Concentrations Of SCN Research Articles

Gaseous signaling molecule H2S as a multitasking signal molecule in ROS metabolism of Oryza sativa under thiocyanate (SCN−) pollution

The induction of disruption in the electronic transport chain by thiocyanate (SCN−) leads to an excessive generation of reactive oxygen species (ROS) within rice (Oryza sativa). Hydrogen sulfide (H2S) assumes a crucial role as a gaseous signaling molecule, holding significant potential in alleviating SCN−-related stress. Nevertheless, there remains a dearth of understanding regarding the intricate interplay between H2S and ROS in Oryza sativa amidst SCN− pollution. In this investigation, a hydroponics-based experiment was meticulously devised to explore how H2S-mediated modifications influence the genetic feedback network governing ROS metabolism within the subcellular organelles of Oryza sativa when exposed to varying effective concentrations (EC20: 24 mg SCN/L; EC50: 96 mg SCN/L; EC75: 300 mg SCN/L) of SCN−. The findings unveiled the enhanced capacity of Oryza sativa to uptake SCN− under H2S + SCN− treatments in comparison to SCN− treatments alone. Notably, the relative growth rate (RGR) of seedlings subjected to H2S + SCN− exhibited a superior performance when contrasted with seedlings exposed solely to SCN−. Furthermore, the application of exogenous H2S yielded a significant reduction in ROS levels within Oryza sativa tissues during SCN− exposure. To elucidate the intricacies of gene regulation governing ROS metabolism at the mRNA level, the 52 targeted genes were categorized into four distinct types, namely: initial regulatory ROS generation genes (ROS-I), direct ROS scavenging genes (ROS-II), indirect ROS scavenging genes (ROS-III), and lipid oxidation genes (ROS-IV). On the whole, exogenous H2S exhibited the capacity to activate the majority of ROS-I ∼ ROS-IV genes within both Oryza sativa tissues at the EC20 concentration of SCN−. However, genetic positive/negative feedback networks emphasized the pivotal role of ROS-II genes in governing ROS metabolism within Oryza sativa. Notably, these genes were predominantly activated within the cytoplasm, chloroplasts, mitochondria, peroxisomes, and the cell wall.

Sulfur oxidation kinetics of Acidithiobacillus caldus and its inhibition on exposure to thiocyanate present in cyanidation tailings wastewater

The sulfur oxidation kinetics of an industrial strain of Acidithiobacillus caldus (At. caldus) cultured on elemental sulfur was explored in batch experiments in the absence and presence of thiocyanate (SCN−), a toxin inherent within cyanidation tailings wastewater. The Contois rate expression accurately described At. caldus sulfate generation (R2 > 0.93) and microbial growth (R2 > 0.87). For a culture maintained at 45 °C a maximum specific growth rate (μmax) of 0.105 h−1, sulfate yield from biomass (Ypx) of 4.8 × 10−9 mg SO42−.cell−1, and Contois affinity coefficient (Kx) of 1.56 × 10−8 mg S.cell−1 were established. The presence of SCN− (0 mg/L - 20 mg/L) in the bulk solution inhibited the microbial system competitively. Moreover, SCN− impeded microbial growth differentially; the rate expression was therefore partitioned with respect to SCN− concentration and inhibition constants (Ki) were determined for each region. Adaptation to discrete concentrations of SCN− (1 mg/L and 20 mg/L) improved SCN− tolerance in At. caldus; however, adapted strains exhibited reduced sulfur oxidation potential when cultured under thiocyanate-free conditions relative to the non-adapted control strain. To describe the adapted systems accurately, the Contois affinity coefficient (Kx) was revised to reflect the suspected metabolic decline. The derived Kx values increased in magnitude and affirmed an innate reduction in microbial substrate affinity or substrate adsorption capacity. Inclusion of these updated Kx constants within the rate equation suitably represented the experimental data for both adapted At. caldus strains with R2 > 0.94. Furthermore, the impact of adaptation on the inhibition kinetics and inhibition mechanism associated with SCN− exposure were reviewed. Thiocyanate inhibited sulfur oxidation non-competitively in the adapted strains, and the shift in inhibition mechanism may be attributed to the compromised metabolic state following adaptation.

