 °C and had a porous structure with a pore size of 41.76 ± 9.76 µm. The MTT and live/dead assays performed on human dermal fibroblast cells demonstrated suitable cell viability and adhesion to the final construct. Further, hemolysis analysis revealed less than a 5% hemolysis rate due to negligible blood cell adhesion. Overall, the prepared hybrid construct demonstrated suitable characteristics as a potential active wound dressing capable of controlled nitric oxide delivery.

Quantum dots for bone tissue engineering

In confronting the global prevalence of bone-related disorders, bone tissue engineering (BTE) has developed into a critical discipline, seeking innovative materials to revolutionize treatment paradigms. Quantum dots (QDs), nanoscale semiconductor particles with tunable optical properties, are at the cutting edge of improving bone regeneration. This comprehensive review delves into the multifaceted roles that QDs play within the realm of BTE, emphasizing their potential to not only revolutionize imaging but also to osteogenesis, drug delivery, antimicrobial strategies and phototherapy. The customizable nature of QDs, attributed to their size-dependent optical and electronic properties, has been leveraged to develop precise imaging modalities, enabling the visualization of bone growth and scaffold integration at an unprecedented resolution. Their nanoscopic scale facilitates targeted drug delivery systems, ensuring the localized release of therapeutics. QDs also possess the potential to combat infections at bone defect sites, preventing and improving bacterial infections. Additionally, they can be used in phototherapy to stimulate important bone repair processes and work well with the immune system to improve the overall healing environment. In combination with current trendy artificial intelligence (AI) technology, the development of bone organoids can also be combined with QDs. While QDs demonstrate considerable promise in BTE, the transition from laboratory research to clinical application is fraught with challenges. Concerns regarding the biocompatibility, long-term stability of QDs within the biological environment, and the cost-effectiveness of their production pose significant hurdles to their clinical adoption. This review summarizes the potential of QDs in BTE and highlights the challenges that lie ahead. By overcoming these obstacles, more effective, efficient, and personalized bone regeneration strategies will emerge, offering new hope for patients suffering from debilitating bone diseases.

Bionanotechnology and bioMEMS (BNM): state-of-the-art applications, opportunities, and challenges

The development of micro- and nanotechnology for biomedical applications has defined the cutting edge of medical technology for over three decades, as advancements in fabrication technology developed originally in the semiconductor industry have been applied to solving ever-more complex problems in medicine and biology. These technologies are ideally suited to interfacing with life sciences, since they are on the scale lengths as cells (microns) and biomacromolecules (nanometers). In this paper, we review the state of the art in bionanotechnology and bioMEMS (collectively BNM), including developments and challenges in the areas of BNM, such as microfluidic organ-on-chip devices, oral drug delivery, emerging technologies for managing infectious diseases, 3D printed microfluidic devices, AC electrokinetics, flexible MEMS devices, implantable microdevices, paper-based microfluidic platforms for cellular analysis, and wearable sensors for point-of-care testing.

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.

Drug delivery strategies for antibiofilm therapy

Although new antibiofilm agents have been developed to prevent and eliminate pathogenic biofilms, their widespread clinical use is hindered by poor biocompatibility and bioavailability, unspecific interactions and insufficient local concentrations. The development of innovative drug delivery strategies can facilitate penetration of antimicrobials through biofilms, promote drug dispersal and synergistic bactericidal effects, and provide novel paradigms for clinical application. In this Review, we discuss the potential benefits of such emerging techniques for improving the clinical efficacy of antibiofilm agents, as well as highlighting the existing limitations and future prospects for these therapies in the clinic.

Nitric oxide-loaded nano- and microparticle platforms serving as potential new antifungal therapeutics

Fungal diseases are a leading threat to human health, especially in individuals with compromised immunity. Although there have been recent important advances in antifungal drug development, antifungal resistance, drug-drug interactions and difficulties in delivery remain major challenges. Among its pleiotropic actions, nitric oxide (NO) is a key molecule in host defense. We have developed a flexible nanoparticle platform that delivers sustained release of NO and have demonstrated the platform's efficacy against diverse bacteria as well as some fungal species. In this work, we investigate the effects of two NO-releasing particles against a panel of important human yeast. Our results demonstrate that the compounds are both effective against diverse yeast, including ascomycota and basidiomycota species, and that NO-releasing particles may be a potent addition to our armamentarium for the treatment of focal and disseminated mycoses.

Synthesis and Characterization of Nitric Oxide-Releasing Ampicillin as a Potential Strategy for Combatting Bacterial Biofilm Formation

Biofilm formation on biomaterial interfaces and the development of antibiotic-resistant bacteria have decreased the effectiveness of traditional antibiotic treatment of infections. In this project, ampicillin, a commonly used antibiotic, was conjugated with S-nitroso-N-acetylpenicillamine (SNAP), an S-nitrosothiol compound (RSNO) used for controlled nitric oxide (NO) release. This novel multifunctional molecule is the first of its kind to provide combined antibiotic and NO treatment of infectious pathogens. Characterization of the molecule included NMR, FTIR, and mass spectrometry. NO release behavior was also measured and compared to pure, unmodified SNAP. When evaluating the antimicrobial efficacy, the synthesized SNAPicillin molecule showed the lowest MIC value against Gram-negative Pseudomonas aeruginosa and Gram-positive methicillin-resistant Staphylococcus aureus compared to ampicillin and SNAP alone. SNAPicillin also displayed enhanced biofilm dispersal and killing of both bacterial strains when treating a 48 h biofilm preformed on a polymer surface. The antibacterial results combined with the biocompatibility of the molecule show great promise for infection prevention and treatment of polymeric interfaces to reduce medical device-related infections.

