Colorimetric Measurement of Deltamethrin Pesticide Using a Paper Sensor Based on Aggregation of Gold Nanoparticles

Deltamethrin (DEL) is one of the most commonly used pyrethroid pesticides that can cause serious harms to the ecological environment and human health. Herein, we have developed a paper-based colorimetric sensor impregnated with gold nanoparticles (AuNPs) for on-site determination of DEL pesticide. AuNPs show obvious color change on paper device with the presence of DEL. Measuring the gray intensity of the AuNPs on the reaction zone of the paper sensor allows accurate quantitative analysis. The detection mechanism of DEL on paper sensor was confirmed by UV-Vis spectrophotometry (UV-Vis), Fourier transform infrared spectroscopy (FT-IR), and transmission electron microscope (TEM). Under optimal conditions, the colorimetric sensor exhibited high sensitivity, rapid detection, and low detection limit within the values stipulated by Chinese detection standards (LOD = 0.584 mg/L). Besides, detecting DEL in vegetable and fruit samples also gave satisfying results, which were much consistent with those obtained by spectrophotometry. Overall, this work provided a user-friendly, cost-effective and visualized detection platform, which could be applied to rapidly detect DEL pesticides in the food safety field.

Synthesis of Symmetrical Acetophenone Azine Derivatives as Colorimetric and Fluorescent Cyanide Chemosensors

Cyanide is a highly toxic anion and poison to the environment. Therefore, fast, effective, and efficient analysis methods to detect cyanide are needed. Herein, symmetrical chemosensor of 2’-hydroxy acetophenone azine (1) and 2’,4’-dihydroxy acetophenone azine (2) has been synthesized tested as colorimetric and fluorescent cyanide chemosensor. The azines were produced from the condensation of acetophenone derivatives with hydrazine hydrate in ethanol under reflux or ultrasonic irradiation methods. Colorimetric and fluorescent chemosensor tests showed selectivity to acetate and cyanide anions in DMSO. The limit of detection (LOD) for colorimetric measurement of cyanide anion was 9.68×10–4 M for compound (1) and 9.63×10–5 M for compound (2), while the fluorescent method showed 15.90×10–4 M for compound (1) and 8.95×10–5 M for compound (2), respectively. In addition, test paper-strips containing sensor 2 indicated noticeable results for 'naked eye' detection of cyanide in an aqueous medium.

Smartphone-based technology for nanomolecular detection of aflatoxin B1 by aptamer-conjugated magnetic nanoparticles

The need for a healthy market in the rapid and accurate screening of a variety of pathogenic agents and toxins in the environment and food has led to an increase in the development of new biosensors, which have ideal characteristics, such as high sensitivity and specificity with rapid detection and simple preparation of the sample. Among the food contaminants, mycotoxins have been identified as a major challenge for the food industry, and rapid and accurate detection has attracted the attention of food inspection and monitoring organisations. In this study, a nanomolecular detection method is described using aflatoxin B1 (AFB1)-specific aptamers attached to streptavidin-coated magnetic nanoparticles. A prominent feature of the AFB1-specific aptamers is a guanine-rich (G-rich) sequence with a G-quadruplex structure after capturing AFB1 molecules and mimicking peroxidase activity. The enzymatic reaction evaluated in the presence of chromogenic substrate and measurement is done by a smartphone-specific application for colorimetric measurement. The results indicated that the assay could measure AFB1 in rice, flour, seed, maize, and pistachio. In addition, the application of hybrid nanomaterial technology resulting from the binding of biotin-labelled aptamers to the surface of streptavidin-coated magnetic nanoparticles minimises preparation and treatment of samples, improves results, and consequently reduces false negative and positive responses in the detection field. This study may eventually lead to the design and development of a fast, sensitive, specific, and on-site AFB1-based nanomolecular colorimetric detection system via a smartphone-based application that can be readily accessible to all applicants, from professionals to manufacturers of foodstuffs.

El color como componente paisajístico en los catálogos de paisaje urbano

Resumen Se puede evidenciar una deficiencia en los procesos de planificación y diseño urbanos con un enfoque paisajístico, y es por lo que el color urbano puede entenderse como un componte significativo que contribuye a consolidar el carácter paisajístico de la ciudad y a delimitar de áreas homogéneas. El presente trabajo tiene como objetivo abordar el color urbano dentro del marco de la construcción de una metodología para la elaboración de catálogos de paisaje urbano (CPU) aplicables en distintas estructuras físico-espaciales urbanas y contextos geográficos. A partir de registros fotográficos en formato de barrido panorámico, capturados en puntos de observación del espacio urbano, y mediante el uso de software, se generan esquemas cromáticos representativos de la imagen paisajística. Desde las fases de identificación y caracterización, el resultado es una interpretación objetiva y cualitativa de la información de medición colorimétrica (sistema de color HSL) que permite relacionar e identificar la composición de color ambiental del paisaje considerando en igual medida a la naturaleza y a la cultura (construcciones antrópicas), y de cómo esto permite orientar planes y proyectos urbanos. Palabras clave: color ambiental, cromática, diseño urbano, espacio urbano, esquemas colorimétricos, paisajismo Abstract A deficiency in urban planning and design processes can be evidenced with a landscape approach, which is why the urban color can be understood as a significant component that contributes to consolidating the landscape character of the city. The work aims to address the urban color in the framework of the construction of a methodology for the elaboration of "Urban Landscape Catalogs" (CPU) applicable in different urban physical-spatial structures and geographical contexts. From photographic records in panoramic scanning format, captured in observation points of the urban space and through the use of software, representative color schemes of the landscape image are generated. From the identification and characterization phases, the result is an objective and qualitative interpretation of the colorimetric measurement information (HSL color system) that allows to relate and identify the environmental color composition of the landscape considering nature and culture in equal measure (anthropic constructions) and how this allows to guide urban plans and projects. Keywords: environmental color, chromatic, urban design, urban space, colorimetric schemes, landscaping Recibido: julio 1 / 2019 Evaluado: septiembre 25 / 2019 Aceptado: noviembre 13 / 2019 Publicado en línea: diciembre de 2019 Actualizado: diciembre de 2019