Transcriptome reveals the crucial role of exogenous hydrogen sulfide in alleviation of thiocyanate (SCN-) toxicity in rice seedlings.

Application of exogenous hydrogen sulfide (H2S) is a novel strategy for alleviation of the adverse effects caused by abiotic stresses. However, little is known about H2S-mediated global molecular response of rice seedlings to thiocyanate (SCN-) exposure. Herein, a hydroponic experiment was carried out to investigate the crucial role of exogenous H2S in alleviation of SCN- toxicity generated at different effective concentrations (EC20: 24.0mg SCN/L, EC50: 96.0mg SCN/L, and EC75: 300.0mg SCN/L) in rice seedlings through transcriptome analysis. The results showed that the total numbers of differentially expressed genes (DEGs, upregulated genes/downregulated genes) in rice roots were 755/313, 1114/3303, and 2184/7427, while they were 427/292, 2134/526, and 2378/890 in rice shoots at EC20, EC50, and EC75 of SCN-, respectively. When exogenous H2S was supplied to rice seedlings exposed to SCN-, the total number of DEGs (upregulated genes/downregulated genes) in rice roots was 1158/316, 1943/2959, and 1737/5392, while it was 2067/937, 2689/683, and 3492/1062 in rice shoots at EC20, EC50, and EC75 of SCN-, respectively. Upregulated DEGs in shoots were positively correlated with SCN- concentration in the presence of exogenous H2S, suggesting its crucial role in regulating the phytotoxicity of SCN-. Gene function and pathway enrichment analyses showed that exogenous H2S triggered "secondary metabolite synthesis," "metabolic pathways," and "signal transduction mechanisms" in rice seedlings corresponding to different effective concentrations of SCN- exposure.

The determination of thiocyanate in the blood plasma and holding water of Amphiprion clarkii after exposure to cyanide.

The illegal practice of cyanide fishing continues throughout the Indo-Pacific. To combat this destructive fishing method, a reliable test to detect whether a fish has been captured using cyanide (CN) is needed. We report on the toxicokinetics of acute, pulsed CN exposure and chronic thiocyanate (SCN) exposure, the major metabolite of CN, in the clownfish species, Amphiprion clarkii. Fish were pulse exposed to 50 ppm CN for 20 or 45 s or chronically exposed to 100 ppm SCN for 12 days and blood plasma levels of SCN were measured. SCN blood plasma levels reached a maximum concentration (301–468 ppb) 0.13–0.17 days after exposure to CN and had a 0.1 to 1.2 day half-life. The half-life of blood plasma SCN after chronic exposure to SCN was found to be 0.13 days. Interestingly, we observed that when a fish, with no previous CN or SCN exposure, was placed in holding water spiked to 20 ppb SCN, there was a steady decrease in the SCN concentration in the holding water until it could no longer be detected at 24 hrs. Under chronic exposure conditions (100 ppm, 12 days), trace levels of SCN (∼40 ppb) were detected in the holding water during depuration but decreased to below detection within the first 24 hrs. Our holding water experiments demonstrate that low levels of SCN in the holding water of A. clarkii will not persist, but rather will quickly and steadily decrease to below detection limits refuting several publications. After CN exposure, A. clarkii exhibits a classic two compartment model where SCN is eliminated from the blood plasma and is likely distributed throughout the body. Similar studies of other species must be examined to continue to develop our understanding of CN metabolism in marine fish before a reliable cyanide detection test can be developed.

