Controllable nitric oxide release in the presence of gold nanoparticles

Nitric oxide-triggering activity of gold-, platinum- and cerium oxide-nanozymes from S-nitrosothiols and diazeniumdiolates

Cardiovascular diseases pose a significant global health challenge, contributing to high mortality rates and impacting overall well-being and quality of life. Nitric oxide (NO) plays a pivotal role as a vasodilator, regulating blood pressure and enhancing blood flow-crucial elements in preventing cardiovascular diseases, making it a prime therapeutic target. Herein, metal-based nanozymes (NZs) designed to induce NO release from both endogenous and exogenous NO-donors are investigated. Successful synthesis of gold, platinum (Pt) and cerium oxide NZs is achieved, with all three NZs demonstrating the ability to catalyze the NO release from various NO sources, namely S-nitrosothiols and diazeniumdiolates. Pt-NZs exhibit the strongest performance among the three NZ types. Further exploration involved investigating encapsulation and coating techniques using poly(lactic-co-glycolic acid) nanoparticles as experimental carriers for Pt-NZs. Both strategies showed efficiency in serving as platforms for Pt-NZs, successfully showing the ability to trigger NO release.

S-nitrosocysteamine-functionalised porous graphene oxide nanosheets as nitric oxide delivery vehicles for cardiovascular applications

Nitric oxide (NO) is a key signalling molecule released by vascular endothelial cells that is essential for vascular health. Low NO bioactivity is associated with cardiovascular diseases, such as hypertension, atherosclerosis, and heart failure and NO donors are a mainstay of drug treatment. However, many NO donors are associated with the development of tolerance and adverse effects, so new formulations for controlled and targeted release of NO would be advantageous. Herein, we describe the design and characterisation of a novel NO delivery system via the reaction of acidified sodium nitrite with thiol groups that had been introduced by cysteamine conjugation to porous graphene oxide nanosheets, thereby generating S-nitrosated nanosheets. An NO electrode, ozone-based chemiluminescence and electron paramagnetic resonance spectroscopy were used to measure NO released from various graphene formulations, which was sustained at >5 × 10-10 mol cm-2 min-1 for at least 3 h, compared with healthy endothelium (cf. 0.5-4 × 10-10 mol cm-2 min-1). Single cell Raman micro-spectroscopy showed that vascular endothelial and smooth muscle cells (SMCs) took up graphene nanostructures, with intracellular NO release detected via a fluorescent NO-specific probe. Functionalised graphene had a dose-dependent effect to promote proliferation in endothelial cells and to inhibit growth in SMCs, which was associated with cGMP release indicating intracellular activation of canonical NO signalling. Chemiluminescence detected negligible production of toxic N-nitrosamines. Our findings demonstrate the utility of porous graphene oxide as a NO delivery vehicle to release physiologically relevant amounts of NO in vitro, thereby highlighting the potential of these formulations as a strategy for the treatment of cardiovascular diseases.

Nitric Oxide: Physiological Functions, Delivery, and Biomedical Applications

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

Polymeric Amines Induce Nitric Oxide Release from S-Nitrosothiols

Catalytic generation of nitric oxide (NO) from NO donors by nanomaterials has enabled prolonged NO delivery for various biomedical applications, but this approach requires laborious synthesis routes. In this study, a new class of materials, that is, polymeric amines including polyethyleneimine (PEI), poly-L-lysine, and poly(allylamine hydrochloride), is discovered to induce NO generation from S-nitrosothiols (RSNOs) at physiological conditions. Controlled NO generation can be readily achieved by tuning the concentration of the NO donors (RSNOs) and polymers, and the type and molecular weight of the polymers. Importantly, the mechanism of NO generation by these polymers is deciphered to be attributed to the nucleophilic reaction between primary amines on polymers and the SNO groups of RSNOs. The NO-releasing feature of the polymers can be integrated into a suite of materials, for example, simply by embedding PEI into poly(vinyl alcohol) (PVA) hydrogels. The functionality of the PVA/PEI hydrogels is demonstrated for Pseudomonas aeruginosa biofilm prevention with a ≈4 log reduction within 6 h. As NO has potential therapeutic implications in various diseases, the identification of polymeric amines to induce NO release will open new opportunities in NO-generating biomaterials for antibacterial, antiviral, anticancer, antithrombotic, and wound healing applications.

