Removal of dyes from water using Citrullus lanatus seed powder in continuous and discontinuous systems.

The objective of this study is to develop a low-cost biosorbent using residual seeds of the Citrullus lanatus fruit for the removal of cationic dyes. Physicochemical parameters such as pH, adsorbent mass, contact time, and temperature were evaluated for their effects on dye removal. The biosorbent is composed of lignin and cellulose, exhibiting a highly heterogeneous surface with randomly distributed cavities and bulges. The adsorption of both dyes was most effective at natural pH with a dosage of 0.8 g L-1. Equilibrium was reached within 120 min, regardless of concentration, indicating rapid kinetics. The Elovich model and pseudo-second-order kinetics were observed for crystal violet and basic fuchsin dye, respectively. The Langmuir model fitted well with the equilibrium data of both dyes. However, the increased temperature had a negative impact on dye adsorption. The biosorbent also demonstrated satisfactory performance (R = 43%) against a synthetic mixture of dyes and inorganic salts, with a small mass transfer zone. The adsorption capacities for crystal violet and basic fuchsin dye were 48.13 mg g-1 and 44.26 mg g-1, respectively. Thermodynamic studies confirmed an exothermic nature of adsorption. Overall, this low-cost biosorbent showed potential for the removal of dyes from aqueous solutions.

In this work, a novel biosorbent was developed using residual Citrullus lanatus fruit seeds that can efficiently remove cationic dyes from aqueous solutions. The biosorbent's composition includes lignin and cellulose, and its surface structure is highly heterogeneous, consisting of randomly distributed cavities and bulges. The biosorbent demonstrated a rapid and efficient adsorption capacity for both crystal violet and basic fuchsin, regardless of dye concentration. Moreover, the biosorbent was successfully employed in the treatment of a synthetic mixture containing several dyes and inorganic salts. Finally, the application of the biosorbent in continuous adsorption showed a low zone of mass transfer and high breakthrough time, indicating it to be an excellent material for fixed-bed operation. Overall, this study provides a low-cost and efficient alternative for the removal of dyes from aqueous solutions, with promising practical applications.

Exploring the promising potential of fallen bamboo leaves (Bambusa bambos) for efficient removal of crystal violet from wastewater.

Fallen bamboo leaves (Bambusa bambos), hereinafter BL have been designed to be transformed into an efficient and sustainable adsorbent for the removal of crystal violet (CV) dye from wastewater with up to 95% scavenging ability. BL have been characterized by Fourier transform infrared (FTIR) spectra, field emission scanning electron microscopy (FESEM), and zero point charge (pHzpc). The maximum adsorption capacity is 30 mg/g at pH 10. Physico-chemical parameters have been investigated concerning pH, contact time, initial concentration, and coexistent ions. Pseudo-second-order kinetics is followed best (R2 =0.999) signifying a chemisorption pathway. Besides, intra-particle diffusion plays a governing role in the film diffusion of crystal violet into the core of the adsorbent. Langmuir isotherm model fits best (R2=0.972) suggesting a uniform, monolayer, and homogeneous adsorption. Regeneration was successful with methanol (65%) and reusability was tested for three cycles and was found to retain activity up to 80%. Analysis of CV containing industrial effluent suggests that a 36.8% reduction is possible with BL. The effect of co-existent ions suggests little influence on the adsorption. Compared to other contemporary and relevant adsorbents, it can be concluded that BL can be exercised for the sustainable decontamination of CV-containing wastewater.

Bambusa bambos, the giant thorny bamboo is an abundantly available plant throughout the year, has been successfully exercised using its fallen leaves to scavenge crystal violet, a cationic dye from water and wastewater. Up to 95% adsorption was noticed at ambient conditions, which when further extrapolated for industrial effluent analysis, shows a remarkable 36.8% decontamination/cycle. With an adsorption capacity of 30 mg/g, it enjoys an edge over contemporary phytosorbents. The process is free from any chemical treatment, green in nature, and sustainable. Abundant availability and economic viability allow an impactful application of fallen bamboo leaves for water and wastewater treatment in a lab-to-land sequence.

Evaluating cottonwood seeds as a low-cost biosorbent for crystal violet removal from aqueous matrics.