Nanomaterials and Coatings for Managing Antibiotic-Resistant Biofilms

Biofilms are a global health concern responsible for 65 to 80% of the total number of acute and persistent nosocomial infections, which lead to prolonged hospitalization and a huge economic burden to the healthcare systems. Biofilms are organized assemblages of surface-bound cells, which are enclosed in a self-produced extracellular polymer matrix (EPM) of polysaccharides, nucleic acids, lipids, and proteins. The EPM holds the pathogens together and provides a functional environment, enabling adhesion to living and non-living surfaces, mechanical stability, next to enhanced tolerance to host immune responses and conventional antibiotics compared to free-floating cells. Furthermore, the close proximity of cells in biofilms facilitates the horizontal transfer of genes, which is responsible for the development of antibiotic resistance. Given the growing number and impact of resistant bacteria, there is an urgent need to design novel strategies in order to outsmart bacterial evolutionary mechanisms. Antibiotic-free approaches that attenuate virulence through interruption of quorum sensing, prevent adhesion via EPM degradation, or kill pathogens by novel mechanisms that are less likely to cause resistance have gained considerable attention in the war against biofilm infections. Thereby, nanoformulation offers significant advantages due to the enhanced antibacterial efficacy and better penetration into the biofilm compared to bulk therapeutics of the same composition. This review highlights the latest developments in the field of nanoformulated quorum-quenching actives, antiadhesives, and bactericides, and their use as colloid suspensions and coatings on medical devices to reduce the incidence of biofilm-related infections.

Recent Developments in Nitric Oxide Donors and Delivery for Antimicrobial and Anti-Biofilm Applications

The use of nitric oxide (NO) is emerging as a promising, novel approach for the treatment of antibiotic resistant bacteria and biofilm infections. Depending on the concentration, NO can induce biofilm dispersal, increase bacteria susceptibility to antibiotic treatment, and induce cell damage or cell death via the formation of reactive oxygen or reactive nitrogen species. The use of NO is, however, limited by its reactivity, which can affect NO delivery to its target site and result in off-target effects. To overcome these issues, and enable spatial or temporal control over NO release, various strategies for the design of NO-releasing materials, including the incorporation of photo-activable, charge-switchable, or bacteria-targeting groups, have been developed. Other strategies have focused on increased NO storage and delivery by encapsulation or conjugation of NO donors within a single polymeric framework. This review compiles recent developments in NO drugs and NO-releasing materials designed for applications in antimicrobial or anti-biofilm treatment and discusses limitations and variability in biological responses in response to the use of NO for bacterial eradiation.

The Two Weapons against Bacterial Biofilms: Detection and Treatment

Bacterial biofilms are defined as complex aggregates of bacteria that grow attached to surfaces or are associated with interfaces. Bacteria within biofilms are embedded in a self-produced extracellular matrix made of polysaccharides, nucleic acids, and proteins. It is recognized that bacterial biofilms are responsible for the majority of microbial infections that occur in the human body, and that biofilm-related infections are extremely difficult to treat. This is related with the fact that microbial cells in biofilms exhibit increased resistance levels to antibiotics in comparison with planktonic (free-floating) cells. In the last years, the introduction into the market of novel compounds that can overcome the resistance to antimicrobial agents associated with biofilm infection has slowed down. If this situation is not altered, millions of lives are at risk, and this will also strongly affect the world economy. As such, research into the identification and eradication of biofilms is important for the future of human health. In this sense, this article provides an overview of techniques developed to detect and imaging biofilms as well as recent strategies that can be applied to treat biofilms during the several biofilm formation steps.

Photoactivatable Nitric Oxide-Releasing Gold Nanocages for Enhanced Hyperthermia Treatment of Biofilm-Associated Infections

With the increasing clinical use of invasive medical devices, various healthcare-associated infections (HAIs) caused by bacterial biofilm colonization of biomedical devices have posed serious threats to patients. The formation of biofilms makes it much more difficult and costly to treat infections. Here, we report a nitric oxide (NO)-releasing gold nanocage (AuNC@NO) that is stimulated by near-infrared (NIR) irradiation to deliver NO and generate hyperthermia for biofilm elimination. AuNC@NO was prepared by immobilizing a temperature-responsive NO donor onto gold nanocages (AuNCs) through thiol-gold interactions. AuNC@NO possesses stable and excellent photothermal conversion efficiency, as well as the characteristics of slow NO release at physiological temperature and on-demand quick NO release under NIR irradiation. Based on these features, AuNC@NO exhibits enhanced in vitro bactericidal and antibiofilm efficacy compared with AuNCs, which could achieve 4 orders of magnitude bacterial reduction and 85.4% biofilm elimination under NIR irradiation. In addition, we constructed an implant biofilm infection model and a subcutaneous biofilm infection model to evaluate the anti-infective effect of AuNC@NO. The in vivo results indicated that after 5 min of 0.5 W cm^-2 NIR irradiation, NO release from AuNC@NO was significantly accelerated, which induced the dispersal of methicillin-resistant Staphylococcus aureus (MRSA) biofilms and synergized with photothermal therapy (PTT) to kill planktonic MRSA that had lost its biofilm protection. Meanwhile, the surrounding tissues showed little damage because of controlled photothermal temperature and toxicity. In view of the above-mentioned results, the AuNC@NO nanocomposite developed in this work reveals potential application prospects as a useful antibiofilm agent in the field of biofilm-associated infection treatment.