Comparison of quantification of selenocyanate and thiocyanate in cultured mammalian cells between HPLC-fluorescence detector and HPLC-inductively coupled plasma mass spectrometer

The simultaneous detection of cyanide (CN), thiocyanate (SCN), and selenocyanate (SeCN) by a HPLC-fluorescence detector (FLD) with the post-column König reaction was recently reported. SCN and SeCN are also detectable by HPLC-inductively coupled plasma mass spectrometry (HPLC-ICP-MS) because sulfur and selenium can be detected, respectively, without any pre- or post-treatment. ICP-MS has high sensitivity for selenium and sulfur detection and is robust to sample matrices. In this study, we compared HPLC-FLD with the post-column König reaction and HPLC-ICP-MS in terms of SCN and SeCN detection sensitivity and linearity. The limit of detection (LOD) for SCN indicated that HPLC-FLD with the post-column König reaction was 354 times more sensitive than HPLC-ICP-MS. Likewise, the LOD for SeCN indicated that HPLC-FLD was 51 times more sensitive than HPLC-ICP-MS. These results demonstrated that HPLC-FLD was a more suitable technique for SeCN and SCN detection than HPLC-ICP-MS. We previously reported that SeCN was generated in selenite-exposed mammalian cells to detoxify excess selenite. HPLC-FLD with the post-column König reaction enabled good separation and detection for quantifying SCN and SeCN in mammalian cell lines exposed to selenite. The intracellular SCN and SeCN concentrations determined by this technique suggested differences in the metabolic capacity for selenite to form SeCN among the cell lines. In addition, since the amount of intracellular SCN and SeCN were significantly decreased by pretreatment of myeloperoxidase (MPO) inhibitors, SCN and SeCN were resulted from the interaction of sulfur and selenium with endogenous CN, respectively, generated with MPO.

Thiocyanate and Organic Carbon Inputs Drive Convergent Selection for Specific Autotrophic Afipia and Thiobacillus Strains Within Complex Microbiomes

Thiocyanate (SCN–) contamination threatens aquatic ecosystems and pollutes vital freshwater supplies. SCN–-degrading microbial consortia are commercially adapted for remediation, but the impact of organic amendments on selection within SCN–-degrading microbial communities has not been investigated. Here, we tested whether specific strains capable of degrading SCN– could be reproducibly selected for based on SCN– loading and the presence or absence of added organic carbon. Complex microbial communities derived from those used to treat SCN–-contaminated water were exposed to systematically increased input SCN concentrations in molasses-amended and -unamended reactors and in reactors switched to unamended conditions after establishing the active SCN–-degrading consortium. Five experiments were conducted over 790 days, and genome-resolved metagenomics was used to resolve community composition at the strain level. A single Thiobacillus strain proliferated in all reactors at high loadings. Despite the presence of many Rhizobiales strains, a single Afipia variant dominated the molasses-free reactor at moderately high loadings. This strain is predicted to break down SCN– using a novel thiocyanate desulfurase, oxidize resulting reduced sulfur, degrade product cyanate to ammonia and CO2 via cyanate hydratase, and fix CO2 via the Calvin–Benson–Bassham cycle. Removal of molasses from input feed solutions reproducibly led to dominance of this strain. Although sustained by autotrophy, reactors without molasses did not stably degrade SCN– at high loading rates, perhaps due to loss of biofilm-associated niche diversity. Overall, convergence in environmental conditions led to convergence in the strain composition, although reactor history also impacted the trajectory of community compositional change.

Electrophysiological impact of thiocyanate on isolated mouse retinal pigment epithelial cells.

Our recent electrophysiological analysis of mouse retinal pigment epithelial (RPE) cells revealed that in the presence of 10 mM external thiocyanate (SCN-), voltage steps generated large transient currents whose time-dependent decay most likely results from the accumulation or depletion of SCN- intracellularly. In the present study, we investigated the effects of more physiologically relevant concentrations of this biologically active anion. In whole cell recordings of C57BL/6J mouse RPE cells, we found that, over the range of 50 to 500 µM SCN-, the amplitude of transient currents evoked by voltage steps was proportional to the extracellular SCN- concentration. Transient currents were also produced in RPE cells when the membrane potential was held constant and the external SCN- concentration was rapidly increased by pressure-ejecting 500 µM SCN- from a second pipette. Other results indicate that the time dependence of currents produced by both approaches results from a change in driving force due to intracellular SCN- accumulation or depletion. Finally, by applying fluorescence imaging and voltage-clamping techniques to BALB/c mouse RPE cells loaded with the anion-sensitive dye MQAE, we demonstrated that in the presence of 200 or 500 µM extracellular SCN-, depolarizing voltage steps increased the cytoplasmic SCN- concentration to an elevated steady state within several seconds. Collectively, these results indicate that, in the presence of physiological concentrations of SCN- outside the RPE, the conductance and permeability of the RPE cell membranes for SCN- are sufficiently large that SCN- rapidly approaches electrochemical equilibrium within the cytoplasm when the membrane voltage or external SCN- concentration is perturbed.

