DNA damage and G2/M arrest in Syrian hamster embryo cells during Malachite green exposure are associated with elevated phosphorylation of ERK1 and JNK1

The synthetic dye malachite green found in food induces cytotoxicity and genotoxicity in four different mammalian cell lines from distinct tissuesw

Malachite green (MG) is a synthetic dye that uses ranges from its application as a tissue dye to that as an antiparasitic in aquaculture. Several studies have reported the presence of this compound in food dyes and in the meat of fish raised in captivity for human consumption, suggesting risks both for the end user and for as those who handle these products because of MG toxic properties described in the literature. Here we evaluated the cytotoxic and genotoxic profiles of MG in four different cell lines (ACP02, L929, MNP01, and MRC-5). Two of these cell lines are stomach cells (normal and cancer lineages) and the potential ingestion of MG makes this a relevant cell type. Cells were treated with MG at concentrations ranging from 0.1 μM to 100 μM, and tested by MTT assay, a differential apoptosis/necrosis assay (EB/OA), the micronucleus test (MN), and the comet assay. MG exhibits dose-dependent cytotoxicity toward all of the tested cell types; higher concentrations of MG cause cell necrosis, while lower concentrations induce apoptosis. MG has a genotoxic profile increasing the rates of micronuclei, nucleoplasmic bridges, nuclear buds, and DNA fragmentation; L929 and MRC-5 showed more sensibility than ACP02 and MNP01.

An insight into the interaction between malachite green oxalate with human serum albumin: Molecular dynamic simulation and spectroscopic approaches

Cationic triarylmethane dyes such as malachite green are aromatic xenobiotic compounds causing environmental pollution. The affinity between hazardous materials and biomolecules makes it important to understand the properties of such compounds. Accordingly, in this study, the possible molecular interaction between this pollutant and the human serum albumin (HSA) was investigated using a combination of molecular docking, molecular dynamic simulation and multi-spectroscopic approaches. The docking results illustrated that malachite green oxalate (MGO) could bind to some of the HSA amino acids with the estimated free energy = -32.93 kJ/mol. Further, the results of the dynamic simulation revealed that MGO had a steady interaction with the protein though increasing flexibility and decreasing the HSA compactness. These results were, therefore, in agreement with those obtained by spectroscopic techniques. The MGO concentration of 0.0005 mM could quench the HSA's intrinsic fluorescence by %16.88. The protein structural changes also revealed that the binding interaction of MGO-HSA was accompanied by an increase in the α-helix and a decrease in the β-sheet of the protein. Overall, this study indicated the suitable molecular modeling interaction of MGO and HSA.

Lethal and sublethal exposure of Hemichromis bimaculatus (Gill, 1862) to malachite green and possible implications for ornamental fish

Malachite green (MG) is a triphenylmethane dye that is widely used in aquaculture as a fungicide, bactericide, ectoparasiticide, and antiprotozoal. There is great debate regarding the potential for this compound to trigger adverse effects. Here, we review the previous findings and then evaluate the lethal and sublethal effects of MG in the species Hemichromis bimaculatus (jewelfish). The lethal concentration for 50% of the fish in 96 h was 1 mg/L. We observed a dose-dependent increase in the percentage of fish mortality as well as physical and behavioral changes. We further found that the highest tested sublethal dose significantly increased the DNA damage index identified using the comet assay (74.97 ± 13.8 at a significant level of P < 0.05 for the 0.75 mg/L concentration), but did not significantly alter the results of the micronucleus test. Although our results suggest that MG confers risks on exposed fish, the findings were significant only at the highest exposure concentration (0.75 mg/L). At lower concentrations (0.25 mg/L and 0.5 mg/L), no adverse effect was observed. The maximum MG concentration recommended for use in ornamental fish farming is 0.2 mg/L. Therefore, our results suggest that, specifically for the parameters analyzed in this work, MG does not have any adverse effect when users strictly adhere to the recommended concentration criteria for ornamental fish.

