Polydopamine Hollow Nanoparticle Functionalized with N-diazeniumdiolates as a Nitric Oxide Delivery Carrier for Antibacterial Therapy

An ultrasound-controllable ROS-responsive nanoplatform for O2 and NO generation to enhance sonodynamic therapy against multidrug-resistant bacterial infections

Antimicrobial sonodynamic therapy (SDT) has broad application potential in the eradication of multidrug-resistant (MDR) bacterial infections due to its non-invasiveness, absence of resistance concern, and high cytotoxicity. However, the hypoxic infection microenvironment and the rapid depletion of O2 during SDT severely limit the therapeutic efficacy of SDT. Herein, an ultrasound-controllable ROS-responsive nanoplatform (FOT/Fe3O4@Lipo-ICG) was constructed and prepared by encapsulating FOT and Fe3O4 nanoparticles (Fe3O4 NPs) within sonosensitiser ICG-modified liposomes. Both in vitro and in vivo, we observed that ICG conjugation on the surface of liposomes could effectively maintain good dispersion and prevent ICG aggregates in complex biological matrices. In addition, liposomes could significantly block the catalytic activity of Fe3O4 NPs, as well as the release of FOT, whereas upon US irradiation, the catalytic activity of Fe3O4 NPs was recovered to catalyse the decomposition of endogenous H2O2 into O2 and ˙OH. Meanwhile, the FOT was successfully released to react with endogenous glutathione to sequentially produce NO. Based on the aforementioned advantages, the FOT/Fe3O4@Lipo-ICG demonstrated potent efficacy in eradicating methicillin-resistant Staphylococcus aureus-induced local infection and sepsis resulting from local infection. Thus, the developed US-controllable nanoplatform offers a promising strategy for enhancing SDT for eradicating MDR bacterial infections.

In Situ Forming of Nitric Oxide and Electric Stimulus for Nerve Therapy by Wireless Chargeable Gold Yarn-Dynamos

Endogenous signals, namely nitric oxide (NO) and electrons, play a crucial role in regulating cell fate as well as the vascular and neuronal systems. Unfortunately, utilizing NO and electrical stimulation in clinical settings can be challenging due to NO's short half-life and the invasive electrodes required for electrical stimulation. Additionally, there is a lack of tools to spatiotemporally control gas release and electrical stimulation. To address these issues, an "electromagnetic messenger" approach that employs on-demand high-frequency magnetic field (HFMF) to trigger NO release and electrical stimulation for restoring brain function in cases of traumatic brain injury is introduced. The system comprises a NO donor (poly(S-nitrosoglutathione), pGSNO)-conjugated on a gold yarn-dynamos (GY) and embedded in an implantable silk in a microneedle. When subjected to HFMF, conductive GY induces eddy currents that stimulate the release of NO from pGSNO. This process significantly enhances neural stem cell (NSC) synapses' differentiation and growth. The combined strategy of using NO and electrical stimulation to inhibit inflammation, angiogenesis, and neuronal interrogation in traumatic brain injury is demonstrated in vivo.

Nitric Oxide-Assisted Photodynamic Therapy for Enhanced Penetration and Hypoxic Bacterial Biofilm Elimination

The presence of a biofilm matrix barrier and hypoxic microenvironment within the biofilm significantly impedes the efficacy of photodynamic therapy for bacterial biofilm infections. Herein, a phototherapeutic nanoagent with type-I photodynamic behavior and nitric oxide (NO) release performance is reported for overcoming biofilm-associated infectious diseases. Sodium nitroprusside (SNP), a NO donor, is loaded onto amino-modified mesoporous silica nanoparticles (MSN) to form MSN@SNP NPs. The resulting nanoparticles are further modified with a porphyrin-based metal-organic framework (Ti-TCPP MOF) to obtain MSN@MOF/SNP NPs (MMS NPs) for phototherapeutic applications. In the hypoxia biofilm microenvironment, the MMS NPs release NO to enhance the biofilm permeability and induce the generation of hydroxyl radical (•OH) and superoxide anion radical (O2 •- ) via Type-I photodynamic pathway under laser irradiation. Subsequently, the biofilm-associated infections are effectively eliminated through reactive oxygen species (ROS) and NO gas synergistic therapy. In addition, NO also stimulates collagen deposition and promotes angiogenesis in vivo. Therefore, the MMS NPs efficiently treat biofilm-related infections, providing an alternative approach to combat biofilm-associated infectious diseases.

An Overview of Stimuli-Responsive Intelligent Antibacterial Nanomaterials

Drug-resistant bacteria and infectious diseases associated with biofilms pose a significant global health threat. The integration and advancement of nanotechnology in antibacterial research offer a promising avenue to combat bacterial resistance. Nanomaterials possess numerous advantages, such as customizable designs, adjustable shapes and sizes, and the ability to synergistically utilize multiple active components, allowing for precise targeting based on specific microenvironmental variations. They serve as a promising alternative to antibiotics with diverse medical applications. Here, we discuss the formation of bacterial resistance and antibacterial strategies, and focuses on utilizing the distinctive physicochemical properties of nanomaterials to achieve inherent antibacterial effects by investigating the mechanisms of bacterial resistance. Additionally, we discuss the advancements in developing intelligent nanoscale antibacterial agents that exhibit responsiveness to both endogenous and exogenous responsive stimuli. These nanomaterials hold potential for enhanced antibacterial efficacy by utilizing stimuli such as pH, temperature, light, or ultrasound. Finally, we provide a comprehensive outlook on the existing challenges and future clinical prospects, offering valuable insights for the development of safer and more effective antibacterial nanomaterials.

Advanced Nitric Oxide Generating Nanomedicine for Therapeutic Applications

Nitric oxide (NO), a gaseous transmitter extensively present in the human body, regulates vascular relaxation, immune response, inflammation, neurotransmission, and other crucial functions. Nitrite donors have been used clinically to treat angina, heart failure, pulmonary hypertension, and erectile dysfunction. Based on NO's vast biological functions, it further can treat tumors, bacteria/biofilms and other infections, wound healing, eye diseases, and osteoporosis. However, delivering NO is challenging due to uncontrolled blood circulation release and a half-life of under five seconds. With advanced biotechnology and the development of nanomedicine, NO donors packaged with multifunctional nanocarriers by physically embedding or chemically conjugating have been reported to show improved therapeutic efficacy and reduced side effects. Herein, we review and discuss recent applications of NO nanomedicines, their therapeutic mechanisms, and the challenges of NO nanomedicines for future scientific studies and clinical applications. As NO enables the inhibition of the replication of DNA and RNA in infectious microbes, including COVID-19 coronaviruses and malaria parasites, we highlight the potential of NO nanomedicines for antipandemic efforts. This review aims to provide deep insights and practical hints into design strategies and applications of NO nanomedicines.

