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1.
Molecules ; 28(3)2023 Jan 30.
Artículo en Inglés | MEDLINE | ID: mdl-36770983

RESUMEN

This work presents the use of a transparent 'Cross Injection Analysis' (CIA) platform as a flow system for chemiluminescence (CL) measurements. The CL-CIA flow device incorporates introduction channels for samples and reagents, and the reaction and detection channels are in one acrylic unit. A photomultiplier tube placed above the reaction channel detects the emitted luminescence. The system was applied to the analysis of (i) Co(II) via the Co(II)-catalyzed H2O2-luminol reaction and (ii) paracetamol via its inhibitory effect on the catalytic activity of Fe(CN)63- on the H2O2-luminol reaction. A linear calibration was obtained for Co(II) in the range of 0.002 to 0.025 mg L-1 Co(II) (r2 = 0.9977) for the determination of Co(II) in water samples. The linear calibration obtained for the paracetamol was 10 to 200 mg L-1 (r2 = 0.9906) for the determination of pharmaceutical products. The sample throughput was 60 samples h-1. The precision was ≤4.2% RSD. The consumption of the samples and reagents was ca. 170 µL per analysis cycle.

2.
Anal Chem ; 94(22): 7892-7900, 2022 06 07.
Artículo en Inglés | MEDLINE | ID: mdl-35609256

RESUMEN

This work presents a fully disposable microchamber for gas generation of a sample solution. The microchamber consists of a cylindrical well-reactor and a paper-based microfluidic lid (µFluidic lid), which also serves as the reagent loading and dispensing unit. The base of the reactor consists of a hydrophobic membrane covering an in-house graphene electrochemical gas sensor. Fabrication of the gas sensor and the three-layer µFluidic lid is described. The µFluidic lid is designed to provide a steady addition of the acid reagent into the sample solution instead of liquid drops from a disposable syringe. There are three steps in the procedure: (i) acidification of the sample in the reactor to generate SO2 gas by the slow dispensing of the acid reagent from the µFluidic lid, (ii) diffusion of the liberated SO2 gas through the hydrophobic membrane at the base of the reactor, and (iii) in situ detection of SO2 by cathodic reduction at the graphene electrode. The device was demonstrated for quantitation of the sulfite preservative in wine without heating or stirring. The selectivity of the analysis is ensured by the combination of the gas-diffusion membrane and the selectivity of the electrochemical sensor. The linear working range is 2-60 mg L-1 SO2, with a limit of detection (3SD of intercept/slope) of 1.5 mg L-1 SO2. This in situ method has the shortest analysis time (8 min per sample) among all voltammetric methods that detect SO2(g) via membrane gas diffusion.


Asunto(s)
Grafito , Vino , Electrodos , Grafito/análisis , Microfluídica , Sulfitos/análisis , Vino/análisis
3.
Molecules ; 26(21)2021 Oct 27.
Artículo en Inglés | MEDLINE | ID: mdl-34770888

RESUMEN

This work presents, for the first time, a new sequential injection analysis (SIA) method to simultaneously analyze degree Brix, orthophosphate and pH in raw cane juice. These key parameters relate to price of harvested sugarcane and quality of cane juice for sugar production. The SIA system employed two detectors: the first detector is a diode-array spectrophotometer, equipped with a regular flow cell, for measurements of degree Brix and orthophosphate. Quantitative of degree Brix (°Bx; ca. % (w/w) sucrose) was based on manipulation of the schlieren effect at the interface between plugs of sample and water. Orthophosphate analysis was carried out based on the molybdenum blue method with significant reduction in consumption of the reagents. Compensation of the schlieren effect from sucrose for determination of orthophosphate was achieved by using a dual-wavelength spectrometric detection. Second detector is a pH-sensing device, called ion-selective field-effect transistors (ISFET). The ISFET is based on the current through the ISFET arising according to the H+ concentration in solution. Our developed SIA system provides linear calibration graphs fitting for purpose in analysis of sugarcane juice (pH: 0-14, °Bx: 1.0-7.0 and P2O5: 20-200 mg L-1). Simultaneous analysis of sugarcane juice for pH, °Bx and P2O5 is carried out within 5 min (12 sample per h). Precision of SIA system is acceptable (RSD < 3%). Our SIA system gave quantitative results insignificantly different, as compared with conventional methods for analysis of pH, °Bx and P2O5 in sugarcane juice.