Nitric Oxide Releasing Delivery Platforms: Design, Detection, Biomedical Applications, and Future Possibilities

Gasotransmitters belong to the subfamily of endogenous gaseous signaling molecules, which find a wide range of biomedical applications. Among the various gasotransmitters, nitric oxide (NO) has an enormous effect on the cardiovascular system. Apart from this, NO showed a pivotal role in neurological, respiratory, and immunological systems. Moreover, the paradoxical concentration-dependent activities make this gaseous signaling molecule more interesting. The gaseous NO has negligible stability in physiological conditions (37 °C, pH 7.4), which restricts their potential therapeutic applications. To overcome this issue, various NO delivering carriers were reported so far. Unfortunately, most of these NO donors have low stability, short half-life, or low NO payload. Herein, we review the synthesis of NO delivering motifs, development of macromolecular NO donors, their advantages/disadvantages, and biological applications. Various NO detection analytical techniques are discussed briefly, and finally, a viewpoint about the design of polymeric NO donors with improved physicochemical characteristics is predicted.

Nonviral siRNA delivery systems for pancreatic cancer therapy

The serious drawbacks of the conventional treatment of pancreatic ductal adenocarcinoma (PDAC) such as nonspecific toxicity and high resistance to chemo and radiation therapy, have prompted the development and application of countless small interfering RNA (siRNA)-based therapeutics. Recent advances in drug delivery systems hold great promise for improving siRNA-based therapeutics and developing a new class of drugs, known as nano-siRNA drugs. However, many fundamental questions, regarding toxicity, immunostimulation, and poor knowledge of nano-bio interactions, need to be addressed before clinical translation. In this review, we provide recent achievements in the design and development of various nonviral delivery vehicles for pancreatic cancer therapy. More importantly, codelivery of conventional anticancer drugs with siRNA as a new revolutionary pancreatic cancer combinational therapy is completely discussed.

Approaches for the inhibition and elimination of microbial biofilms using macromolecular agents

Biofilms are complex three-dimensional structures formed at interfaces by the vast majority of bacteria and fungi. These robust communities have an important detrimental impact on a wide range of industries and other facets of our daily lives, yet their removal is challenging owing to the high tolerance of biofilms towards conventional antimicrobial agents. This key issue has driven an urgent search for new innovative antibiofilm materials. Amongst these emerging approaches are highly promising materials that employ aqueous-soluble macromolecules, including peptides, proteins, synthetic polymers, and nanomaterials thereof, which exhibit a range of functionalities that can inhibit biofilm formation or detach and destroy organisms residing within established biofilms. In this Review, we outline the progress made in inhibiting and removing biofilms using macromolecular approaches, including a spotlight on cutting-edge materials that respond to environmental stimuli for "on-demand" antibiofilm activity, as well as synergistic multi-action antibiofilm materials. We also highlight materials that imitate and harness naturally derived species to achieve new and improved biomimetic and biohybrid antibiofilm materials. Finally, we share some speculative insights into possible future directions for this exciting and highly significant field of research.

Recent advances in the development of nitric oxide-releasing biomaterials and their application potentials in chronic wound healing

Chronic wounds, such as pressure ulcers, vascular ulcers and diabetic foot ulcers (DFUs), often stay in a state of pathological inflammation and suffer from persistent infection, excess inflammation, and hypoxia, thus they are difficult to be healed. Nitric oxide (NO) plays a critical role in the regulation of various wound healing processes, including inflammatory response, cell proliferation, collagen formation, antimicrobial action and angiogenesis. The important role of NO in wound healing attracts intensive research focus on NO-based wound healing therapy. However, the application of NO gas therapy needs to resolve the intrinsic shortcomings of gas therapy, such as short storage and release times as well as temporal and spatial uncontrollability of the release mode. So far, various types of NO donors, including organic nitrates (RONO2), nitrites (RONO), S-nitrosothiols (RSNOs), nitrosamines, N-diazeniumdiolates (NONOates), and metal-NO complexes, have been developed to solidify gaseous NO and they were further encapsulated in or conjugated onto a variety of biomaterial vectors to develop NO delivery systems. NO synthetic enzyme mimics to catalyze the production and release of NO from l-arginine have also been developed. This paper reviews recent advances of NO donors, biomaterial vectors, thus-formed NO delivery systems, as well as recently emerged NO synthetic enzyme mimics. Furthermore, this review also summarizes the functions of NO releasing biomaterials that would benefit chronic wound healing, including antibacterial properties and the promotion of angiogenesis, as well as the convenient combination of light/thermal induced NO release with light/thermal therapies, and the prospects for future developing trends in this area.