In this study, cottonwood seeds (CWS) were introduced as a novel, green, and low-cost biosorbents for the removal of crystal violet (CV) dye from aqueous solutions. To illustrate the characteristics of CWS, surface morphology, Fourier-transform infrared spectroscopy, field emission scanning electron microscopes, and energy dispersive X-ray spectroscopy techniques were employed. Important adsorption variables (i.e., equilibrium time, solution pH, CWS amount, CV concentration, and temperature) were systematically studied. Maximum CV dye adsorption was observed at pH 10 using 20 mg of the adsorbent. Different adsorption isotherms were investigated, and the results were more accurately consistent with the Langmuir model (R2 = 0.992). The maximum capacity of adsorption was 153.85 mg g-1 at 60 min. The kinetic data were examined by different models and a pseudo-second-order model supplied the best correlation between experimental data. Investigated thermodynamic parameters at different temperatures illustrated that the CV adsorption procedure was spontaneous and endothermic with an increase in entropy. The percentage removal and the relative standard deviations for the real sample analysis were in the range of 89-98% and 4.9-9.5%, respectively. High adsorption capacity and low equilibrium time demonstrated that CWS is an impressive biosorbent for dye pollutants uptakes from aqueous solutions and real industrial wastewater samples.

A novel, green, available, and low-cost cottonwood seeds were introduced for the removal of crystal violet from aqueous media. In terms of adsorption capacity and contact time, cottonwood seeds show excellent performance compared to the other low-cost biosorbents previously reported for the adsorption of the organic dye from wastewater. The use of cottonwood seeds to remove environmental pollutants has not been introduced yet.

Film wrap nanoparticle system with the graphene nano-spacer for SERS detection.

Film wrap nanoparticle system (FWPS) is proposed and fabricated to perform SERS effect, where the Ag nanoparticle was completely wrapped by Au film and the double-layered graphene was selected as the sub-nano spacer. In this system, the designed nanostructure can be fully rather than partly used to generate hotspots and absorb probe molecules, compared to the nanoparticle to nanoparticle system (PTPS) or nanoparticle to film system (PTFS). The optimal fabricating condition and performance of this system were studied by the COMSOL Multiphysics. The simulation results show that the strongly large-scale localized electromagnetic field appears in the whole space between the Ag nanoparticle and Au film. The experimental results show that the FWPS presents excellent sensitivity (crystal violet (CV): 10-11 M), uniformity, stability and high enhancement factor (EF: 2.23×108). Malachite green (MG; 10-10 M) on the surface of fish and DNA strands with different base sequence (A, T, C) were successfully detected. These advanced results indicate that FWPS is highly promising to be applied for the detection of environmental pollution and biomolecules.

Paper-Based Versatile Surface-Enhanced Raman Spectroscopy Chip with Smartphone-Based Raman Analyzer for Point-of-Care Application.

With the advanced development of miniaturized Raman spectroscopy, surface-enhanced Raman spectroscopy (SERS) has extended its applications into the field of point-of-care testing (POCT) and demonstrated its great significance by virtue of its noninvasive property and capability of fingerprint identification. In the SERS-based analysis and/or sensing system, the preparation of a low-cost, high-performance SERS substrate is critically important. In this manuscript, vacuum filtration is utilized to fabricate the silver nanoparticles (AgNPs)-embedded nylon filter membrane (ANFM) as flexible paper-based SERS chips. By characterizing the typical analytes with a miniaturized smartphone-based Raman analyzer, the proposed SERS chips have successfully demonstrated good sensitivity, repeatability, and stability. The lowest concentration as detected can approach 1 pmol for rhodamine 6G (RH6G) and 10 pmol for both crystal violet (CV) and malachite green (MG), respectively. With the help of the microporous structure of the membrane, the ANFM-based SERS chips can implement the separation of small molecules from a complex mixture and can achieve "purified" SERS signals of targeted molecules. Besides, with the function of antifriction resistance and flexibility, the ANFM can serve as SERS papers to preconcentrate the contaminates by multiple swapping and further enhance the SERS signals for point-of-care analysis. Therefore, we demonstrate multifunctions of the flexible ANFM-based SERS chips, which provide a promising solution for the POCT analysis with the SERS technique on account of their flexibility and low fabrication cost.

