Biosynthesis of gold and silver nanoparticles using Parkinsonia florida leaf extract and antimicrobial activity of silver nanoparticles

In this work, the biosynthesis of gold and silver nanoparticles from a leaf extract of Parkinsonia florida (P. florida) is reported. The P. florida leaf extract was analyzed by a phytochemical screening, by measuring the DPPH radical scavenging activity, and by Fourier-transform infrared spectroscopy (FT-IR). The phytochemical screening results indicated that biomolecules like carbohydrates, phenols, proteins, aminoacids, saponins, and flavonoids present in P. florida leaf extract might have participated in the chemical reduction of the metallic salts and further colloidal stabilization. The FT-IR results from leaf extract functional groups support the role of surface modification with the presence of residues of phenols, proteins, aminoacids, saponins, and flavonoids. The formation of metallic nanoparticles was confirmed by optical absorption spectroscopy with characteristic absorption bands at 550 nm and 430 nm, for gold and silver nanoparticles, respectively. Zeta potential for gold nanoparticles presents negative values in the range of 10 +/- 1 to 16 +/- 1 mV, depending on the amount of leaf extract used during the synthesis reaction. Similarly, zeta potential values for silver nanoparticles were in the range of -5 +/- 1 to 16 +/- 1 mV. STEM images revealed the average particles sizes in the range from 10 to 15 nm, and 10 to 57 nm, for gold and silver nanoparticles respectively. The silver nanoparticles presented good antibacterial activity, inhibiting the growth of Staphylococcus aureus and Escherichia coli.National Council of Science and Technology (CONACyT) [INFR-226208-2014, INFR-255791-2015]; CONACYTOpen access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Mathematical modeling and parametrical analysis of the temperature dependency of control drug release from biodegradable nanoparticles

In this study we describe a mathematical analysis that considers the temperature effects of the controlled drug release process from biodegradable poly-D,L-lactide-co-glycolide (PLGA) nanoparticles. Temperature effects are incorporated and applied to two drug release models. The first one consists of a two-stage release process that considers only simultaneous contributions of initial burst and nanoparticle degradation–relaxation (BR model). The second one is a three release stage model that considers, additionally, a simultaneous drug diffusion (BRD model) step. In these models, the temperature dependency of the release parameters, initial burst constant, kb, the rate of degradation–relaxation constant, kr, time to achieve 50% of release, tmax, and effective diffusion coefficient constant (De), are determined using mathematical expressions analogous to the Arrhenius equation. The temperature dependent models are used to analyze the release of previously encapsulated Rhodamine 6G dye as a model drug in polyethylene glycol modified PLGA nanoparticles. The experimental data used to develop the mathematical model was obtained from release studies carried out in phosphate buffer pH 7.4 at 37 °C, 47 °C, and 57 °C. Multiphasic release behaviors with an overall increase rate associated with the incubation temperature were observed. The study incorporates a parametrical analysis that can evaluate diverse temperature variation effects of the controlled release parameters for the two models.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Aqueous-Organic Phase Transfer of Gold and Silver Nanoparticles Using Thiol-Modified Oleic Acid

The handling of metallic nanoparticles often requires their dispersion into several polar and nonpolar solvents. Solid-phase stages or polymer-based ligands are commonly required to complete the transfer. The construction of a thiol ligand based in oleic acid, and its ability to efficiently assist in gold and silver nanoparticle aqueous-organic phase transfer is reported. After the transfer, the particles are completely dispersed in an organic solvent, preserving their diameter and morphology, as confirmed by ultraviolet-visible spectroscopy and scanning transmission electron micrographs.National Council of Science and Technology of Mexico (CONACYT) [I0007-2013-02, 206489, INFR-2014-01, 226208]; Secretariat of Public Education of Mexico (SEP) [UNISON-PTC-222 DSA/103.5/15/7356]; CONACYT [PDCPN201401-247326]Open Access Journal.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Aqueous-Organic Phase Transfer of Gold and Silver Nanoparticles Using Thiol-Modified Oleic Acid

The handling of metallic nanoparticles often requires their dispersion into several polar and nonpolar solvents. Solid-phase stages or polymer-based ligands are commonly required to complete the transfer. The construction of a thiol ligand based in oleic acid, and its ability to efficiently assist in gold and silver nanoparticle aqueous–organic phase transfer is reported. After the transfer, the particles are completely dispersed in an organic solvent, preserving their diameter and morphology, as confirmed by ultraviolet–visible spectroscopy and scanning transmission electron micrographs

Memoria del tercer encuentro internacional sobre el poder en el pasado y el presente de América Latina

Este volumen está compuesto por diecisiete trabajos que abordan temas relativos a las manifestaciones, tanto democráticas como autoritarias, de un aspecto de la realidad que está presente en la vida de toas las personas: el poder. En ocasiones, constituyen reflexiones teóricas, pero en su mayoría enfrentan problemas sobre el pasado y presente de México, sin omitir el proceso electoral que culminará en las elecciones que ya están inmersas la clase política y la opinión pública del país