Nitrogen-cycling processes under long-term compound heavy metal(loids) pressure around a gold mine: Stimulation of nitrite reduction.

Mining and tailings deposition can cause serious heavy metal(loids) pollution to the surrounding soil environment. Soil microorganisms adapt their metabolism to such conditions, driving alterations in soil function. This study aims to elucidate the response patterns of nitrogen-cycling microorganisms under long-term heavy metal(loids) exposure. The results showed that the diversity and abundance of nitrogen-cycling microorganisms showed negative feedback to heavy metal(loids) concentrations. Denitrifying microorganisms were shown to be the dominant microorganisms with over 60% of relative abundance and a complex community structure including 27 phyla. Further, the key bacterial species in the denitrification process were calculated using a random forest model, where the top three key species (Pseudomonas stutzei, Sphingobium japonicum and Leifsonia rubra) were found to play a prominent role in nitrite reduction. Functional gene analysis and qPCR revealed that nirK, which is involved in nitrite reduction, significantly accumulated in the most metal-rich soil with the increase of absolute abundance of 63.86%. The experimental results confirmed that the activity of nitrite reductase (Nir) encoded by nirK in the soil was increased at high concentrations of heavy metal(loids). Partial least squares-path model identified three potential modes of nitrite reduction processes being stimulated by heavy metal(loids), the most prominent of which contributed to enhanced nirK abundance and soil Nir activity through positive stimulation of key species. The results provide new insights and preliminary evidence on the stimulation of nitrite reduction processes by heavy metal(loids).

Nitrite facilitated transformation of halophenols in ice.

This study investigated the expediated transformation of halophenols in the presence of nitrite (NO2-) under slightly acidic conditions in ice, whereas such transformation was negligible in liquid water at 4 °C. We proposed that this phenomenon was attributed to the freeze-concentration effect, incurring a pH drop and the aggregation of NO2- and halophenols within the liquid-like grain boundary layer amid ice crystals. Within this micro-environment, NO2- underwent protonation to generate reactive nitrous acid (HNO2) and nitrosonium ions (NO+) that facilitate the nitration and oxidation of halophenols. When 10 µÐœ halophenol was treated by freezing in the presence of 5 µÐœ NO2-, the total yields of nitrated products reached 2.4 µÐœ and 1.4 µÐœ within 12 h for 2-chlorophenol (2CP) and 2-bromophenol (2BP), respectively. NO+ drove oxidative coupling reactions, generating hydroxyl polyhalogenated diphenyl ethers (OH-PBDEs) and hydroxyl polyhalogenated diphenyls via C-O or C-C coupling. These two pathways were intricately intertwined. The presence of natural organic matter (NOM) mitigated the formation of nitrated products and completely suppressed the coupling products. This study offers valuable insights into the fate of halophenols in ice and suggests potential pathways for the formation of nitrophenolic compounds and OH-PBDEs in natural cold environments. These findings also open up a new avenue in environmental chemistry research.

Electrokinetics of nitrite to ammonia conversion in the neutral medium over a platinum surface.

Polycrystalline Pt electrode was employed to selectively convert nitrite ions ([[EQUATION]]) into useful nitrogenous compound through electrochemical reduction reaction in neutral medium. According to adsorptive stripping analysis, the reduction process produced nitric oxide (NO) on the surface of Pt electrode. The spectroscopic test and gas chromatographic studies discovered the presence of ammonia (NH3) in the electrolyzed solution, suggesting the transformation of adsorbed NO into NH3 during the reverse scan. Scan rate dependent investigation was performed to elucidate kinetic information relating to this reaction on Pt surface. From Ep vs scan rate (υ) and jp vs υ (logarithmic plot), it was found that the conversion of [[EQUATION]] ion into NO is an irreversible reaction which relies on the diffusion of [[EQUATION]] ions to electrode surface. The Tafel analysis unveiled that the first electron transfer sets the overall reaction rate, having formal reduction potential, E0' = -0.46 V and standard heterogeneous rate constant, k0 = [[EQUATION]] cm s-1. Reductive transfer coefficient (α) is another kinetics parameter, which was found to be approximate 0.77 from the difference between Ep and Ep/2 of the voltammograms obtained over scan rate range 0.005 V s-1 to 0.250 V s-1, indicating a stepwise process.

