ABSTRACT
Negatively charged liposomes accomplished both functions as a reducing and stabilizing agent in the synthesis of gold nanotriangles (GNTs). Liposomes are based on a mixture of phospholipids phosphatidylcholine/phosphoglycerol, and they were used as a template phase to perform the GNTs. The method was evaluated under different conditions such as temperature, reaction time, phosphoglycerol chain length, and precursor concentration. Isotropic and anisotropic gold nanoparticles are formed simultaneously during the synthesis. Therefore, by combining centrifugation and depletion flocculation strategies, the sample was concentrated in terms of GNTs from 15% crude to 80% by using sodium dodecyl sulfate (SDS). As a result, a green colored dispersion was obtained containing highly purified, well-defined, negatively charged GNTs, where the edge length of most particles is centered in the range of 60-80 nm with an average thickness of 7.8 ± 0.1 nm. By this purification process, it was possible to highly increase the yield in terms of GNTs. Other surfactants [cetyltrimethylammonium chloride (CTAC), hexadecyltrimethylammonium bromide (CTAB), Tween 20, and dodecyldimethylammonium bromide] were evaluated during the purification stage, and both CTAB and CTAC show similar results to those obtained by using SDS. These GNTs are potential candidates for future applications in molecular imaging, photothermal therapy, drug delivery, biosensing, and photodynamic therapy.
ABSTRACT
Graphite electrodes were modified with triangular (AuNTrs) or spherical (AuNPs) nanoparticles and further modified with fructose dehydrogenase (FDH). The present study reports the effect of the shape of these nanoparticles (NPs) on the catalytic current of immobilized FDH pointing out the different contributions on the mass transfer-limited and kinetically limited currents. The influence of the shape of the NPs on the mass transfer-limited and the kinetically limited current has been proved by using two different methods: a rotating disk electrode (RDE) and an electrode mounted in a wall jet flow-through electrochemical cell attached to a flow system. The advantages of using the wall jet flow system compared with the RDE system for kinetic investigations are as follows: no need to account for substrate consumption, especially in the case of desorption of enzyme, and studies of product-inhibited enzymes. The comparison reveals that virtually identical results can be obtained using either of the two techniques. The heterogeneous electron transfer (ET) rate constants (kS) were found to be 3.8 ± 0.3 s-1 and 0.9 ± 0.1 s-1, for triangular and spherical NPs, respectively. The improvement observed for the electrode modified with AuNTrs suggests a more effective enzyme-NP interaction, which can allocate a higher number of enzyme molecules on the electrode surface. Graphical abstract The shape of gold nanoparticles has a crucial effect on the catalytic current related to the oxidation of D-(-)-fructose to 5-keto-D-(-)-fructose occurring at the FDH-modified electrode surface. In particular, AuNTrs have a higher effect compared with the spherical one.
Subject(s)
Carbohydrate Dehydrogenases/metabolism , Fructose/metabolism , Gold/chemistry , Metal Nanoparticles/chemistry , Catalysis , Electrodes , Kinetics , Microscopy, Electron, Transmission , Spectrophotometry, Ultraviolet , Spectroscopy, Near-InfraredSubject(s)
Iodine Deficiency , Malnutrition , Nutritional Sciences , Peru , Public Policy , Congresses as TopicABSTRACT
Cada año, la FAO marca la pauta de la realidad alimentaria a nivel mundial. Asimismo, señala los preceptos que nuestro trabajo profesional debe abordar. Este año el lema de Seguridad Alimentaria: desafíos del cambio climático y la bio-energía, nos da una visión de la desatención a la naturaleza y el producto de ella. No estamos preparando al mundo para afrontar grandes cambios. Los alientos pasarán a ser parte de sociedades elitistas, y ello debido a la transformación de los hábitats y sus integrantes. Los suelos parecen no producir lo mismo que antes. Nos encaminamos a la escasez. Ponemos en peligro la alimentación de muchas poblaciones. Es decir no hay Seguridad Alimentaria. Y como si fuera poco, el gasto de energía de la población mundial se incrementa de forma alarmante. Tanta es la demanda existente, que la fuente de energía más accesible lo forman plantaciones alimentarias. De ahí obtenemos la bio-energía. El mundo parece jugar con su propia vida, y el rol del Nutricionista no puede quedar de lado, sabiendo que la humanidad está arriesgando el valor más preciado, su perpetuidad.