Asunto(s)
Industria de Alimentos , Jugos de Frutas y Vegetales/análisis , Concentración de Iones de Hidrógeno , Fosfatos/análisis , Saccharum/química , Azúcares/análisis
4.
Anal Chem ; 89(12): 6710-6718, 2017 06 20.
Artículo en Inglés | MEDLINE | ID: mdl-28528548

RESUMEN

Taylor dispersion analysis (TDA) allows the determination of the molecular diffusion coefficient (D) or the hydrodynamic radius (Rh) of a solute from the peak broadening of a plug of solute in a laminar Poiseuille flow. The main limitation plaguing the broader applicability of TDA is the lack of a sensitive detection modality. UV absorption is typically used with TDA but is only suitable for UV-absorbing or derivatized compounds. In this work, we present a development of the TDA method for non-UV absorbing compounds by using a universal detector based on refractive index (RI) sensing with backscattering interferometry (BSI). BSI was interfaced to a capillary electrophoresis-UV instrument using a polyimide coated fused silica capillary and an in-house designed flow-cell assembly. Polysaccharides were selected to demonstrate the application of TDA-BSI for size characterization. Under the conditions of validity of TDA, D and Rh average values and the entire Rh distributions were obtained from the (poly)saccharide taylorgrams, including non-UV absorbing polymers.

5.
Malar J ; 14: 88, 2015 Feb 21.
Artículo en Inglés | MEDLINE | ID: mdl-25889240

RESUMEN

BACKGROUND: Invasion of host erythrocytes by Plasmodium falciparum is central to the pathogenesis of malaria. Invasion involves recognition events between erythrocyte receptors and ligands on the merozoite, the invasive blood form of the parasite. Identifying and characterizing host-parasite interactions is impeded by the biochemical challenges of working with membrane-embedded glycoprotein receptors. For example, the interaction between P. falciparum erythrocyte binding antigen 175 (PfEBA175) and glycophorin A (GYPA) depends on post-translational modifications that are not easily added in recombinant expression systems, and the use of native GYPA is limited by the hydrophobic transmembrane region, making it difficult to biochemically manipulate. It would, therefore, be desirable to perform quantitative binding assays with receptors embedded within the membranes of intact human erythrocytes. METHODS: The extracellular region of GYPA was over-expressed as a soluble protein in HEK293E cells. This protein was characterized, sialylated and evaluated for binding to the PfEBA175 protein. The label-free and free-solution assay, backscattering interferometry (BSI), was used to perform binding assays of two well-characterized P. falciparum invasion ligands to intact unmodified human erythrocytes. RESULTS: Findings indicate that the post-translational modifications present on native GYPA are required for it to bind recombinant PfEBA175 and that these modifications cannot be recapitulated in vitro using mammalian overexpression methods. Here, BSI was used to obtain quantitative, high fidelity interaction determinations on intact, unmodified erythrocytes. Using BSI and purified recombinant proteins constituting the entire ectodomains of the P. falciparum merozoite ligands PfEBA175 and PfRH5, K Ds of 1.1 µM and 50 nM were measured for the PfRH5-BSG and PfEBA175-GYPA interactions, respectively, in good agreement with previous biophysical measurements of these interactions. CONCLUSIONS: These results demonstrate that BSI can be used to detect and quantify the interactions of two merozoite invasion ligands with their receptors on intact human erythrocytes. BSI assays were performed on unlabelled, free-solution proteins in their native environment, requiring only nanomoles of recombinant protein. This study suggests that BSI can be used to investigate host-parasite protein interactions without the limitations of other assay platforms, and therefore represents a valuable new method to investigate the molecular mechanisms involved in erythrocyte invasion by P. falciparum.


