Certification of Equivalent Spherical Diameters of Silica Nanoparticles in Water - Certified Reference Material ERM®-FD100

This report describes the certification of the equivalent spherical diameters of silica nanoparticles suspended in aqueous solution, Certified Reference Material (CRM) ERM-FD100®. The CRM has been certified by the European Commission, Joint Research Centre, Institute for Reference Materials and Measurements (IRMM), Geel, BE. The intended use of this ERM-FD100 is to check the performance of instruments and methods that determine the particle diameter of nanoparticles (particle size ranging from approximately 1 nm to approximately 100 nm) suspended in a liquid medium. It is available in 10 mL pre-scored amber glass ampoules containing approximately 9 mL of suspension. The CRM was prepared from commercially available colloidal silica (Koestrosol 1530, Chemiewerk Bad Koestritz GmbH, DE). Certification of the CRM included testing of the homogeneity and stability of the ampouled diluted raw material, as well as the characterisation using an intercomparison approach. The material has been certified for the equivalent diameter of the silica nanoparticles in aqueous suspension using different methods. Certified values are the cumulants dynamic light scattering (DLS) intensity-weighted harmonic mean particle diameter, the line-start centrifugal liquid sedimentation (CLS) intensity-based modal (Stokes) particle diameter, the electron microscopic (transmission electron microscopy (TEM)/ scanning electron microscopy (SEM)) number-based modal particle diameter and the small angle X-ray scattering (SAXS) intensity-weighted average particle diameter. Indicative values have been established for the volume-weighted mean equivalent spherical diameter via the SAXS method and for the zeta potential via the electrophoretic mobility (ELM) method. Additional informational values are given for the volume-weighted mean diameter via the DLS method, and the pH value of the ERM-FD100 suspension. Uncertainties are expanded uncertainties estimated in accordance with the Guide to the expression of uncertainty in measurement (GUM) with a coverage factor of k = 2, corresponding to a confidence interval of about 95 %. An exception is the mean equivalent volume-weighted diameter determined by the SAXS method which has a coverage factor of 2.8.JRC.DG.D.2-Reference material

The Structure and Properties of Soluble Phosphate Based Glasses

The recent discipline of tissue engineering has developed innovative degradable and non-degradable (dependant upon application) materials in combination with low toxicity and good biocompatibility. The major focus of these new technologies is to guide the regenerative process. The aim of this project was to take the regenerative tissue healing process a step further by developing a material which not only guides the tissue regeneration process, but also enhances it and has a degradation profile that is tailored to the tissue and on degradation, leaves no toxic or irritating debris behind to cause any tissue reaction. The chosen material was a soluble phosphate based glass, modified with CaO, Na2O, MgO, K2O and/or CaF2. Materials have been developed in order to work as closely as possible to the natural phase of bone, within the limitations imposed by the glass forming process. 5 different glass systems have been synthesised via conventional glass making procedures and the solubility process has been investigated via weight loss experiments and ion and pH measurements. All materials were soluble with different degradation processes, depending on the composition of the glass. Glasses with low CaO content showed a linear relationship between weight loss per unit area and time. Glasses with higher CaO content show an increasing non-linearity in their weight loss behaviour. The pH showed a significant increase in the first stages of degradation, which was explained by cation-exchange processes taking place from the material to the solution and vice versa. The ion concentration in solution was found to increase with time as expected and it mirrored the weight loss curves. Preliminary cell culture tests (MTT tests) using the MG63 human osteoblast cell line were established to test the biocompatibility of the soluble extracts from the different glasses. The tests revealed that glasses with low CaO content, i.e. high solubility, showed reduced proliferation below the control line of tissue culture plastic. Proliferation was however similar to the control line or above for glasses with CaO contents higher than 30 mol%, i.e. low solubility. The best test results, with enhanced proliferation was seen for glass with the highest CaO content. The MTT test results look very promising for materials with a high calcium oxide content, indicating biocompatibility with enhanced cell proliferation. There was also evidence that small amounts of K2O and MgO affected cell proliferation. Structural analysis was carried out using DTA and MAS-NMR spectroscopy. The results from the glasses were found to be in line with X-ray analysis of similar glass-ceramics, which had been analysed in earlier studies. Thermal analysis revealed multi-crystallisation events as evidenced by the presence of one or two crystallisation peaks with more than two or three corresponding melting points. The use of MAS-NMR spectroscopy showed that two species, Q1 and Q2 formed the basis of the glass structure and it was possible to identify the dominant Q2 species as Na4Ca(PO3)6. The Q1 species is represented by (Ca3(PO4)2 or Na2P2O7). However, it was up to the present time not possible to identify the Q1 species unambiguously. The work has shown that it is possible to synthesise biodegradable glasses for hard tissue surgery, whose composition is close to the inorganic phase of bone. Biocompatibility studies have helped to define optimal compositions and it is therefore hoped that the results from this study will contribute towards future implant research utilising soluble glasses