Transcriptome analysis of Oryza sativa in responses to different concentrations of thiocyanate.

Effective concentrations of potassium thiocyanate (KSCN) to rice seedlings were experimentally determined using relative growth rate as a sensitive endpoint. Agilent 44-K rice microarray was used to profile the molecular responses of rice seedlings exposed to thiocyanate ion (SCN-) at three different effective concentrations (EC10, EC20, and EC50). A total of 18,498 known genes were collected from SCN-treated rice microarray analysis. Out of all, 1603, 1882, and 5085 differentially expressed genes (DEGs) were observed at EC10, EC20, and EC50 concentrations, respectively. More upregulated/downregulated DEGs were detected in shoots than in roots after SCN- exposure. Gene functions and pathway enrichment analysis of DEGs indicated that different effective concentrations of SCN- resulted in multiple enriched GO categories and KEGG pathways and outcomes were quite tissue-specific. Different regulations and adaptations of gene expression in molecular function (MF), biological process (BP), and cellular components (CC) were observed in rice tissues at different effective concentrations of SCN-, suggesting their different responsive and adaptive strategies. Information collected here presents a detailed description of SCN-induced alternations of gene expression in rice seedlings and provide valuable information for further searching specific genes participating in transportation, phytotoxic responses, and detoxification of SCN- in rice seedlings.

Thiocyanate-induced labilization of schwertmannite: Impacts and mechanisms

Schwertmannite is an amorphous iron(III)-oxyhydroxysulfate that forms in acid mine drainage (AMD) environments. The characteristic of high heavy metal adsorption capability makes schwertmannite a potentially useful, environmentally friendly material in wastewater treatment. Unstable schwertmannite is prone to recrystallization. Understanding the mechanisms that induce schwertmannite labilization and affect its capacity to remove heavy metals are of great environmental and geochemical significance. Thiocyanate (SCN¯) is a hazardous pseudohalide that is also normally found in AMD. However, little is known about the impact of Fe(III)-binding ligand SCN¯ on schwertmannite stability and its subsequent capacity to bind trace elements. Here, we investigated the adsorption of SCN¯ on schwertmannite and subsequent mineral transformation to characterize this little-known process. The appearance of Fe2+ indicated that the interactions between schwertmannite and SCN¯ may involve complexation and reduction reactions. Results showed that the majority of the adsorbed-SCN¯ was immobilized on schwertmannite during the 60-days transformation. The transformation rates of schwertmannite increased with increasing concentrations of SCN¯. Goethite was detected as the dominant transformation product with or without SCN¯. The mechanisms of SCN¯-promoted dissolution of schwertmannite can be described as follows: (1) formation of Fe(III)–NCS complexes on the schwertmannite surface and in solution, a process which increases the reactivity of solid phase Fe(III); (2) the extraction of Fe(III) from schwertmannite by SCN¯ and subsequent schwertmannite dissolution; and (3) the formation of secondary minerals from extracted Fe(III). These findings may improve AMD treatment strategies and provide insight into the use and potential reuse of schwertmannite as a trace element sorbent.

Diatomite strengthen COD and ammonia removal from an micro-aerobic EGSB reactor treating coking wastewater