Regulation of Nitric Oxide (NO) Release by Membrane Fluidity in Ruthenium Nitrosyl Complex-Embedded Phospholipid Vesicles

Incorporating water-insoluble nitric oxide (NO)-releasing molecules into biocompatible vesicles may allow for the tunable control of NO release on a specific target site. In vesicles, membrane fluidity plays an important role and influences the final therapeutic efficiency of drugs loaded into the vesicles. Hence, we aimed to investigate the effect of lipid fluidity on the NO release behavior of the photo-controllable ruthenium nitrosyl (Ru-NO) complex. In this regard, a new photoactive ruthenium nitrosyl complex (L.Ru-NO) with amphiphilic terpyridine ligand was synthesized and characterized in detail. L.Ru-NO was incorporated with commercial phospholipids to form nanoscale vesicles L.Ru-NO@Lip. The photoactive {Ru-NO}⁶ type complex released NO in the organic solvent CH₃CN and aqueous liposome solution by irradiating under low-intensity blue light (λ = 410 nm, 3 W). To demonstrate the effect of lipid structure and fluidity on NO release, four different liposome systems L.Ru-NO@Lip1-4 were prepared by using phospholipids such as DOPC, DSPC, DPPC, and DMPC having different chain lengths and saturation. The NO-releasing abilities of these liposomes in aqueous medium were studied by UV-vis spectrum, colorimetric Greiss, and fluorescent DAF assay. The results show that the rate of NO release could be easily tuned by varying the lipid fluidity. The effect of temperature and pH on NO release was also studied. Further, the complex L.Ru-NO and liposomes L.Ru-NO@Lip1 were assayed as an antibacterial agent against the strains of bacteria Escherichia coli and Staphylococcus aureus.

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

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

In situ synthesis of ultrafine Cu2O on layered double hydroxide for electrochemical detection of S-nitrosothiols

The identification and quantitation of S-nitrosothiols (RSNO) has aroused enormous levels of attention, due to RSNO have many roles in vivo. Here, we synthesized the nanocomposites of ultrafine Cu₂O/layered double hydroxide (u-Cu₂O/LDH) by the in situ topotactic reduction of a Cu²⁺-containing LDH with ascorbic acid under gentle conditions and applied these u-Cu₂O/LDH to detect and monitor RSNO. Electrochemical signals of u-Cu₂O/LDH exhibited a wide N-acetyl-S-nitrosopenicillamine detection range from 5.0 nM-4.0 μM and 4.0 μM-400 μM, with a low detection limit of 1.58 nM. The sensor also exhibited good performance for other RSNO, such as S-nitrosoglutathione, S-nitrosocysteine, and S-nitrosohomocysteine with corresponding limits of detection at 1.94 nM, 1.23 nM and 1.62 nM, respectively. The high levels of selectivity and sensitivity to RSNO in complex biological environments can be attributed to the abundance of exposed active sites, and the underlying support structure. In addition, u-Cu₂O/LDH also exhibited dynamic nitric oxide (NO) monitoring ability from living cells. Collectively, these results reveal that u-Cu₂O/LDH exhibit a remarkable ability to quantify RSNO levels in complex samples, and could therefore provide new tools for exploring ultrafine nanomaterials as a potential biosensor to investigate biological events.

Ceria Nanoparticles as an Unexpected Catalyst to Generate Nitric Oxide from S-Nitrosoglutathione

Ceria nanoparticles (NPs) are widely reported to scavenge nitric oxide (NO) radicals. This study reveals evidence that an opposite effect of ceria NPs exists, that is, to induce NO generation. Herein, S-nitrosoglutathione (GSNO), one of the most biologically abundant NO donors, is catalytically decomposed by ceria NPs to produce NO. Ceria NPs maintain a high NO release recovery rate and retain their crystalline structure for at least 4 weeks. Importantly, the mechanism of this newly discovered NO generation capability of ceria NPs from GSNO is deciphered to be attributed to the oxidation of Ce³⁺ to Ce⁴⁺ on their surface, which is supported by X-ray photoelectron spectroscopy and density functional theory analysis. The prospective therapeutic effect of NO-generating ceria NPs is evaluated by the suppression of cancer cells, displaying a significant reduction of 93% in cell viability. Overall, this report is, to the authors' knowledge, the first study to identify the capability of ceria NPs to induce NO generation from GSNO, which overturns the conventional concept of them acting solely as a NO-scavenging agent. This study will deepen our knowledge about the therapeutic effects of ceria NPs and open a new route toward the NO-generating systems for biomedical applications.