The role of nitric oxide in ocular surface physiology and pathophysiology

Nitric oxide (NO) has a wide array of biological functions including the regulation of vascular tone, neurotransmission, immunomodulation, stimulation of proinflammatory cytokine expression and antimicrobial action. These functions may depend on the type of isoform that is responsible for the synthesis of NO. NO is found in various ocular tissues playing a pivotal role in physiological mechanisms, namely regulating vascular tone in the uvea, retinal blood circulation, aqueous humor dynamics, neurotransmission and phototransduction in retinal layers. Unregulated production of NO in ocular tissues may result in production of toxic superoxide free radicals that participate in ocular diseases such as endotoxin-induced uveitis, ischemic proliferative retinopathy and neurotoxicity of optic nerve head in glaucoma. However, the role of NO on the ocular surface in mediating physiology and pathophysiological processes is not fully understood. Moreover, methods used to measure levels of NO in the biological samples of the ocular surface are not well established due to its rapid oxidation. The purpose of this review is to highlight the role of NO in the physiology and pathophysiology of ocular surface and propose suitable techniques to measure NO levels in ocular surface tissues and tears. This will improve the understanding of NO's role in ocular surface biology and the development of new NO-based therapies to treat various ocular surface diseases. Further, this review summarizes the biochemistry underpinning NO's antimicrobial action.

NO donors and NO delivery methods for controlling biofilms in chronic lung infections

Nitric oxide (NO), the highly reactive radical gas, provides an attractive strategy in the control of microbial infections. NO not only exhibits bactericidal effect at high concentrations but also prevents bacterial attachment and disperses biofilms at low, nontoxic concentrations, rendering bacteria less tolerant to antibiotic treatment. The endogenously generated NO by airway epithelium in healthy populations significantly contributes to the eradication of invading pathogens. However, this pathway is often compromised in patients suffering from chronic lung infections where biofilms dominate. Thus, exogenous supplementation of NO is suggested to improve the therapeutic outcomes of these infectious diseases. Compared to previous reviews focusing on the mechanism of NO-mediated biofilm inhibition, this review explores the applications of NO for inhibiting biofilms in chronic lung infections. It discusses how abnormal levels of NO in the airways contribute to chronic infections in cystic fibrosis (CF), chronic obstructive pulmonary disease (COPD), and primary ciliary dyskinesia (PCD) patients and why exogenous NO can be a promising antibiofilm strategy in clinical settings, as well as current and potential in vivo NO delivery methods. KEY POINTS : • The relationship between abnormal NO levels and biofilm development in lungs • The antibiofilm property of NO and current applications in lungs • Potential NO delivery methods and research directions in the future.

Photoresponsive Micelles Enabling Codelivery of Nitric Oxide and Formaldehyde for Combinatorial Antibacterial Applications

It is of particular interest to develop new antibacterial agents with low risk of drug resistance development and low toxicity toward mammalian cells to combat pathogen infections. Although gaseous signaling molecules (GSMs) such as nitric oxide (NO) and formaldehyde (FA) have broad-spectrum antibacterial performance and the low propensity of drug resistance development, many previous studies heavily focused on nanocarriers capable of delivering only one GSM. Herein, we developed a micellar nanoparticle platform that can simultaneously deliver NO and FA under visible light irradiation. An amphiphilic diblock copolymer of poly(ethylene oxide)-b-poly(4-((2-nitro-5-(((2-nitrobenzyl)oxy)methoxy)benzyl)(nitroso)amino)benzyl methacrylate) (PEO-b-PNNBM) was successfully synthesized through atom transfer radical polymerization (ATRP). The resulting diblock copolymer self-assembled into micellar nanoparticles without premature NO and FA leakage, whereas they underwent phototriggered disassembly with the corelease of NO and FA. We showed that the NO- and FA-releasing micellar nanoparticles exhibited a combinatorial antibacterial performance, efficiently killing both Gram-negative (e.g., Escherichia coli) and Gram-positive (e.g., Staphylococcus aureus) bacteria with low toxicity to mammalian cells and low hemolytic property. This work provides new insights into the development of GSM-based antibacterial agents.

Nanotechnology approaches for global infectious diseases

Infectious diseases are a major driver of morbidity and mortality globally. Treatment of malaria, tuberculosis and human immunodeficiency virus infection are particularly challenging, as indicated by the ongoing transmission and high mortality associated with these diseases. The formulation of new and existing drugs in nano-sized carriers promises to overcome several challenges associated with the treatment of these diseases, including low on-target bioavailability, sub-therapeutic drug accumulation in microbial sanctuaries and reservoirs, and low patient adherence due to drug-related toxicities and extended therapeutic regimens. Further, nanocarriers can be used for formulating vaccines, which represent a major weapon in our fight against infectious diseases. Here we review the current burden of infectious diseases with a focus on major drivers of morbidity and mortality. We then highlight how nanotechnology could aid in improving existing treatment modalities. We summarize our progress so far and outline potential future directions to maximize the impact of nanotechnology on the global population.