Multifunctional two-dimensional Bi2Se3 nanodiscs for anti-inflammatory therapy of inflammatory bowel diseases

The overexpression of reactive oxygen and nitrogen species (RONS) in the colonic mucosa destroys the mucosa and its barrier, accelerating the occurrence of inflammatory bowel disease (IBD). The elimination of RONS from the inflammatory colon has proven effective in alleviating IBD. Although many nanoantioxidants have been developed, preparing robust and efficient nano-antioxidants remains challenging. Herein, by modifying bismuth selenide (Bi₂Se₃) nanodiscs with polyvinylpyrrolidone (PVP), a multifunctional nanozyme based on 2D nanomaterials was developed for the treatment of IBD. By eliminating multiple RONS, such as hydroxyl radicals (•OH), superoxide anions (O₂^-•), nitric oxide (NO), and Bi₂Se₃ nanodiscs enhanced cellular survival after H₂O₂ stimulation. As evidenced by colonic injury, reduced body weight, spleen index, and proinflammatory cytokine levels in mice, RONS clearance alleviated intestinal inflammation in a prevention and delay model of acute colitis. 16S rDNA amplicon sequencing reveals that Bi₂Se₃ nanodiscs had the potential to regulate intestinal flora, increase the proportion of Firmicutes to Bacteroidetes, inhibit Proteobacteria bacteria, and restore intestinal homeostasis. This study highlights the use of Bi₂Se₃ nanodiscs with excellent biocompatibility, multienzyme functionality, and RONS scavenging ability as treatments for IBD without apparent adverse effects. STATEMENT OF SIGNIFICANCE: RONS were efficiently scavenged by Bi₂Se₃ nanodiscs. Bi₂Se₃ nanodiscs could be as a promising and potentially safe theraeputic agent for IBD. The gut microbiota could be modulated by Bi₂Se₃ nanodiscs.

Enhanced Bacterial-Infected Wound Healing by Nitric Oxide-Releasing Topological Supramolecular Nanocarriers with Self-Optimized Cooperative Multi-Point Anchoring

Polymeric systems that provide cationic charges or biocide-release therapeutics are used to treat the bacteria-infected wound. However, most antibacterial polymers based on topologies with restricted molecular dynamics still do not satisfy the clinical requirements due to their limited antibacterial efficacy at safe concentrations in vivo. Here a NO-releasing topological supramolecular nanocarrier with rotatable and slidable molecular entities is reported to provide conformational freedom to promote the interactions between the carrier and the pathogenic microbes, hence greatly improving the antibacterial performance. With improved contacting-killing and efficient delivery of NO biocide from the molecularly dynamic cationic ligand design, the NO-loaded topological nanocarrier achieves excellent antibacterial and anti-biofilm effects via destroying the bacterial membrane and DNA. MRSA-infected rat model is also brought out to demonstrate its wound-healing effect with neglectable toxicity in vivo. Introducing flexible molecular motions into therapeutic polymeric systems is a general design to enhance the healing of a range of diseases.

Using Compartments to Model Drug Delivery from Biodegradable Polymers

Polymeric drug delivery systems can improve patient compliance, decrease toxicity and prolong therapeutic effects for a wide range of therapeutic treatments, by controlling drug release. Polymer delivery system development can be facilitated by mathematical models. We present here a new compartmental model that will be more familiar to pharmaceutical professionals and equally as effective as common diffusion equation-based models. The compartmental model considers both polymer degradation and drug diffusion to predict drug release. The model is adapted into three different geometries for different polymer delivery scenarios: membranes, fibres and particles. Model parameters are derived in terms of diffusion coefficients. Polymer-drug binding interactions and distributions of fibre/particle diameters are incorporated to the model. The model is validated by comparison to common diffusion equation-based solutions and fitting to experimental data. It is shown how the model for drug release can be incorporated into existing distribution models to predict plasma concentrations of an in vivo administration. A user-friendly Python implementation of the model is available on Github, at https://github.com/spirt-t/compartments_model.

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.

Nitric-Oxide-Modulatory Materials for Biomedical Applications

Nitric oxide (NO) is an endogenous signaling molecule that participates in various physiological and biological pathways associated with vasodilation, immune response, and cell apoptosis. Interestingly, NO has versatile and distinct functions in vivo depending on its concentration and the duration of exposure; it aids cellular proliferation at nanomolar concentrations but causes cellular death at micromolar concentrations. Therefore, achieving the precise and on-demand modulation of microenvironmental NO concentrations has become a major research target in biomedical fields. To this end, many studies have investigated feasible means for developing functional moieties that can either exogenously donate or selectively scavenge NO. However, these advances are limited by poor stability and a lack of target specificity, which represent two significant obstacles regarding the spatiotemporal adjustment of NO in vivo. Our group has addressed this issue by contributing to the development of next-generation NO-modulatory materials over the past decade. Over this period, we utilized various polymeric, inorganic, and hybrid systems to enhance the bioavailability of traditional NO donors or scavengers in an attempt to maximize their clinical usage while also minimizing their unwanted side effects. In this Account, strategies regarding the rational design of NO-modulatory materials are first summarized and discussed, depending on their specific purposes. These strategies include chemical approaches for encapsulating traditional NO donors inside specific vehicles; this prevents spontaneous NO release and allows said donors to be exposed on-demand, under a certain stimulus. The current status of these approaches and the recent contributions of other groups are also comprehensively discussed here to ensure an objective understanding of the topic. Moreover, in this paper, we discuss strategies for the selective depletion of NO from local inflammatory sites, where the overproduction of NO is problematic. Finally, the major challenges for current NO-modulatory systems are discussed, and requirements are outlined that need to be tackled to achieve their future therapeutic development. Starting from this current, relatively early stage of development, we propose that, through continuous efforts to surmount existing challenges, it will be possible in the future to achieve clinical translations regarding NO-modulatory systems. This Account provides insightful guidelines regarding the rational design of NO-modulatory systems for various biomedical applications. Moreover, it can facilitate the achievement of previously unattainable goals while revolutionizing future therapeutics.

