Direct Visual Determination Research Articles

A colorimetric immuno-microarray for the quantitation and direct visualization of illicit drugs in body fluids.

The design and testing of integrated colorimetric microarray immunochips (immuno-microarrays) are reported for the quantitation and direct visual determination of multiple illicit drugs (e.g., morphine, cocaine and amphetamine) in body fluids. Such an immuno-microarray platform utilizes a competitive immunoassay format, which is based on silver staining for quantitative detection and multicolor staining for direct visualization (i.e., qualitative identification) of analytes present in the sample. Under optimized conditions, the dynamic response ranges of 3.7-1000, 1.1-300 and 1.5-300 ng mL-1 were achieved for amphetamine, cocaine, and morphine, respectively, which are wider towards low concentrations than those of standard enzyme-linked immunosorbent assay (ELISA) tests. The limits of detection (LODs) for morphine, cocaine, and amphetamine were determined to be 1.5 ± 0.1, 1.1 ± 0.1 and 3.7 ± 0.2 ng mL-1, respectively in oral fluids, which meet government regulations for law enforcement. The obvious advantages of multiplexing, simultaneous visual recognition, and accurate quantitation make the on-site detection feasible, confirming that such a colorimetric immuno-microarray holds promise for practical applications.

Measuring cloud point pressures by image analysis: A simple and reproducible alternative method to direct visual determination

In this work, we propose an easy to implement and use methodology to measure cloud point pressures in supercritical carbon dioxide without the need for a specific setup. This method is based on the analysis of images issued from the video recording of solution changes occurring while the pressure is changed. This alternative analytical method demonstrates higher repeatability, higher accuracy than direct visual determination and enables in the case of complex architectures like block copolymers to infer additional information from cloud point measurements.

Morphological Characterization and Determination of Aflatoxin-Production Potentials of Aspergillus flavus Isolated from Maize and Soil in Kenya

This study aimed at morphologically identifying Aspergillus flavus in soil and maize and at determining their aflatoxin-producing potentials. Five hundred and fourteen isolates obtained from maize and soil in Kenya were cultivated on Czapeck Dox Agar, Malt Extract Agar, Sabouraud Dextrose Agar, Potato Dextrose Agar, and Rose-Bengal Chloramphenicol Agar. Isolates were identified using macro-morphological characteristics. Micromorphological characteristics were determined using slide cultures. Aflatoxin production was determined by direct visual determination of the UV fluorescence of colonies on Coconut Agar Medium, Yeast Extract Sucrose agar, and Yeast Extract Cyclodextrin Sodium Deoxycholate agar and by Thin Layer Chromatography. Forty-three presumptive A. flavus isolates were identified; aflatoxin was detected in 23% of the isolates by UV fluorescence screening and in 30% by Thin-Layer Chromatography (TLC). The aflatoxins produced were: aflatoxin B1 (AFB1), aflatoxin B2 (AFB2), and aflatoxin G1 (AFG1); some isolates produced only AFB1, whereas others produced either AFB1 and AFB2 or AFB1 and AFG1. The highest incidence of A. flavus (63%) and aflatoxin production (28%) was recorded in samples from Makueni District. Isolates from Uasin Gishu (21%) and Nyeri (5%) were non-aflatoxigenic. Bungoma District recorded 11% positive isolates of which 2% were aflatoxin producers. The occurrence of aflatoxin-producing A. flavus emphasises the need for measures to eliminate their presence in food crops.

The dynamic behavior of the early dental caries lesion in caries-active adults and implications.