The performance of one-stage micro-aerobic MAEGSB (OMAEGSB) reactor and two-stage MAEGSB (TMAEGSB) reactor treating actual coking wastewater with and without supplement of diatomite were investigated. The investigation has demonstrated that the two-stage MAEGSB reactor system treating actual coking wastewater could keep high COD and NH3-N removal with supplement of diatomite. With only 24h hydraulic retention time (HRT) (12h for MAEGSB I and 12h for MAEGSB II ), when without diatomite supplement, the TMAEGSB reactor system could attain 72.6% COD average removal and 25.8% NH3-N average removal. However, with 6g•L−1•d−1 diatomite supplement, the TMAEGSB reactor system could keep 84.3% COD average removal and 78.8%-92.8% NH3-N average removal. Such high NH3-N removal efficiency of the TMEGSB was because of the high phenol and thiocyanate (SCN) removal in the MAEGSB I reactor (97.9% and 77.9%) and correspondingly the low influent phenol and SCN concentration for the MAEGSB II reactor (33.9 mg•L−1 and 10.4 mg•L−1). Diatomite supplement could ensure stable and highly efficient phenol and SCN removal in the MAEGSB I reactor. Using TMAEGSB reactor system with diatomite supplement was a simple and high effectively strategy for treatment of actual coking wastewater.

Synergistic inhibition of anaerobic ammonium oxidation (anammox) activity by phenol and thiocyanate

Coke-oven wastewater discharged from the steel-manufacturing process is phenol and thiocyanate (SCN)-rich wastewater, which inhibits microbial activities in biological wastewater treatment processes. In the present study, synergistic inhibition of anaerobic ammonium oxidation (anammox) activity by phenol and SCN was examined by batch incubation and continuous operation of an anammox reactor. The comparison of anammox activities determined in the batch incubation, in which the anammox biomass was anoxically incubated with 10–250 mg L−1 of i) phenol, ii) SCN, or iii) both phenol and SCN, showed that synergistic inhibition by phenol and SCN was greater than the inhibitions by phenol or SCN alone. The synergistic inhibition by phenol and SCN was further investigated by operating an up-flow column anammox reactor for 262 d. The removal efficiencies of NH4+ and NO2− deteriorated when phenol and SCN concentrations in the influent increased to 16 and 32 mg L−1, respectively, and the inhibition of anammox activity was further investigated by a15NO2− tracer experiment. Addition of phenol and SCN resulted in a population shift of anammox bacteria, and the dominant species changed from “Candidatus Kuenenia stuttgartiensis” to “Ca. Brocadia sinica”. The relative abundance of Azoarcus and Thiobacillus 16S rRNA gene reads increased during the operation, suggesting that they were responsible for the anaerobic phenol and SCN degradation. The present study is the first to document the synergistic inhibition of anammox activity by phenol and SCN and the microbial consortia involved in the nitrogen removal as well as the phenol and SCN degradations.

Effects of Environmental Parameters on Thiocyanate Biodegradation byBurkholderia phytofirmansCandidate Strain ST01hv

Our previous work (published in Letters in Applied Microbiology 2013) showed that Burkholderia phytofirmans candidate strain ST01hv can degrade thiocyanate (SCN−), a common contaminant from gold ore processing. However, the impacts of major environmental parameters on the biodegradation activity of this strain must be characterized to implement it in bioremediation efforts. In this study, several environmental factors, including pH, the concentrations of SCN−, phosphate, and ammonium, and the type and concentration of organic carbon, were tested for effects on the efficiency of SCN− biodegradation by the bacterium. Results showed that SCN− biodegradation occurred within a range of pH values (6.0 ± 0.2 to 8.0 ± 0.2), with an optimum between 7.0 and 7.5. SCN− breakdown depended on initial ammonium and SCN− concentrations, as well as the availability of phosphate. At lower ammonium and SCN− levels (<60 and <220 mg/L, respectively), the extent of biodegradation was greater, while at higher concentrations (≥60 and 350–1,500 mg/L), these substances acted as inhibitors. Different carbon substrates showed different degrees of influence, with glucose (4.0 g/L, the highest amount of available C at 133 mM C/L medium) providing the best results (i.e., complete SCN− breakdown after 4 days). The tested environmental parameters are relevant to industrial environments such as mining- and coking-contaminated soils, and the results from this work will inform strategies for SCN− bioremediation.