Antimicrobial, anti-adhesive and anti-biofilm potential of biosurfactants isolated from Pediococcus acidilactici and Lactobacillus plantarum against Staphylococcus aureus CMCC26003.

Biosurfactants (BS) are amphipathic compounds produced by diverse groups of microorganisms exhibiting various biological activities. The current study aimed to assess antimicrobial, anti-adhesive and anti-biofilm activities of BS isolated from lactic acid bacteria (LAB), including Pediococcus acidilactici and Lactobacillus plantarum against Staphylococcus aureus CMCC 26003 in vitro. Cell-bound BS from both Pediococcus acidilactici and Lactobacillus plantarum were extracted, and their surface activities were evaluated by oil spreading assay. As quantified by crystal violet method, BS inhibited adhesion and biofilm formation of Staphylococcus aureus in a dose-dependent manner. The above findings were further supported by results of scanning electron microscopy. These two kinds of BS affect expressions of biofilm-related genes (cidA, icaA, dltB, agrA, sortaseA and sarA) and interfere with the release of signaling molecules (AI-2) in quorum sensing systems. Biological activities observed for BS produced by tested LAB suggest prospects for their use against Staphylococcus aureus biofilm-related infections.

Antibacterial and anti-biofilm activity, and mechanism of action of pleurocidin against drug resistant Staphylococcus aureus.

The abuse of antibiotics has resulted in the emergence of multi-drug-resistant bacteria. Staphylococcus aureus is a frequent cause of infections, and antibiotic-resistant S. aureus has become a serious problem. Antimicrobial peptides play an important role in innate immunity and are attracting increasing attention as alternative antibiotics. In a previous study, pleurocidin, derived from winter flounder, was identified as a 25-amino acid antimicrobial peptide with no cytotoxicity toward mammalian cells and low hemolytic activity. In the present study, pleurocidin was observed to exhibit antimicrobial activity against gram-positive and gram-negative bacteria, especially against drug resistant S. aureus. Pleurocidin retained its antibacterial activity against drug resistant S. aureus in the presence of a physiological salt concentration. Membrane depolarization assays and propidium iodide uptake indicated that pleurocidin kills bacteria by damaging the integrity of the bacterial membrane. DNA binding assays revealed that pleurocidin binds to DNA. Thus, pleurocidin targets not only the bacterial membrane, but also their DNA. S. aureus biofilms have become a serious problem because of increased resistance to antibiotics. Therefore, we investigated the effect of pleurocidin on biofilm inhibition and eradication using crystal violet staining and microscopic observation. Pleurocidin inhibited and eradicated biofilms at low concentrations. Taken together, the results suggested that pleurocidin is a promising candidate therapeutic agent to treat drug-resistant bacteria and biofilm-related infections.

Modified xanthan gum for crystal violet uptake: kinetic, isotherm, and thermodynamic behaviors.

Modified xanthan gum (XG-AM-TTE) was employed as an adsorbent to study the adsorption behavior, thermodynamics and kinetics of crystal violet (CV) from an aqueous solution. Fourier transform infrared spectroscopy analysis indicates that the functional groups present in the adsorbent, such as carboxyl, ester and hydroxyl groups, are included on the external surface of the material, and these groups are potential active sites for interaction with CV. According to X-ray diffraction results, the structure of XG-AM-TTE after CV adsorption became more disordered, and the microstructure change is an indication of effective adsorption of CV to the surface, with CV becoming remarkably dispersed in the adsorbent according to the scanning electron microscopy observations. The adsorption kinetics and adsorption equilibrium were best described by the pseudo-second-order model and Freundlich isotherms, respectively. The thermodynamic parameters, as the Gibbs-free energy (ΔG), enthalpy (ΔH) and entropy (ΔS), indicated that the adsorption is a spontaneous, endothermic and entropy increase process. The maximum adsorption capacity of XG-AM-TTE was 183 ± 12 mg/g, suggesting that XG-AM-TTE is an efficient adsorbent.

Biosorption of crystal violet dye using inactive biomass of the fungus Diaporthe schini.