To describe the full range of behavior of the visible, noncavitated, early caries lesion in caries-active adults with substantial fluoride exposure, and to consider implications. The data were from the Xylitol for Adult Caries Trial (X-ACT) collected annually for 33 months using condensed ICDAS caries threshold criteria. Individual tooth surfaces having a noncavitated caries lesion were included, and the patterns of transition to each subsequent annual clinical examination to sound, noncavitated or cavitated, filled or crowned were determined. The resulting sets of patterns for an individual tooth surface, looking forward from its first appearance as a noncavitated lesion, were combined into one of four behavior profiles classified as reversing, stable, oscillating, or continuously progressing, or were excluded if not part of the caries continuum. The distributions of profile types were assessed using the Rao-Scott chi-square test, which adjusts for clustering of tooth surfaces within teeth. Inter- and intra-examiner kappa scores demonstrated acceptable calibration at baseline and annually. 8084 tooth surfaces from 543 subjects were included. The distribution of profile types differed significantly between coronal and root surfaces. Overall, two-thirds of all coronal noncavitated lesions were first seen at baseline, half reversed, over a fifth were stable, 15% oscillated, and only 8.3% progressed to cavitation, filled, or crowned in 33 months or less (6.3% consistently Progressed plus 2.0% inconsistently, a subset of oscillating, which oscillated before progressing to cavitation). Approximal, smooth, and occlusal coronal surfaces each were significantly different in their individual distributions of profile types. Xylitol showed no significant and consistent effect on this distribution by tooth surface type. This was in keeping with the X-ACT's lack of effect of xylitol at the noncavitated plus cavitated lesion thresholds combined. This study demonstrated the full dynamic range of early caries lesion behavior. The great majority were not progressive, and few (8.3%) became cavitated over 33 months in caries-active adults using fluorides. Important caries management implications favoring recorded longitudinal monitoring, prevention of active risks, and minimal restoration only after direct visual determination of cavitation are discussed.

A neutral red desiccated coconut agar for rapid detection of aflatoxigenic fungi and visual determination of aflatoxins

Desiccated coconut agar is the conventional medium used for the detection of aflatoxigenic fungi and direct visual determination of aflatoxins. In this study, an improved medium was developed by the incorporation of 0.2% (v/v) neutral red dye into desiccated coconut agar. The medium was formulated by a 2×3 factorial design of neutral red and phenol red stains at three concentration levels. The formulated medium was evaluated for performance by screening for the minimal time required by each Aspergillus species to produce pigments and fluorescence of agar. The medium was also employed for detection of aflatoxigenic fungi and direct visual determination of aflatoxins in foods and fish-meal. The neutral red desiccated coconut agar (NRDCA) as compared to the conventional desiccated coconut agar (DCA) had a light pink background as opposed to the white background of the DCA which often interferes with the visibility of fluorescence. The time of pigmentation and fluorescence production on NRDCA was 28 and 38 h respectively as compared with 33 and 44 h of DCA and 41 and 48 h of palm kernel agar (PKA: an alternative culture medium for cultivation of aflatoxigenic fungi with a reddish pink background). Furthermore, aflatoxigenic moulds were detected in all food commodities and fish-meal after 60 hours of incubation. The highest percentage of aflatoxigenic moulds (62.5%) was detected in yam flour with NRDCA while the lowest percentage (4.46%) was detected with PKA on rice. In addition, aflatoxins were produced in high amounts in food commodities in which aflatoxigenic moulds were detected and there was a significant positive correlation (r=0.4, P<0.05) between the isolates and aflatoxin concentration of the food samples. Rice (a major staple food for Nigerians) had the highest total aflatoxin concentration of 140, 220 and 205 µg/kg on DCA, NRDCA and PKA respectively, while ‘gari’ had the least concentration of 45, 50 and 40 µg/kg. These values were far above the NAFDAC recommended level of 10 µg/kg for unprocessed foods in Nigeria and therefore a source of concern. In addition the study also reveals that Aspergillus nomius can produce aflatoxins B1 in copious amounts on NRDCA, contrary to previous reports of its production in minute quantities on laboratory media. The benefit of this study lies in the rapid analysis and simplified technique for the detection of aflatoxigenic fungi and visual determination of aflatoxins.

Evaluation of the detection techniques of toxigenic Aspergillus isolates.