Inhibition Kinetics of Iron Oxidation by &lt;i&gt;Leptospirillum ferriphilum&lt;/i&gt; to Residual Thiocyanate Present in Bioremediated Cyanidation Tailings Wastewater

Inhibition of iron oxidation by Leptospirillum ferriphilum in the presence of thiocyanate (SCN-) was studied in small-scale batch experiments. The L. ferriphilum culture was challenged with SCN- over a range of 0 mg/l to 10 mg/l. The data showed that L. ferriphilum was able to utilise ferrous iron at low-level concentrations of SCN- (0.25 mg/l to 1.75 mg/l), however exhibited a reduction in oxidation rate relative to the control (0 mg/l). Moreover, introduction of SCN- at low-level concentrations resulted in a lag in iron oxidation activity, specifically at concentrations of 1 mg/l, 1.25 mg/l and 1.75 mg/l. No iron oxidation was observed at SCN- concentrations above 1.75 mg/l, indicating complete inhibition. As L. ferriphilum is the dominant iron oxidising bacteria within biooxidation tanks, evidence of sustained iron oxidation activity at low-level SCN- concentrations affirms the potential of recycling bioremediated cyanidation wastewater within biooxidation circuits in bioprocesses for gold recovery from sulfidic minerals as residual SCN- concentrations in remediated effluent are reportedly lower than 0.25 mg/l. The inhibition kinetics of this system need to be explored further in order to develop a deeper understanding of the system such that it may be applied to inform process operation.

Optimizing the use of Sinapis alba seed meal extracts as a source of thiocyanate (SCN−) for the lactoperoxidase system

The multi-component lactoperoxidase system (LPSys) is used for improving food safety and requires thiocyanate (SCN−) as a substrate for the generation of antimicrobial hypothiocyanite (OSCN−). Production of OSCN− is usually limited by intrinsic concentrations of SCN− or else SCN− must be supplied from a synthetic source. Our objective was to optimize the production of OSCN− in the LPSys using SCN− derived from glucosinolates present in yellow mustard (Sinapis alba) seed meal. Thiocyanate was produced from S. alba seed meal by shaking a 1:20 (w:w) meal:H2O mixture at 70 °C for 10 min. Increasing the exogenous H2O2 to an equimolar concentration (500 μM) of SCN− further increased OSCN− production, whereas H2O2 concentrations in excess of SCN− enhanced OSCN− decay. Glucose and glucose oxidase (GOx) were substituted for H2O2 to sustain OSCN− production resulting in an optimized LPSys containing 4.92 U/mL lactoperoxidase, 64 mM glucose, 342 U/L GOx, and 500 μM SCN−. Maximum OSCN− in the optimized system was 40 μM, a concentration that is predicted to have antimicrobial effects, thus demonstrating the potential of the low value S. alba seed meal as source of SCN− for preparing a generally recognized as safe LPSys.

Characterization and speciation modelling of cyanide in effluent from an active slimes dam

The utilization of cyanide in the process of gold extraction is an environmental concern as this pollutant is discharged with the tailings. The distribution and fate of cyanide in the environment upon release from the tailings dumps depends on its physical-chemical speciation. The present study was conducted to assess the presence of cyanide species in drainage water from an active slimes dam that receives effluent from a gold reprocessing plant in the Central Rand goldfield (south of Johannesburg, South Africa). Water samples were collected from decant pipes draining water from the top of the slimes dam as well as from a solution trench constructed around the dam. Efflorescent salt crusts and algae were also sampled along the solution trench to assess the extent of cyanide contamination and its promulgation from the slimes. Water samples presented varying chemistry with samples collected from the pipes recording low pH (between 2 and 4) with concentrations of weak acid dissociable cyanide (CNWAD) varying between 5.635 mg L-1 and 8.525 mg L-1. Water samples from the trench were less acidic (pH ranged between 5 and 7) with an average concentration of CNWAD of 21.72 mg L-1. These values are far greater than the limit of 0.50 mg L-1 set by the authorities through the 'Best Practice guidelines' for any effluent exiting a metallurgical treatment facility. Copper and iron cyanide complexes were the most abundant cyanide complexes in the water samples. The pH and conductivity of the solution prepared by the dissolution of the salt crusts (10 g in 50 mL of deionized water) were 3.44 and 1.611 mScm-1, respectively. High concentrations (198.4mg kg-1) of CNT were obtained in the crusts and these were predominantly strong acid dissociable cyanides (CNSAD) of Fe and Co. The presence of iron cyanides was evident from the bluish-green crusts (Prussian blue) observed around the site, indicating the extent of cyanide contamination. A very low pH (2.39) was recorded for the algae, with elevated concentrations of SCN- and OCN- that are byproducts of chemical conversion of cyanide. The Visual MINTEQ geochemical modelling code was used to complement the analytical methods in characterizing the speciation of cyanide. The simulations predicted the presence of the following metal-cyanide complexes in water samples as well as in the solid materials: Fe(CN)63-, Fe(CN)6(aq), NaFe(CN)62-, KFe(CN)62-, Ni(CN)42-, Zn(CN)42-, CaFe(CN)6-, NiH(CN)4- and NiH3(CN)4+. This study revealed that cyanide remains persistent in its immediate environment following its release from slimes dams, an issue of concern as some residential areas have developed in the proximity of such facilities. The major highlight of this work has been the comprehensive characterization of cyanide speciation by using geochemical modelling to complement analytical techniques. This is important in understanding the potential risk posed by this pollutant.