Sandalwood-derived carbon quantum dots as bioimaging tools to investigate the toxicological effects of malachite green in model organisms

Malachite green is an N-methylated diaminophenylmethane dye that has generated much concern over its suggestive carcinogenic nature. After its excessive use in aquaculture industry as an effective ectoparasitide, much debate was raised over its toxicological effects leading to scientific studies conducted on animal models. Even after several bans, malachite green is still easily available in many parts of the world and unscrupulously even used to give green vegetables a fresher look. This study aims to address this concern by systematically studying the toxicological effects of malachite green through bioimaging in plant and animal cell and tissue. Sandalwood-derived carbon quantum dots have been used as a bioimaging tool since they are non-cytotoxic and show excellent fluorescence properties. Onion tissues demonstrate the translocation of the dye inside cells having high affinity for the nuclei and cell walls. Toxicological effects on the growth of Vigna radiata (mung beans) have been studied methodically. Bioimaging of the transverse cross-section of the dye-treated plant root shows a significant difference from the control. In animal cells, dose-dependent decrease in cell viability of MG-63 cells was observed with MG. CQD showed good fluorescence in both cytoplasm and nucleus of MG63 cells. In addition, CQDs were employed as a great tool for bioimaging of the histopathologically adverse effects of MG in Golden hamster animal model. This study showed CQDs could be used as an alternative non-site specific fluorescent probe for cell and tissue imaging for better visualization of cell and tissue architectural changes.

The gut microbiota: a new perspective on the toxicity of malachite green (MG)

Gut microbiome critically contributes to host health status. Thus, investigating the relationship between the gut microbiome and toxic chemicals is a hot topic in toxicology research. Exposure to malachite green (MG) has been linked to various health disorders. Thus, exploring the gut microbiota changes in response to MG would provide a new perspective on the toxicity effects of this chemical substance. MG exposure resulted in the significantly lower alpha diversity (Mann-Whitney U test, z = - 6.83, p = 0.00) but higher beta diversity (Mann-Whitney U test, z = - 1.98, p = 0.04) of gut microbiota, and significantly decreased ecosystem stability (alpha and beta variability; Mann-Whitney U test, all p < 0.05) of gut microbial communities. Gut bacterial networks showed that the interactions became more complex and stronger after MG exposure, which could decrease the stability of the network. Changes in gut microbiota composition were mainly reflected in the enrichment of opportunistic bacteria (i.e., Aeromonas and Vibrio) and the depression of fermentative bacteria (i.e., Bacteroides and Paludibacter). MG exposure leads to a significantly increased gut permeability (lipopolysaccharide-binding protein; Mann-Whitney U test, z = - 6.92, p = 0.00), which could reduce the host selective pressures on particular bacterial species (such as members in Aeromonas and Vibrio). This result was further supported by the weakened importance of a deterministic microbial assembly after MG exposure. All these findings indicated that MG exposed fishes might have more possibilities to be infected, as demonstrated by the enrichment of opportunistic pathogenic bacteria, high-level immune responses, and increased gut permeability. These findings greatly improve our understanding of the toxicity effects of MG.

PLLA nanofibrous paper-based plasmonic substrate with tailored hydrophilicity for focusing SERS detection

We report a new paper-based surface enhanced Raman scattering (SERS) substrate platform contributed by a poly(l-lactic acid) (PLLA) nanofibrous paper adsorbed with plasmonic nanostructures, which can circumvent many challenges of the existing SERS substrates. This PLLA nanofibrous paper has three-dimensional porous structure, extremely clean surface with good hydrophobicity (contact angle is as high as 133.4°), and negligible background interference under Raman laser excitation. Due to the strong electrostatic interaction between PLLA nanofiber and cetyltrimethylammonium bromide (CTAB) molecules, the CTAB-coated gold nanorods (GNRs) are efficiently immobilized onto the fibers. Such a hydrophobic paper substrate with locally hydrophilic SERS-active area can confine analyte molecules and prevent the random spreading of molecules. The confinement leads to focusing effect and the GNRs-PLLA SERS substrate is found to be highly sensitive (0.1 nM Rhodamine 6G and malachite green) and exhibit excellent reproducibility (∼8% relative standard deviation (RSD)) and long-term stability. Furthermore, it is also cost-efficient, with simple fabrication methodology, and demonstrates high sample collection efficiency. All of these benefits ensure that this GNRs-PLLA substrate is a really perfect choice for a variety of SERS applications.