Influence of residual anaerobic granular sludge (AnGS) from anaerobically digested molasses wastewater in aerobic granular sludge reactor.

This study investigated the impact of residual anaerobic granular sludge (AnGS) from anaerobic digesters treating molasses wastewater on ammonium reduction in a downstream aerobic granular sludge (AGS) reactor. Two conditions were tested: raw (high AnGS concentration) and settled (low AnGS concentration) anaerobically digested molasses wastewaters were fed into the AGS reactor. With the introduction of raw wastewater, enhanced nitrite accumulation at 30 % and improved total inorganic nitrogen (TIN) removal at 11 % were observed compared to 1 % nitrite accumulation and 8 % TIN removal with the introduction of settled wastewater. However, AnGS adversely affected other aspects of reactor performance, increasing effluent solid content and decreasing soluble chemical oxygen demand removal efficiency from 20 % in the low AnGS condition to 11 % in the high AnGS condition. Despite the observed retention of AnGS in the reactor, no significant bioaugmentation effects on the microbial community of the AGS were observed. Aerobic granular sludge was consistently observed in both conditions. The study suggests that AnGS may act as a nucleus for granule formation, helping to maintain granule stability in a disturbed environment. This study offers a systematic understanding of the impact of AnGS on subsequent nitrogen removal process using AGS, aiding in the decision making in the treatment of high solid anaerobic digestate.

Construction of portable hydrogel kits with self-ratio optical bimodal detection and smartphone imaging for on-site nitrite screening.

Accurate on-site detection of nitrite in complex matrices remains a significant challenge. Herin, we construct a self-ratio optical bimodal portable kit via co-assembling NaErF4:0.5%Tm@NaYF4@NaYbF4:0.5%Tm@NaYF4 (Er:Tm@Yb:Tm) and nitrogen-doped carbon platinum nanomaterials (Pt/CN) in sodium alginate (SA) hydrogel. Pt/CN nanomaterials are synthesized by high-temperature sintering using a zinc-based zeolite imidazolium framework as a sacrificial template. The Pt/CN nanozyme possesses excellent oxidase-like activity to produce the oxidation state 3,3',5,5'-tetramethylbenzidine (oxTMB). Nitrite mediates diazotization of oxTMB to trigger the change of absorption signals, accompanying the ratio fluorescence response of the Er:Tm@Yb:Tm. Crucially, Er:Tm@Yb:Tm and Pt/CN are embedded in SA hydrogel to fabricate a portable kit with efficient and sensitive performance. An image processing algorithm is used to analyze the nitrite-induced signal change of the portable hydrogel kit, resulting in detection limits of 0.63 µM. This method has great potential for point-of-care applications due to its reliability, long-term stability, accuracy, sensitivity, and portability.

Enhancing Localized Electron Density over Pd1.4Cu Decorated Oxygen Defective TiO2-x Nanoarray for Electrocatalytic Nitrite Reduction to Ammonia.

Electrocatalytic nitrite (NO2 -) reduction to ammonia (NH3) is a promising method for reducing pollution and aiding industrial production. However, progress is limited by the lack of efficient selective catalysts and ambiguous catalytic mechanisms. This study explores the loading of PdCu alloy onto oxygen defective TiO2-x, resulting in a significant increase in NH3 yield (from 70.6 to 366.4 µmol cm-2 h-1 at -0.6 V vs reversible hydrogen electrode) by modulating localized electron density. In situ and operando studies illustrate that the reduction of NO2 - to NH3 involves gradual deoxygenation and hydrogenation. The process also demonstrated excellent selectivity and stability, with long-term durability in cycling and 50 h stability tests. Density functional theory (DFT) calculations elucidate that the introduction of PdCu alloys further amplified electron density at oxygen vacancies (Ovs). Additionally, the Ti─O bond is strengthened as the d-band center of the Ti 3d rising after PdCu loading, facilitating the adsorption and activation of *NO2. Moreover, the presence of Ovs and PdCu alloy lowers the energy barriers for deoxygenation and hydrogenation, leading to high yield and selectivity of NH3. This insight of controlling localized electron density offers valuable insights for advancing sustainable NH3 synthesis methods.