Colorimetric detection of thiocyanate based on anti-aggregation of gold nanoparticles in the presence of cetyltrimethyl ammonium bromide

A facile, highly sensitive and selective colorimetric strategy for thiocyanate (SCN−) detection is proposed based on anti-aggregation of gold nanoparticles (AuNPs) which was induced by surfactant cetyltrimethyl ammonium bromide (CTAB). A certain concentration of aggregation agent CTAB is responsible for a visible color change of AuNPs from wine red to blue. The aggregations of AuNPs decrease with increasing concentrations of SCN−, which can be monitored by an ultraviolet–visible spectrophotometer or the naked eyes. The limit of the detection (LOD) is 0.1μM by the naked eyes and 6.5nM by UV–vis spectroscopy with the linear range from 0.1 to 1.5μM. The applicability of our detection system is also verified by analysis of SCN− in milk samples and satisfactory results were obtained.

Serum 8,12-iso-iPF2α-VI Isoprostane Marker of Oxidative Damage and Cognition Deficits in Children with Konzo

We sought to determine whether motor and cognitive deficits associated with cassava (food) cyanogenic poisoning were associated with high concentrations of F2-isoprostanes, well-established indicators of oxidative damage. Concentrations of serum F2-isoprostanes were quantified by LC-MS/MS and anchored to measures of motor proficiency and cognitive performance, which were respectively assessed through BOT-2 (Bruininks/Oseretsky Test, 2nd Edition) and KABC-II (Kaufman Assessment Battery for Children, 2nd edition) testing of 40 Congolese children (21 with konzo and 19 presumably healthy controls, overall mean age (SD): 9.3 (3.2) years). Exposure to cyanide was ascertained by concentrations of its main metabolite thiocyanate (SCN) in plasma and urine. Overall, SCN concentrations ranged from 91 to 325 and 172 to 1032 µmol/l in plasma and urine, respectively. Serum isoprostanes ranged from 0.1 to 0.8 (Isoprostane-III), 0.8 to 8.3 (total Isoprostane-III), 0.1 to 1.5 (Isoprostane-VI), 2.0 to 9.0 (total Isoprostane-VI), or 0.2 to 1.3 ng/ml (8,12-iso-iPF2α-VI isoprostane). Children with konzo poorly performed at the BOT-2 and KABC-II testing relative to presumably healthy children (p<0.01). Within regression models adjusting for age, gender, motor proficiency, and other biochemical variables, 8,12-iso-iPF2α-VI isoprostane was significantly associated with the overall cognitive performance (β = −32.36 (95% CI: −51.59 to −13.03; P<0.001). This model explained over 85% of variation of the KABC-II score in children with konzo, but was not significant in explaining the motor proficiency impairment. These findings suggest that cognitive deficits and, possibly, brain injury associated with cassava poisoning is mediated in part by oxidative damage in children with konzo. 8,12-iso-iPF2α-VI isoprostane appears to be a good marker of the neuropathogenic mechanisms of konzo and may be used to monitor the impact of interventional trials to prevent the neurotoxic effects of cassava cyanogenic poisoning.