An inactive biomass of a new fungus recently discovered, Diaporthe schini, was evaluated for the biosorption of crystal violet (CV) in simulated textile effluents. The characterization assays were performed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and N2 adsorption/desorption isotherms. The influences of pH and biosorbent dosage on the biosorption capacity were evaluated. Kinetics, equilibrium and thermodynamic studies were also carried out. Characterization techniques showed an amorphous biosorbent, with a rough surface containing irregular particles and surface area of 6.5 m2 g-1. The most adequate values of pH and biosorbent dosage were 7.5 and 0.4 g L-1, respectively. The Elovich kinetic model and the Sips equilibrium model were suitable to fit the experimental data. The biosorption capacity increased with temperature, reaching a maximum biosorption capacity of 642.3 mg g-1 at 328 K. The biosorption was a spontaneous and endothermic process. Diaporthe schini inactive biomass was an interesting biosorbent to treat colored effluents, presenting efficiency of 87% in the decolorization of a simulated dye house effluent.

Polymicrobial antibiofilm activity of the membranotropic peptide gH625 and its analogue.

This work illustrates a new role for the membranotropic peptide gH625 and its derivative gH625-GCGKKK in impairing formation of polymicrobial biofilms. Mixed biofilms composed of Candida and bacterial species cause frequently infections and failure of medical silicone devices and also show a major drug resistance than single-species biofilms. Inhibition and eradication of biofilms were evaluated by complementary methods: XTT-reduction, and crystal violet staining (CV). Our results indicate that gH625-GCGKKKK, better than the native peptide, strongly inhibited formation of mixed biofilms of clinical isolates of C. tropicalis/S. marcescens and C. tropicalis/S. aureus and reduced the biofilm architecture, interfering with cell adhesion and polymeric matrix, as well as eradicated the long-term polymicrobial biofilms on silicone surface.

Anti-Candida activity of antidepressants sertraline and fluoxetine: effect upon pre-formed biofilms.

As an opportunistic fungal pathogen Candida spp. has the ability to form biofilms. The most prescribed drugs for Candida infections, azoles, have shown to be less effective when biofilms are present. In addition, increasing treatment costs and the fact that most prescribed antifungal drugs have only fungistatic activity justify the search for new treatment strategies. One promising approach is third generation antidepressants, selective serotonin re-uptake inhibitors (SSRIs), because of their proven antifungal activity against several Candida spp. Thus, the aim of this work was to determine the ability of two commonly used SSRIs, fluoxetine and sertraline, to impair both biofilm metabolic viability and biofilm biomass. The in vitro effect of fluoxetine and sertraline was individually tested against biofilm metabolic viability and biofilm biomass using the MTT assay and the Crystal Violet assay, respectively. For both drugs, a dose-dependent reduction on both biofilm metabolism and biomass was present. At high concentrations, fluoxetine was able to reduce biofilm metabolism by 96% (C. krusei) and biofilm biomass by 82% (C. glabrata), when compared to the control. At similar conditions, sertraline achieved a reduction of 88% on biofilm biomass (C. glabrata) and 90% on biofilm metabolism (C. parapsilosis). Moreover, fluoxetine showed interesting anti-biofilm activity at previously reported planktonic MIC values and even at sub-MIC values. These results reinforce the potential interest of SSRIs as anti-biofilm agents to be study to counteract resistance phenomena on candidosis.

Theoretical Calculation and Experimental Verification Demonstrated the Impossibility of Finding Haptens Identifying Triphenylmethane Dyes and Their Leuco Metabolites Simultaneously.

Detection of triphenylmethane dyes (TDs), especially the widely used malachite green (MG) and crystal violet (CV), plays an important role in safety control of aquatic products. There are two chromatic forms of TDs: oxidized or reduced. Usually, only one form can be detected by reported ELISA antibodies. In this article, molecular shape superimposing and quantum mechanics calculation were employed to elucidate the differences between MG, CV, and their reduced chromatic forms (leucomalachite green, LMG and leucocrystal violet, LCV). A potential hapten was rationally designed and synthesized. Polyclonal antibodies were raised through immunizing New Zealand white rabbits and BALB/C mice. We tested the cross-reactivity ratios between the hapten and TDs. The cross-reactivity ratios were correlated with the difference in surface electrostatic potential. The determination coefficients (r²) of the correlations are 0.901 and 0.813 for the rabbit and mouse antibody, respectively. According to this linear model, the significant difference in the atomic charge seemed to make it impossible to find a hapten that can produce antibodies with good cross-reactivities with both reduced and oxidized TDs.

