Acidified Nitrite Solution Research Articles

Preparation of Nitric Oxide Releasing Solution and Assessment of in Vitro Efficacy on Sars-Cov-2 Virus Using Plaque Assay

In our present research, a method for preparing acidified nitrite solution comprising of biocompatible liquids which is able to release an active ingredient Nitric oxide (NO) gas at a pH scope of 3-4 is revealed. By performing an In-Vitro viral plaque assays, the cytopathic effect of NO on respiratory virus such as SARS-CoV-2 was determined. We discovered that the number of plaques reduced in a dose dependent manner as viral entities were found sensitive towards NO gas. Hence, we assert that our NO releasing acidified nitrite solution is relevant as it has shown a cytopathic effect and inhibited the replication of respiratory viruses like SARS-CoV-2 and other rhinovirus spp. Besides, a convenient and portable delivery system has been provided for administration of NO gas instead of cylinder-based system.

Unprecedented cleavage of -N-N- bond of ligand and phenyl ring nitration during nitric oxide (NO) reactivity studies: new ruthenium nitrosyl complex and photoinduced liberation of NO

A two-step procedure was used to make the ruthenium nitrosyl complex [Ru(L3)(PPh3)(NO)Cl2] (1a). The product generated when ligand L1 and [Ru(PPh3)3Cl2] reacted to an acidified nitrite solution treatment. Single-crystal X-ray diffraction was used to determine the crystal structure of (1a). Complex (1a) has a {Ru–NO}6 moiety in the Enemark–Feltham notation and was found to be diamagnetic in nature. Photolytic cleavage of metal-bound NO in (1a) was observed under ultraviolet light, and photoreleased free NO was trapped by reduced myoglobin. The amount of photoreleased NO was estimated by the Griess assay. DFT computations were also performed to authenticate the electronic properties of (1a).

Unprecedented oxidation of aldimine to carboxamido function during reactivity studies on ruthenium complex with acidified nitrite solution: Synthesis of ruthenium nitrosyl complex having {RuNO}6 moiety and photorelease of coordinated NO

Ruthenium(II) complex namely [Ru(L1)(PPh3)Cl2] (1) [where L1 = N-(pyridin-2-ylmethylene)quinolin-8-amine] derived from the tridentate ligand containing two pyridine and one imine donors was synthesized. This ruthenium(II) complex was treated with acidified nitrite solution to afford a ruthenium nitrosyl complex [Ru(L2)(PPh3)(NO)Cl](ClO4) (2) [where L2 = N-(quinolin-8-yl)picolinamide]. These complexes were characterized by elemental analysis, electronic absorption, NMR (1H and 31P NMR) and IR spectral studies. The molecular structure of 2 was confirmed by X-ray crystallography and the redox property of metal centers was investigated. During nitrosylation of complex 1, we found out the oxidation of imine functional group to amide functional group in the nitrosyl complex (2). Here, we also examined probable mechanism of nitric oxide (NO) mediated oxidation of imine to carboxamido group. The resultant nitrosyl complex 2 was found to be photoactive and could deliver NO on demand upon illumination of light.

Biofouling and scaling control of reverse osmosis membrane using one-step cleaning-potential of acidified nitrite solution as an agent

Biofouling is generally regarded as a major issue in reverse osmosis (RO) membrane filtration. Two-step chemical cleanings with alkaline and acidic agents are typically applied to restore the treatment capacity. In this study, the feasibility of one-step cleaning using free nitrous acid (FNA) was investigated as a novel low cost cleaning agent. The FNA cleaning solution was prepared by acidification of a sodium nitrite solution with hydrochloric acid. Seven fouled RO membranes collected from full-scale wastewater recycling and desalination plants were used to perform lab-scale cleaning trials. Membrane fouling characterisation revealed six of out of seven membranes were mainly bio-fouled, while one membrane was severely fouled by calcium carbonate. This study showed the feasibility of using FNA at pH 3.0 for biomass removal as well as for calcium carbonate scaling removal. The results from the lab-scale cleaning tests suggested that FNA can be used as a single cleaning agent for both biofouling and scaling removal. Cost analysis showed that FNA is a cost-effective solution for biofouling and scaling removal in RO filtration applications.