Rapid and reproducible analysis of thiocyanate in real human serum and saliva using a droplet SERS-microfluidic chip

As thiocyanate (SCN−) acts as an important biomarker in human health assessment, there remains an urgent need to realize rapid and reproducible analysis of SCN− in body fluids. Here, a droplet microfluidic device has been designed and fabricated for SCN− detection in real human serum and saliva using the surface enhanced Raman scattering (SERS) technique. Only a few minutes are needed for the whole detection process which simply cost a few microliters of real sample. Gold@silver core–shell nanorods (Au@Ag NRs) with a large SERS enhancement factor were selected to capture SCN− ions in body fluids. The intensity of SERS peak at around 2100cm−1, which originates from the –C≡N stretching mode, was used to indicate the concentrations of SCN− ions. Importantly, by generating a droplet environment for mixing reagents and acquiring signals, this microfluidic platform possesses the advantages of an improved reproducibility and reduced time consumption. For practical applications, the SERS-microfluidic system is capable to achieve rapid analysis of SCN− in the presence of human serum, which is very important for realizing the detection in real biological samples. Additionally, SCN− in saliva samples was detected in the SERS-microfluidic chip and the results provide useful information for distinguishing between smokers and nonsmokers.

Cyanide Toxicokinetics: The Behavior of Cyanide, Thiocyanate and 2-Amino-2-Thiazoline-4-Carboxylic Acid in Multiple Animal Models

Cyanide causes toxic effects by inhibiting cytochrome c oxidase, resulting in cellular hypoxia and cytotoxic anoxia, and can eventually lead to death. Cyanide exposure can be verified by direct analysis of cyanide concentrations or analyzing its metabolites, including thiocyanate (SCN(-)) and 2-amino-2-thiazoline-4-carboxylic acid (ATCA) in blood. To determine the behavior of these markers following cyanide exposure, a toxicokinetics study was performed in three animal models: (i) rats (250-300 g), (ii) rabbits (3.5-4.2 kg) and (iii) swine (47-54 kg). Cyanide reached a maximum in blood and declined rapidly in each animal model as it was absorbed, distributed, metabolized and eliminated. Thiocyanate concentrations rose more slowly as cyanide was enzymatically converted to SCN(-). Concentrations of ATCA did not rise significantly above the baseline in the rat model, but rose quickly in rabbits (up to a 40-fold increase) and swine (up to a 3-fold increase) and then fell rapidly, generally following the relative behavior of cyanide. Rats were administered cyanide subcutaneously and the apparent half-life (t1/2) was determined to be 1,510 min. Rabbits were administered cyanide intravenously and the t1/2 was determined to be 177 min. Swine were administered cyanide intravenously and the t1/2 was determined to be 26.9 min. The SCN(-) t1/2 in rats was 3,010 min, but was not calculated in rabbits and swine because SCN(-) concentrations did not reach a maximum. The t1/2 of ATCA was 40.7 and 13.9 min in rabbits and swine, respectively, while it could not be determined in rats with confidence. The current study suggests that cyanide exposure may be verified shortly after exposure by determining significantly elevated cyanide and SCN(-) in each animal model and ATCA may be used when the ATCA detoxification pathway is significant.

Sequential Injection Analysis of Thiocyanate Ions Using a Microfluidic Polymer Chip with an Embedded Ion-Selective Electrode

A sequential injection analysis (SIA) system for the determination of SCN(-) ion using a microfluidic polymer chip with an embedded SCN(-) ion-selective electrode (SCN(-)-ISE) as a detector was developed. Under the optimal flow conditions of the SIA system, the SCN(-)-ISE showed a good linear relationship between peak heights and logarithmic concentrations of SCN(-) ion with a Nernstian slope of 59.4 ± 3.8 mV decade(-1) in a concentration range from 1.0 × 10(-5) to 1.0 × 10(-1) mol dm(-3). Sample throughput of the present system for the determination of SCN(-) ion was approximately 12 samples h(-1). The proposed SIA system was applied to the determination of the level of SCN(-) ion in human saliva samples.