Comparative Evaluation of the Photostability of Carbamazepine Polymorphs and Cocrystals

Carbamazepine (CBZ), a widely used antiepileptic, is known to be sensitive to light. The aim of this study was to evaluate the photostabilities of three cocrystals of CBZ (CBZ–succinic acid (SUC), CBZ–saccharin (SAC) form I, and CBZ–SAC form II) illuminated with a D65 fluorescent lamp compared with those of the conventional solid forms: CBZ polymorphs (forms I, II, and III). The order of discoloration determined using a colorimetric measurement was almost consistent with that of the degradation rates estimated using Fourier-transform infrared reflection–absorption spectroscopy, and these parameters of CBZ polymorphs increased in the order of form III, form I, and form II. CBZ–SUC and CBZ–SAC form I significantly suppressed the discoloration and degradation of CBZ compared with the raw CBZ, while CBZ–SAC form II facilitated the discoloration and degradation of CBZ. These results were supported by the results from the low-frequency Raman spectroscopy. The molecular mobility estimated using solid-state nuclear magnetic resonance 1H spin–lattice relaxation time strongly correlated with the degradation rate constant, indicating that molecular mobility significantly decreased following the formation of CBZ–SUC and CBZ–SAC form I and resulted in higher photostability. Overall, CBZ–SUC and CBZ–SAC form I are photostable forms and cocrystallization was proven to be an effective approach to improving the photostability of a photolabile drug.

A Novel Thiazolyl Schiff Base: Antibacterial and Antifungal Effects and In Vitro Oxidative Stress Modulation on Human Endothelial Cells

Schiff bases (SBs) are chemical compounds displaying a significant pharmacological potential. They are able to modulate the activity of many enzymes involved in metabolism and are found among antibacterial, antifungal, anti-inflammatory, antioxidant, and antiproliferative drugs. A new thiazolyl-triazole SB was obtained and characterized by elemental and spectral analysis. The antibacterial and antifungal ability of the SB was evaluated against Gram-positive and Gram-negative bacteria and against three Candida strains. SB showed good antibacterial activity against L. monocytogenes and P. aeruginosa; it was two times more active than ciprofloxacin. Anti-Candida activity was twofold higher compared with that of fluconazole. The effect of the SB on cell viability was evaluated by colorimetric measurement on cell cultures exposed to various SB concentrations. The ability of the SB to modulate oxidative stress was assessed by measuring MDA, TNF-α, SOD1, COX2, and NOS2 levels in vitro, using human endothelial cell cultures exposed to a glucose-enriched medium. SB did not change the morphology of the cells. Experimental findings indicate that the newly synthetized Schiff base has antibacterial activity, especially on the Gram-negative P. aeruginosa, and antifungal activity. SB also showed antioxidant and anti-inflammatory activities.

Nonprescription Bleaching versus Home Bleaching with Professional Prescriptions: Which One is Safer? A Comprehensive Review of Color Changes and Their Side Effects on Human Enamel

Objectives This study evaluates the efficacy and safety of the professionally prescribed and nonprescription over-the-counter (OTC) bleaching agents. Materials and Methods Extracted human upper central incisors were prepared and stained with red wine for 14 days before being subjected to four different bleaching agents: professionally prescribed opalescence PF 15%, VOCO Perfect Bleach 10%, nonprescription OTC Crest 3D Whitestrips, and Whitelight Teeth Whitening System. Colorimetric measurement was performed with Vita Easyshade Handheld Spectrophotometer, enamel surface microhardness measured using Vickers Hardness machine, and surface roughness was evaluated with profilometer, before and after bleaching. Scanning electron microscope (SEM) evaluation and atomic force microscopy were conducted postbleaching. Statistical Analysis The data were analyzed with t-test, two-way ANOVA, one-way ANOVA, and Turkey’s test at a significance level of 5%. Results All bleaching products have the same efficacy to whiten stained enamel. Opalescence PF 15% showed significant increase in the microhardness (92.69 ± 68.316). All groups demonstrated significant increase in surface roughness (p < 0.05). SEM evaluation showed that Opalescence PF 15% resulted in same microscopic appearance as unbleached enamel, while VOCO Perfect Bleach 10%, Whitelight Teeth Whitening System and Crest 3D Whitestrips demonstrated mild to moderate irregularities and accentuated irregularities, respectively. Conclusion Professionally prescribed bleaching agent of Opalescence PF 15% is effective tin whitening the teeth, while the other bleaching products may be effective but also have deleterious effects on the enamel.