Synthetic Antimicrobial Polymers in Combination Therapy: Tackling Antibiotic Resistance

Antibiotic resistance is a critical global healthcare issue that urgently needs new effective solutions. While small molecule antibiotics have been safeguarding us for nearly a century since the discovery of penicillin by Alexander Fleming, the emergence of a new class of antimicrobials in the form of synthetic antimicrobial polymers, which was driven by the advances in controlled polymerization techniques and the desire to mimic naturally occurring antimicrobial peptides, could play a key role in fighting multidrug resistant bacteria in the near future. By harnessing the ability to control chemical and structural properties of polymers almost at will, synthetic antimicrobial polymers can be strategically utilized in combination therapy with various antimicrobial coagents in different formats to yield more potent (synergistic) outcomes. In this review, we present a short summary of the different combination therapies involving synthetic antimicrobial polymers, focusing on their combinations with nitric oxide, antibiotics, essential oils, and metal- and carbon-based inorganics.

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.

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.

Nanomaterial Nitric Oxide Delivery in Traumatic Orthopedic Regenerative Medicine

Achieving bone fracture union after trauma represents a major challenge for the orthopedic surgeon. Fracture non-healing has a multifactorial etiology and there are many risk factors for non-fusion. Environmental factors such as wound contamination, infection, and open fractures can contribute to non-healing, as can patient specific factors such as poor vascular status and improper immunologic response to fracture. Nitric oxide (NO) is a small, neutral, hydrophobic, highly reactive free radical that can diffuse across local cell membranes and exert paracrine functions in the vascular wall. This molecule plays a role in many biologic pathways, and participates in wound healing through decontamination, mediating inflammation, angiogenesis, and tissue remodeling. Additionally, NO is thought to play a role in fighting wound infection by mitigating growth of both Gram negative and Gram positive pathogens. Herein, we discuss recent developments in NO delivery mechanisms and potential implications for patients with bone fractures. NO donors are functional groups that store and release NO, independent of the enzymatic actions of NOS. Donor molecules include organic nitrates/nitrites, metal-NO complexes, and low molecular weight NO donors such as NONOates. Numerous advancements have also been made in developing mechanisms for localized nanomaterial delivery of nitric oxide to bone. NO-releasing aerogels, sol- gel derived nanomaterials, dendrimers, NO-releasing micelles, and core cross linked star (CCS) polymers are all discussed as potential avenues of NO delivery to bone. As a further target for improved fracture healing, 3d bone scaffolds have been developed to include potential for nanoparticulated NO release. These advancements are discussed in detail, and their potential therapeutic advantages are explored. This review aims to provide valuable insight for translational researchers who wish to improve the armamentarium of the feature trauma surgeon through use of NO mediated augmentation of bone healing.

Methionine-based carbon monoxide releasing polymer for the prevention of biofilm formation

A new water-soluble methionine-based CO releasing polymer shows slow and spontaneous release of CO with sustained-release kinetics, preventing biofilm formation against Pseudomonas aeruginosa.

Copper-doped metal–organic frameworks for the controlled generation of nitric oxide from endogenous S-nitrosothiols

We report the synthesis of a catalyst, copper-doped zeolitic imidazolate framework ZIF-8, that generates nitric oxide from naturally occurring endogenous nitric oxide donors, S-nitrosoglutathione and S-nitrosocysteine.

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.

State-of-the-art polymeric nanoparticles as promising therapeutic tools against human bacterial infections

Infectious diseases kill over 17 million people a year, among which bacterial infections stand out. From all the bacterial infections, tuberculosis, diarrhoea, meningitis, pneumonia, sexual transmission diseases and nosocomial infections are the most severe bacterial infections, which affect millions of people worldwide. Moreover, the indiscriminate use of antibiotic drugs in the last decades has triggered an increasing multiple resistance towards these drugs, which represent a serious global socioeconomic and public health risk. It is estimated that 33,000 and 35,000 people die yearly in Europe and the United States, respectively, as a direct result of antimicrobial resistance. For all these reasons, there is an emerging need to find novel alternatives to overcome these issues and reduced the morbidity and mortality associated to bacterial infectious diseases. In that sense, nanotechnological approaches, especially smart polymeric nanoparticles, has wrought a revolution in this field, providing an innovative therapeutic alternative able to improve the limitations encountered in available treatments and capable to be effective by theirselves. In this review, we examine the current status of most dangerous human infections, together with an in-depth discussion of the role of nanomedicine to overcome the current disadvantages, and specifically the most recent and innovative studies involving polymeric nanoparticles against most common bacterial infections of the human body.

Stimuli-responsive polymeric nanomaterials for rheumatoid arthritis therapy

Rheumatoid arthritis (RA) is a long-term inflammatory disease derived from an autoimmune disorder of the synovial membrane. Current therapeutic strategies for RA mainly aim to hamper the macrophages' proliferation and reduce the production of pro-inflammatory cytokines. Therefore, the accumulation of therapeutic agents targeted at the inflammatory site should be a crucial therapeutic strategy. Nowadays, the nanocarrier system incorporated with stimuli-responsive property is being intensively studied, showing the potentially tremendous value of specific therapy. Stimuli-responsive (i.e., pH, temperature, light, redox, and enzyme) polymeric nanomaterials, as an important component of nanoparticulate carriers, have been intensively developed for various diseases treatment. A survey of the literature suggests that the use of targeted nanocarriers to deliver therapeutic agents (nanotherapeutics) in the treatment of inflammatory arthritis remains largely unexplored. The lack of suitable stimuli-sensitive polymeric nanomaterials is one of the limitations. Herein, we provide an overview of drug delivery systems prepared from commonly used stimuli-sensitive polymeric nanomaterials and some inorganic agents that have potential in the treatment of RA. The current situation and challenges are also discussed to stimulate a novel thinking about the development of nanomedicine.