Malachite green interacts with the membrane skeletal protein, spectrin

Energy minimized complex of MG with the self association domain of spectrin.

Coffee-ring effect-based simultaneous SERS substrate fabrication and analyte enrichment for trace analysis

Based on the "coffee-ring effect", we developed a highly efficient SERS platform which integrates the fabrication of SERS-active substrates and the preconcentration of analytes into one step. The high sensitivity, robustness, reproducibility and simplicity make this platform ideal for on-site analysis of small volume samples at low concentrations in complex matrices.

Biosorption of malachite green from aqueous solutions by Pleurotus ostreatus using Taguchi method

Dyes released into the environment have been posing a serious threat to natural ecosystems and aquatic life due to presence of heat, light, chemical and other exposures stable. In this study, the Pleurotus ostreatus (a macro-fungus) was used as a new biosorbent to study the biosorption of hazardous malachite green (MG) from aqueous solutions. The effective disposal of P. ostreatus is a meaningful work for environmental protection and maximum utilization of agricultural residues.The operational parameters such as biosorbent dose, pH, and ionic strength were investigated in a series of batch studies at 25°C. Freundlich isotherm model was described well for the biosorption equilibrium data. The biosorption process followed the pseudo-second-order kinetic model. Taguchi method was used to simplify the experimental number for determining the significance of factors and the optimum levels of experimental factors for MG biosorption. Biosorbent dose and initial MG concentration had significant influences on the percent removal and biosorption capacity. The highest percent removal reached 89.58% and the largest biosorption capacity reached 32.33 mg/g. The Fourier transform infrared spectroscopy (FTIR) showed that the functional groups such as, carboxyl, hydroxyl, amino and phosphonate groups on the biosorbent surface could be the potential adsorption sites for MG biosorption. P. ostreatus can be considered as an alternative biosorbent for the removal of dyes from aqueous solutions.

Low expression of ERK signaling pathway affecting proliferation, cell cycle arrest and apoptosis of human gastric HGC-27 cells line

This study was carried out for the first time to examine the potential role and the underlying mechanisms of Lycopene in the gastric cancer HGC-27 cells. HGC-27 cells were seeded onto heat-sterilized coverslips in six-well plates and exposed to Lycopene (5, 10, 20, 30 and 40 μmol/L) for periods of 72 h at 37 °C. Results showed that Lycopene (5, 10, 20, 30 and 40 μmol/L) dose-dependently increased NBT positive rate and decreased lactate dehydrogenase activity in HGC-27 cells. In addition, Lycopene (5, 10, 20, 30 and 40 μmol/L) inhibited proliferation and induced G0-G1 phase cell cycle arrest in HGC-27 cells. Western blot and FQRT-PCR analysis showed that Lycopene decreased pERK and extracellular signal-regulated kinase (ERK) protein and mRNA expression in a dose-dependent manner. These findings demonstrate that Lycopene inhibited gastric cancer HGC-27 cells growth and stimulated its apoptosis via the suppressing ERK signaling pathway.

Triphenylmethane dye activation of beta-arrestin

β-Arrestins regulate G protein-coupled receptor signaling as competitive inhibitors and protein adaptors. Low molecular weight biased ligands that bind receptors and discriminate between the G protein dependent arm and β-arrestin, clathrin-associated arm of receptor signaling are considered therapeutically valuable as a result of this distinctive pharmacological behavior. Other than receptor agonists, compounds that activate β-arrestins are not available. We show that within minutes of exposure to the cationic triphenylmethane dyes malachite green and brilliant green, tissue culture cells recruit β-arrestins to clathrin scaffolds in a receptor-activation independent manner. In the presence of these compounds, G protein signaling is inhibited, ERK and GSK3β signaling are preserved, and the recruitment of the beta2-adaptin, AP2 adaptor complex to clathrin as well as transferrin internalization is reduced. Moreover, malachite green binds β-arrestin2-GFP coated immunotrap beads relative to GFP only coated beads. Triphenylmethane dyes are FDA approved for topical use on newborns as components of triple-dye preparations and are not approved but used effectively as aqueous antibiotics in fish husbandry. As possible carcinogens, their chronic ingestion in food preparations, particularly through farmed fish, is discouraged in the U.S. and Europe. Our results indicate triphenylmethane dyes as a result of novel pharmacology may have additional roles as β-arrestin/clathrin pathway signaling modulators in both pharmacology research and clinical therapy.