An injectable and biodegradable hydrogel incorporated with photoregulated NO generators to heal MRSA-infected wounds

The development of degradable hydrogel fillers with high antibacterial activity and wound-healing property is urgently needed for the treatment of infected wounds. Herein, an injectable, degradable, photoactivated antibacterial hydrogel (MPDA-BNN6@Gel) was developed by incorporating BNN6-loaded mesoporous polydopamine nanoparticles (MPDA-BNN6 NPs) into a fibrin-based hydrogel. After administration, MPDA-BNN6@Gel created local hyperthermia and released large quantities of NO gas to treat methicillin-resistant Staphylococcus aureus infection under the stimulation of an 808 nm laser. Experiments confirmed that the bacteria were eradicated through irreversible damage to the cell membrane, genetic metabolism, and material energy. Furthermore, in the absence of laser irradition, the fibrin and small amount of NO that originated from MPDA-BNN6@Gel promoted wound healing in vivo. This work indicates that MPDA-BNN6@Gel is a promising alternative for the treatment of infected wounds and provides a facile tactic to design a photoregulated bactericidal hydrogel for accelerating infected wound healing. STATEMENT OF SIGNIFICANCE: The development of a degradable hydrogel with high antibacterial activity and wound-healing property is an urgent need for the treatment of infected wounds. Herein, an injectable, degradable, and photo-activated antibacterial hydrogel (MPDA-BNN6@Gel) has been developed by incorporating BNN6-loaded mesoporous polydopamine nanoparticles (MPDA-BNN6 NPs) into a fibrin-based hydrogel. After administration of MPDA-BNN6@Gel, the MPDA-BNN6@Gel could generate local hyperthermia and release large quantities of NO gas to treat the methicillin-resistant Staphylococcus aureus infection under the irradiation of 808 nm laser. Furthermore, in the absence of a laser, the fibrin and a small amount of NO originating from MPDA-BNN6@Gel could promote wound healing in vivo.

Enabling Antibacterial and Antifouling Coating via Grafting of a Nitric Oxide-Releasing Ionic Liquid on Silicone Rubber

Infections caused by bacteria and biofilms on the surfaces of biomedical devices and implants pose serious threats to public health. Herein, a nitric oxide (NO) gas-releasing quaternary ammonium-type ionic liquid (IL)-based coating on polydimethylsiloxane (PDMS), PDIL-NO, with effective and long-acting antibacterial and antifouling properties was prepared. N-(2-((2, 3-Dimethylbut-3-enoyl)oxy)ethyl)-N, N-dimethyloctan-1-aminium bromide (IL-Br), and 2-methyl-2-propenoic acid 2-(2-methoxyethoxy) ethyl ester were covalently grafted onto the surfaces of PDMS by a thiol-ene click chemical reaction, followed by incorporation of l-proline anions (Pro^-) through anion exchange with Br^- to adsorb NO gas. The prepared PDIL-NO showed a prolonged NO-releasing time (>1440 min) and a relatively high concentration (88 μM). Additionally, PDIL-NO possessed good and long-term antimicrobial activity, and could effectively reduce the adsorption of bovine serum albumin and adhesion of bacteria, as well as inhibit wound infection and reduce inflammation in vivo due to the synergetic effect of IL and the released NO. This study may provide a new approach to combat bacterial infections associated with biomedical devices and implants.

Nitric oxide boosters as defensive agents against COVID-19 infection: an opinion

In the prevailing covid times, scientific community is busy in developing vaccine against COVID-19. Under such fascination this article describes the possible role of nitric oxide (NO) releasers in aiding the immune system of a human body against this dreadful pandemic disease. Despite some prodrug antiviral compounds are in practice to recover the patients suffering from covid-19, however, co-morbidity deaths are highest among the total deaths happened so far. This concurrence of a number of diseases in a patient along with this viral infection is indicative of the poor immunity. Literature background supports the use of NO as immunity boosting agent and hence, the nitric oxide releasing compounds could act as lucrative in this context. Some dietary suggestions of NO-containing food items have also been introduced in this article. Also, the profound effect of NO in relieving symptomatic severity of covid-19 has been opined in this work.Communicated by Ramaswamy H. Sarma.

Exploring BODIPY derivatives as photosensitizers for antibacterial photodynamic therapy

There is urgently needed to develop efficient and safe antimicrobials to replace traditional antibiotics for fighting drug-resistant bacteria. Antimicrobial photodynamic therapy (aPDT), which is a promising antimicrobial strategy that can minimize antibiotic resistance and reduce systemic side effects. Boron-dipyrromethene (BODIPY) is a type of fascinating photosensitizers (PSs) for improving aPDT due to the tunable structures and photophysical features. Herein, six kinds of BODIPY derivatives (BDP1-BDP6) modified with different atoms or groups such as iodine atoms, thiophene, cyano, phenyl, aldehyde and nitro groups were synthesized and their photophysical behaviors were characterized. The results indicated that BDP3, which had 2, 6-diiodo and 8-phenyl substitution, was the best PS candidate with the highest reactive oxygen species (ROS) generation efficacy. BDP3 and BDP5 could rapidly kill Staphylococcus aureus (S. aureus) with the minimum inhibitory concentration (MIC) of 10 nM upon illumination. They also possessed excellent biofilm inhibition ability against S. aureus and could efficaciously restrain the formation of bacterial biofilm. The results of Live/Dead staining assay and scanning electron microscopy (SEM) demonstrated that BDP3 destroyed the cell membrane structure of bacteria by generating ROS, which ultimately led to bacterial lysis and death. Finally, the biosafety evaluation toward the mouse fibroblasts (L929 cells) suggested BDP3 had good cytocompatibility. This work exhibits the great potential of rational designs of PS for aPDT applications.

