Analytical metrology for nanomaterials: Present achievements and future challenges

Analytical control of imatinib in bioanalytical samples using graphene quantum dots sensing

An analytical method for the determination of imatinib (IMA, the primary treatment for chronic myeloid leukemia), based on the fluorescence properties of graphene quantum dots (GQDs), is reported in this work. The method is addressed to the analytical control of IMA in biological and pharmaceutical samples, due to the present interest in the control of the doses of this anticancer drug, as well as the therapeutic monitoring. The whole method involves the use of a solid-phase extraction (SPE) procedure, followed by an evaporation step, for the treatment of biological samples. For that, tC18 sorbent cartridges were used. After the sample treatment, the solution containing the analyte was mixed with an aqueous solution of GQDs at pH 7.2, and the fluorescent quenching of GQDs was measured. IMA was determined in the 10-250 µg L-1 range, with a limit of detection of 21 µg L-1 and a precision of 1.5% as relative standard deviation, measured in terms of reproducibility. The recovery for biological samples was in the 84-113% range.

The Combined ICP-MS, ESEM-EDX, and HAADF-STEM-EDX Approach for the Assessment of Metal Sub-Micro- and Nanoparticles in Wheat Grain

Metal sub-microparticles (SMPs) and nanoparticles (NPs) presence in food is attributable to increasing pollution from the environment in raw materials and finished products. In the present study, a multifaceted analytical strategy based on Environmental Scanning Electron Microscopy and High-Angle Annular Dark-Field-Scanning Transmission Electron Microscopy coupled with Energy-Dispersive X-ray Spectroscopy (ESEM-EDX, HAADF-STEM-EDX) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) was proposed for the detection and characterization of metal and metal-containing SMPs and NPs in durum wheat samples, covering a size measurement range from 1 nm to multiple µm. ESEM-EDX and ICP-MS techniques were applied for the assessment of SMP and NP contamination on the surface of wheat grains collected from seven geographical areas characterized by different natural and anthropic conditions, namely Italy, the USA, Australia, Slovakia, Mexico, Austria, and Russia. ICP-MS showed significant differences among the mean concentration levels of metals, with the USA and Italy having the highest level. ESEM-EDX analysis confirmed ICP-MS concentration measurements and measured the highest presence of particles < 0.8 µm in size in samples from Italy, followed by the USA. Less marked differences were observed when particles < 0.15 µm were considered. HAADF-STEM-EDX was applied to a selected number of samples for a preliminary assessment of internal contamination by metal SMPs and NPs, and to expand the measurable particle size range. The multifaceted approach provided similar results for Fe-containing SMPs and NPs. ICP-MS and ESEM-EDX also highlighted the presence of a significant abundance of Ti- and Al-containing particles, while for STEM-EDX, sample preparation artifacts complicated the interpretation. Finally, HAADF-STEM-EDX results provided relevant information about particles in the low nm range, since, by applying this technique, no particles smaller than 50 nm were observed in accordance with ESEM-EDX.

Implications of analytical nanoscience in pharmaceutical and biomedical fields: A critical view

This review summarizes recent progress performed in the design and application of analytical tools and methodologies using nanomaterials for pharmaceutical analysis, and specifically new nanomedicines at distinct phases of development and translation from preclinical to clinical stages. Over the last 10-15 years, a growing number of studies have utilized various nanomaterials, including carbon-based, metallic nanoparticles, polymeric nanomaterials, materials based on biological molecules, and composite nanomaterials as tools for improving the analysis of pharmaceutical products. New and more complex nanomaterials are currently being explored to influence different stages of the analytical process. These materials provide unique properties to support the extraction of analytes in complex samples, increase the selectivity and efficiency of chromatographic separations, and improve the analytical properties of many sensor applications. Indeed, nanomaterials, including electrochemical detection approaches and biosensing, are expanding at a remarkable rate. Furthermore, the analytical performance of numerous approaches to determine drugs in different matrices can be significantly improved in terms of precision, detection limits, selectivity, and time of analysis. However, the quality control and metrological characterization of the currently synthesized nanomaterials still depend on the development of new and improved analytical methodologies, and the application of specific and improved instrumentation. Therefore, there is still much to explore about the properties of nanomaterials which need to be determined even more precisely and accurately.