Potential of Araucaria angustifolia bark as adsorbent to remove Gentian Violet dye from aqueous effluents.

Araucaria angustifolia bark (AA-bark), a waste generated in wood processing, was evaluated as a potential adsorbent to remove Gentian Violet (GV) dye from aqueous solutions. The AA-bark presented an amorphous structure with irregular surface and was composed mainly of lignin and holocellulose. These characteristics indicated that the adsorbent contains available sites to accommodate the dye molecules. The GV adsorption on AA-bark was favored at pH 8.0 with adsorbent dosage of 0.80 g L-1. Pseudo-nth order model was adequate to represent the adsorption kinetics of GV on AA-bark. A fast adsorption rate was verified, with the equilibrium being attained within 30 min. Equilibrium data were well represented by the Langmuir model. The maximum adsorption capacity was 305.3 mg g-1. Adsorption was spontaneous, favorable and endothermic. AA-bark was able to treat a simulated dye house effluent, reaching color removal values of 80%. An excellent performance was found in fixed bed experiments, where the length of the mass transfer zone was only 5.38 cm and the breakthrough time was 138.5 h. AA-bark can be regenerated two times using HNO3 0.5 mol L-1. AA-bark can be used as a low-cost material to treat colored effluents in batch and fixed bed adsorption systems.

Modeling adsorption kinetic of crystal violet removal by electrocoagulation technique using bipolar iron electrodes.

This paper studies the removal of crystal violet (CV) dye by electrocoagulation (EC) process using bipolar iron electrodes. Numerous operating parameters such as initial CV solution concentration, speed of agitation, number of electrodes, type and quantity of supporting electrolyte, temperature- and initial pH were investigated. A complete removal of 10 mg/L CV was achieved within 10 min at pH 7, 0.5 g NaCl, 1 LCV, 750 rpm, 9 sheets, 17.36 mAcm2, and 25 °C. The performed energy-dispersive X-ray spectroscopy (EDAX), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) analyses confirmed the adsorption of CV onto the insoluble iron hydroxide flocs. Amongst the studied adsorption isotherms models, Langmuir and Dubinin-Radushkevich were the most applicable. The kinetic of adsorption of CV onto flocs during the EC operation was studied using the pseudo-first-order, pseudo-second-order, and intraparticulate diffusion models, with results affirming that the adsorption process proceeded according to the pseudo-second-order model. The study of thermodynamic parameters (ΔG0, ΔH0, and ΔS0,) of the CV removal at different temperatures reflected the feasibility of the spontaneous randomness of endothermic adsorption, especially at lower temperatures. The multiple regression equation of the removal of CV by EC technique under the different studied conditions was predicted.

Dalbavancin reduces biofilms of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus epidermidis (MRSE).

Activity of dalbavancin against methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus epidermidis (MRSE) in biofilm was investigated and the microbicidal biofilm concentrations (MBC) were determined. Biofilms obtained from ten MRSA and ten MRSE bloodstream isolates, collected from patients in the General Hospital of Vienna between 2012 and 2015, were incubated with dalbavancin in trypticase soy broth (TSB) in serial dilution from 0.0625 mg/l to 256 mg/l using a microtiter plate biofilm model. The plates were incubated for 24 h at 37 ° C and 50% humidity. Biofilms were fixed with 2.5% glutaraldehyde and stained with crystal violet. Subsequently the optical density (OD620) was used to measure the MBC, defined as the concentration of dalbavancin leading to a 50% reduction of biofilm. MBC for MRSA was 1 mg/l-4 mg/l (minimal inhibitory concentrations (MIC) 0.0312 mg/l-0.064 mg/l). MBC for MRSE was 2 mg/l-16 mg/l (MIC 0.023 mg/l-0.0625 mg/l). Dalbavancin successfully reduced MRSA and MRSE in biofilms, and therefore provides a promising option for the treatment of biofilm-associated infections.