Acquired methemoglobinemia in a third trimester puerpera and her premature infant with sodium nitrite poisoning: A case report.

BACKGROUND: The common cause of sodium nitrite poisoning has shifted from previous accidental intoxication by exposure or ingestion of contaminated water and food to recent alarming intentional intoxication as an employed method of suicide/exit. The subsequent formation of methemoglobin (MetHb) restricts oxygen transport and utilization in the body, resulting in functional hypoxia at the tissue level. In clinical practice, a mismatch of cyanotic appearance and oxygen partial pressure usually contributes to the identification of methemoglobinemia. Prompt recognition of characteristic mismatch and accurate diagnosis of sodium nitrite poisoning are prerequisites for the implementation of standardized systemic interventions. CASE SUMMARY: A pregnant woman was admitted to the Department of Critical Care Medicine at the First Affiliated Hospital of Harbin Medical University due to consciousness disorders and drowsiness 2 h before admission. Subsequently, she developed vomiting and cyanotic skin. The woman underwent orotracheal intubation, invasive mechanical ventilation (IMV), and correction of internal environment disturbance in the ICU. Her premature infant was born with a higher-than-normal MetHb level of 3.3%, and received detoxification with methylene blue and vitamin C, supplemental vitamin K1, an infusion of fresh frozen plasma, as well as respiratory support via orotracheal intubation and IMV. On day 3 after admission, the puerpera regained consciousness, evacuated the IMV, and resumed enteral nutrition. She was then transferred to the maternity ward 24 h later. On day 7 after admission, the woman recovered and was discharged without any sequelae. CONCLUSION: MetHb can cross through the placental barrier. Level of MetHb both reflects severity of the sodium nitrite poisoning and serves as feedback on therapeutic effectiveness.

Acute nitrite exposure causes gut microbiota dysbacteriosis and proliferation of pathogenic Photobacterium in shrimp.

Nitrite exposure has become a significant concern in the aquaculture industry, posing a severe threat to aquatic animals such as shrimp. While studies have reported the adverse effects of nitrite on shrimp growth, the part played by the gut microbiota in shrimp mortality resulting from nitrite exposure is poorly understood. Here, the effects of nitrite on shrimp gut bacterial community were investigated using 16S rRNA amplicon sequencing, bacterial isolation, genomic analysis, and infection experiments. Compared to the control_healthy group, changes in the bacterial composition of the nitrite_dead group were associated with reduced abundance of specific beneficial bacteria and increased abundance of certain pathogenic bacteria. Notably, members of the Photobacterium genus were found to be significantly enriched in the nitrite_dead group. Genomic analysis of a representative Photobacterium strain (LvS-8n3) revealed a variety of genes encoding bacterial toxins, including hemolysin, adhesin, and phospholipase. Furthermore, it was also found that LvS-8n3 exhibits strong pathogenicity, probably due to its high production of pathogenic factors and the ability to utilize nitrite for proliferation. Therefore, the proliferation of pathogenic Photobacterium species appears pivotal for driving shrimp mortality caused by nitrite exposure. These findings provide novel insights into the disease mechanism in shrimp under conditions of environmental change.

Intrinsic oxidase-mimicking activity of nitrite upon visible light illumination and its colorimetric detection in saliva.