Stepwise immobilization of keratin-dopamine conjugates and gold nanoparticles on PET sheets for potential vascular graft with the catalytic generation of nitric oxide

Gold nanoparticles(AuNPs) are capable to catalyze the nitric oxide (NO) generation from endogenous and exogenous donors, thereby promoting re-endothelialization and inhibiting intimal hyperplasia and thrombosis. Herein, keratin-dopamine conjugates were synthesized and then immobilized on the surface of the pre-aminolyzed poly(ethylene terephthalate) (PET) via self-polymerization of dopamine residue, following by the formation of AuNPs in situ without extra reductant. The modified PET sheets(PET-AuNPs) could promote the growth of HUVECs while inhibit the proliferation of HUASMCs due to their catalytic generation of NO from GSNO. In addition, these sheets exhibited antibacterial properties and good blood compatibility without hemolysis. Taken together, this strategy for designing prosthetic vascular grafts to treat cardiovascular diseases has great potential.

Transient Vasodilation in Mouse 4T1 Tumors after Intragastric and Intravenous Administration of Gold Nanoparticles

Gold nanoparticles (AuNPs) are foreseen as a promising tool in nanomedicine, both as drug carriers and radiosensitizers. They have been also proposed as a potential anticancer drug due to the anti-angiogenic effect in tumor tissue. In this work we investigated the effect of citrate-coated AuNPs of nominal diameter 20 nm on the growth and metastatic potential of 4T1 cells originated from a mouse mammary gland tumor inoculated into the mammary fat pad of Balb/ccmdb mice. To evaluate whether AuNPs can prevent the tumor growth, one group of inoculated mice was intragastrically (i.g.) administered with 1 mg/kg of AuNPs daily from day 1 to day 14 after cancer cell implantation. To evaluate whether AuNPs can attenuate the tumor growth, the second group was intravenously (i.v.) administered with 1 or 5 mg/kg of AuNPs, twice on day 5 and day 14 after inoculation. We did not observe any anticancer activity of i.v. nor i.g. administered AuNPs, as they did not affect neither the primary tumor growth rate nor the number of lung metastases. Unexpectedly, both AuNP treatment regimens caused a marked vasodilating effect in the tumor tissue. As no change of potential angiogenic genes (Fgf2, Vegfa) nor inducible nitric oxygenase (Nos2) was observed, we proposed that the vasodilation was caused by AuNP-dependent decomposition of nitrosothiols and direct release of nitric oxide in the tumor tissue.

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.

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.

Enzyme Mimics for the Catalytic Generation of Nitric Oxide from Endogenous Prodrugs

The highly diverse biological roles of nitric oxide (NO) in both physiological and pathophysiological processes have prompted great interest in the use of NO as a therapeutic agent in various biomedical applications. NO can exert either protective or deleterious effects depending on its concentration and the location where it is delivered or generated. This double-edged attribute, together with the short half-life of NO in biological systems, poses a major challenge to the realization of the full therapeutic potential of this molecule. Controlled release strategies show an admirable degree of precision with regard to the spatiotemporal dosing of NO but are disadvantaged by the finite NO deliverable payload. In turn, enzyme-prodrug therapy techniques afford enhanced deliverable payload but are troubled by the inherent low stability of natural enzymes, as well as the requirement to control pharmacokinetics for the exogenous prodrugs. The past decade has seen the advent of a new paradigm in controlled delivery of NO, namely localized bioconversion of the endogenous prodrugs of NO, specifically by enzyme mimics. These early developments are presented, successes of this strategy are highlighted, and possible future work on this avenue of research is critically discussed.

Photochemistry of nitric oxide and S-nitrosothiols in human skin

Nitric oxide (NO) is related to a wide range of physiological processes such as vasodilation, macrophages cytotoxicity and wound healing. The human skin contains NO precursors (NOx). Those are mainly composed of nitrite (NO2-), nitrate (NO3-), and S-nitrosothiols (RSNOs) which forms a large NO store. These NOx stores in human skin can mobilize NO to blood stream upon ultraviolet (UV) light exposure. The main purpose of this study was to evaluate the most effective UV light wavelength to generate NO and compare it to each NO precursor in aqueous solution. In addition, the UV light might change the RSNO content on human skin. First, we irradiated pure aqueous solutions of NO2- and NO3- and mixtures of NO2- and glutathione and NO3- and S-nitrosoglutathione (GSNO) to identify the NO release profile from those species alone. In sequence, we evaluated the NO generation profile on human skin slices. Human skin was acquired from redundant plastic surgical samples and the NO and RSNO measurements were performed using a selective NO electrochemical sensor. The data showed that UV light could trigger the NO generation in skin with a peak at 280-285 nm (UVB range). We also observed a significant RSNO formation in irradiated human skin, with a peak at 320 nm (UV region) and at 700 nm (visible region). Pre-treatment of the human skin slice using NO2- and thiol (RSHs) scavengers confirmed the important role of these molecules in RSNO formation. These findings have important implications for clinical trials with potential for new therapies.

