Validation of a particle tracking analysis method for the size determination of nano- and microparticles.

&lt;p&gt;Particle tracking analysis (PTA) is an emerging technique suitable for size analysis of particles with external dimensions in the nano- and sub-micrometre scale range. Only limited attempts have so far been made to investigate and quantify the performance of the PTA method for particle size analysis. This article presents the results of a validation study during which selected colloidal silica and polystyrene latex reference materials with particle sizes in the range of 20 nm to 200 nm were analysed with NS500 and LM10-HSBF NanoSight instruments and video analysis software NTA 2.3 and NTA 3.0. Key performance characteristics such as working range, linearity, limit of detection, limit of quantification, sensitivity, robustness, precision and trueness were examined according to recommendations proposed by EURACHEM. A model for measurement uncertainty estimation following the principles described in ISO/IEC Guide 98-3 was used for quantifying random and systematic variations. For nominal 50 nm and 100 nm polystyrene and a nominal 80 nm silica reference materials, the relative expanded measurement uncertainties for the three measurands of interest, being the mode, median and arithmetic mean of the number-weighted particle size distribution, varied from about 10% to 12%. For the nominal 50 nm polystyrene material, the relative expanded uncertainty of the arithmetic mean of the particle size distributions increased up to 18% which was due to the presence of agglomerates. Data analysis was performed with software NTA 2.3 and NTA 3.0. The latter showed to be superior in terms of sensitivity and resolution.&lt;/p&gt;</p

Physical Characterization of Nanomaterials in Dispersion by Transmission Electron Microscopy in a Regulatory Framework

&lt;p&gt;TEM is one of the few techniques that can identify nanoparticles according to the current definitions. This chapter focuses on the different steps required to analyze dispersed nanomaterials by TEM. Methodologies to obtain homogeneous and stable dispersions of colloidal nanomaterials and powders are presented. The preparation of TEM specimens to obtain a representative distribution of particles on the grid is discussed. The application of TEM imaging methods, electron diffraction and analytical TEM to obtain complementary information on the size, morphology, crystallographic structure, electronic structure and composition of nanomaterials is reviewed.&lt;/p&gt; &lt;p&gt;In a qualitative TEM analysis the key properties of the physical form of the nanomaterial under which it is exposed to in vitro and in vivo test systems are described based on TEM micrographs. Subsequently, a quantitative analysis which includes detection, classification and measurement of primary particle properties, and validation of the measurement results can be performed. The possibility to extract 3D information by fractal analysis of electron micrographs of aggregated nanomaterials with a fractal-like structure is explored&lt;/p&gt;</p

Characterization of the TiO2 E171 food additive

&lt;p&gt;E171 (Titanium dioxide) is an EC approved food additive (EC 1129/2011), authorized to be used as color in foodstuffs. It is widely used for its refractive properties (shiny coating, UV protection) in the food and pharmaceutical industries. It is intended and assumed to be present in bulk form. A nanofraction may be present.Dispersion is crucial step to characterize the particle properties of food additives as it allows to separate the primary particles. To better characterize titanium dioxide food additives (E171) their dispersion method was optimized.&lt;/p&gt; &lt;p&gt;A dispersion methodology based on the Guiot and Spalla approach was applied. It electrosterically stabilizes the (nano)materials, dispersed by sonication, using BSA at a pH determined by zeta potential measurement. Dispersion efficiency was examined by descriptive TEM and using a combination of TEM imaging and image analysis. The latter approach allows to assess the distribution of the particle properties (size, shape, surface structure) quantitatively. For both the pristine TiO2 food additive E171 and the JRC TiO2 representative test material zeta-potential measurement allowed to identify the conditions (pH) where a stable dispersion with a minimal level of agglomeration was observed. The stability of the dispersion was confirmed by descriptive TEM: preparing dispersions of TiO2 through a pH adjustment provides a stable dispersion of single primary particles and small aggregates and agglomerates.&lt;/p&gt; &lt;p&gt;Under the optimized conditions, the minimal external dimension of the primary particles could be measured more precisely and accurately by a combination of EM imaging and image analysis than in metastable conditions, such that the materials could be better classified according to the EC definition of a nanomaterial.&lt;/p&gt;</p

Engineering a nanopore with co-chaperonin function.

&lt;p&gt;The emergence of an enzymatic function can reveal functional insights and allows the engineering of biological systems with enhanced properties. We engineered an alpha hemolysin nanopore to function as GroES, a protein that, in complex with GroEL, forms a two-stroke protein-folding nanomachine. The transmembrane co-chaperonin was prepared by recombination of GroES functional elements with the nanopore, suggesting that emergent functions in molecular machines can be added bottom-up by incorporating modular elements into preexisting protein scaffolds. The binding of a single-ring version of GroEL to individual GroES nanopores prompted large changes to the unitary nanopore current, most likely reflecting the allosteric transitions of the chaperonin apical domains. One of the GroEL-induced current levels showed fast fluctuations (&lt;1 ms), a characteristic that might be instrumental for efficient substrate encapsulation or folding. In the presence of unfolded proteins, the pattern of current transitions changed, suggesting a possible mechanism in which the free energy of adenosine triphosphate binding and hydrolysis is expended only when substrate proteins are occupied.&lt;/p&gt;</p