TiO2/Ag-based photodeposited catalyst boosted electrochemiluminescence of ninhydrin-hydrogen peroxide system for ultrasensitive sensing of copper (II)

Photodeposited TiO2/Ag nanocomposites were generally used to be a friendly catalyst for degrading organic contaminant in environmental field. However, electrochemiluminescence (ECL) sensing analysis based on photocatalysts remains a significant challenge. Herein, polyvinylimide (PEI)-TiO2/Ag nanocomposites (PEI-TiO2/AgNCPs) film with reduced graphene oxide(r-GO) was constructed as a sensing interface for copper(II) ECL detection. TiO2/Ag nanocomposites was prepared by reversed phase microemulsion method and photodeposition technique. Moreover, it was discovered that a small amount of Cu2+ could obviously boost the ECL signal of ninhydrin-hydrogen peroxide system. Signal amplification was achieved by using the synergistic effect between r-GO and TiO2/Ag nanocomposites, and the efficiently concentrated effect of PEI to Cu2+. Furthermore, the investigation showed that ECL mechanism of ninhydrin-hydrogen peroxide system was attributed to the generated hydroxyl radical and superoxide anion during the several type of reactions. Thus for the first time, an ultrasensitive ECL approach for detecting Cu2+ could be performed using ninhydrin as an ECL signal probe and hydrogen peroxide as a co-reaction reagent. Under the suitable circumstances, the proposed method showed an excellent linear relationship in the concentration range of Cu2+ from 1.0 fM to 5.0 nM. Detection limit was estimated to be as low as 0.26 fM. The sensing interface expanded the application of photodeposited TiO2/Ag nanocomposites in ultrasensitive ECL detection. It has potential applications in other components and biological analysis.

Simple and rapid formic acid sample treatment for the isolation of HgSe nanoparticles from animal tissues

The present work explores for the first time the potential of formic acid on the extraction of tiemannite (HgSe) nanoparticles from seabird tissues, in particular giant petrels. Mercury (Hg) is considered one of the top ten chemicals of major public health concern. However, the fate and metabolic pathways of Hg in living organisms remain unknown. Methylmercury (MeHg), largely produced by microbial activity in the aquatic ecosystems is biomagnified in the trophic web. HgSe is considered the end-product of MeHg demethylation in biota and an increasing number of studies focuses on the characterization of this solid compound to understand its biomineralization. In this study, a conventional enzymatic treatment is compared with a simpler and environmentally friendly extraction by using formic acid (5 mL of = 50 % formic acid) as exclusive reagent. The analyses by spICP-MS of the resulting extracts from a variety of seabird biological tissues (liver, kidneys, brain, muscle) reveal comparable results by both extraction approaches in terms of nanoparticles stability and extraction efficiency. Therefore, the results included in this work demonstrate the good performance of employing organic acid as simple, cost effective and green procedure to extract HgSe nanoparticles from animal tissues. Moreover, an alternative consisting of a classical enzymatic procedure but with ultrasonic assistance reducing the extraction time from 12 h to 2 min is also described for the first time. The sample processing methodologies developed, combined with spICP-MS, have emerged as powerful tools for the rapid screening and quantification of HgSe nanoparticles in animal tissues. Finally, this combination allowed us to identify the possible occurrence of Cd particles and As particles associated with HgSe NPs in seabirds.

Quantitative Element-Sensitive Analysis of Individual Nanoobjects

A reliable and quantitative material analysis is crucial for assessing new technological processes, especially to facilitate a quantitative understanding of advanced material properties at the nanoscale. To this end, X-ray fluorescence microscopy techniques can offer an element-sensitive and non-destructive tool for the investigation of a wide range of nanotechnological materials. Since X-ray radiation provides information depths of up to the microscale, even stratified or buried arrangements are easily accessible without invasive sample preparation. However, in terms of the quantification capabilities, these approaches are usually restricted to a qualitative or semi-quantitative analysis at the nanoscale. Relying on comparable reference nanomaterials is often not straightforward or impossible because the development of innovative nanomaterials has proven to be more fast-paced than any development process for appropriate reference materials. The present work corroborates that a traceable quantification of individual nanoobjects can be realized by means of an X-ray fluorescence microscope when utilizing rather conventional but well-calibrated instrumentation instead of reference materials. As a proof of concept, the total number of atoms forming a germanium nanoobject is quantified using soft X-ray radiation. Furthermore, complementary dimensional parameters of such objects are reconstructed.