Near-infrared laser-controlled nitric oxide-releasing gold nanostar/hollow polydopamine Janus nanoparticles for synergistic elimination of methicillin-resistant Staphylococcus aureus and wound healing

Recently, nitric oxide (NO) has received increasing interest in combat against bacteria-induced infections because of its ability to sensitize and enhance the antibacterial effectiveness of many therapeutic approaches such as antibiotics. However, high-efficient loading and controlled release of NO remain a big challenge. In the present work, a type of gold nanostar/hollow polydopamine Janus nanostructure (GNS/HPDA JNPs) with precise near infrared (NIR)-controlled NO release property was fabricated using a facile seed-mediated method. Upon NIR laser irradiation, the NO-releasing GNS/HPDA JNPs (GNS/HPDA-BNN6) exhibited a synergistic photothermal and NO antibacterial effect by significantly inhibiting the growth and biofilm formation of both Gram-negative and Gram-positive bacterial strains, including methicillin-resistant Staphylococcus aureus (MRSA). An in-depth mechanism study revealed that two pathways were mainly involved in the synergistic photothermal and NO antibacterial effect. In one pathway, the synergistic effect severely destroyed the bacterial membrane by causing leakage of intracellular components such as DNA. In another pathway, the synergistic effect largely disturbed bacterial metabolism by regulating relative metabolic genes, followed by enhancing ROS generation to cause intracellular GSH depletion and DNA damage. More importantly, the synergistic effect significantly diminished the drug resistance of MRSA by downregulating the expression of the drug-resistant gene mecA and some relative multidrug efflux pumps (e.g., SepA and Tet38). An in vivo evaluation using a rat model with MRSA-infected wounds indicated that the synergistic photothermal and NO effect of GNS/HPDA-BNN6 can effectively eliminate MRSA from wounds, thereby alleviating inflammation and promoting wound healing. STATEMENT OF SIGNIFICANCE: Multidrug-resistant (MDR) bacteria have become a big threat to mankind, and therefore, the development of innovative antibacterial agents with high antibacterial efficiency is urgently required. Nanomaterial-mediated nitric oxide (NO) therapy is a promising strategy to effectively combat MDR bacteria through a synergistic antibacterial effect. Here, a gold nanostar/hollow polydopamine Janus nanostructure with precise near infrared (NIR) light-controlled NO release property (GNS/HPDA-BNN6) was developed. Both in vitro and in vivo evaluations demonstrated that GNS/HPDA-BNN6 could effectively eliminate methicillin-resistant Staphylococcus aureus (MRSA) from infected wounds and promote wound healing through a synergistic photothermal and NO therapeutic effect. Remarkably, the synergistic effect significantly diminished the drug resistance of MRSA by downregulating the expression of some drug-resistant genes and multidrug efflux pumps.

Magnetic Responsive Release of Nitric Oxide from an MOF-Derived Fe3O4@PLGA Microsphere for the Treatment of Bacteria-Infected Cutaneous Wound

Nitric oxide (NO) is an essential endogenous signaling molecule regulating multifaceted physiological functions in the (cardio)vascular, neuronal, and immune systems. Due to the short half-life and location-/concentration-dependent physiological function of NO, translational application of NO as a novel therapeutic approach, however, awaits a strategy for spatiotemporal control on the delivery of NO. Inspired by the magnetic hyperthermia and magneto-triggered drug release featured by Fe₃O₄ conjugates, in this study, we aim to develop a magnetic responsive NO-release material (MagNORM) featuring dual NO-release phases, namely, burst and steady release, for the selective activation of NO-related physiology and treatment of bacteria-infected cutaneous wound. After conjugation of NO-delivery [Fe(μ-S-thioglycerol)(NO)₂]₂ with a metal-organic framework (MOF)-derived porous Fe₃O₄@C, encapsulation of obtained conjugates within the thermo-responsive poly(lactic-co-glycolic acid) (PLGA) microsphere completes the assembly of MagNORM. Through continuous/pulsatile/no application of the alternating magnetic field (AMF) to MagNORM, moreover, burst/intermittent/slow release of NO from MagNORM demonstrates the AMF as an ON/OFF switch for temporal control on the delivery of NO. Under continuous application of the AMF, in particular, burst release of NO from MagNORM triggers an effective anti-bacterial activity against both Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli). In addition to the magneto-triggered bactericidal effect of MagNORM against E. coli-infected cutaneous wound in mice, of importance, steady release of NO from MagNORM without the AMF promotes the subsequent collagen formation and wound healing in mice.

A Versatile Calcium Phosphate Nanogenerator for Tumor Microenvironment-activated Cancer Synergistic Therapy

Gas therapy is an emerging "green" cancer treatment strategy; however, its outcome often restricted by the complexity, diversity, and heterogeneity of tumor. Herein, a tumor targeting and tumor microenvironment-activated calcium phosphate nanotheranostic system (denoted as GCAH) is constructed for effective synergistic cancer starvation/gas therapy. GCAH is obtained by a facile biomineralization strategy using glucose oxidase (GOx) as a biotemplate, followed by loading of l-Arginine (L-Arg) and modification of hyaluronic acid (HA) to allow special selectivity for glycoprotien CD44 overexpressed cancer cells. This nanotheranostic system not only exhausts the glucose nutrients in tumor region by the GOx-triggered glucose oxidation, the generated H₂ O₂ can oxidize L-Arg into NO under acidic tumor microenvironment for enhanced gas therapy. As such, there are significant enhancement effects of starvation therapy and gas therapy through the cascade reactions of GOx and L-Arg, which yields a remarkable synergistic therapeutic effect for 4T1 tumor-bearing mice without discernible toxic side effects.

Multifunctional BODIPY for effective inactivation of Gram-positive bacteria and promotion of wound healing

Bacterial infectious diseases and antimicrobial resistance seriously endanger human health, so alternative therapies for bacterial infections are urgently needed. Recently, photodynamic therapy against bacteria has shown great potential because of its high efficiency and low acquired resistance. Here, we design and synthesize a dipyrromethene boron difluoride (BODIPY) photosensitizer containing a guanidine group LIBDP for combating bacterial infections. The positively charged guanidine can destroy the bacterial membrane and inhibit the proliferation of bacteria to a certain extent. Upon light irradiation, LIBDP can produce reactive oxygen species (ROS), which can destroy the pre-formed biofilm and induce potent antibacterial activity. In addition, the guanidine of LIBDP can be oxidized to nitric oxide (NO) by the generated ROS, which can not only improve the antibacterial effect, but also promote wound healing. The strategy in this work paves the way for synthesizing high-performance antibacterial materials.