Engineering natural materials as surface-enhanced Raman spectroscopy substrates for in situ molecular sensing

Surface-enhanced Raman spectroscopy (SERS) is a powerful analytical tool. However, its applications for in situ detection of target molecules presented on diverse material surfaces have been hindered by difficulties in rapid fabricating SERS-active substrates on the surfaces of these materials through a simple, low-cost, and portable approach. Here, we demonstrate our attempt to address this issue by developing a facile and versatile method capable of in situ generating silver nanoparticle film (SNF) on the surfaces of both artificial and natural materials in a simple, cheap, practical, and disposable manner. Taking advantage of the high SERS enhancement ability of the prepared SNF, the proposed strategy can be used for in situ inspecting herbicide and pesticide residues on vegetables, as well as the abuse of antiseptic in aquaculture industry. Therefore, it opens new avenues for advancing the application prospects of SERS technique in the fields of food safety, drug security, as well as environment monitoring.

Lycium barbarum polysaccharide stimulates proliferation of MCF-7 cells by the ERK pathway

AIMS

The aim of this study was to investigate the anti-proliferative effect of Lycium barbarum polysaccharide (LBP) on MCF-7 cells.

MAIN METHODS

MCF-7 cells were treated with 0, 10, 30, 100, and 300 μg/ml LBP for 24 h. The cell cycle distribution was analyzed by flow cytometry. MEK inhibitor, U1206 also was added in MCF-7 cells to deal with LBP (300 μg/ml) for different times (0, 2, 4, 6, 8, 16, 24 h). Western blotting was used to indicate changes in the levels of ERK (extracellular signal-regulated protein kinase) and phosphorylation-ERK (p-ERK) to compare the relationship between ERK activity and LBP. The expressions of p53, p-p53 and p21 were observed by western blotting to analyze the relationship between p53 and ERK which was under the treatment of LBP.

KEY FINDINGS

The MCF-7 cell cycle was arrested in S phase with the treatment of LBP. The LBP can also activate ERK, which may be associated with p53 pathway. There was a dose-dependent increase in the relation between the degree of ERK activation and LBP.

SIGNIFICANCE

LBP induces the anti-proliferation of MCF-7 cells by activating ERK.

Malachite green toxicity assessed on Asian catfish primary cultures of peripheral blood mononuclear cells by a proteomic analysis

The potential genotoxic and carcinogenic properties reported for malachite green (MG) and the frequent detection of MG residues in fish and fish products, despite the ban of MG, have recently generated great concern. Additional toxicological data are required for a better understanding of the mechanism of action and a more comprehensive risk assessment for the exposure of fish to this fungicide. To date, the use of fish peripheral blood mononuclear cells (PBMCs) has not been exploited as a tool in the assessment of the toxicity of chemicals. However, PBMCs are exposed to toxicants and can be easily collected by blood sampling. The present study aims at better understanding the effects of MG by a proteomic analysis of primary cultured PBMC from the Asian catfish, Pangasianodon hypophthalmus, exposed to MG. The two lowest concentrations of 1 and 10 ppb were selected based on the MTS (water soluble tetrazolium salts) cytotoxicity test. Using a proteomic analysis (2D-DIGE), we showed that 109 proteins displayed significant changes in abundance in PBMC exposed during 48 h to MG. Most of these proteins were successfully identified by nano LC-MS/MS and validated through the Peptide and Protein Prophet of Scaffold™ software, but only 19 different proteins were considered corresponding to a single identification per spot. Our data suggest that low concentrations of MG could affect the mitochondrial metabolic functions, impair some signal transduction cascades and normal cell division, stimulate DNA repair and disorganize the cytoskeleton. Altogether, these results confirm that the mitochondrion is a target of MG toxicity. Further studies on the identified proteins are needed to better understand the mechanisms of MG toxicity in fish produced for human consumption.