Small molecules with enzyme-like properties have recently attracted considerable attention. Herein, we discovered that nitrite possesses intrinsic oxidase-mimicking activity upon visible light, catalyzing the oxidation of the typical chromogenic substrate in the absence of H2O2. Notably, nitrite exhibited a markedly high value of Kcat, approximately 4, 7, and 4000-fold greater than that of Acr+-Mes, Eosin Y, and Diacetyl, respectively. Comprehensive investigation elucidated that O2•⁻ and •OH are the primary reactive oxygen species (ROS) responsible for the oxidation of 3,3',5,5'-tetramethylbenzidine dihydrochloride hydrate (TMB). Leveraging the linear correlation between the absorbance of oxidized TMB (oxTMB) at 652 nm and nitrite concentration, a simple colorimetric approach for nitrite detection was successfully established in the range of 1-75 µM with a detection limit of 0.14 µM. Moreover, the proposed strategy could be applied to determine the nitrite concentration in saliva, exhibiting a great prospect for clinical diagnosis. This work contributes novel insights into the exploration of small-molecule enzyme mimics.

Individual evaluation of nitrite and free nitrous acid inhibition on anammox activity.

The anammox reaction simultaneously utilizes ammonia and nitrite as substrates; however, high nitrite concentrations act as strong inhibitors of the reaction. In this study, inhibition by NO2- and free nitrous acid (FNA) was separately evaluated in continuous feeding tests using different biomass carriers. The influent NO2- concentration was increased under pH 7.6, where FNA is less likely to affect anammox activity. A continuous test using polyethylene glycol (PEG) gel carriers containing immobilized anammox bacteria showed that the inhibition ratio was 13% when the NO2--N concentration in the reactor was 350 mg L-1 (FNA ≤0.06 mg L-1). The relationship between NO2- concentration in the reactor and inhibition ratio increased linearly. Evaluation of the inhibitory effect of FNA by increasing the influent NO2- concentration at pH 6.4, where FNA is easily formed, demonstrated that the relationship between FNA and inhibition ratio could be fitted to a sigmoid curve, and the 50% inhibitory concentration (IC50) of FNA was 0.88 mg L-1. A similar test performed using polyvinyl alcohol carriers containing anammox bacteria on their surface showed the same trend as the PEG gel carriers, with the IC50 for FNA at 0.70 mg L-1. These results indicate that the inhibitory effect of FNA on anammox activity was greater than that of NO2-. The evaluation of these two factors helped identify important operational indicators of the stable application of anammox processes.

The Potential Substitution of Oyster Shell Powder for Phosphate in Pork Patties Cured with Chinese Cabbage and Radish Powder.

The use of natural ingredients in meat processing has recently gained considerable interest, as consumers are increasingly attracted to clean-label meat products. However, limited research has been conducted on the use of natural substitutes for synthetic phosphates in the production of clean-label meat products. Therefore, this study aimed to explore the potential of oyster shell powder as a substitute for synthetic phosphates in pork patties cured with Chinese cabbage or radish powders. Four different groups of patties were prepared using a combination of 0.3% or 0.6% oyster shell powder and 0.4% Chinese cabbage or radish powder, respectively. These were compared with a positive control group that contained added nitrite, phosphate, and ascorbate and a negative control group without these synthetic ingredients. The results showed that patties treated with oyster shell powder had lower (p<0.05) cooking loss, thickness and diameter shrinkage, and lipid oxidation than the negative control but had lower (p<0.05) residual nitrite content and curing efficiency than the positive control. However, the use of 0.6% oyster shell powder adversely affected the curing process, resulting in a decreased curing efficiency. The impact of the vegetable powder types tested in this study on the quality attributes of the cured pork patties was negligible. Consequently, this study suggests that 0.3% oyster shell powder could serve as a suitable replacement for synthetic phosphate in pork patties cured with Chinese cabbage or radish powders. Further research on the microbiological safety and sensory evaluation of clean-label patties during storage is required for practical applications.

Use of poppers (nitrite inhalants) among young men who have sex with men with HIV: A clinic-based qualitative study.