Optimization of nitric oxide donors for investigating biofilm dispersal response in Pseudomonas aeruginosa clinical isolates

Pseudomonas aeruginosa biofilms contribute heavily to chronic lung infection in cystic fibrosis patients, leading to morbidity and mortality. Nitric oxide (NO) has been shown to disperse P. aeruginosa biofilms in vitro, ex vivo and in clinical trials as a promising anti-biofilm agent. Traditional NO donors such as sodium nitroprusside (SNP) have been extensively employed in different studies. However, the dosage of SNP in different studies was not consistent, ranging from 500 nM to 500 μM. SNP is light sensitive and produces cyanide, which may lead to data misinterpretation and inaccurate predictions of dispersal responses in clinical settings. New NO donors and NO delivery methods have therefore been explored. Here we assessed 7 NO donors using P. aeruginosa PAO1 and determined that SNP and Spermine NONOate (S150) successfully reduced > 60% biomass within 24 and 2 h, respectively. While neither dosage posed toxicity towards bacterial cells, chemiluminescence assays showed that SNP only released NO upon light exposure in M9 media and S150 delivered much higher performance spontaneously. S150 was then tested on 13 different cystic fibrosis P. aeruginosa (CF-PA) isolates; most CF-PA biofilms were significantly dispersed by 250 μM S150. Our work therefore discovered a commercially available NO donor S150, which disperses CF-PA biofilms efficiently within a short period of time and without releasing cyanide, as an alternative of SNP in clinical trials in the future. KEY POINTS: • S150 performs the best in dispersing P. aeruginosa biofilms among 7 NO donors. • SNP only releases NO in the presence of light, while S150 releases NO spontaneously. • S150 successfully disperses biofilms formed by P. aeruginosa cystic fibrosis clinical isolates.

Self-targeting, zwitterionic micellar dispersants enhance antibiotic killing of infectious biofilms-An intravital imaging study in mice

Extracellular polymeric substances (EPS) hold infectious biofilms together and limit antimicrobial penetration and clinical infection control. Here, we present zwitterionic micelles as a previously unexplored, synthetic self-targeting dispersant. First, a pH-responsive poly(ε-caprolactone)-block-poly(quaternary-amino-ester) was synthesized and self-assembled with poly(ethylene glycol)-block-poly(ε-caprolactone) to form zwitterionic, mixed-shell polymeric micelles (ZW-MSPMs). In the acidic environment of staphylococcal biofilms, ZW-MSPMs became positively charged because of conversion of the zwitterionic poly(quaternary-amino-ester) to a cationic lactone ring. This allowed ZW-MSPMs to self-target, penetrate, and accumulate in staphylococcal biofilms in vitro. In vivo biofilm targeting by ZW-MSPMs was confirmed for staphylococcal biofilms grown underneath an implanted abdominal imaging window through direct imaging in living mice. ZW-MSPMs interacted strongly with important EPS components such as eDNA and protein to disperse biofilm and enhance ciprofloxacin efficacy toward remaining biofilm, both in vitro and in vivo. Zwitterionic micellar dispersants may aid infection control and enhance efficacy of existing antibiotics against remaining biofilm.

Photomediated post-fabrication modification of azlactone-functionalized gels for the development of hydrogel actuators

We report an approach for the photomediated post-fabrication modification of reactive, azlactone-containing gels using light-initiated deprotection of amines caged with 2-(nitrophenyl)propyloxycarbonyl (NPPOC). Photomediated modification of these gels can be used to generate a gradient in chemical functionality. When functionalized with tertiary amine groups, these gradient gels exhibit rapid and reversible shape deformations in response to changes in pH.

Free radical-releasing systems for targeting biofilms

The recent rise in antibiotic drug resistance and biofilm formation by microorganisms has driven scientists from different fields to develop newer strategies to target microorganisms responsible for infectious diseases. There is a growing interest in free radicals as therapeutic agents for antimicrobial applications. However, limitations such as short half-life has hindered their usage. Currently, several research groups are exploring various biomaterials that can prolong the half-life, increase storage duration and control the release of the therapeutic ranges of free radicals required for different applications, including biofilm eradication. This review paper initially provides a background to, and theoretical knowledge on, free radicals; and then proceeds to review studies that have employed various free radical-incorporated drug delivery systems as an approach to target biofilm formation and eradication. Some of the free radical releasing systems highlighted include polymers, nanoparticles and hydrogels, with a focus on biofilm eradication, where they impact significantly. The various challenges associated with their application are also discussed. Further, the review identifies future research and strategies that can potentiate the application of free radical-incorporated drug delivery systems for inhibiting biofilm formation and eradicating formed biofilms.