Ruthenium–Nitrosyl Complexes Derived from Ligands Containing Two Carboxylate Functional Groups and Studies on the Photolability of Coordinated NO

AbstractRuthenium complexes [RuIII(L1)(PPh3)2(Cl)] (1) and [RuIII(L2)(PPh3)2(Cl)] (2) (in which L1H2 and L2H2 are iminodiacetic acid and pyridine‐2,6‐dicarboxylic acid, respectively, and H stands for a dissociable proton) derived from the ligands that contain two carboxylate groups were synthesized and characterized. These complexes were treated with in situ generated NO derived from acidified nitrite solution, which afforded the formation of two {Ru–NO}6 complexes [Ru(L1)(PPh3)2(NO)](ClO4) (1a) and [Ru(L2)(PPh3)2(NO)](ClO4) (2a). The molecular structure of the representative complex [Ru(L2)(PPh3)2(NO)](ClO4) (2a) was determined using X‐ray crystallography. Characterization of complexes 1a and 2a by IR and NMR spectroscopic studies revealed the presence of {Ru–NO}6 species with S = 0 ground state. ESI‐MS data also supported the formation of 1a and 2a. Exposure to UV light promoted rapid loss of NO from both ruthenium nitrosyls to generate RuIII photoproducts of the type [Ru(L)(PPh3)2(S)](ClO4) (in which S stands for solvent). The quantum yields of NO photorelease for complexes 1a and 2a were measured using a chemical actinometry study. The NO released in solution was estimated using the Griess reagent, and the results were compared with the data obtained from sodium nitroprusside (SNP). A 2,2‐diphenyl‐1‐picrylhydrazine (DPPH) radical quenching assay was performed to estimate the amount of generated reactive nitrogen species and/or reactive oxygen species under aerobic conditions during photolysis of NO.

Nitric oxide donor superparamagnetic iron oxide nanoparticles

This work reports a new strategy for delivering nitric oxide (NO), based on magnetic nanoparticles (MNPs), with great potential for biomedical applications. Water-soluble magnetic nanoparticles were prepared through a co-precipitation method by using ferrous and ferric chlorides in acidic solution, followed by a mercaptosuccinic acid (MSA) coating. The thiolated nanoparticles (SH-NPs) were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), and vibrating sample magnetometry (VSM). The results showed that the SH-NPs have a mean diameter of 10nm and display superparamagnetic behavior at room temperature. Free thiol groups on the magnetite surface were nitrosated through the addition of an acidified nitrite solution, yielding nitrosated magnetic nanoparticles (SNO-NPs). The amount of NO covalently bound to the nanoparticles surface was evaluated by chemiluminescense. The SNO-NPs spontaneously released NO in aqueous solution at levels required for biomedical applications. This new magnetic NO-delivery vehicle has a great potential to generate desired amounts of NO directed to the target location.

Ruthenium(III) Cyclometalates Obtained by Site‐Specific Orthometallation and Their Reactivity with Nitric Oxide: Photoinduced Release and Estimation of NO Liberated from the Ruthenium Nitrosyl Complexes

AbstractCyclometalated RuIII complexes [Ru(LSB1)(PPh3)2Cl] (1), [LSB1H2 = 2‐(3‐nitrobenzylideneamino)phenol], and [Ru(LSB2)(PPh3)2Cl] (2), [LSB2H2 = 4‐methyl‐2‐(3‐nitrobenzylideneamino)phenol and H = dissociable protons], were synthesized by site‐specific orthometallation and characterized by spectroscopic and electrochemical studies. Complexes 1 and 2 were treated with in situ generated nitric oxide (NO), derived from an acidified nitrite solution, which afforded the ruthenium nitrosyl complexes [Ru(LSB3H)(PPh3)2(NO)Cl](ClO4) (1a) and [Ru(LBOX)(PPh3)2(NO)Cl](ClO4) (2a), respectively, [LSB3H2 = 4‐nitro‐2‐(3‐nitrobenzylideneamino)phenol, LBOXH = 5‐methyl‐7‐nitro‐2‐(3‐nitrophenyl)benzoxazole and H = dissociable protons]. Complexes 1a and 2a were found to be diamagnetic and were characterized by 1H NMR and 31P NMR spectral studies. Both 1a and 2a exhibited νNO in the range 1800–1835 cm–1 in the IR spectra. Molecular structures of σ‐aryl ruthenium nitrosyl complexes 1a·CH3OH·2CH2Cl2·H2O and 2a·2CH2Cl2 were determined by X‐ray crystallography. Nitrosylation at the metal centre, oxidative cyclization and ligand nitration were authenticated from the crystal structures. The redox properties of the metal centre were investigated. In both the nitrosyl complexes 1a and 2a, coordinated NO was found to be photolabile. The amount of photoreleased NO was estimated by using the Griess reagent and the data was compared with that obtained from sodium nitroprusside (SNP). The role of the nitro group in the ligand frame was discussed with regard to orthometallation, NO reactivity and photolability.