Impact of Gram stain results on initial treatment selection in patients with ventilator-associated pneumonia: a retrospective analysis of two treatment algorithms.

BACKGROUND: Ventilator-associated pneumonia (VAP) is a common and serious problem in intensive care units (ICUs). Several studies have suggested that the Gram stain of endotracheal aspirates is a useful method for accurately diagnosing VAP. However, the usefulness of the Gram stain in predicting which microorganisms cause VAP has not been established. The purpose of this study was to evaluate whether a Gram stain of endotracheal aspirates could be used to determine appropriate initial antimicrobial therapy for VAP. METHODS: Data on consecutive episodes of microbiologically confirmed VAP were collected from February 2013 to February 2016 in the ICU of a tertiary care hospital in Japan. We constructed two hypothetical empirical antimicrobial treatment algorithms for VAP: a guidelines-based algorithm (GLBA) based on the recommendations of the American Thoracic Society-Infectious Diseases Society of America (ATS-IDSA) guidelines and a Gram stain-based algorithm (GSBA) which limited the choice of initial antimicrobials according to the results of bedside Gram stains. The GLBA and the GSBA were retrospectively reviewed for each VAP episode. The initial coverage rates and the selection of broad-spectrum antimicrobial agents were compared between the two algorithms. RESULTS: During the study period, 219 suspected VAP episodes were observed and 131 episodes were assessed for analysis. Appropriate antimicrobial coverage rates were not significantly different between the two algorithms (GLBA 95.4% versus GSBA 92.4%; p = 0.134). The number of episodes for which antimethicillin-resistant Staphylococcus aureus agents were selected as an initial treatment was larger in the GLBA than in the GSBA (71.0% versus 31.3%; p < 0.001), as were the number of episodes for which antipseudomonal agents were recommended as an initial treatment (70.2% versus 51.9%; p < 0.001). CONCLUSIONS: Antimicrobial treatment based on Gram stain results may restrict the administration of broad-spectrum antimicrobial agents without increasing the risk of treatment failure. TRIAL REGISTRATION: UMIN-CTR, UMIN000026457 . Registered 8 March 2017 (retrospectively registered).

Application of experimental design and derivative spectrophotometry methods in optimization and analysis of biosorption of binary mixtures of basic dyes from aqueous solutions.

Simultaneous biosorption of malachite green (MG) and crystal violet (CV) on biosorbent Yarrowia lipolytica ISF7 was studied. An appropriate derivative spectrophotometry technique was used to evaluate the concentration of each dye in binary solutions, despite significant interferences in visible light absorbances. The effects of pH, temperature, growth time, initial MG and CV concentration in batch experiments were assessed using Design of Experiment (DOE) according to central composite second order response surface methodology (RSM). The analysis showed that the greatest biosorption efficiency (>99% for both dyes) can be obtained at pH 7.0, T=28°C, 24h mixing and 20mgL-1 initial concentrations for both MG and CV dyes. The quadratic constructed equation ability for fitting experimental data is judged based on criterions like R2 values, significant p and lack-of-fit value strongly confirm its high adequacy and applicability for prediction of revel behavior of the system under study. The proposed model showed very high correlation coefficients (R2=0.9997 for CV and R2=0.9989 for MG), while supported by closeness of predicted and experimental value. A kinetic analysis was carried out, showing that for both dyes a pseudo-second order kinetic model adequately describes the available data. The Langmuir isotherm model in single and binary components has better performance for description of dyes biosorption with maximum monolayer biosorption capacity of 59.4 and 62.7mgg-1 in single component and 46.4 and 50.0mgg-1 for CV and MB in binary components, respectively. The surface structure of biosorbents and the possible biosorbents-dyes interactions between were also evaluated by Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). The values of thermodynamic parameters including ΔG° and ΔH° strongly confirm which method is spontaneous and endothermic.

Simultaneous spectrophotometric determination of crystal violet and malachite green in water samples using partial least squares regression and central composite design after preconcentration by dispersive solid-phase extraction.