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.

Hollow polydopamine nanoparticles loading with peptide RL-QN15: a new pro-regenerative therapeutic agent for skin wounds

BACKGROUND

Although the treatments of skin wounds have greatly improved with the increase in therapeutic methods and agents, available interventions still cannot meet the current clinical needs. Therefore, the development of new pro-regenerative therapies remains urgent. Owing to their unique characteristics, both nanomaterials and peptides have provided novel clues for the development of pro-regenerative agents, however, more efforts were still be awaited and anticipated.

RESULTS

In the current research, Hollow polydopamine (HPDA) nanoparticles were synthesized and HPDA nanoparticles loading with RL-QN15 (HPDAlR) that was an amphibian-derived peptide with obvious prohealing activities were prepared successfully. The characterization, biodistribution and clearance of both HPDA nanoparticles and HPDAlR were evaluated, the loading efficiency of HPDA against RL-QN15 and the slow-releasing rate of RL-QN15 from HPDAlR were also determined. Our results showed that both HPDA nanoparticles and HPDAlR exerted no obvious toxicity against keratinocyte, macrophage and mice, and HPDA nanoparticles showed no prohealing potency in vivo and in vitro. Interestingly, HPDAlR significantly enhanced the ability of RL-QN15 to accelerate the healing of scratch of keratinocytes and selectively modulate the release of healing-involved cytokines from macrophages. More importantly, in comparison with RL-QN15, by evaluating on animal models of full-thickness injured skin wounds in mice and oral ulcers in rats, HPDAlR showed significant increasing in the pro-regenerative potency of 50 and 10 times, respectively. Moreover, HPDAlR also enhanced the prohealing efficiency of peptide RL-QN15 against skin scald in mice and full-thickness injured wounds in swine.

CONCLUSIONS

HPDA obviously enhanced the pro-regenerative potency of RL-QN15 in vitro and in vivo, hence HPDAlR exhibited great potential in the development of therapeutics for skin wound healing.

Hierarchically porous metal hydroxide/metal-organic framework composite nanoarchitectures as broad-spectrum adsorbents for toxic chemical filtration

We demonstrate that the hierarchically porous metal hydroxide/metal-organic framework composite nanoarchitectures exhibit broad-spectrum removal activity for three chemically distinct toxic gases, viz. acid gases, base gases, and nitrogen oxides. A facile and general in-situ hydrolysis strategy combined with gentle ambient pressure drying (APD) was utilized to integrate both Zr(OH)₄ and Ti(OH)₄ with the amino-functionalized MOF-808 xerogel (G808-NH₂). The M(OH)₄/G808-NH₂ xerogel composites manifested 3D crystalline porous networks and substantially hierarchical porosity, with controllable amounts of amorphous M(OH)₄ nanoparticles residing at the edge of xerogel particles. Microbreakthrough tests were performed under both dry and moist conditions to evaluate the filtration capabilities of the composites against three representative compounds: SO₂, NH₃, and NO₂. Compared with the pristine G808-NH₂ xerogel, the incorporation of M(OH)₄ effectively enhanced the broad-spectrum toxic chemical mitigation ability of the material, with the highest SO₂, NH₃, and NO₂ breakthrough uptake reaching 74.5, 55.3, and 394.0 mg/g, respectively. Post-breakthrough characterization confirmed the abundant M-OH groups with diverse binding configurations, alongside the unsaturated M (IV) centers on the surface of M(OH)₄ provided extra adsorption sites for irreversible toxic chemical capture besides Van der Waals driven physisorption. The ability to achieve high-capacity adsorption and strong retention for multiple contaminants is of great significance for real-world filtration applications.

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.

Polydopamine antibacterial materials

Recently, the development of polydopamine (PDA) has demonstrated numerous excellent performances in free radical scavenging, UV shielding, photothermal conversion, and biocompatibility. These unique properties enable PDA to be widely used as efficient antibacterial materials for various applications. Accordingly, PDA antibacterial materials mainly include free-standing PDA materials and PDA-based composite materials. In this review, an overview of PDA antibacterial materials is provided to summarize these two types of antibacterial materials in detail, including the fabrication strategies and antibacterial mechanisms. The future development and challenges of PDA in this field are also presented. It is hoped that this review will provide an insight into the future development of antibacterial functional materials based on PDA.

Mechanism Insight into Rapid Photodriven Sterilization Based on Silver Bismuth Sulfide Quantum Dots

Microbial contamination and the prevalence of resistant bacteria is considered a worldwide public health problem. Therefore, recently, great efforts have been made to develop photoresponsive platforms for the simultaneous photodynamic antibacterial (PDA) and photothermal antibacterial (PTA) therapy processes as mediated by specific light. However, owing to the absorption mismatches of the photothermal agents and photodynamic photosensitizers, it has been discovered that many synergistic photoresponsive antibacterial platforms cannot be excited by a single-wavelength light. In this study, silver bismuth sulfide quantum dots (AgBiS₂ QDs) identified from the literature as a near-infrared light (NIR) that triggers bifunctional materials with simultaneous photodynamic and photothermal effects for photoresponsive bacterial killing were used. Specifically, AgBiS₂ QDs were successfully synthesized via a bottom-up approach, using polyethylenimine (PEI) as an assistant molecule. With PEI wrapping, the attachment between the negatively charged membrane surfaces of the bacterial cells and AgBiS₂ QDs was enhanced via the electrostatic interactions. The photodriven antibacterial activity of AgBiS₂ QDs was then investigated against both S. aureus and E. coli. The results revealed a significant reduction in bacterial survival. The killing effect was found to be independent of the AgBiS₂ QDs, and redox potentials controlled the photogenerated electrons that thermodynamically favored the formation of multiple reactive oxygen species (ROS). A possible phototriggered antibacterial mechanism was then proposed in which the AgBiS₂ QDs are anchored first to the bacterial surface and then induce breaking on its outer membrane by high local heat and ROS under single 808 nm NIR laser illumination to finally induce bacterial death.