Potential toxicity and affinity of triphenylmethane dye malachite green to lysozyme

Malachite green is a triphenylmethane dye that is used extensively in many industrial and aquacultural processes, generating environmental concerns and health problems to human being. In this contribution, the complexation between lysozyme and malachite green was verified by means of computer-aided molecular modeling, steady state and time-resolved fluorescence, and circular dichroism (CD) approaches. The precise binding patch of malachite green in lysozyme has been identified from molecular modeling and ANS displacement, Trp-62, Trp-63, and Trp-108 residues of lysozyme were earmarked to possess high-affinity for this dye, the principal forces in the lysozyme-malachite green adduct are hydrophobic and π-π interactions. Steady state fluorescence proclaimed the complex of malachite green with lysozyme yields quenching through static type, which substantiates time-resolved fluorescence measurements that lysozyme-malachite green conjugation formation has an affinity of 10(3)M(-1). Moreover, via molecular modeling and also CD data, we can safely arrive at a conclusion that the polypeptide chain of lysozyme partially destabilized upon complexation with malachite green. The data emerged here will help to further understand the toxicological action of malachite green in human body.

Cytotoxicity of water-soluble mPEG-SH-coated silver nanoparticles in HL-7702 cells

Silver nanoparticles (AgNPs) are being used widely and increasingly in various products and medical supplies due to their antibacterial activity. However, little is known about the impacts of the AgNPs. Herein, The primary purpose of this study was to investigate the cytotoxic effect of AgNPs in the human liver cell line (HL-7702). The water-soluble α-Methoxy-poly (ethylene glycol)-ω-mercapto (mPEG-SH)-coated AgNPs (40 nm) were synthesized, which showed superior stabilization and uniform dispersion in culture medium. The effect of mPEG-SH-coated silver nanoparticles on cell viability, leakage of lactate dehydrogenase (LDH), oxidative stress, mitochondrial membrane potential (MMP), and cell cycle was evaluated after the cells were treated with nanoparticles. The results showed that the coated AgNPs could be taken up by cells, decreased cell viability in dose- and time-dependent manners at dosage levels between 6.25 and 100.00 μg/mL, caused membrane damage (LDH leakage), and decreased the activities of superoxide dismutase and glutathione peroxides. The level of malondialdehyde, an end product of lipid peroxidation, was also increased in AgNPs-exposed cells. Moreover, flow cytometric analysis showed that AgNP exposure decrease MMP and cause G₂/M phase arrest. Thus, our data suggest that mPEG-SH-coated AgNPs have the potential toxicity that is associated with oxidative stress, apoptosis, and DNA damage.

Proteomic analysis of blood cells in fish exposed to chemotherapeutics: evidence for long term effects

Proteomics technology are increasingly used in ecotoxicological studies to characterize and monitor biomarkers of exposure. The present study aims at identifying long term effects of malachite green (MG) exposure on the proteome of peripheral blood mononuclear cells (PBMC) from the Asian catfish, Pangasianodon hypophthalmus. A common (0.1 ppm) concentration for therapeutic treatment was applied twice with a 72 h interval. PBMC were collected directly at the end of the second bath of MG (T1) and after 1 month of decontamination (T2). Analytical 2D-DIGE gels were run and a total of 2551±364 spots were matched. Among them, MG induced significant changes in abundance of 116 spots with no recovery after one month of decontamination. Using LC-MS/MS and considering single identification per spot, we could identify 25 different proteins. Additionally, MG residues were measured in muscle and in blood indicating that leuco-MG has almost totally disappeared after one month of decontamination. This work highlights long term effects of MG treatment on the PBMC proteome from fish intended for human consumption.

Simultaneous determination of malachite green, enrofloxacin and ciprofloxacin in fish farming water and fish feed by liquid chromatography with solid-phase extraction

An effective and sensitive method for simultaneous analysis of malachite green (MG), enrofloxacin (ENFLX) and ciprofloxacin (CPFLX) by liquid chromatography-diode array detection with solid-phase extraction (SPE) is developed. The conditions of SPE and LC were investigated and optimised. The effective separation of these compounds was achieved using a ZY1104 C18 column (250 × 4.6 mm, 5 μm) with 20 mM tetrabutyl ammonium bromide (pH 3.0)-acetonitrile as mobile phase and gradient elution. The diode array detection was used at 278 nm for ENFLX and CPFLX and at 613 nm for MG. Under the optimal conditions, the method LOD values of MG, ENFLX and CPFLX were 0.01, 0.07 and 0.10 μg L( -1) for fish farming water samples and 1.5, 10.5 and 15 μg kg( -1) for fish feed samples, respectively. The relative recoveries of the three analytes were achieved to be 76.7-82.3% with the RSDs (n = 5) of 3.2-4.6% for spiked fish farming water samples and 78.8-93.7% with the RSDs (n = 5) of 3.1-4.8% for spiked fish feed samples.