Nitrite inhalants (poppers) are associated with HIV transmission and commonly used among young men who have sex with men (YMSM), a group at increased risk for HIV. Significant research gaps exist in understanding the context in which YMSM use poppers. Qualitative interviews were conducted with 15 YMSM (22-31 years) with HIV to better understand the context in which poppers are used and their impacts on HIV care outcomes, such as care retention and antiretroviral adherence. The Social Ecological Model was applied to understand intrapersonal, interpersonal, community, and system level influences on popper use. Factors influencing popper use included: ubiquity of popper use in sexual settings, introduction to poppers by casual sexual partners, patient-HIV provider communication surrounding poppers, neighborhood, substance use and HIV care systems, and the legal status of poppers. Implications for clinical care, public health, policy, and future research are discussed.

Development of an accurate hand-held sensing platform for nitrite detection based on nitrogen-doped carbon dots.

As is well known, excessive nitrite can seriously pollute the environment and can harm human health. Although existing methods can be used to determine nitrite content, they still have some drawbacks, such as relatively complicated operation and expensive equipment. Herein, a hand-held sensing platform (HSP) for NO2- determination was developed. First, ammonia-rich nitrogen-doped carbon dots with orange-yellow emission were designed and synthesised, which were suitable as fluorescent probes because of their good optical properties and stability. Then, the HSP based on fluorescence using photoelectric conversion technology was designed and manufactured using three-dimensional printing technology. Under optimum conditions, the voltage (V/V0) of the proposed HSP showed good linearity for NO2- detection in the range of 10-500 µM, with a detection limit of 1.95 µM. This portable sensor showed good stability, accuracy and reliability in detecting actual water and meat samples, which may ensure food safety in practical applications. Moreover, the HSP is compact, portable and easily assembled and is suitable for on-site real-time detection, which shows great application potential and prospects.

Sudden sulfamethoxazole shock leads to nitrite accumulation in microalgae-nitrifying bacteria consortia: Physiological responses and light regulating strategy.

Antibiotic shock may potentially impact the performance of promising microalgae-nitrifying bacteria consortia (MNBC) processes. This study investigated physiological behaviors of MNBC under sulfamethoxazole (SMX) shock (mg/L level) and verified a light regulating strategy for improving process performance. Results showed that SMX shock did not affect ammonium removal but caused nitrite accumulation, resulting from combined effects of excessive reactive oxidative species (ROS) production, inhibited microalgal photosynthetic activity, upregulated expressions of amoA and hao, and downregulated expression of nxrA. Moreover, high ammonium concentration aggravated nitrite accumulation and reduced ammonium removal owing to significantly reduced dissolved oxygen (DO). Increasing light intensity enhanced microalgal photo-oxygenation and promoted expressions of all nitrification-related genes, thus improving ammonium removal and alleviating nitrite accumulation. A central composite design coupled with response surface methodology (CCD-RSM) further demonstrated the negative impacts of SMX shock and high ammonium on MNBC and the effectiveness of the light regulation in maintaining stable process performance. This study provides theoretical basis for physiological responses and regulatory strategy of the MNBC process facing short-term antibiotic shock.

A temperature-resilient anammox process for efficient treatment of rare earth element tailings wastewater via synergistic nitrite supply of partial nitritation and partial denitrification.

Rare earth elements result in substantial tailings wastewater with high ammonium and nitrate during extraction. In this study, a temperature-resilient Anammox process was employed for efficient treatment of rare earth element tailings wastewater through implementing synergistic nitrite supply by partial nitritation (PN) and partial denitrification (PD). Enhancing temperature resilience of Anammox process relies on dynamic management of DO and COD inputs to shift the dominant nitrite supplier from PN to PD, stable PD (NAR ≥ 90 %) can boost nitrogen removal by Anammox to 97.8 %. The nitrogen removal rate and nitrogen removal efficiency at 10.6 °C could maintain at 0.12 kgN/m3·d-1 and 92.5 %, respectively. Microbial analysis reveals that Nitrosomonas, Thauera, and Candidatus_Kuenenia are the predominant genera responsible for nitrite supply and nitrogen removal, localized within the gas channels of granules, flocs, and micro-granules, respectively. Keeping the influent C/NO3--N ratio below 1.7 is ideal to prevent overgrowth of Thauera and maintain system stability.