Nitric Oxide-Releasing Polymeric Materials for Antimicrobial Applications: A Review

Polymeric materials releasing nitric oxide have attracted significant attention for therapeutic use in recent years. As one of the gaseous signaling agents in eukaryotic cells, endogenously generated nitric oxide (NO) is also capable of regulating the behavior of bacteria as well as biofilm formation in many metabolic pathways. To overcome the drawbacks caused by the radical nature of NO, synthetic or natural polymers bearing NO releasing moiety have been prepared as nano-sized materials, coatings, and hydrogels. To successfully design these materials, the amount of NO released within a certain duration, the targeted pathogens and the trigger mechanisms upon external stimulation with light, temperature, and chemicals should be taken into consideration. Meanwhile, NO donors like S-nitrosothiols (RSNOs) and N-diazeniumdiolates (NONOates) have been widely utilized for developing antimicrobial polymeric agents through polymer-NO donor conjugation or physical encapsulation. In addition, antimicrobial materials with visible light responsive NO donor are also reported as strong and physiological friendly tools for rapid bacterial clearance. This review highlights approaches to delivery NO from different types of polymeric materials for combating diseases caused by pathogenic bacteria, which hopefully can inspire researchers facing common challenges in the coming 'post-antibiotic' era.

Antibiofilm Platform based on the Combination of Antimicrobial Polymers and Essential Oils

The development of potent strategies to counter microbial biofilm is an urgent priority in healthcare. The majority of bacterial infections in humans are biofilm related, however, effective treatments are still lacking especially for combating multidrug-resistant (MDR) strains. Herein, we report an effective antibiofilm platform based on the use of synthetic antimicrobial polymers in combination with essential oils, where the antimicrobial polymers play a secondary role as delivery vehicle for essential oils. Two ternary antimicrobial polymers consisting of cationic primary amines, low-fouling oligo(ethylene glycol) and hydrophobic ethylhexyl groups were synthesized in the form of random and block copolymers, and mixed with either carvacrol or eugenol. Coadministration of these compounds improved the efficacy against Pseudomonas aeruginosa biofilms compared to the individual compounds. We observed about a 60-75% and 70-85% biofilm inhibition effect for all tested combinations against wild-type P. aeruginosa PAO1 and MDR strain PA37, respectively, upon 6.5 h of incubation time. While both random and block copolymers demonstrated similar biofilm inhibition potencies in combination with essential oils, only the block copolymer acted synergistically with essential oils in killing biofilm. Treatment of PAO1 biofilm for 20 min with the block copolymer-oil combinations resulted in the killing of >99.99% of biofilm bacteria. This synergistic bactericidal activity is attributed to the targeted delivery of essential oils to the biofilm, driven by the electrostatic interaction between positively charged delivery vehicles, in the form of polymeric micelles, and negatively charged bacteria. This study thus highlights the advantage of combining essential oils and antimicrobial polymers as an effective avenue for antibacterial applications.

Depriving Bacterial Adhesion-Related Molecule to Inhibit Biofilm Formation Using CeO2 -Decorated Metal-Organic Frameworks

The formation of bacterial biofilm is one of the causes of antimicrobial resistance, often leading to persistent infections and a high fatality rate. Therefore, there is an urgent need to develop novel and effective strategies to inhibit biofilm formation. Adenosine triphosphate (ATP) plays an important role in bacterial adhesion and biofilm formation through stimulating cell lysis and extracellular DNA (eDNA) release. Herein, a simple and robust strategy for inhibiting biofilm formation is developed using CeO₂ -decorated porphyrin-based metal-organic frameworks (MOFs). The function of extracellular ATP (eATP) can be inhibited by CeO₂ nanoparticles, leading to the disruption of the initial adhesion of bacteria. Furthermore, planktonic bacteria can be killed by cytotoxic reactive oxygen species (ROS) generated by MOFs. As a consequence, the synergic effect of eATP deprivation and ROS generation presents excellent capacity to prevent biofilm formation, which may provide a new direction for designing flexible and effective biofilm-inhibiting systems.

WITHDRAWN: A star copolymer consisting of a β-cyclodextrin core and poly(amidoamine) dendron arms for co-delivering nitric oxide and triclosan for combined antibacterial effect

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The advanced role of carbon quantum dots in nanomedical applications

Carbon quantum dots (CQDs) have emerged as a potential material in the diverse fields of biomedical applications due to their numerous advantageous properties including fluorescence, water solubility, biocompatibility, low toxicity, small size and ease of modification, inexpensive scale-up production, and versatile conjugation with other nanoparticles. Thus, CQDs became a preferable choice in various biomedical applications such as nanocarriers for drugs, therapeutic genes, photosensitizers, and antibacterial molecules. Further, their potentials have also been verified in multifunctional diagnostic platforms, cellular and bacterial bio-imaging, development of theranostics nanomedicine, etc. This review provides a concise insight into the progress and evolution in the field of CQD research with respect to methods/materials available in bio-imaging, theranostics, cancer/gene therapy, diagnostics, etc. Further, our discussion is extended to explore the role of CQDs in nanomedicine which is considered to be the future of biomedicine. This study will thus help biomedical researchers in tapping the potential of CQDs to overcome various existing technological challenges.