Activation of checkpoint kinase 2 by 3,3'-diindolylmethane is required for causing G2/M cell cycle arrest in human ovarian cancer cells

We evaluated the effect of 3,3'-diindolylmethane (DIM) in ovarian cancer cells. DIM treatment inhibited the growth of SKOV-3, TOV-21G, and OVCAR-3 ovarian cancer cells in both a dose- and time-dependent manner with effective concentrations ranging from 40 to 100 muM. Growth-inhibitory effects of DIM were mediated by cell cycle arrest in G(2)/M phase in all the three cell lines. G(2)/M arrest was associated with DNA damage as indicated by phosphorylation of H(2)A.X at Ser139 and activation of checkpoint kinase 2 (Chk2) in all the three cell lines. Other G(2)/M regulatory molecules such as Cdc25C, Cdk1, cyclin B1 were down-regulated by DIM. Cycloheximide or Chk2 inhibitor pretreatment abrogated not only activation of Chk2 but also G(2)/M arrest and apoptosis mediated by DIM. To further establish the involvement of Chk2 in DIM-mediated G(2)/M arrest, cells were transfected with dominant-negative Chk2 (DN-Chk2). Blocking Chk2 activation by DN-Chk2 completely protected cells from DIM-mediated G(2)/M arrest. These results were further confirmed in Chk2 knockout DT40 lymphoma cells, in which DIM failed to cause cell cycle arrest. These results clearly indicate the requirement of Chk2 activation to cause G(2)/M arrest by DIM in ovarian cancer cells. Moreover, blocking Chk2 activation also abrogates the apoptosis-inducing effects of DIM. Furthermore, our results show that DIM treatment cause ROS generation. Blocking ROS generation by N-acetyl cysteine protects the cells from DIM-mediated G(2)/M arrest and apoptosis. Our results establish Chk2 as a potent molecular target of DIM in ovarian cancer cells and provide the rationale for further clinical investigation of DIM.

A portable surface-enhanced Raman scattering sensor integrated with a lab-on-a-chip for field analysis

An integrated real-time sensing system that uses a portable Raman spectrometer and a micropillar array chip has been developed for field analysis. The problem of poor detection sensitivity, caused by miniaturization in the portable Raman spectrometer, was overcome by using the surface-enhanced Raman scattering (SERS) technique. The problem of poor reproducibility in the SERS detection, caused by different particle sizes and inhomogeneous degrees of aggregation, was also overcome by using continuous flow and homogeneous mixing between the analytes and nanocolloidal silver in a micropillar array microfluidic chip. Two hazardous materials, dipicolinic acid and malachite green, were quantitatively analysed using our integrated portable Raman sensor system. The observed limit of detection was estimated to be 200 ppb and 500 ppb, respectively. Our proposed analytical method, using a micropillar array PDMS chip and a portable SERS system, offers a rapid and reproducible trace detection capability for hazardous materials in the field.

Mycobacterium smegmatis mc2 155 fbiC and MSMEG_2392 are involved in triphenylmethane dye decolorization and coenzyme F420 biosynthesis