Novel solution-gated transistor sensor-based SnO2 epitaxial thin films grown by pulsed laser deposition for nitrite detection.

A solution-gate controlled thin-film transistor with SnO2 epitaxial thin films (SnO2-SGTFT) is successfully utilized for highly sensitive detection of nitrite. The SnO2 films are deposited as channel materials on a c-plane sapphire (c-Al2O3) substrate through pulsed laser deposition (PLD), with superior crystal quality and out-of-plane atomic ordering. PtAu NPs/rGO nanocomposites are electrodeposited on a gold electrode to function as a transistor gate to further enhance the nitrite catalytic performance of the device. The change in effective gate voltage due to the electrooxidation of nitrite on the gate electrode is the primary sensing mechanism of the device. Based on the inherent amplification effect of transistors, the superior electrical properties of SnO2, and the high electrocatalytic activity of PtAu NPs/rGO, the SnO2-SGTFT sensor has a low detection limit of 0.1 nM and a wide linear detection range of 0.1 nM ~ 50 mM at VGS = 1.0 V. Furthermore, the sensor has excellent characteristics such as rapid response time, selectivity, and stability. The practicability of the device has been confirmed by the quantitative detection of nitrite in natural lake water. SnO2 epitaxial films grown by PLD provide a simple and efficient way to fabricate nitrite SnO2-SGTFT sensors in environmental monitoring and food safety, among others. It also provides a reference for the construction of other high-performance thin-film transistor sensors.

Nitrate and Nitrite Exposure Induces Visual Impairments in Adult Zebrafish.

Nitrate and nitrite have emerged as increasingly common environmental pollutants, posing significant risks to various forms of life within ecosystems. To understand their impact on the visual system of zebrafish, adult zebrafish were exposed to environmentally relevant concentrations of nitrate (10 mg/L) and nitrite (1 mg/L) for 7 days. Visual behaviors were examined using optomotor and avoidance response. The eyeballs of the zebrafish were collected for H&E staining, IHC, and qPCR. Exposure decreased visual behavior and the thickness of most retinal layers. Exposure decreased expression of pax6a, pax6b, gpx1a, and bcl2a. Exposure increased expression of esr1, esr1a, esr2b, cyp19a1b, sod1a, nos2a, casps3, and tp53, and increased retinal brain aromatase expression by IHC. Collectively, our findings demonstrate that nitrate and nitrite exposure negatively impacted the visual system of adult zebrafish, highlighting the potential hazards of these environmental pollutants on aquatic organisms.

Repeated dose, 28-day oral toxicity study of curcumin, anthocyanins, and sodium nitrite in Wistar rats.

OBJECTIVE: The goal of the present study was to examine the repeated dose 28-day oral toxicity of curcumin, anthocyanins, and sodium nitrite in Wistar rats. METHODS: For this purpose, forty-eight male Wistar rats were randomly divided into 8 groups (n = 6 each), encompassing untreated controls and experimental groups treated with curcumin, anthocyanins, and sodium nitrite. Three rats from each group were sacrificed by cervical dislocation under di-ethyl ether anesthesia after 2 and 4 weeks of therapy, respectively. Blood samples were collected for serum chemistry. All of the animals' livers, hearts, and kidneys were removed and sent for histopathological examination. RESULTS: After two weeks of inquiry, certain groups displayed higher hematological values, while others had lower values compared to the control group. AST, CK, and LDH enzyme activity were higher in groups 2-8, but urea concentrations were higher in groups 6 and 8. After four weeks, the Hb, MCH, and MCHC values in group 4 were greater, as were the WBC levels in groups 4 and 6, whereas other groups had lower MCV and WBC values. The weekly body weight gain was insignificantly different between treatment groups. Throughout the experiment, none of the animals perished. Male rats' liver, kidney, and heart underwent histopathological changes after ingesting curcumin, sodium nitrite, and anthocyanin. CONCLUSION: Based on the findings, rats were more detrimental when curcumin, sodium nitrite, and anthocyanin were ingested together than when they were consumed individually, as evidenced by histopathological abnormalities in the liver, kidneys, and heart.