Photocleavage of Coordinated NO under Visible Light from Two Different Classes of Organometallic Ruthenium Nitrosyl Complexes: Reversible Binding of Phenolato Function

The structurally similar Ru(III) complexes [Ru(LSB1)(PPh3)2Cl] (1), where LSB1H2 = 2-(4-chlorobenzylidineamino)phenol and H = dissociable protons, and [Ru(LAZ1)(PPh3)2Cl] (2), where LAZ1H2 = 4-methyl-2-(p-tolyldiazenyl)phenol and H = dissociable protons, were reacted with in situ generated NO derived from acidified nitrite solution. These reactivity studies on 1 and 2 afforded the complexes [Ru(LSB2H)(PPh3)2(NO)Cl](ClO4) (1a) and [Ru(LAZ2H)(PPh3)2(NO)Cl](ClO4) (2a), respectively, where LSB2H = 2-(4-chlorobenzylidineamino)-4-nitrophenol, LAZ2H = 4-methyl-2-nitro-6-(p-tolyldiazenyl)phenol, and H = dissociable proton. Complexes 1a and 2a were found to be diamagnetic and were characterized by 1H and 31P NMR spectral studies. Both 1a and 2a exhibited νNO bands near 1800 cm−1 in their IR spectra. The molecular structures of 1a·CH2Cl2·3H2O and 2a·2H2O were determined by X-ray crystallography, and NO coordination as well as ligand nitration were authenticated from the crystal structure. In both of the nitrosyl complexes coordinated NO was found to be photolabile under visible light and photocleaved NO was transferred to reduced myoglobin. The photolability of NO in 1a and 2a afforded the complexes [Ru(LSB2)(PPh3)2Cl] (1b) and [Ru(LAZ2)(PPh3)2Cl] (2b), respectively, and the molecular structure of 1b·2CH2Cl2 was confirmed by an X-ray crystal structure solution. A novel type of reversible binding of the phenolato function to the metal center was revealed during NO coordination and photocleavage.

Antibacterial Nitric Oxide‐Releasing Polyester for the Coating of Blood‐Contacting Artificial Materials

The emergence of multidrug-resistant bacteria associated with blood-contacting artificial materials is a growing health problem, which demands new approaches in the field of biomaterials research. In this study, a poly(sulfhydrylated polyester) (PSPE) was synthesized by the polyesterification reaction of mercaptosuccinic acid with 3-mercapto-1,2-propanediol and blended with poly(methyl methacrylate) (PMMA) from solution, leading to solid PSPE/PMMA films, with three different PSPE : PMMMA mass ratios. These films were subsequently S-nitrosated through the immersion in acidified nitrite solution, yielding poly(nitrosated)polyester/PMMA (PNPE/PMMA) films. A polyurethane intravascular catheter coated with PNPE/PMMA was shown to release nitric oxide (NO) in phosphate buffered saline solution (pH 7.4) at 37 degrees C at rates of 4.6 nmol/cm(2)/h in the first 6 h and 0.8 nmol/cm(2)/h in the next 12 h. When used to coat the bottom of culture plates, NO released from these films exerted a potent dose- and time-dependent antimicrobial activity against Staphylococcus aureus and a multidrug-resistant Pseudomonas aeruginosa strains. This antibacterial effect of PSPE/PMMA films opens a new perspective for the coating of blood-contacting artificial materials, for avoiding their colonization with highly resistant bacteria.

Nitrosation and nitrosylation of haemoproteins and related compounds. Part 3. Attack at the vinyl groups of protoporphyrin dimethyl ester. X-Ray analysis of 81(E)-82-nitroprotoporphyrin dimethyl ester

Treatment of heptaethyl(vinyl)porphyrin (1) with acidified nitrite solution gives a greenish porphyrin which is shown to be 21(E)-3,7,8,12,13,17,18-heptaethyl-2-(2-nitrovinyl)porphyrin, (2). Protoporphyrin dimethyl ester (3) similarly treated gives a mixture of compounds, including two greenish porphyries which are formulated as the analogous 3(8)-(2-nitrovinyl)-8(3)-vinyldeuteroporphyrin derivatives. The less-polar isomer was crystalline and shown to be 81(E)-82-nitroprotoporphyrin dimethyl ester (4) by X-ray analysis. Crystals are triclinic, space group P, a= 10.591(4), b= 12.967(1), c= 14.203(2)A, α= 105.79(1), β= 94.91(3), γ= 94.99(2)°. The structure was solved by direct methods and refined to R 0.082.

Nitrous acid in the atmosphere and laboratory experiments on its photolysis

Low concentrations of nitrous acid in air were estimated by a differential absorption method. Over a three-month period, atmospheric concentrations at one location in southern England varied between 0.4 and 11 ppb while those of nitrogen dioxide varied between 4 and 21 ppb. The highest proportion of acid was found in air which had passed over the industrial regions of W. Europe. In the laboratory, concentrations of about 1 ppm of nitrous acid with less than 0.03 ppm of nitrogen dioxide were produced by blowing air over a shallow layer of very dilute acidified nitrite solution. Exposure of the vapour to the light from a pyrex-shielded mercury arc caused decomposition, with production of nitrogen dioxide. This decomposition was apparently prevented by some olefins. The experiments did not support the view that nitrous acid is a source of hydroxyl radicals in the atmosphere. DOI: 10.1111/j.2153-3490.1974.tb01964.x