Strategies for engineering advanced nanomedicines for gas therapy of cancer

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

Nanosized copper(ii) oxide/silica for catalytic generation of nitric oxide from S-nitrosothiols

The findings of this study suggest that copper(ii) oxide–silica nanoparticles produce NO from the GSNO species at physiological conditions in situ and could be used for designing biomedical materials with NO generating activity.

Crystal-facet-dependent denitrosylation: modulation of NO release from S-nitrosothiols by Cu2O polymorphs

Nitric oxide (NO), a gaseous small molecule generated by the nitric oxide synthase (NOS) enzymes, plays key roles in signal transduction. The thiol groups present in many proteins and small molecules undergo nitrosylation to form the corresponding S-nitrosothiols. The release of NO from S-nitrosothiols is a key strategy to maintain the NO levels in biological systems. However, the controlled release of NO from the nitrosylated compounds at physiological pH remains a challenge. In this paper, we describe the synthesis and NO releasing ability of Cu2O nanomaterials and provide the first experimental evidence that the nanocrystals having different crystal facets within the same crystal system exhibit different activities toward S-nitrosothiols. We used various imaging techniques and time-dependent spectroscopic measurements to understand the nature of catalytically active species involved in the surface reactions. The denitrosylation reactions by Cu2O can be carried out multiple times without affecting the catalytic activity.

Urban Particulate Matter-Induced Decomposition of S-Nitrosoglutathione Relevant to Aberrant Nitric Oxide Biological Signaling

Exposure to airborne particulate matter (PM) is associated with hazardous effects on human health. Soluble constituents of PM may be released in biological fluids and disturb the precisely tuned nitric oxide signaling processes. The influence of aqueous extracts from two types of airborne urban PM (SRM 1648a, a commercially available sample, and KR PM2.5, a sample collected "in-house" in Krakow, Poland) on the stability of S-nitrosoglutathione (GSNO) was investigated. The particle interfaces had no direct effect on the studied reaction, but extracts obtained from both samples facilitated NO release from GSNO. The effectiveness of NO release was significantly affected by glutathione (GSH) and ascorbic acid (AscA). Examination of the combined influence of Cu²⁺ , Fe³⁺ , and reductants on GSNO stability revealed copper to be the main GSNO decomposing species. Computational models of nitrosothiols interacting with metal oxide substrates and solvated metal ions support these claims. The study stresses the importance of the interplay between metal ions and biological reductants in S-nitrosothiols decomposition.

Biocompatible and Antibacterial Nitric Oxide-Releasing Pluronic F-127/Chitosan Hydrogel for Topical Applications

Nitric oxide (NO) is involved in physiological processes, including vasodilatation, wound healing and antibacterial activities. As NO is a free radical, designing drugs to generate therapeutic amounts of NO in controlled spatial and time manners is still a challenge. In this study, the NO donor S-nitrosoglutathione (GSNO) was incorporated into the thermoresponsive Pluronic F-127 (PL)-chitosan (CS) hydrogel, with an easy and economically feasible methodology. CS is a polysaccharide with known antimicrobial properties. Scanning electron microscopy, rheology and differential scanning calorimetry techniques were used for hydrogel characterization. The results demonstrated that the hydrogel has a smooth surface, thermoresponsive behavior and good mechanical stability. The kinetics of NO release and GSNO diffusion from GSNO-containing PL/CS hydrogel demonstrated a sustained NO/GSNO release, in concentrations suitable for biomedical applications. The GSNO-PL/CS hydrogel demonstrated a concentration-dependent toxicity to Vero cells, and antimicrobial activity to Pseudomonas aeruginosa (minimum inhibitory concentration and minimum bactericidal concentration values of 0.5 µg·mL-1 of hydrogel, which corresponds to 1 mmol·L-1 of GSNO). Interestingly, the concentration range in which the NO-releasing hydrogel demonstrated an antibacterial effect was not found to be toxic to the Vero mammalian cell. Thus, the GSNO-PL/CS hydrogel is a suitable biomaterial for topical NO delivery applications.