In this paper, a simple, fast, and inexpensive method is introduced for the simultaneous spectrophotometric determination of crystal violet (CV) and malachite green (MG) contents in aquatic samples using partial least squares regression (PLS) as a multivariate calibration technique after preconcentration by graphene oxide (GO). The method was based on the sorption and desorption of analytes onto GO and direct determination by ultraviolet-visible spectrophotometric techniques. GO was synthesized according to Hummers method. To characterize the shape and structure of GO, FT-IR, SEM, and XRD were used. The effective factors on the extraction efficiency such as pH, extraction time, and the amount of adsorbent were optimized using central composite design. The optimum values of these factors were 6, 15 min, and 12 mg, respectively. The maximum capacity of GO for the adsorption of CV and MG was 63.17 and 77.02 mg g-1, respectively. Preconcentration factors and extraction recoveries were obtained and were 19.6, 98% for CV and 20, 100% for MG, respectively. LOD and linear dynamic ranges for CV and MG were 0.009, 0.03-0.3, 0.015, and 0.05-0.5 (µg mL-1), respectively. The intra-day and inter-day relative standard deviations were 1.99 and 0.58 for CV and 1.69 and 3.13 for MG at the concentration level of 50 ng mL-1, respectively. Finally, the proposed DSPE/PLS method was successfully applied for the simultaneous determination of the trace amount of CV and MG in the real water samples.

Simultaneous determination of binary solution of triphenylmethane dyes in complex matrices onto magnetic amino-rich SWCNT using second-order calibration method.

This study suggested a new method for simultaneous quantification of two dyes in complex matrices using second-order data by spectrophotometry. Second-order data was generated simply without any expensive instrument using two independent variables including wavelength and the monotonic addition of sodium dodecyl sulfate. Solid-phase extraction (SPE) based on amino-rich magnetic single-walled carbon nanotube as an adsorbent was employed prior to second-order data generation. SPE optimization was performed by Box-Behnken design, and parameters and their interaction which were dependent on the simultaneous extraction of dyes were examined. Competitive Langmuir and Freundlich isotherms for a binary system and individual dyes could all represent the equilibrium data well. The second-order data was processed by parallel factor analysis (PARAFAC and PARAFAC2) and multivariate curve resolution-alternating least squares (MCR-ALS). Figures of merit of the model including a limit of detection of 3.0 and 2.5 ng mL-1 for crystal violet and malachite green, respectively, were estimated using the MCR-ALS method. The combination of the second-order calibration and SPE presents an easy and versatile method for determination of the mixture of two dyes in the presence of uncalibrated interferences in environmental water, synthetic, and fish samples with the recoveries of 94-104.

Comparison of the antifungal activity of micafungin and amphotericin B against Candida tropicalis biofilms.

OBJECTIVES: Candida tropicalis is the fourth most common cause of candidaemia in hospitalized patients and associated mortality is high. C. tropicalis frequently causes biofilm-related infections. Echinocandins and amphotericin B show potent in vitro activity against C. albicans biofilms, but their activity against C. tropicalis biofilms has received little attention. METHODS: We studied production of biofilm by 54 C. tropicalis isolates from blood and the antifungal susceptibility of these isolates to micafungin, amphotericin B and liposomal amphotericin B. Biofilm production was measured using the crystal violet assay to determine biomass and the XTT reduction assay to determine metabolic activity. The antifungal susceptibility of planktonic and sessile cells was measured using the EUCAST EDef 7.2 procedure and XTT reduction assay, respectively. The sessile MIC endpoint of SMIC80 was defined as an 80% reduction in the metabolic activity of the biofilm treated with the antifungal compared with the control well. RESULTS: The three drugs were very active against the isolates in planktonic form, with micafungin showing the highest activity (P < 0.001). Micafungin was the most active agent against C. tropicalis biofilms (P < 0.001). In contrast, liposomal amphotericin B showed poor antifungal activity. CONCLUSIONS: Micafungin was the most active drug against C. tropicalis biofilm. Although the echinocandins and liposomal amphotericin B are considered very active against Candida spp. biofilms, this is not true for C. tropicalis, as liposomal amphotericin B showed poor antifungal activity against biofilms.