Radical Releasing Anti-Tuberculosis Agents and the Treatment of Mycobacterial Tuberculosis Infections - An Overview

The treatment and management of tuberculosis (TB) is a major global concern. Approved drugs for the treatment of TB to date displayed various modes of action which can be grouped into radical releasing and non-radical releasing anti TB agents. Radical releasing agents are of special interest because they diffuse directly into the mycobacterium cell wall, interact with the host cell DNA causing DNA strand breakages and fatal destabilization of the DNA helix inhibiting nucleic acid synthase. As a therapeutic agent with aforementioned activity, nitroimidazoles and most especially bicyclic nitroimidazoles are currently in clinical use for the treatment of tuberculosis. However, the approved drugs, pretomanid (PR) and delamanid (DE) are limited in their nitric oxide radical (NO•) releasing abilities to cause effective bactericidity. It is believed that their bactericidal activity can be improved by harnessing alternative strategies to increase NO• release. The last decade has witness the strategic inclusion of NO-donors into native drugs to improve their activities and/or reverse resistance. The rationale behind this strategy is the targeting of NO• release at specific therapeutic sites. This review therefore aims to highlight various radical releasing agents that may be effective in the treatment of TB. The review also investigates various structural modification to PR and DE and suggests alternative strategies to improve NO• release as well as some applications where NO-donor hybrid drugs have been used with good therapeutic effect.

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.

Recent Advances in a Polydopamine-Mediated Antimicrobial Adhesion System

The drug resistance developed by bacteria during antibiotic treatment has been a call to action for researchers and scientists across the globe, as bacteria and fungi develop ever increasing resistance to current drugs. Innovative antimicrobial/antibacterial materials and coatings to combat such infections have become a priority, as many infections are caused by indwelling implants (e.g., catheters) as well as improving postsurgical function and outcomes. Pathogenic microorganisms that can exist either in planktonic form or as biofilms in water-carrying pipelines are one of the sources responsible for causing water-borne infections. To combat this, researchers have developed nanotextured surfaces with bactericidal properties mirroring the topographical features of some natural antibacterial materials. Protein-based adhesives, secreted by marine mussels, contain a catecholic amino acid, 3,4-dihydroxyphenylalanine (DOPA), which, in the presence of lysine amino acid, empowers with the ability to anchor them to various surfaces in both wet and saline habitats. Inspired by these features, a novel coating material derived from a catechol derivative, dopamine, known as polydopamine (PDA), has been designed and developed with the ability to adhere to almost all kinds of substrates. Looking at the immense potential of PDA, this review article offers an overview of the recent growth in the field of PDA and its derivatives, especially focusing the promising applications as antibacterial nanocoatings and discussing various antimicrobial mechanisms including reactive oxygen species-mediated antimicrobial properties.

Melanin-Like Nanomedicine in Photothermal Therapy Applications

Photothermal therapy (PTT) mediated by nanomaterial has become an attractive tumor treatment method due to its obvious advantages. Among various nanomaterials, melanin-like nanoparticles with nature biocompatibility and photothermal conversion properties have attracted more and more attention. Melanin is a natural biological macromolecule widely distributed in the body and displays many fascinating physicochemical properties such as excellent biocompatibility and prominent photothermal conversion ability. Due to the similar properties, Melanin-like nanoparticles have been extensively studied and become promising candidates for clinical application. In this review, we give a comprehensive introduction to the recent advancements of melanin-like nanoparticles in the field of photothermal therapy in the past decade. In this review, the synthesis pathway, internal mechanism and basic physical and chemical properties of melanin-like nanomaterials are systematically classified and evaluated. It also summarizes the application of melanin-like nanoparticles in bioimaging and tumor photothermal therapy (PTT)in detail and discussed the challenges they faced in clinical translation rationally. Overall, melanin-like nanoparticles still have significant room for development in the field of biomedicine and are expected to applied in clinical PTT in the future.

Nitric oxide as a therapeutic option for COVID-19 treatment: a concise perspective

Among several possible therapies applicable for treating COVID-19, nitric oxide therapy has also gained considerable interest. This article describes the same with mechanistic details.

Polydopamine-based nanomaterials and their potentials in advanced drug delivery and therapy

Polydopamine (PDA) has shown great potentials in biomedical fields due largely to its unique physicochemical properties, including high photothermal transfer efficiency, excellent drug binding capacity, versatile adhesion ability, sensitive pH responsibility and great biocompatibility and biodegradability. These properties confer PDA-based nanoparticles the potentials either as the drug carriers for advanced drug delivery or as the bioactive agents for photothermal therapy, imaging and biosensing. This review aims to provide a comprehensive understanding of PDA, its polymerization mechanisms and the potentials of PDA-based nano-systems in treating various diseases, including cancer, diabetes, inflammation, bacterial infection and Parkinson's disease. In addition, the concerns of PDA in biomedical use are also discussed.

Bio-Applications of Multifunctional Melanin Nanoparticles: From Nanomedicine to Nanocosmetics

Bioinspired nanomaterials are ideal components for nanomedicine, by virtue of their expected biocompatibility or even complete lack of toxicity. Natural and artificial melanin-based nanoparticles (MNP), including polydopamine nanoparticles (PDA NP), excel for their extraordinary combination of additional optical, electronic, chemical, photophysical, and photochemical properties. Thanks to these features, melanin plays an important multifunctional role in the design of new platforms for nanomedicine where this material works not only as a mechanical support or scaffold, but as an active component for imaging, even multimodal, and simple or synergistic therapy. The number of examples of bio-applications of MNP increased dramatically in the last decade. Here, we review the most recent ones, focusing on the multiplicity of functions that melanin performs in theranostics platforms with increasing complexity. For the sake of clarity, we start analyzing briefly the main properties of melanin and its derivative as well as main natural sources and synthetic methods, moving to imaging application from mono-modal (fluorescence, photoacoustic, and magnetic resonance) to multi-modal, and then to mono-therapy (drug delivery, anti-oxidant, photothermal, and photodynamic), and finally to theranostics and synergistic therapies, including gene- and immuno- in combination to photothermal and photodynamic. Nanomedicine aims not only at the treatment of diseases, but also to their prevention, and melanin in nature performs a protective action, in the form of nanopigment, against UV-Vis radiations and oxidants. With these functions being at the border between nanomedicine and cosmetics nanotechnology, recently examples of applications of artificial MNP in cosmetics are increasing, paving the road to the birth of the new science of nanocosmetics. In the last part of this review, we summarize and discuss these important recent results that establish evidence of the interconnection between nanomedicine and cosmetics nanotechnology.

