Graphene-Based Adsorbents for Arsenic, Fluoride, and Chromium Adsorption: Synthesis Methods Review.

Water contamination around the world is an increasing problem due to the presence of contaminants such as arsenic, fluoride, and chromium. The presence of such contaminants is related to either natural or anthropogenic processes. The above-mentioned problem has motivated the search for strategies to explore and develop technologies to remove these contaminants in water. Adsorption is a common process employed for such proposals due to its versatility, high adsorption capacity, and lower cost. In particular, graphene oxide is a material that is of special interest due to its physical and chemical properties such as surface area, porosity, pore size as well as removal efficiency for several contaminants. This review shows the advances, development, and perspectives of materials based on GO employed for the adsorption of contaminants such as arsenite, arsenate, fluoride, and hexavalent chromium. We provided a detailed discussion of the synthesis techniques and their relationship with the adsorption capacities and other physical properties as well as pH ranges employed to remove the contaminants. It is concluded that the adsorption capacity is not proportional to the surface area in all the cases; instead, the synthesis method, as well as the functional groups, play an important role. In particular, the sol-gel synthesis method shows better adsorption capacities.

New PEPTIR-2.0 Peptide Designed for Use as Recognition Element in Electrochemical Biosensors with Improved Specificity towards E. coli O157:H7.

The detection of pathogens through alternative methodologies based on electrochemical biosensors is being studied. These devices exhibit remarkable properties, such as simplicity, specificity, and high sensitivity in monitoring pathogens. However, it is necessary to continue conducting studies that adequately improve these characteristics, especially the recognition molecule. This work aims to design and evaluate a new peptide, named PEPTIR-2.0, as a recognition molecule in electrochemical biosensors to detect E. coli O157:H7 in water. PEPTIR-2.0 was obtained from modifications of the PEPTIR-1.0 peptide sequence, which was previously reported and exhibited excellent properties for detecting and quantifying this pathogenic microorganism. PEPTIR-1.0 is a peptide analogous to the TIR (Translocated Intimin Receptor) protein capable of interacting with the Intimin outer membrane. The basis of this study was to obtain, by using bioinformatics tools, a molecule analogous to PEPTIR-1.0 that maintains its three-dimensional structure but increases the hydrophobic interactions between it and Intimin, since these intermolecular forces are the predominant ones. The designed PEPTIR-2.0 peptide was immobilized on screen-printed electrodes modified with gold nanoparticles. The detection capacity of E. coli O157:H7 in water was evaluated using electrochemical impedance spectroscopy in the presence of other microorganisms, such as P. aeruginosa, S. aureus, and non-pathogenic E. coli. The results showed that PEPTIR-2.0 confers remarkable specificity to the biosensor towards detecting E. coli, even higher than PEPTIR-1.0.

Prevalencia de defectos del esmalte dental en niños y adolescentes colombianos / Prevalence of dental enamel defects in children and adolescents from Pasto, Colombia

Introducción: el objetivo de esta investigación fue establecer la prevalencia de defectos del esmalte dental (DE) en niños y adolescentes de Pasto, Colombia. Métodos: quinientos noventa y nueve niños y adolescentes entre 6 y 15 años de edad, de tres corregimientos de Pasto, Colombia, fueron examinados clínicamente para determinar la presencia de opacidad por flúor e hipoplasia del esmalte. Literatura científica y fotografías en color de la cavidad oral fueron estudiadas previamente por dos examinadores, con el propósito de diagnosticar DE en estos corregimientos. La severidad de la opacidad por flúor fue valorada de acuerdo al índice de Dean y la hipoplasia del esmalte al índice de Silberman. Resultados: la prevalencia de DE en niños y adolescentes fue de 49,9% (IC al 95%: 45,8%-53,9%). La mayoría de ellos, 85,3%, presentaron opacidades por flúor (OPF) y 14,7% hipoplasias del esmalte. El tipo de severidad predominante de OPF fue moderada (73,7%). Las OPF fueron más prevalentes en mujeres (86,3%) que en hombres (84,2%) (p > 0,05); mientras que la hipoplasia del esmalte fue más frecuente en hombres (15,8%) que en mujeres (13,7%) (p>0,05). Las hipoplasias del esmalte fueron observadas blancas-cremosas y cafés, y fueron encontradas más frecuentemente en dientes permanentes incisivos centrales superiores. Conclusiones: la prevalencia de DE fue elevada en estos corregimientos. Las opacidades por flúor fueron las más frecuentes y se mostraron moderadas de acuerdo con el índice de Dean. Nuevos diseños de investigación son requeridos para establecer la exposición a diferentes niveles de flúor en estas comunidades. Estos resultados ciertamente representan un problema de salud pública.

Introduction: the objective of this study was to estimate the prevalence of dental enamel defects (ED) in children and adolescents from Pasto, Colombia. Methods: five hundred and ninety-nine children and adolescents aged 6 to 15 years from three municipalities of Pasto, Colombia were clinically examined for fluoride opacity and enamel hypoplasia. Scientific literature and color photographs of the oral cavity were previously studied by two examiners in order to diagnose ED in these municipalities. Severity of fluoride opacity was assessed with Dean’s index and enamel hypoplasia with Silberman’s index. Results: ED prevalence in children and adolescents was 49.9% (95% CI: 45.8% - 53.9%). Most of them, 85.3%, had fluoride opacities (FOP) and 14.7% enamel hypoplasia. The predominant type of FOP severity was the moderate level (73.7%). FOP were more prevalent in females (86.3%) than in males (84.2%) (p > 0.05), while enamel hypoplasia was more frequent in males (15.8%) than in females (13.7%) (p > 0.05). Enamel hypoplasia appeared as creamy-white and brown lesions and were most frequently found in permanent upper central incisors. Conclusions. ED prevalence was high in these municipalities. Fluoride opacities were the most frequent and were classified as moderate according to Dean’s index. New studies are required to establish levels of fluoride exposure in these communities. Certainly, these findings represent a public health problem.