Enhanced antibacterial efficacy of nitric oxide releasing thermoplastic polyurethanes with antifouling hydrophilic topcoats

Surface fouling is one of the leading causes of infection associated with implants, stents, catheters, and other medical devices. The surface chemistry of medical device coatings is important in controlling and/or preventing fouling. In this study, we have shown that a combination of nitric oxide releasing hydrophobic polymer with a hydrophilic polymer topcoat can significantly reduce protein attachment and subsequently reduce bacterial adhesion as a result of the synergistic effect. Nitric oxide (NO) is a well-known potent antibacterial agent due to its adverse reactions on microbial cell components. Owing to the surface chemistry of hydrophilic polymers, they are suitable as antifouling topcoats. In this study, four biomedical grade polymers were compared for protein adhesion and NO-release behavior: CarboSil 2080A, silicone rubber, SP60D60, and SG80A. SP60D60 was found to resist protein adsorption up to 80% when compared to the other polymers while CarboSil 2080A maintained a steady NO flux even after 24 hours (∼0.50 × 10-10 mol cm-2 min-1) of soaking in buffer solution with a loss of less than 3% S-nitroso-N-acetylpenicillamine (SNAP), the NO donor molecule, in the leaching analysis. Therefore, CarboSil 2080A incorporated with SNAP and top-coated with SP60D60 was tested for antibacterial efficacy after exposure to fibrinogen, an abundantly found protein in blood. The NO-releasing CarboSil 2080A with the SP60D60 top-coated polymer showed a 96% reduction in Staphylococcus aureus viable cell count compared to the control samples. Hence, the study demonstrated that a hydrophilic polymer topcoat, when applied to a polymer with sustained NO release from an underlying SNAP incorporated hydrophobic polymer, can reduce bacterial adhesion and be used as a highly efficient antifouling, antibacterial polymer for biomedical applications.

Effect of chemical structure of S-nitrosothiols on nitric oxide release mediated by the copper sites of a metal organic framework based environment

The effect of chemical structure of different biologically compatible S-nitrosothiols on the solvation environment at catalytic copper sites in a metal organic framework (MOF) suspended in a solution of ethanol is probed using computational methods. The use of a copper based MOF as a storage vehicle and catalyst (copper sites of the MOF) in the controlled and sustained release of chemically stored nitric oxide (NO) from S-nitrosocysteine has been shown to occur both experimentally and computationally [J. Am. Chem. Soc., 2012, 134, 3330-3333; Phys. Chem. Chem. Phys., 2015, 17, 23403]. Previous studies on a copper based MOF, namely HKUST-1, concluded that modifications in the R-group of s-nitrosothiols and/or organic linkers of MOFs led to a method capable of modulating NO release. In order to test the hypothesis that larger R-groups slow down NO release, four different RSNOs (R = cysteine, N-acetylcysteine, N-acetyl-d,l-penicillamine or glutathione) of varying size were investigated, which in turn required the use of a larger copper based MOF. Due to its desirable copper centers and more extensive framework, MOF-143, an analog of HKUST-1 was chosen to further explore both the effect of different RSNOs as well as MOF environments on NO release. Condensed phase classical molecular dynamics simulations are utilized to study the effect of the complex MOF environment as well as the chemical structure and size of the RSNO on the species on the catalytic reaction. The results indicate that in addition to the size of the RSNO species and the organic linkers within the MOF, the reaction rates can be modulated by the molecular structure of the RSNO and furthermore combining different RSNO species can also be used to tune the rate of NO release.

