Abstract
This work describes the optimization of a methodology for the reduction of silver ions from silver nanoparticle suspensions obtained from low-yield laboratory procedures. The laboratory synthesis of silver nanoparticles following a bottom-up approach starting from silver nitrate, originates silver ions that were not reduced to their fundamental state for nanoparticles creation at the end of the process. However, it is well known that silver ions can easily influence chemical assays due to their chemical reactivity properties and can limit biological assays since they interfere with several biological processes, namely intracellular ones, leading to the death of living cells or organisms. As such, the presence of silver ions is highly undesirable when conducting biological assays to evaluate the influence of silver nanoparticles. We report the development of an easy, low-cost, and rapid methodology that is based on cation exchange resins to minimize the silver ion content in a raw suspension of silver nanoparticles while preserving the integrity of the nanomaterials. This procedure preserves the physical-chemical properties of the nanoparticles, thus allowing the purified nanoparticulate systems to be biologically tested. Different types of cationic resins were tested, and the developed methodology was optimized by changing several parameters. A reduction from 92% to 10% of free silver/total silver ratio was achieved when using the Bio-Rad 50W-X8 100–200 mesh resin and a contact time of 15 min. Filtration by vacuum was used to separate the used resin from the nanoparticles suspension, allowing it to be further reused, as well as the purified AgNPs suspension.
Highlights
From wastewater treatment to textile products, from food supplements to cosmetics, and from pharmaceutical products to food packaging materials, silver nanoparticles (AgNPs) are widely used for their properties, mainly their peculiar interaction with light and their potential to interfere with vital cellular processes [1]
It is worth mentioning that many methodologies for the separation and/or purification of silver nanoparticles (AgNPs) from different matrices are in development, many of which are based on magnetic based schemes, chromatography, centrifugation, electrophoresis, selective precipitation, and extraction [2,3]
Ag (Total) and Ag (AgNPs) concentrations in the raw suspension were determined, and afterwards, an aliquot of 10 mL suspension was put in contact with a weighed mass of resin, which was manually shaken for 5 s at 20 min intervals
Summary
From wastewater treatment to textile products, from food supplements to cosmetics, and from pharmaceutical products to food packaging materials, silver nanoparticles (AgNPs) are widely used for their properties, mainly their peculiar interaction with light and their potential to interfere with vital cellular processes [1]. It is worth mentioning that many methodologies for the separation and/or purification of silver nanoparticles (AgNPs) from different matrices are in development, many of which are based on magnetic based schemes, chromatography, centrifugation, electrophoresis, selective precipitation, and extraction [2,3]. These methods are often used for Ag speciation and imply AgNPs disintegration for quantification measurements, making their posterior use unfeasible.
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