Asunto(s)
Antígenos de Protozoos/metabolismo , Proteínas Portadoras/metabolismo , Eritrocitos/parasitología , Glicoforinas/metabolismo , Interacciones Huésped-Parásitos , Plasmodium falciparum/fisiología , Procesamiento Proteico-Postraduccional , Proteínas Protozoarias/metabolismo , Antígenos de Protozoos/genética , Proteínas Portadoras/genética , Eritrocitos/metabolismo , Glicoforinas/genética , Interferometría , Malaria Falciparum/parasitología , Malaria Falciparum/fisiopatología , Plasmodium falciparum/genética , Proteínas Protozoarias/genética , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo
6.
Talanta ; 272: 125815, 2024 May 15.
Artículo en Inglés | MEDLINE | ID: mdl-38402737

RESUMEN

Taylor dispersion analysis (TDA) is a simple and absolute method to determine the hydrodynamic radius of solutes that respond to UV or fluorescence detections. To broaden the application range of TDA, it is necessary to develop new detection modes. This study aims to study capacitively coupled contactless conductivity detector (C4D) for the analysis of charged macromolecules. The detection sensitivities and hydrodynamic radii were compared for a C4D detector and a UV detector on positively or negatively charged polymers responding both to UV and C4D (poly-L-lysine and poly(acrylamide-co-2-acrylamido-1-methyl-propanesulfonate). The influence of the composition of the background electrolyte on the detection sensitivity has been studied and optimized for C4D detection. The influence of the molar mass and of the polymer chemical charge density on the C4D and UV sensitivities of detection have been investigated based on well-characterized copolymers samples of different molar masses and charge densities. The advantages and disadvantages compared to UV detection, as well as the range of applicability of C4D detection in TDA were identified. C4D detection can be an alternative method for sizing charged polymers of reasonable molar mass (typically below 105 g mol-1) that do not absorb in UV. A decline in the sensitivity of detection in C4D was observed for higher molar masses.

7.
Anal Methods ; 16(16): 2489-2495, 2024 Apr 25.
Artículo en Inglés | MEDLINE | ID: mdl-38502566

RESUMEN

Iron deficiency anemia (IDA) is a condition characterized by lower-than-average iron (Fe) levels in the body, affecting a substantial number of young children and pregnant women globally. Existing diagnostic methods for IDA rely on invasive analysis of stored Fe in ferritin from blood samples, posing challenges, especially for toddlers and young children. To address this issue, saliva has been proposed as a non-invasive sample matrix for IDA diagnosis. However, conventional Fe analysis techniques often necessitate complex and costly instrumentation. This study presents the first non-invasive, saliva-based preliminary screening test for IDA using a nitrocellulose lateral flow system. In this study, we introduce a novel approach using the ferroin reaction with bathophenanthroline (Bphen) and ferrous (Fe2+) ions to quantify Fe levels in saliva. Our methodology involves a capillary flow-driven microfluidic device integrated into a lateral flow system utilizing nitrocellulose membranes. Here, we present the first instance of saliva on a nitrocellulose substrate to detect salivary Fe levels. The optimized system yielded a linear response over the 1-200 ppm range in buffer solution, with a limit of detection (LoD) of 5.6 ppm. Furthermore, the system demonstrated a linear response in pooled saliva samples across the 1-1000 ppm range, with a LoD of 55.1 ppm. These results underscore the potential of our capillary flow-driven microfluidic device as a viable non-invasive diagnostic tool for IDA, particularly in remote and resource-limited settings.


Asunto(s)
Anemia Ferropénica , Hierro , Saliva , Humanos , Saliva/química , Anemia Ferropénica/diagnóstico , Hierro/análisis , Femenino , Límite de Detección , Técnicas Analíticas Microfluídicas/instrumentación , Técnicas Analíticas Microfluídicas/métodos , Colodión/química , Dispositivos Laboratorio en un Chip
8.
Spectrochim Acta A Mol Biomol Spectrosc ; 302: 123076, 2023 Dec 05.
Artículo en Inglés | MEDLINE | ID: mdl-37392537

RESUMEN

In the period of the corona virus disease 2019 (COVID-19) outbreak, an alcohol-based hand sanitizer is one of the most in-demand products for disinfection purposes. Two major concerns are adulteration of methanol, which causes toxicity to human health, and the concentration of legal alcohol in hand sanitizers due to their effect on antivirus. In this work, the first report of the entire quality assessment of alcohol-based hand sanitizers in terms of detection of methanol adulteration and quantification of ethanol is presented. Detection of adulterated methanol is carried out based on Schiff's reagent after the oxidation of methanol to formaldehyde, giving a bluish-purple solution to detect at 591 nm. In cases where a colorless solution is observed, an iodoform reaction with turbidimetric detection is then performed for quantitative analysis of legal alcohol (ethanol or isopropanol). To comply with the regulation of quality assessment of alcohol-based hand sanitizers, a regulation chart with four safety zones is also presented, employing a combination of two developed tests. The coordinates of a point (x, y) obtained from the two tests are extrapolated to the safety zone in the regulation chart. The regulation chart also showed consistency of analytical results as compared with the gas chromatography-flame ionization detector.