Thermo-resistance of ESKAPE-panel pathogens, eradication and growth prevention of an infectious biofilm by photothermal, polydopamine-nanoparticles in vitro

Nanotechnology offers many novel infection-control strategies that may help prevent and treat antimicrobial-resistant bacterial infections. Here, we synthesized polydopamine, photothermal-nanoparticles (PDA-NPs) without further surface-functionalization to evaluate their potential with respect to biofilm-control. Most ESKAPE-panel pathogens in suspension with photothermal-nanoparticles showed three- to four-log-unit reductions upon Near-Infra-Red (NIR)-irradiation, but for enterococci only less than two-log unit reduction was observed. Exposure of existing Staphylococcus aureus biofilms to photothermal-nanoparticles followed by NIR-irradiation did not significantly kill biofilm-inhabitants. This indicates that the biofilm mode of growth poses a barrier to penetration of photothermal-nanoparticles, yielding dissipation of heat to the biofilm-surrounding rather than in its interior. Staphylococcal biofilm-growth in the presence of photothermal-nanoparticles could be significantly prevented after NIR-irradiation because PDA-NPs were incorporated in the biofilm and heat dissipated inside it. Thus, unmodified photothermal nanoparticles have potential for prophylactic infection-control, but data also constitute a warning for possible development of thermo-resistance in infectious pathogens.

Polydopamine-based nanoreactors: synthesis and applications in bioscience and energy materials

Polydopamine (PDA)-based nanoreactors have shown exceptional promise as multifunctional materials due to their nanoscale dimensions and sub-microliter volumes for reactions of different systems. Biocompatibility, abundance of active sites, and excellent photothermal conversion have facilitated their extensive use in bioscience and energy storage/conversion. This minireview summarizes recent advances in PDA-based nanoreactors, as applied to the abovementioned fields. We first highlight the design and synthesis of functional PDA-based nanoreactors with structural and compositional diversity. Special emphasis in bioscience has been given to drug/protein delivery, photothermal therapy, and antibacterial properties, while for energy-related applications, the focus is on electrochemical energy storage, catalysis, and solar energy harvesting. In addition, perspectives on pressing challenges and future research opportunities regarding PDA-based nanoreactors are discussed.

Inhibition of Host Arginase Activity Against Staphylococcal Bloodstream Infection by Different Metabolites

Staphylococcus aureus is a notorious bacterial pathogen that often causes soft tissue and bloodstream infections and invariably garners resistance mechanisms against new antibiotics. Modulation of the host immune response by metabolites is a powerful tool against bacterial infections, but has not yet been used against S. aureus infections. In this study, we identified four metabolite biomarkers: L-proline, L-isoleucine, L-leucine, and L-valine (PILV), through a metabolomics study using animal models of S. aureus bloodstream infection. The exogenous administration of each metabolite or of PILV showed anti-infective effects, and a higher protection was achieved with PILV in comparison to individual metabolites. During the staphylococcal infection, the expression of most host arginase and nitric oxide synthase (NOS) isozymes was simultaneously induced in mouse liver, kidney, and blood samples. However, the induction of arginase isozymes was dramatically stronger than that of NOS isozymes. This elevated arginase activity was inhibited by the metabolite biomarkers thus killing S. aureus, and PILV exhibited the strongest inhibition of arginase activity and bacterial inhibition. The suppression of arginase activity also contributed to the metabolite-mediated phagocytic killing of S. aureus in mouse and human blood. Our findings demonstrate the metabolite-mediated arginase inhibition as a therapeutic intervention for S. aureus infection.

The evolving landscape for cellular nitric oxide and hydrogen sulfide delivery systems: A new era of customized medications

Nitric oxide (NO) and hydrogen sulfide (H2S) are industrial toxins or pollutants; however, both are produced endogenously and have important biological roles in most mammalian tissues. The recognition that these gasotransmitters have a role in physiological and pathophysiological processes has presented opportunities to harness their intracellular effects either through inhibition of their production; or more commonly, through inducing their levels and or delivering them by various modalities. In this review article, we have focused on an array of NO and H2S donors, their hybrids with other established classes of drugs, and the various engineered delivery platforms such a fibers, polymers, nanoparticles, hydrogels, and others. In each case, we have reviewed the rationale for their development.

Antibiotic-Free Antibacterial Strategies Enabled by Nanomaterials: Progress and Perspectives

Bacterial infection is one of the top ten leading causes of death globally and the worst killer in low-income countries. The overuse of antibiotics leads to ever-increasing antibiotic resistance, posing a severe threat to human health. Recent advances in nanotechnology provide new opportunities to address the challenges in bacterial infection by killing germs without using antibiotics. Antibiotic-free antibacterial strategies enabled by advanced nanomaterials are presented. Nanomaterials are classified on the basis of their mode of action: nanomaterials with intrinsic or light-mediated bactericidal properties and others that serve as vehicles for the delivery of natural antibacterial compounds. Specific attention is given to antibacterial mechanisms and the structure-performance relationship. Practical antibacterial applications employing these antibiotic-free strategies are also introduced. Current challenges in this field and future perspectives are presented to stimulate new technologies and their translation to fight against bacterial infection.

Nanoparticles modified by polydopamine: Working as "drug" carriers

Inspired by the mechanism of mussel adhesion, polydopamine (PDA), a versatile polymer for surface modification has been discovered. Owing to its unique properties like extraordinary adhesiveness, excellent biocompatibility, mild synthesis requirements, as well as distinctive drug loading approach, strong photothermal conversion capacity and reactive oxygen species (ROS) scavenging facility, various PDA-modified nanoparticles have been desired as drug carriers. These nanoparticles with diverse nanostructures are exploited in multifunctions, consisting of targeting, imaging, chemical treatment (CT), photodynamic therapy (PDT), photothermal therapy (PTT), tissue regeneration ability, therefore have attracted great attentions in plenty biomedical applications. Herein, recent progress of PDA-modified nanoparticle drug carriers in cancer therapy, antibiosis, prevention of inflammation, theranostics, vaccine delivery and adjuvant, tissue repair and implant materials are reviewed, including preparation of PDA-modified nanoparticle drug carriers with various nanostructures and their drug loading strategies, basic roles of PDA surface modification, etc. The advantages of PDA modification in overcoming the existing limitations of cancer therapy, antibiosis, tissue repair and the developing trends in the future of PDA-modified nanoparticle drug carriers are also discussed.