Mycobacteria can tolerate relatively high concentrations of triphenylmethane dyes such as malachite green and methyl violet. To identify mycobacterial genes involved in the decolorization of malachite green, a transposon mutant library of Mycobacterium smegmatis mc2 155 was screened for mutants unable to decolorize this dye. One of the genes identified was MSMEG_5126, an orthologue of Mycobacterium bovis fbiC encoding a 7,8-didemethyl-8-hydroxy-5-deazariboflavin (FO) synthase, which is essential for the biosynthesis of the electron carrier coenzyme F420. The other gene identified was MSMEG_2392, encoding an alanine-rich protein with a DUF121 domain. The minimum inhibitory concentrations (MICs) for malachite green and methyl violet of the six fbiC mutants and two MSMEG_2392 mutants were one-third and one-fifth, respectively, of the MIC of the parent strain M. smegmatis mc2 155. Representative fbiC and MSMEG_2392 mutant strains were also sensitive to oxidative stress caused by the redox-cycling agents plumbagin and menadione, and the sensitivity was reversed in the complemented strains. HPLC analysis of representative fbiC and MSMEG_2392 strains revealed that, while the fbiC mutant lacked both coenzyme F420 and FO, the MSMEG_2392 mutant contained FO but not coenzyme F420. These results indicate that MSMEG_2392 is involved in the biosynthesis of coenzyme F420.

Spectrophtometric determination of malachite green in fish farming water samples after cloud point extraction using nonionic surfactant Triton X-100

A novel and sensitive cloud point extraction procedure for the determination of trace amounts of malachite green by spectrophotometry was developed. Malachite green was extracted at pH 2.5 mediated by micelles of nonionic surfactant Triton X-100. The extracted surfactant-rich phase was diluted with ethanol and its absorbance was measured at 630 nm. The effect of different variables such as pH, Triton X-100 concentration, cloud point temperature and time and diverse ions was investigated and optimum conditions were established. The calibration graph was linear in the range of 4-500 ng mL(-1) of malachite green in the initial solution with r=0.9996 (n=10). Detection limit based on three times the standard deviation of the blank (3S(b)) was 1.2 ng mL(-1) and the relative standard deviation (R.S.D.) for 20 and 300 ng mL(-1) of malachite green was 1.48 and 1.13% (n=8), respectively. The method was applied to the determination of malachite green in different fish farming and river water samples.

Fast and sensitive trace analysis of malachite green using a surface-enhanced Raman microfluidic sensor

A rapid and highly sensitive trace analysis technique for determining malachite green (MG) in a polydimethylsiloxane (PDMS) microfluidic sensor was investigated using surface-enhanced Raman spectroscopy (SERS). A zigzag-shaped PDMS microfluidic channel was fabricated for efficient mixing between MG analytes and aggregated silver colloids. Under the optimal condition of flow velocity, MG molecules were effectively adsorbed onto silver nanoparticles while flowing along the upper and lower zigzag-shaped PDMS channel. A quantitative analysis of MG was performed based on the measured peak height at 1615 cm(-1) in its SERS spectrum. The limit of detection, using the SERS microfluidic sensor, was found to be below the 1-2 ppb level and this low detection limit is comparable to the result of the LC-Mass detection method. In the present study, we introduce a new conceptual detection technology, using a SERS microfluidic sensor, for the highly sensitive trace analysis of MG in water.

Confirmatory analysis of malachite green, leucomalachite green, crystal violet and leucocrystal violet in salmon by liquid chromatography–tandem mass spectrometry

A method has been developed to analyse for malachite green (MG), leucomalachite green (LMG), crystal violet (CV) and leucocrystal violet (LCV) residues in salmon. Salmon samples were extracted with acetonitrile:McIIIvain pH 3 buffer (90:10 v/v), sample extracts were purified on a Bakerbond strong cation exchange solid phase extraction cartridge. Aliquots of the extracts were analysed by LC-MS/MS. The method was validated in salmon, according to the criteria defined in Commission Decision 2002/657/EC. The decision limit (CCalpha) was 0.17, 0.15, 0.35 and 0.17 microg kg(-1), respectively, for MG, LMG, CV and LCV and for the detection capability (CCbeta) values of 0.30, 0.35, 0.80 and 0.32 microg kg(-1), respectively, were obtained. Fortifying salmon samples (n=6) in three separate assays, show the accuracy to be between 77 and 113% for MG, LMG, LCV and CV. The precision of the method, expressed as RSD values for the within-laboratory reproducibility, for MG, LMG and LCV at the three levels of fortification (1, 1.5 and 2.0 microg kg(-1)), was less than 13%. For CV a more variable precision was obtained, with RSD values ranging between 20 and 25%.