Asunto(s)
COVID-19 , Desinfectantes para las Manos , Humanos , Metanol/análisis , Etanol/análisis
9.
Anal Sci ; 39(8): 1385-1390, 2023 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-37101098

RESUMEN

Exported durians from Thailand are sometimes immersed in curcumin to give the fruits a good appearance. Curcumin is regarded as non-toxic additive, however some importing countries prohibited use of any additive to fresh fruits and vegetables. This work aims to develop a rapid, low cost and convenient cotton swab device for curcumin detection. The detection principle involves a colorimetric acid-base characteristic of curcumin. Curcumin in an acidic/neutral solution presents a bright yellow color, while it displays an intense orange-red color in basic solution. A cotton swab acted for both sample collection and as a sensing platform. A pre-moistened swab was used to wipe a durian surface. Afterward, a NaOH solution was dropped onto the swab. A distinct orange-red color appearing on the swab indicates the presence of curcumin. The cotton swab was applied for qualitative analysis of curcumin contaminated on durian husks via visual detection. The developed device provided good reliability, 93.75% (36 samples). Furthermore, the device was demonstrated for quantitative determination using camera detection. Two linear calibrations were obtained in ranges of 10-75 and 75-250 mg L-1, with a detection limit of 3.2 mg L-1. The method was also successfully applied to quantification of curcumin in durians (three samples) and dietary supplements (two samples). The test can be done in a few minutes. The developed device was established as an useful tool for food safety and control of contamination by curcumin in an on-site application.


Asunto(s)
Bombacaceae , Curcumina , Reproducibilidad de los Resultados , Colorimetría/métodos , Inocuidad de los Alimentos
10.
ACS Omega ; 8(12): 11213-11219, 2023 Mar 28.
Artículo en Inglés | MEDLINE | ID: mdl-37008150

RESUMEN

In this work, we propose a new design for paper-based analytical devices (PADs) that eliminate the need to use a micropipette for sample introduction. With this design, a PAD is equipped with a distance-based detection channel that is connected to a storage channel that indicates the volume of a sample introduced into the PAD. The analyte in the sample solution reacts with a colorimetric reagent deposited into the distance-based detection channel as the sample solution flows into the storage channel where the volume is measured. The ratio of the lengths of the detection channel and that of the storage channel (D/S ratio) are constant for a sample containing a certain concentration, which is independent of the introduced volume. Therefore, the PADs permit volume-independent quantification using a dropper instead of a micropipette because the length of the storage channel plays the role of a volume gauge to estimate the introduced sample volume. In this study, the D/S ratios obtained with a dropper were comparable to those obtained with a micropipette, which confirmed that precise volume control is unnecessary for this PAD system. The proposed PADs were applied to the determinations of iron and bovine serum albumin using bathophenanthroline and tetrabromophenol blue as colorimetric reagents, respectively. The calibration curves showed good linear relationships with coefficients of 0.989 for iron and 0.994 for bovine serum albumin, respectively.

11.
Anal Sci ; 38(3): 533-540, 2022 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-35359271

RESUMEN

In this work, we present for the first time, a simplified fabrication of a laminated paper-based analytical device (LPAD) with a free-mobile app, Palette Cam, for image analysis. A filter paper is cut in a rectangular shape (9 × 3 cm) and placed between a top laminating sheet with punched holes and a bottom laminating sheet. The holes allow accessibility of liquid on the paper. Thermal lamination is then employed to complete the fabrication of LPAD. Our simplified design reduces a tedious alignment of small pieces of paper to the holes. We demonstrated the LPAD with an analysis of salicylic acid in pharmaceutical products. Each 4 µL of ferric reagent and sample was dispensed on the LPAD. Smartphone was used to capture images. The RGB (red green blue) color intensity from the Palette Cam was converted into a logarithm color ratio. Our LPAD is simplified, cost-effective and able to be a portable device.