Antibiofilm Nitric Oxide-Releasing Polydopamine Coatings

The growing number of patient morbidity related to nosocomial infections has placed an importance on the development of new antibacterial coatings for medical devices. Here, we utilize the versatile adhesion property of polydopamine (pDA) to design an antibacterial coating that possesses low-fouling and nitric oxide (NO)-releasing capabilities. To demonstrate this, glass substrates were functionalized with pDA via immersion in alkaline aqueous solution containing dopamine, followed by grafting of low-fouling polymer (poly(ethylene glycol) (PEG)) via Michael addition and subsequent formation of N-diazeniumdiolate functionalities (NO precursors) by purging with NO gas. X-ray photoelectron spectroscopy confirmed the successful grafting of PEG and formation of N-diazeniumdiolate on polydopamine-coated substrates. NO release from the coating was observed over 2 days, and NO loading is tunable by the pDA film thickness. The antibacterial efficiency of the coatings was assessed using Gram-negative Pseudomonas aeruginosa (i.e., wild-type PAO1 and multidrug-resistant PA37) and Gram-positive Staphylococcus aureus (ATCC 29213). The NO-releasing PEGylated pDA film inhibited biofilm attachment by 96 and 70% after exposure to bacterial culture solution for 24 and 36 h, respectively. In contrast, films that do not contain NO failed to prevent biofilm formation on the surfaces at these time points. Furthermore, this coating also showed 99.9, 97, and 99% killing efficiencies against surface-attached PAO1, PA37, and S. aureus bacteria. Overall, the combination of low-fouling PEG and antibacterial activity of NO in pDA films makes this coating a potential therapeutic option to inhibit biofilm formation on medical devices.

Quaternary Ammonium Salt-Based Cross-Linked Micelles to Combat Biofilm

Due to self-produced extracellular polymeric substances (EPS), biofilms are hard to eradicate by common antimicrobials. Herein, a new quaternary ammonium salt based cross-linked micelle (QAS@CM) was created to combat biofilms. The QAS@CM adsorbed first onto the biofilm surface through multicharged interaction, then penetrated the EPS in the form of nanoparticles and diffused throughout the films. By responding to the biofilm acid/lipase microenvironment, these nanoparticles would further break into quaternary ammonium oligomers and act as the polyvalent inhibitors to effectively destroy the established biofilm and kill the corresponding bacteria within it.

Linker chemistry dictates the delivery of a phototoxic organometallic rhenium(i) complex to human cervical cancer cells from core crosslinked star polymer nanoparticles

We have investigated core-crosslinked star polymer nanoparticles designed with tunable release chemistries as potential nanocarriers for a photoactive Re(i) organometallic complex. The nanoparticles consisted of a brush poly(oligo-ethylene glycol)methyl ether acrylate (POEGA) corona and a cross-linked core of non-biodegradable N,N'-methylenebis(acrylamide) (MBAA) and either pentafluorophenyl acrylate (PFPA), 3-vinyl benzaldehyde (VBA) or diacetone acrylamide (DAAM). Each star was modified with an amine functionalized photodynamic agent (i.e. a rhenium(i) organometallic complex) resulting in the formation of either a stable amide bond (POEGA-star-PFPA), or hydrolytically labile aldimine (POEGA-star-VBA) or ketimine bonds (POEGA-star-DAAM). These materials revealed linker dependent photo- and cytotoxicity when tested in vitro against non-cancerous lung fibroblast MRC-5 cells and HeLa human cervical cancer cells: the toxicity results correlated with final intracellular Re concentrations.

Inducing angiogenesis with the controlled release of nitric oxide from biodegradable and biocompatible copolymeric nanoparticles

PURPOSE

Nitric oxide (NO) can be clinically applied at low concentrations to regulate angiogenesis. However, studies using small molecule NO donors (N-diazeniumdiolate, S-nitrosothiol, etc) have yet to meet clinical requirements due to the short half-life and initial burst-release profile of NO donors. In this study, we report the feasibility of methoxy poly(ethylene glycol)-b-poly(lactic-co-glycolic acid) (mPEG-PLGA) nanoparticles (NPs) as NO-releasing polymers (NO-NPs) for inducing angiogenesis.

MATERIALS AND METHODS

The mPEG-PLGA copolymers were synthesized by typical ring-opening polymerization of lactide, glycolide and mPEG as macroinitiators. Double emulsion methods were used to prepare mPEG-PLGA NPs incorporating hydrophilic NONOate (dieth-ylenetriamine NONOate).

RESULTS

This liposomal NP encapsulates hydrophilic diethylenetriamine NONOate (70%±4%) more effectively than other previously reported materials. The application of NO-NPs at different ratios resulted in varying NO-release profiles with no significant cytotoxicity in various cell types: normal cells (fibroblasts, human umbilical vein endothelial cells and epithelial cells) and cancer cells (C6, A549 and MCF-7). The angiogenic potential of NO-NPs was confirmed in vitro by tube formation and ex vivo through an aorta ring assay. Tubular formation increased 189.8% in NO-NP-treated groups compared with that in the control group. Rat aorta exhibited robust sprouting angiogenesis in response to NO-NPs, indicating that NO was produced by polymeric NPs in a sustained manner.

CONCLUSION

These findings provide initial results for an angiogenesis-related drug development platform by a straightforward method with biocompatible polymers.