A new certified reference material for size analysis of nanoparticles

A certified reference material, ERM-FD100, for quality assurance of various nanoparticle sizing methods, was developed by the Institute for Reference Materials and Measurements. The material was prepared from an industrially-sourced colloidal silica containing nanoparticles with a nominal equivalent spherical diameter of 20 nm. The homogeneity and stability of the candidate reference material was assessed by means of dynamic light scattering and centrifugal liquid sedimentation. Certification of the candidate reference material was based on a global interlaboratory comparison in which 34 laboratories participated with various analytical methods (DLS, CLS, EM, SAXS, ELS). After scrutinising the interlaboratory comparison data, 4 different certified particle size values, specific for the corresponding analytical method, could be assigned. The good comparability of results allowed the certification of the colloidal silica material for nanoparticle size analysis.JRC.D.2-Standards for Innovation and sustainable Developmen

Interlaboratory Comparison for the Measurement of Particle Size and Zeta Potential of Silica Nanoparticles in an Aqueous Suspension

The Institute for Reference Materials and Measurements has organised an interlaboratory comparison (ILC) to allow the participating laboratories to demonstrate their proficiency in particle size and zeta potential measurements on monomodal aqueous suspensions of silica nanoparticles in the 10–100 nm size range. The main goal of this ILC was to identify competent collaborators for the production of certified nanoparticle reference materials. 38 laboratories from four different continents participated in the ILC with different methods for particle sizing and determination of zeta potential. Most of the laboratories submitted particle size results obtained with centrifugal liquid sedimentation (CLS), dynamic light scattering (DLS) or electron microscopy (EM), or zeta potential values obtained via electrophoretic light scattering (ELS). The results of the laboratories were evaluated using method-specific z scores, calculated on the basis of consensus values from the ILC. For CLS (13 results) and EM (13 results), all reported values were within the ±2 |z| interval. For DLS, 25 of the 27 results reported were within the ±2 |z| interval, the two other results were within the ±3 |z| interval. The standard deviations of the corresponding laboratory mean values varied between 3.7 and 6.5%, which demonstrates satisfactory interlaboratory comparability of CLS, DLS and EM particle size values. From the received test reports, a large discrepancy was observed in terms of the laboratory’s quality assurance systems, which are equally important for the selection of collaborators in reference material certification projects. Only a minority of the participating laboratories is aware of all the items that are mandatory in test reports compliant to ISO/IEC 17025 (ISO General requirements for the competence of testing and calibration laboratories. International Organisation for Standardization, Geneva, 2005b). The absence of measurement uncertainty values in the reports, for example, hindered the calculation of zeta scores.JRC.D.2-Reference material

The Use of Colloidal Silica Reference Material IRMM-304 for Quality Control in Nanoparticle Sizing by Dynamic Light Scattering and Centrifugal Sedimentation

The behaviour of nanoparticles in air or liquids depends on their morphology and size. The ability to accurately measure the particle size is therefore primordial to assess the potential applications and risks associated with nanoparticles. Reference Materials (RMs) can be used to demonstrate reiliability of particle sizing techniques and the comparability of their results. Only few RMs of commercially relevant nanoparticles are available. In response to this, the Institute for Reference Materials and Measurements (IRMM) has produced a nanoparticle RM, IRMM-304, which is primarily intended for quality control, method development and interlaboratory comparisons. IRMM-304 consists tof an aqueous suspension of silica nanoparticles with a nominal diameter of 40 nm. The assigned values have established by dynamic light scattering (frequency and cumulants method) and centrifugal sedimentation. This paper gives examples of how IRMM-304 can be used in daily laboratory practice and quality control.JRC.DG.D.2-Reference material