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Multifunctional PDA-modified drug systems are introduced in terms of classification, synthesis and drug loading strategies.

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Basic roles of PDA surface modification in the drug systems are discussed.

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Biomedical applications and unique advantages of the PDA-modified nanoparticle working as drug carriers are illustrated.

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Challenges and perspectives for future development are proposed.

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.

Melanin-Like Nanomaterials for Advanced Biomedical Applications: A Versatile Platform with Extraordinary Promise

Developing efficient, sustainable, and biocompatible high-tech nanoplatforms derived from naturally existing components in living organisms is highly beneficial for diverse advanced biomedical applications. Melanins are nontoxic natural biopolymers owning widespread distribution in various biosystems, possessing fascinating physicochemical properties and playing significant physiological roles. The multifunctionality together with intrinsic biocompatibility renders bioinspired melanin-like nanomaterials considerably promising as a versatile and powerful nanoplatform with broad bioapplication prospects. This panoramic Review starts with an overview of the fundamental physicochemical properties, preparation methods, and polymerization mechanisms of melanins. A systematical and well-bedded description of recent advancements of melanin-like nanomaterials regarding diverse biomedical applications is then given, mainly focusing on biological imaging, photothermal therapy, drug delivery for tumor treatment, and other emerging biomedicine-related implementations. Finally, current challenges toward clinical translation with an emphasis on innovative design strategies and future striving directions are rationally discussed. This comprehensive and detailed Review provides a deep understanding of the current research status of melanin-like nanomaterials and is expected to motivate further optimization of the design of novel tailorable and marketable multifunctional nanoplatforms in biomedicine.

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.

Sustained Nitric Oxide-Providing Small Molecule and Precise Release Behavior Study for Glaucoma Treatment

Incidence ofglaucoma, a severe disease leading to irreversible loss of vision, is increasing with global aging populations. Lowering intraocular pressure (IOP) is the only proven treatment method for glaucoma. Nitric oxide (NO) is an emerging material targeting the conventional outflow pathway by relaxing the trabecular meshwork (TM). However, there is little understanding on the NO level effective in IOP lowering without toxicity. Here, we report a novel long-term NO-releasing polydiazeniumdiolate (NOP) that enables lowering IOP via the conventional outflow pathway. NOP is composed of carbon-bound polydiazeniumdiolate, a stable NO donor moiety. NO release was monitored with accurate parameters by real-time detection of gas and analysis of the accumulated release profile. Based on the NO release information, the selected safe level of NOP exhibited effective TM relaxation and a potential IOP lowering effect in vivo without side effects. This work provides new insights into nitric oxide release behavior that should be considered for glaucoma treatment.

Antimicrobial Nitric Oxide Releasing Contact Lens Gels for the Treatment of Microbial Keratitis

Microbial keratitis is a serious sight threatening infection affecting approximately two million individuals worldwide annually. While antibiotic eye drops remain the gold standard treatment for these infections, the significant problems associated with eye drop drug delivery and the alarming rise in antimicrobial resistance has meant that there is an urgent need to develop alternative treatments. In this work, a nitric oxide releasing contact lens gel displaying broad spectrum antimicrobial activity against two of the most common causative pathogens of microbial keratitis is described. The contact lens gel is composed of poly-ε-lysine (pεK) functionalized with nitric oxide (NO) releasing diazeniumdiolate moieties which enables the controlled and sustained release of bactericidal concentrations of NO at physiological pH over a period of 15 h. Diazeniumdiolate functionalization was confirmed by Fourier transform infrared (FTIR), and the concentration of NO released from the gels was determined by chemiluminescence. The bactericidal efficacy of the gels against Pseudomonas aeruginosa and Staphylococcus aureus was ascertained, and between 1 and 4 log reductions in bacterial populations were observed over 24 h. Additional cell cytotoxicity studies with human corneal epithelial cells (hCE-T) also demonstrated that the contact lens gels were not cytotoxic, suggesting that the developed technology could be a viable alternative treatment for microbial  keratitis.

Nitric Oxide-Scavenging Nanogel for Treating Rheumatoid Arthritis

Nitric oxide (NO), a radical gas molecule produced by nitric oxide synthase, plays a key role in the human body. However, when endogenous NO is overproduced by physiological disorders, severe inflammatory diseases such as rheumatoid arthritis (RA) can occur. Therefore, scavenging NO may be an alternative strategy for treating inflammatory disorders. In our previous study, we developed a NO-responsive macrosized hydrogel by incorporating a NO-cleavable cross-linker (NOCCL); here, we further evaluate the effectiveness of the NO-scavenging nanosized hydrogel (NO-Scv gel) for treating RA. NO-Scv gel is simply prepared by solution polymerization between acrylamide and NOCCL. When the NO-Scv gel is exposed to NO, NOCCL is readily cleaved by consuming the NO molecule, as demonstrated in a Griess assay. As expected, the NO-Scv gel reduces inflammation levels by scavenging NO in vitro and shows excellent biocompatibility. Furthermore, the more promising therapeutic effect of the NO-Scv gel in suppressing the onset of RA is observed in vivo in a mouse RA model when compared to the effects of dexamethasone, a commercial drug. Therefore, our findings suggest the potential of the NO-Scv gel for biomedical applications and further clinical translation.

Versatile Polydopamine Platforms: Synthesis and Promising Applications for Surface Modification and Advanced Nanomedicine

As a mussel-inspired material, polydopamine (PDA), possesses many properties, such as a simple preparation process, good biocompatibility, strong adhesive property, easy functionalization, outstanding photothermal conversion efficiency, and strong quenching effect. PDA has attracted increasingly considerable attention because it provides a simple and versatile approach to functionalize material surfaces for obtaining a variety of multifunctional nanomaterials. In this review, recent significant research developments of PDA including its synthesis and polymerization mechanism, physicochemical properties, different nano/microstructures, and diverse applications are summarized and discussed. For the sections of its applications in surface modification and biomedicine, we mainly highlight the achievements in the past few years (2016-2019). The remaining challenges and future perspectives of PDA-based nanoplatforms are discussed rationally at the end. This timely and overall review should be desirable for a wide range of scientists and facilitate further development of surface coating methods and the production of PDA-based materials.