Asunto(s)
Aplicaciones Móviles , Papel , Preparaciones Farmacéuticas , Ácido Salicílico , Teléfono Inteligente
12.
Anal Methods ; 14(25): 2461-2470, 2022 06 30.
Artículo en Inglés | MEDLINE | ID: mdl-35713109

RESUMEN

This work presents the first paper-based electrochemical device, or ePAD, for direct detection of adulterated sibutramine in slimming products. The ePAD was fabricated using a screen-printing technique for defining the hydrophilic area for sample loading and for the working, reference and counter electrodes. The ePAD gave reproducible responses comparable to both conventional rod electrodes and commercial screen-printed electrodes (SPEs). Use of paper to fabricate the ePAD device provides advantages over the conventional SPE platforms (e.g. glass, ceramics and polymers) in terms of biocompatibility, strong capillary action and environmental friendliness. To detect sibutramine, square wave voltammetry was employed after sample loading on the circular hydrophilic area. The linear range is 2.51 to 83.7 mg L-1 sibutramine, with a precision of 6 %RSD (n = 3) and an instrumental limit of detection (3SD of intercept/slope) of 2.46 mg L-1 sibutramine. Recovery of spiked samples ranged from 83 to 116%. The samples were capsules, slimming coffee powders and nutraceutical beverages. The samples were appropriately diluted to give concentrations within the linear calibration range. Filtration of undissolved solids found with the capsules and coffee powder samples was not required, demonstrating that the method is not susceptible to solid particles. The ePAD is cost-effective (

Asunto(s)
Café , Ciclobutanos , Análisis Costo-Beneficio , Electrodos
13.
Spectrochim Acta A Mol Biomol Spectrosc ; 282: 121662, 2022 Dec 05.
Artículo en Inglés | MEDLINE | ID: mdl-35905612

RESUMEN

New chemosensors, L1-L3, based on the coumarin Schiff base scaffold with substituent modifications, have been designed and synthesized. The chemosensors L1-L3 exhibited the absorbance and fluorescence spectral changes that can discriminate Co2+, Ni2+, and Cu2+ ions. Sensor L1 demonstrated the ability to respond to Co2+, Ni2+, and Cu2+ ions. Remarkably, the slight modification of substituent on L2 has been observed to cause selective binding to Ni2+ and Cu2+ ions while L3 can specifically detect Cu2+ ions. The in-situ formation of metal and ligand complexes was determined by Job's plot analysis. The limit of detection and the sensing ability of all probes are estimated to be within the range of safe drinking water. Incorporation of the sensing compounds into a paper-based detection system using a laminated paper-based analytical device (LPAD) was demonstrated and found to be consistent to those obtained from the batchwise solution measurements.


Asunto(s)
Colorimetría , Colorantes Fluorescentes , Aminocumarinas , Cobre/análisis , Colorantes Fluorescentes/química , Iones/análisis , Espectrometría de Fluorescencia
14.
ACS Appl Mater Interfaces ; 14(5): 6810-6817, 2022 Feb 09.
Artículo en Inglés | MEDLINE | ID: mdl-35094511

RESUMEN

Intermolecular interactions between an electron-rich aromatic hydroquinone (HQ) with its electron deficient counterpart, benzoquinone (BQ), result in the formation of a quinhydrone charge-transfer complex. Herein, we report a novel quinhydrone-type complex between pillar[5]quinone (P[5]Q) and HQ. Characterized by a suite of spectroscopic techniques including 1H NMR, UV-visible, and FTIR together with PXRD, SEM, BET, CV, and DFT modeling studies, the stability of the complex is determined to be due to an electron-proton transfer reaction coupled with a complementary donor-acceptor interaction. The selectivity of P[5]Q toward HQ over other dihydroxybenzene isomers allows for not only the naked-eye detection of HQ but also its selective liquid-liquid extraction and recovery from aqueous media.