Analytical chemistry of engineered nanomaterials: Part 1. Scope, regulation, legislation, and metrology (IUPAC Technical Report)

Analytical chemistry is crucial for understanding the complex behavior observed for engineered nanomaterials (ENMs). A variety of analytical chemistry techniques and methodological approaches are used for isolation/purification and determination of the composition of pristine nanomaterials and for the detection, identification, and quantification of nanomaterials in nano-enabled consumer products and the complex matrices found in cosmetics, food, and environmental and biological samples. Adequate characterization of ENMs also requires physicochemical characterization of number of other properties, including size, shape, and structure. The requirement for assessment of a number of ENM properties frequently requires interdisciplinary approaches and multi-modal analysis methods. This technical report starts with an overview of ENMs definitions and classification, their properties, and analytical scenarios encountered with the analysis of both pristine nanomaterials and complex matrices containing different nanomaterials. An evaluation of the current status regarding nanomaterial identification and characterization for regulatory purposes and legislation, including emerging regulations and related scientific opinions, is provided. The technical report also presents a large and critical overview of the metrology of nanomaterials, including available reference materials and the development and validation of standardized methods that are currently available to address characterization and analysis challenges. The report focuses mainly on chemical analysis techniques and thus it is complementary to previous IUPAC technical reports focused on characterizing the physical parameters of ENMs and on nanotoxicology.

Size characterization of nanomaterials in environmental and biological matrices through non-electron microscopic techniques

Engineered nanomaterials (ENs) can enter the environment, and accumulate in food chains, thereby causing environmental and health problems. Size characterization of ENs is critical for further evaluating the interactions among ENs in biological and ecological systems. Although electron microscope is a powerful tool in obtaining the size information, it has limitations when studying nanomaterials in complex matrices. In this review, we summarized non-electron microscope-based techniques, including chromatography-based, mass spectrometry-based, synchrotron radiation- and neutron-based techniques for detecting the size of ENs in environmental and biological matrices. The advantages and disadvantages of these techniques were highlighted. The perspectives on size characterization of ENs in complex matrices were also presented.

Analytical Methods for Nanomaterial Determination in Biological Matrices

Nanomaterials are materials in which at least one of the three dimensions ranges from 1 to 100 nm, according to the International Organization for Standardization (ISO). Nanomaterials can be categorized according to various parameters, such as their source, their shape, and their origin. Their increasing use in industrial settings, everyday items, electronic devices, etc. poses an environmental and biological risk that needs to be assessed and appropriately addressed. The development of reliable analytical methods for both characterization and quantification of nanomaterials in various matrices is essential. This review summarized the recent trends in analytical methodologies for the characterization and determination of nanoparticles in biological matrices.

Speciation of platinum nanoparticles in different cell culture media by HPLC-ICP-TQ-MS and complementary techniques: A contribution to toxicological assays

Toxicological studies of nanoparticles (NPs) are highly demanded nowadays but they are very challenging. In the in vitro assays, the understanding of the role of cell culture media is crucial to derive a proper interpretation of the toxicological results and to do so, new analytical tools are necessary. In this context, an analytical strategy based on reversed-phase liquid chromatography hyphenated to inductively coupled plasma-triple quadrupole mass spectrometry (HPLC-ICP-TQ-MS) has been developed for the first time for the detection and characterization of both 5 and 30 nm PtNPs, as well as ionic platinum species, in commonly used cell culture media. For this purpose, Dulbecco's Modified Eagle Medium, DMEM-high glucose, DMEM-F12, DMEM 31053-028, and Roswell Park Memorial Institute, RPMI-1640 (supplemented with 10% fetal bovine serum (FBS) and antibiotics) at several incubation times (24, 48, and 96 h at 37 °C) were tested. After a careful optimization and analytical performance, the developed method allows to simultaneously study the oxidation process, leading to the release of ionic species, and the increase in the hydrodynamic volume of PtNPs, probably related to the formation of new biological entities (protein corona). The magnitude of both processes was found to be dependent on the tested cell culture media and incubation times. Dynamic light scattering (DLS) and high-resolution scanning electron microscopy (HR-SEM) were used as complementary techniques to study the important process of both soft and hard protein corona formation. The feasibility of the HPLC-ICP-TQ-MS to get relevant information for toxicological studies has been demonstrated and in light of our results, the influence of the cell culture media on the behavior of PtNPs should not be underestimated.