Interaction of gold nanoparticles mediated by captopril and S-nitrosocaptopril: the effect of manganese ions in mild acid medium

We report herein results regarding reactivity and assembly of citrate-capped gold nanoparticles (AuNPs) mediated by captopril (cap) and S-nitrosocaptopril (NOcap), two angiotensin converting enzyme inhibitors and antihypertensive agents. The results were compared with that of cysteine (Cys), a thiol-containing amino acid found in plasma. The interparticle interactions were characterized by monitoring the evolution of the surface plasmon resonance band using the spectrophotometric method. The original gold nanoparticles were efficiently modified by small amounts of Mn(+2) ions, which are adsorbed onto the surface of 15.4 nm citrate-capped gold nanoparticles, giving rise to manganese-gold nanoparticles (Mn-AuNPs) that, in mild acid medium, have proved to be highly sensitive and a rapid colorimetric detection method for thiols. Depending on the concentration of the Mn(+2) ions the aggregation of AuNPs can be rapidly induced. The kinetics of the assembly process has been studied. Good first-order kinetics has been observed, with the exception of captopril-mediated nanoparticle aggregation at low concentration of either cap or acid. The rate of Cys-mediated assembly of gold nanoparticles in aqueous 10 mM acetic acid is more than 20-times faster than pure AuNPs and concentrations of Cys as low as 34 nM can be detected in less than 40 min under conditions of stable Mn-AuNPs. Similar effects were observed with cap or NOcap. The assembly-disassembly reversibility is shown with cap and NOcap and depends highly on pH.

Gold Nanoparticle-Based Facile Detection of Human Serum Albumin and Its Application as an INHIBIT Logic Gate

In this work, a facile colorimetric method is developed for quantitative detection of human serum albumin (HSA) based on the antiaggregation effect of gold nanoparticles (Au NPs) in the presence of HSA. The citrate-capped Au NPs undergo a color change from red to blue when melamine is added as a cross-linker to induce the aggregation of the NPs. Such an aggregation is efficiently suppressed upon the adsorption of HSA on the particle surface. This method provides the advantages of simplicity and cost-efficiency for quantitative detection of HSA with a detection limit of ∼1.4 nM by monitoring the colorimetric changes of the Au NPs with UV-vis spectroscopy. In addition, this approach shows good selectivity for HSA over various amino acids, peptides, and proteins and is qualified for detection of HSA in a biological sample. Such an antiaggregation effect can be further extended to fabricate an INHIBIT logic gate by using HSA and melamine as inputs and the color changes of Au NPs as outputs, which may have application potentials in point-of-care medical diagnosis.

Glutathione-facilitated design and fabrication of gold nanoparticle-based logic gates and keypad lock

In this paper, we describe how we developed a simple design and fabrication method for logic gates and a device by using a commercially available tripeptide, namely glutathione (GSH), together with metal ions and disodium ethylenediaminetetraacetate (EDTA) to control the dispersion and aggregation of gold nanoparticles (NPs). With the fast adsorption of GSH on gold NPs and the strong coordination of GSH with metal ions, the addition of GSH and Pb(2+) ions immediately resulted in the aggregation of gold NPs, giving rise to an AND function. Either Pb(2+) or Ba(2+) ions induced the aggregation of gold NPs in the presence of GSH, supporting an OR gate. Based on the fact that EDTA has a strong capacity to bind metal ions, thus preventing the aggregation of gold NPs, an INHIBIT gate was also fabricated. More interestingly, we found that the addition sequence of GSH and Hg(2+) ions influenced the aggregation of gold NPs in a controlled manner, which was used to design a sequential logic gate and a three-input keypad lock for potential use in information security. The GSH strategy addresses concerns of low cost, simple fabrication, versatile design and easy operation, and offers a promising platform for the development of functional logic systems.

Functional gold nanoparticles for the storage and controlled release of nitric oxide: applications in biofilm dispersal and intracellular delivery

Gold nanoparticles (size 10 nm) were designed to store and release nitric oxide (NO), by functionalizing their surfaces with functional polymers modified with NO-donor molecules. Firstly, block copolymer chains consisting of poly(oligoethylene glycol methyl ether methacrylate)-b-poly(vinyl benzyl chloride) (P(OEGMA)-b-PVBC)) were prepared using RAFT polymerization. The chloro-functional groups were then reacted with hexylamine, to introduce secondary amine groups to the copolymer chains. The block copolymers were then grafted onto the surface of gold nanoparticles, exploiting the end-group affinity for gold - attaining grafting densities of 0.6 chain per nm². The secondary amine functional groups were then converted to N-diazeniumdiolate NO donor molecules via exposure to NO gas at high pressure (5 atm). The NO-bearing, gold nanoparticles were characterized using a range of techniques, including transmission electron microscopy, dynamic light scattering (DLS), thermal gravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). The nanoparticles displayed slow release of the nitric oxide in biological media. Proof of potential utility was then demonstrated in two different application areas: Pseudomonas aeruginosa biofilm dispersal and cancer cell cytotoxicity.