Scientists Develop Separation Procedure for Gold Nanoparticles

This method will find widespread applications, including identification of gold-based nanomaterials in consumer products

The use of nanomaterials is constantly increasing in all industrial sectors, in particular in biomedicine with applications in diagnostics and therapeutics. Gold nanoparticles have already several applications in biology and medicine; they are also used in consumer products such as cosmetics.

The effects of nanoscale objects on biological systems and their potential toxicity are currently the focus of widespread investigations. Since size, composition and surface chemistry of nanoparticles play an important role, the fractionation and characterisation of mixtures of nanoparticles is a key requirement for the assessment of their properties in toxicology testing or for their identification and size determination in consumer products.

In this paper, scientists working within the European Commission Joint Research Centre, Institute for Health and Consumer Protection (JRC-IHCP) developed a procedure for the efficient separation, size determination, chemical characterization and quantification of the relative number of particles of different size starting from complex gold nanoparticle (AuNP) mixtures.

The authors show that using two state-of-the-art techniques - asymmetric flow-field-flow fractionation (AF4) and high sensitive UV-Vis detection - it is possible to separate, characterize, and quantify the correct number size distribution of gold nanoparticle mixtures of various sizes in the 5-60nm range. The size of the collected nanoparticles fractions can be determined both in solution and in the solid state, and their surface chemistry characterized by Nuclear magnetic resonance (NMR). In this context, the standard approach based on dynamic light scattering (DLS) measurements - a technique widely used since the 70s but whose accuracy is limited - gave misleading information.

The authors conclude that the use of AF4 technique will find widespread applications in two scenarios: for the preparation of NP samples with narrow particles distributions (in the process of "size purification" after the synthesis of AuNP) and for the identification and characterization of gold-based nanomaterials in consumer products. This latter scenario is made all the more urgent by the continuous increase in the use of nanoparticles in several consumer products and the recent introduction in the EU legislation of labelling requirements for the presence of nanomaterials in cosmetics.

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