Validation of Dynamic Light Scattering and Centrifugal Liquid Sedimentation Methods for Nanoparticle Characterisation

A variety of techniques exists to analyse the size and size distribution of nanoparticles in a suspension. However, neither full method validation reports nor suitable reference materials with properly assigned values traceable to SI are easily found in the literature or on the market, respectively. This paper presents results of in-house validation studies of Dynamic Light Scattering (DLS) and Differential Centrifugal Sedimentation (DCS) methods. Repeatability and intermediate precision were assessed using the IRMM 304 reference Materials (silica nanoparticles suspended in an aqueous solution) to estimate the uncertainty contribution from within-day or day-to-day variation effects. Relative standard and expanded uncertainties were calculated with the goal to obtain a reliable measurement uncertainty valid for measuring silica nanoparticles of for particles with similar density and size range. The validated methods will be used in the certification of nanoparticle reference materials.JRC.D.2-Reference material

Validation of Dynamic Light Scattering and Differential Centrifugal Sedimentation Methods for Nanoparticle Characterisation

A variety of techniques exists to analyse the size distribution of nanoparticles in a suspension. However, neither full method validation reports nor suitable reference materials with properly assigned values traceable to SI are easily found in literature or on the market, respectively. This paper presents results of in-house validation studies of Dynamic Light Scattering 9DLS) and Differential Centrifugal Sedimentation (DCS) methods. Repeatability and intermediate precision were assessed using the IRMM-304 reference material (silica nanoparticles suspended in an aqueous solution) to estimate the uncertainty contribution from within-day or day-to-day variation effects. Combined and expanded uncertainties were calculated with the goal to obtain a reliable measurement uncertainly valid for measuring silica nanoparticles or for particles with similar density and size range. The validated method will be used in the certification of nanoparticle reference materials.JRC.DG.D.2-Reference material

A Colloidal Silica Reference Material for Nanoparticle Sizing by Means of Dynamic Light Scattering and Centrifugal Liquid Sedimentation

IRMM-304 is a new nanoparticle reference material (RM) consisting of silica nanoparticles suspended in an aqueous solution, of which the particle size was characterized by dynamic light scattering (DLS) and centrifugal liquid sedimentation (CLS). The homogeneity and stability of IRMM-304 were confirmed and three method-specific mean particle sizes around a nominal particle size of 40nm were assigned to the material. The characterization tests have revealed a systematic deviation between the measurement results obtained with DLS and CLS. The availability of IRMM-304 makes it possible to study this difference between methods. Several possible causes for differences between the DLS and CLS results are suggested and preliminarily investigated, such as the interaction between particle and suspending medium, the particle shape and the effect of polydispersity on the size averaging procedure. These investigations are one illustration of the potential role of IRMM-304 and other nanoparticle RMs in the development, comparison, improved understanding, and quality assurance of nanoparticle sizing methods.JRC.D.2-Reference material

Introductory Guide to Nanometrology

This Guide introduces the reader to the science of measurements at the nanoscale, that is nanometrology. It is aimed at researchers in the nanotechnology area, for whom the metrology aspect is new, and at metrologists, interested in knowing about the specifics of metrology at the nanoscale. The Guide does not give an exhaustive review of the field. Rather it is intended to increase the general awareness of nanometrology, and its basic challenges. In a first section, three main questions are addressed: 1. What is (nano)metrology? 2. Why is nanometrology important? 3. What are the main challenges for nanometrology? The Guide continues with a section on the meaning of a number of generic metrology concepts. In the third section, the Guide illustrates some of the identified nanometrological challenges with practical examples and case studies from three different application areas (thin films, surface structures and nanoparticles). A final subsection is devoted to the emerging issue of metrology for nanobiotechnologyJRC.DG.D.2-Reference material