Biocompatible silver nanoparticles prepared with amino acids and a green method.

The synthesis of nanoparticles is usually carried out by chemical reduction, which is effective but uses many toxic substances, making the process potentially harmful to the environment. Hence, as part of the search for environmentally friendly or green synthetic methods, this study aimed to produce silver nanoparticles (AgNPs) using only AgNO3, Milli-Q water, white light from a xenon lamp (Xe) and amino acids. Nanoparticles were synthetized using 21 amino acids, and the shapes and sizes of the resultant nanoparticles were evaluated. The products were characterized by UV-Vis, zeta potential measurements and transmission electron microscopy. The synthesis of silver nanoparticles with tryptophan and tyrosine, methionine, cystine and histidine was possible through photoreduction method. Spherical nanoparticles were produced, with sizes ranging from 15 to 30 nm. Tryptophan does not require illumination nor heating, and the solution color changes immediately after the mixing of reagents if sodium hydroxide is added to the solution (pH = 10). The Xe illumination acts as sodium hydroxide in the nanoparticles synthesis, releases H+ and allows the reduction of silver ions (Ag+) in metallic silver (Ag0).

Aminolevulinic acid with gold nanoparticles: a novel theranostic agent for atherosclerosis.

In this study, 5-aminolevulinic acid (ALA) gold nanoparticles (ALA:AuNPs) functionalized with polyethylene glycol (PEG) were synthesized and administered to rabbits to evaluate their use in clinical practice as theranostic agents for atherosclerosis. This was done by measuring the porphyrin fluorescence extracted from the rabbits' blood and feces. An increase in blood and feces porphyrin emission after ALA:AuNP administration suggests that ALA was incorporated by gold nanoparticles, its structure was preserved, and a rapid conversion into endogenous porphyrins occurred, overloading the synthetic pathway that led to protoporphyrin IX (PPIX) accumulation. This finding indicated that this method can aid in the early diagnosis and therapy of atherosclerosis with high sensitivity.

A simple and effective method to synthesize fluorescent nanoparticles using tryptophan and light and their lethal effect against bacteria.

A simple, environmentally friendly and cost-effective method was used to synthesize silver nanoparticles using tryptophan and light. To prepare the nanoparticles, the following components were used: deionized water, silver nitrate, light and tryptophan. The effects of the tryptophan concentration and light exposure time on the formation of tryptophan silver nanoparticles (Tnnps) were studied. The synthesized Tnnps were characterized using transmission electron microscopy (TEM), absorption and fluorescence spectroscopy and zeta potential measurements. The synthesized Tnnps were nearly spherical, with sizes of approximately 17 nm. In addition, the antibacterial activity of Tnnps was determined by monitoring the growth curves of strains of Escherichia coli, Pseudomonas aeruginosa, Staphylococcus epidermidis, Serratia marcescens, and Enterococcus faecalis using the microdilution test. The Minimum Inhibitory Concentration (MIC) for 4 of 5 tested bacteria was determined to be between 20.0 and 17.5 µg/mL for 48 h and between 22.5 and 20.0 µg/mL for 72 h.