Aflatoxins are difuranocoumarin derivatives produced by some Aspergillus species through a polyketide pathway. Mycotoxins are considered hazardous and there is a need for accurate detection of each toxin. Several screening methods for direct visual determination of aflatoxins and ochratoxin A (OTA) production have been reported. These methods rely on using different types of coconut culture media, methylated â-cyclodextrin and ammonium hydroxide vapour tests. However, our results showed that use of these techniques were not sufficiently sensitive for all Aspergillus species and suggested a simple thin layer chromatography (TLC) as a sensitive and reliable technique for detection of aflatoxins and OTA produced by Aspergillus and Eurotium species. Key words: Aspergillus, Eurotium , Mycotoxins detection, thin layer chromatography.

Mechanism of Reactive Wetting and Direct Visual Determination of the Kinetics of Self-Assembled Monolayer Formation

Reactive wetting (RW) of alkane thiols and disulfides on gold is studied experimentally using the wet stamping technique. Theoretical description based on Langevin dynamics is developed to explain the experimental results and to clarify the physical processes underlying RW. In this description, thermal fluctuations of the three-phase contact line combine with the surface reaction to gradually build a low-energy self-assembled monolayer (SAM) onto which the front propagates. The results of the model match the experiments and allow determination of the kinetic rate constants of SAM formation.

Palm kernel agar: An alternative culture medium for rapid detection of aflatoxins in agricultural commodities

The feasibility of using palm kernel agar (PKA) as an alternative culture medium to desiccated coconut agar (DCA), the conventional medium for the recovery of aflatoxigenic fungi from mixed cultures and the detection of aflatoxigenic fungi and direct visual determination of aflatoxins in agricultural commodities was assessed. The medium recovered aflatoxigenic fungi in 48 h from mixed cultures and agricultural commodities in 58 h as compared to 62 h obtained for the two treatments on desiccated coconut medium. Aflatoxigenic fungi were detected in all the agricultural commodities except for onions with maize having the highest value of 13.18% (w/w) followed by melon (10.97), yam flour (10.23) and groundnut (8.52) as against 11.48, 10.0, 6.92 and 8.52% (w/w) obtained for DCA. All aflatoxigenic strains produced a characteristic yellow pigmentation on a pink background and blue or blue green fluorescence of palm kernel agar Under long wave UV light (366nm) as against the white background of DCA, which often interferes with fluorescence with corresponding yield of aflatoxins. This shows that the medium is able to efficiently detect aflatoxin production through direct visual observation of fluorescence. Palm kernel agar (PKA) can therefore be routinely used as an alternative culture medium for screening aflatoxigenic fungi and direct visual determination of aflatoxins in agricultural commodities since it is faster and has a unique pink background for easy identification

Development of a method for direct visual determination of aflatoxin production by colonies of the Aspergillus flavus group

This report describes a simple, rapid and reliable method for screening the aflatoxin production by moulds of the Aspergillus flavus group. Strains were cultivated on yeast extract agar to which methylated β-cyclodextrin derivative plus sodium desoxycholate was added. Production of aflatoxins was readily detectable by direct visualisation of a beige ring surrounding colonies after an incubation time of 3 days at 28 °C. When this ring was examined under UV light, it exhibited blue fluorescence. The presence of aflatoxins was confirmed by extracting the medium with chloroform and examining the extracts by HPLC with fluorescence detection.

Geohydrologic use of lithofacies maps in glaciated areas

Subsurface conditions may differ considerably from conditions indicated by surficial geologic maps, particularly in glaciated areas. Therefore, it is advantageous to use a series of lithofacies maps as a sequence of overlays plotted on transparent paper. Such maps permit direct visual determination of the lithology and areal extent of aquifers and indicate areas of possible stream losses or gains. They indicate areas and boundaries of confining layers and, in some places, they may be used to delineate areas of water‐table and artesian conditions. They are especially useful in determining buried channels in glaciated areas. The porosity of rock units making up an aquifer may be plotted on a lithofacies map, and the product of the volume of each lithologic type and the porosity provides an estimate of the total water in storage. In addition, if the water‐bearing properties are known, the quantity of water moving through an aquifer and the amount available to wells may be determined. Lithofacies maps also aid in the explanation of complex changes in water quality.