15.
Forensic Sci Int ; 329: 111084, 2021 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-34752997

RESUMEN

This work presents two simple methods for estimating the firing distance from the gunshot residues (GSRs) on fabric targets. Four types of fabric targets, namely twill weave denim cotton-polyester (80/20), jersey knitting 100% cotton, plain weave cotton-polyester (80/20) and plain weave cotton-polyester (60/40), were employed. The firing tests were carried out using these white fabrics as targets at distances of 5-100 cm, respectively. In the first method, digital images of the black GSRs on fabric materials were recorded inside an illuminated box and the inverted gray intensity values were plotted against the firing distances. Since the plots of all fabrics are not significantly different, the estimation of firing distance employs the same exponential curve for all test fabrics. Although simple, the imaging method is not suitable for dark-colored materials. A chemical-based method was therefore developed as an alternative method. In the second method, a small disposable microfluidic paper-based analytical device (µPAD) was employed for detecting Pb(II) extracted from the GSRs. The µPAD method uses the measurement of the length of a narrow band of a pink color resulting from reaction between rhodizonate reagent and the Pb(II) extract. The plots indicated that the data of thick denim material are significantly different to other test fabrics which are much thinner. These three fabrics share the same estimation curve. However, it is recommended that the separate estimation curve for denim materials must be used. Both methods are suitable for short range firing distance, no further than 60 cm, since at greater distances the inverted gray intensity and the 'band-length' methods are unable to detect the GSRs.

16.
Membranes (Basel) ; 10(5)2020 May 18.
Artículo en Inglés | MEDLINE | ID: mdl-32443480

RESUMEN

This study presents a simple flow-based system for the determination of the preservative agent sulfite in food and beverages. The standard method of conversion of sulfite ions into SO2 gas by acidification is employed to separate the sulfite from sample matrices. The sample is aspirated into a donor stream of sulfuric acid. A membrane gas-liquid separation unit, also called a 'gas-diffusion (GD)' unit, incorporating a polytetrafluoroethylene (PTFE) hydrophobic membrane allows the generated gas to diffuse into a stream of deionized water in the acceptor line. The dissolution of the SO2 gas leads to a change in the conductivity of water which is monitored by an in-line capacitively coupled contactless conductivity detector (C4D). The conductivity change is proportional to the concentration of sulfite in the sample. In this work, both clear (wine) and turbid (fruit juice and extracts of dried fruit) were selected to demonstrate the versatility of the developed method. The method can tolerate turbidity up to 60 Nephelometric Turbidity Units (NTUs). The linear range is 5-25 mg L-1 SO32- with precision < 2% RSD. The flow system employs a peristaltic pump for propelling all liquid lines. Quantitative results of sulfite were statistically comparable to those obtained from iodimetric titration for the wine samples.

17.
EXCLI J ; 18: 467-476, 2019.
Artículo en Inglés | MEDLINE | ID: mdl-31423125

RESUMEN

Chikungunya virus (CHIKV), a re-emerging infectious arbovirus, causes Chikungunya fever that is characterized by fever, skin rash, joint pain, arthralgia and occasionally death. Despite it has been described for 66 years already, neither potential vaccine nor a specific drug is available yet. During CHIKV infection, interferon type I signaling pathway is stimulated and releases hundreds of interferon stimulated genes (ISGs). Our previous study reported that IFI16, a member of ISGs, is up-regulated during CHIKV virus infection and the suppression of the gene resulted in increased virus replication. Furthermore, our group also found that inflammasome activation can inhibit CHIKV infection in human foreskin cells (HFF1). Concomitantly, it has been reported that IFI16 activates the inflammasome to suppress virus infection. Therefore, we have hypothesized that IFI16 could be involved in CHIKV infection. In this study, we confirmed the expression level of IFI16 by Western blotting analysis and found that IFI16 was up-regulated following CHIKV infection in both HFF1 and human embryonic kidney cells. We next investigated its antiviral activity and found that forced expression of IFI16 completely restricted CHIKV infection while endogenous silencing of the gene markedly increased virus replication. Furthermore, we have discovered that IFI16 inhibited CHIKV replication, at least, in cell-to-cell transmission as well as the diffusion step. Interestingly, IFI16 also exerted its antiviral activity against Zika virus (ZIKV) infection, the global threat re-emerging virus can cause microcephaly in humans. Taken together, this study provides the first evidence of an antivirus activity of IFI16 during in vitro arbovirus infection, thus expanding its antiviral spectrum that paves the way to further development of antiviral drugs and vaccines.