The Effect of Dietary Nitrate on the Oral Microbiome and Salivary Biomarkers in Individuals with High Blood Pressure.

BACKGROUND: Green leafy vegetables (GLV) contain inorganic nitrate, an anion with potential prebiotic effects on the oral microbiome. However, it remains unclear whether GLV and pharmacological supplementation [potassium nitrate (PN)] with a nitrate salt induce similar effects on the oral microbiome. OBJECTIVES: This study aimed to compare the effect of GLV with PN supplementation on the oral microbiome composition and salivary biomarkers in individuals with high blood pressure. METHODS: Seventy individuals were randomly allocated to 3 different groups to follow a 5-wk dietary intervention. Group 1 consumed 300 mg/d of nitrate in form of GLV. Group 2 consumed pills with 300 mg/d of PN and low-nitrate vegetables. Group 3 consumed pills with potassium chloride (placebo: PLAC) and low-nitrate vegetables. The oral microbiome composition and salivary biomarkers of oral health were analyzed before and after the dietary intervention. RESULTS: The GLV and PN groups showed similar microbial changes, probably nitrate-dependent, including an increase in the abundance of Neisseria, Capnocytophaga, Campylobacter species, and a decrease in Veillonella, Megasphaera, Actinomyces, and Eubacterium species after the treatment. Increased abundance of Rothia species, and reduced abundance of Streptococcus, Prevotella, Actinomyces, and Mogibacterium species were observed in the GLV group, which could be nitrate-independent. GLV and PN treatments increased salivary pH, but only GLV treatment showed an increase in the salivary buffering capacity and a reduction of lactate. CONCLUSION: The combination of nitrate-dependent and nitrate-independent microbial changes in the GLV group has a stronger effect to potentially improve oral health biomarkers compared with PN.

Fabrication of Highly Sensitive and Selective Nitrite Colorimetric Sensor Based on the Enhanced Peroxidase Mimetic Activity of Using Acetic Acid Capped Zinc Oxide Nanosheets.

Nitrite ions (NO2-), as one of the leading type-A inorganic-anion, showing significant-effects in the aquatic environment and also to humans health. Whereas, the higher uptake causes detrimental threat to human health leading to various chronic diseases, thus demanding efficient, reliable and convenient method for its monitoring. For this purpose, in the present research study we have fabricated the mimetic nonozyme like catalyst based colorimetric nitrite sensor. The acetic acid capped Zinc Oxide (ZnO) nanosheets (NSs) were introduce as per-oxidase mimetic like catalyst which shows high efficiency towards the oxidative catalysis of colorless tetramethylbenzidine (TMB) to oxidized-TMB (blue color) in the presence of Hydrogen-peroxide (H2O2). The present nitrite ions will stimulate the as formed oxidized-TMB (TMBox), and will caused diazotization reaction (diazotized-TMBox), which will not only decreases the peak intensity of UV-visible peak of TMBox at 652 nm but will also produces another peak at 446 nm called as diazotized-TMBox peak, proving the catalytic reaction between the nitrite ions and TMBox. Further, the prepared colorimetric sensor exhibits better sensitivity with a wider range of concentration (1 × 10-3-4.50 × 10-1 µM), lowest limit of detection (LOD) of 0.22 ± 0.05 nM and small limit of quantification (LOQ) 0.78 ± 0.05 nM having R2 value of 0.998. Further, the colorimetric sensor also manifest strong selectivity towards NO2- as compared to other interference in drinking water system. Resultantly, the prepared sensor with outstanding repeatability, stability, reproducibility, re-usability and its practicability in real water samples also exploit its diverse applications in food safety supervision and environmental monitoring.