Fracture Areas Quantitative Investigating of Bending-Torsion Fatigued Low-Alloy High-Strength Steel

In this study, the impact of pseudo-random non-proportional bending-torsion fatigue loadings proportion on the fatigue life and the fracture surface topography was analyzed. Investigation was carried out for 24 specimens made of S355J2 steel with 11 different ratios of maximum stresses λ. For these cases, after the fatigue tests, the surface topography measurements were carried out using an optical profilometer, using the focus variation method. Three fracture zones were analyzed for each specimen: (1) total; (2) propagation; (3) rupture, taking into account the root average square height Sq and void volume Vv parameters. The results pointed that ratio of maximum stresses λ is the most influenced on volume surface parameters represented by void volume at a given height Vv, in the rupture area. A new fatigue loading parameter P was used, depending on fatigue life T and ratio of maximum stresses λ, which shows very good correlation in 4th degree type of fit, to void volume Vv parameter for the rupture area.

Screening-confirmation strategy for nanomaterials involving spectroscopic analytical techniques and its application to the control of silver nanoparticles in pastry samples

The full characterization of nanomaterials (NMs), which requires a range of different and expensive equipment, is not always necessary to meet certain demands of information. Qualitative analytical methods are ideal alternatives when only a piece of information is required. In this work, a qualitative method for the screening of NMs has been developed and statistically validated for the first time, with silver nanoparticles (AgNPs) as a proof of concept. It is based on the generation of chemiluminescence of the luminol/Ag⁺ system in alkaline media in the presence of AgNPs. Measurements are obtained in a short time with a simple instrument. Probability of detection (POD) curves were constructed at three cut-off values next to the limit of detection of the chemiluminescent method. The unreliability region (UR) was from 0.50 to 1.82 μg L^-1. Currently, no regulation on AgNPs exists, but the present method was successfully tested for a hypothetical threshold of 2.5 μg L^-1 of 40 nm AgNPs. The method was applied to silver colored pearls, with silver (E-174) or aluminum (E-173) coating, used for decoration of pastry. Performance parameters such as false negative and positive rates as well as specificity, sensitivity and reliability rates were calculated for validation. The results of the screening method were confirmed by asymmetric flow field flow fractionation coupled to inductively coupled plasma mass spectrometry (AF4-ICP-MS). The proposed screening method is simple, fast, economic, and easy to transfer to routine laboratories in the field of food safety.

Evaluation of hydrodynamic chromatography coupled to inductively coupled plasma mass spectrometry for speciation of dissolved and nanoparticulate gold and silver

In this study, hydrodynamic chromatography coupled to inductively coupled plasma mass spectrometry has been evaluated for the simultaneous determination of dissolved and nanoparticulate species of gold and silver. Optimization of mobile phase was carried out with special attention to the column recovery of the different species and the resolution between them. Addition of 0.05 mM penicillamine to the mobile phase allowed the quantitative recovery of ionic gold and gold nanoparticles up to 50 nm, whereas 1 mM penicillamine was necessary for quantitative recovery of ionic silver and silver nanoparticles up to 40 nm. The resolution achieved between ionic gold and 10-nm gold nanoparticles was 0.7, whereas it ranged between 0.31 and 0.93 for ionic silver and 10-nm silver nanoparticles, depending on the composition of mobile phase. Best-case mass concentration detection limits for gold and silver species were 0.05 and 0.75 μg L^-1, respectively. The developed methods allowed the simultaneous detection of nanoparticulate and dissolved species of gold and silver in less than 10 min. Size determination and quantification of gold and silver species were carried out in different dietary supplements, showing good agreement with the results obtained by electron microscopy and total and ultrafiltrable contents, respectively. Due to the attainable resolution, the quality of the quantitative results is affected by the relative abundance of nanoparticulate and dissolved species of the element and the size of the nanoparticles if present.