18.
Talanta ; 188: 74-80, 2018 Oct 01.
Artículo en Inglés | MEDLINE | ID: mdl-30029441

RESUMEN

In flow analysis, such as flow injection analysis, liquid lens is formed at the boundary between two adjacent liquid media which have different refractive indices. Light refraction at the liquid interface gives the so-called 'schlieren signal'. Schlieren effect is both concentration-dependent and temperature-dependent. In this work, the schlieren signal from temperature difference was quantitatively investigated for application in enthalpimetric measurement. The schlieren phenomena was then exploited for chemical analysis. A thermal insulated single flow line manifold was constructed using deionized water at 23 °C as the carrier. Deionized water at various temperatures in the range of 5-85 °C was injected into the carrier flow. A correlation between the schlieren signal and sample temperature was observed. A heat exchanger unit (HEU), consisting of a small volume glass-reaction chamber with a surrounding water jacket, was constructed. The unit was thermally insulated in a double layer cylindrical PVC unit. For demonstrating the applicability of temperature-dependent schlieren effect in chemical analysis, the exothermic oxidation reaction between acid dichromate and ethanol or ascorbic acid was employed with heat transferring to the surrounding water layer. When an aliquot of water from the HEU is injected into the constant temperature flow line the observed schlieren signal was dependent on the analyte concentration. Linear calibration (r2 > 0.99) were obtained covering the concentration range of ethanol and ascorbic acid as found in samples. The developed flow system provides good precision (RSD < 5%) with sample throughput of 4 sample h-1. The system were applied to the determination of ethanol in Thai white spirit and ascorbic acid in vitamin C tablets, respectively. The quantitative results obtained from the schlieren method were in agreement with the comparative methods.

19.
Anal Sci ; 34(1): 83-89, 2018.
Artículo en Inglés | MEDLINE | ID: mdl-29321464

RESUMEN

A low-cost and user-friendly microfluidic paper-based analytical device (µPAD) was developed for identification of bullet hole from gunshot residue (GSR) on cotton fabric target. The device (25 × 82 mm) is made of filter paper with a printed pattern consisting of a circular sample loading reservoir (6 mm i.d.), a circular waste reservoir (4 mm i.d.) and a straight flow channel (3 mm wide and 60 mm long). A sticker with a ruler scale in millimeters was mounted alongside the channel. The straight channel is first impregnated with rhodizonate and dried at ambient temperature. Tartrate extract of the target fabric is loaded on the sample reservoir. If Pb(II) ions are present in the extract, pink streak of Pb(II)-rhodizonate precipitate is formed as the sample solution flows from the reservoir along the channel. The length of the pink strip is employed to estimate the firing distance.

20.
ACS Chem Neurosci ; 8(10): 2132-2138, 2017 10 18.
Artículo en Inglés | MEDLINE | ID: mdl-28783953

RESUMEN

Ceftriaxone, a ß-lactam antibiotic, has been reported to act independently of its antimicrobial actions to normalize perturbed central nervous system glutamate levels, principally by elevating expression of glial glutamate transporters. Identification of a specific, high-affinity target for ceftriaxone could significantly impact therapeutic development for multiple brain disorders, ranging from neurodegenerative disorders to addiction. Recently, we identified a glial-expressed Caenorhabditis elegans gene, swip-10, that encodes a metallo-ß-lactamase domain-containing protein, and limits glutamate-dependent changes in dopamine neuron excitability. Bioinformatic analyses identified MBLAC1 as the likely mammalian orthologue of swip-10. Using cyanogen bromide immobilized ceftriaxone for affinity capture experiments and backscattering interferometry to monitor MBLAC1 binding of unmodified ceftriaxone, we obtained evidence for specific, high affinity (KD = 2.2 µM) binding of ceftriaxone to MBLAC1. We discuss our findings with respect to MBLAC1 as a potentially exclusive, high-affinity binding partner of ceftriaxone in the CNS, and the path forward in the development of novel, MBLAC1-based therapeutics.


Asunto(s)
Antibacterianos/metabolismo , Ceftriaxona/metabolismo , Hidrolasas/metabolismo , Sistema de Transporte de Aminoácidos X-AG/metabolismo , Animales , Antibacterianos/farmacología , Caenorhabditis elegans , Ceftriaxona/farmacología , Sistema Nervioso Central/efectos de los fármacos , Sistema Nervioso Central/metabolismo , Ratones
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