A method based on asymmetric flow field flow fractionation hyphenated to inductively coupled plasma mass spectrometry for the monitoring of platinum nanoparticles in water samples

An analytical methodology based on asymmetric flow field flow fractionation hyphenated to inductively coupled plasma mass spectrometry (AF4-ICP-MS) has been developed for monitoring citrate coated platinum nanoparticles (PtNPs) of different sizes (5, 30, and 50 nm) in water samples. Several factors have been optimized, such as carrier composition, AF4 separation program, focusing step or cross flow values. Under the optimum conditions, PtNPs can be fractionated in about 30 min in a single run with quantitative recoveries of the membrane (100 ± 7%, n = 5). The optimized method has been successfully applied to study transformations, not only in size but also surface modifications, of PtNPs in synthetic and natural water samples over time. The effect of organic matter was specifically studied, and it was found to be a critical parameter. The analytical strategy followed in this work can be very useful to develop further environmental studies involving PtNPs.

Contributions of Capillary Electrophoresis in Analytical Nanometrology: A Critical View

An overview on the increasing role of capillary electrophoresis in characterization and direct analysis of nanomaterials is herein presented. The niche of electrophoretic approaches in nanometrology is so relevant that nonmetallic, metal, metal oxide nanoparticles, and quantum dots have been analyzed to be targeted via capillary electrophoresis with conventional detection systems or coupling arrangements aimed at increasing selectivity and sensitivity toward either pristine or conjugated nanoparticles. Moreover, parameters altering intrinsic properties of nanoparticles may be optimized to gather the desired results and identify nanomaterials according to their size, shape, or associations with binding agents. The usefulness and quickness of capillary electrophoresis for quantifying or screening ultrasmall-sized particles enables this technique to set an example for analysis of standards or previously synthesized nanostructures in research or routine laboratories. Abundant evidence of the suitability of electrophoretic approaches for characterization and direct determination of nanomaterials in actual samples has been provided in this review, together with a discussion about hyphenation with state-of-the art detectors and comparison between capillary electrophoresis with other separation approaches. This permits scientific community to be optimistic in the short term.

Natural TiO2-Nanoparticles in Soils: A Review on Current and Potential Extraction Methods

The monitoring of anthropogenic TiO2-nanoparticles in soils is challenged by the knowledge gap on their characteristics of the large natural TiO2-nanoparticle pool. Currently, no efficient method is available for characterizing natural TiO2-nanoparticles in soils without an extraction procedure. Considering the reported diversity of extraction methods, the following article reviews and discusses their potential for TiO2 from soils, focusing on the selectivity and the applicability to complex samples. It is imperative to develop a preparative step reducing analytical interferences and producing a stable colloidal dispersion. It is suggested that an oxidative treatment, followed by alkaline conditioning and the application of dispersive agents, achieve such task. This enables the further separation and characterization through size or surface-based separation (i.e., hydrodynamic fractionation methods, filtration or sequential centrifugation). Meanwhile, cloud point extraction, gel electrophoresis, and electrophoretic deposition have been studied on various nanoparticles but not on TiO2-nanoparticles. Furthermore, industrially applied methods in, for example, kaolin processing (flotation and flocculation) are interesting but require further improvements on terms of selectivity and applicability to soil samples. Overall, none of the current extraction methods is sufficient toward TiO2; however, further optimization or combination of orthogonal techniques could help reaching a fair selectivity toward TiO2.

Nanomaterials in speciation analysis of metals and metalloids

Nanomaterials have draw extensive attention from the scientists in recent years mainly due to their unique and attractive thermal, mechanical and electronic properties, as well as high surface to volume ratio and the possibility for surface functionalization. Whereas mono functional nanomaterials providing a single function, the preparation of core/shell nanoparticles allows different properties to be combined in one material. Their properties have been extensively exploited in different extraction techniques to improve the efficiency of separation and preconcentration, analytical selectivity and method reliability. The aim of this paper is to provide an updated revision of the most important features and application of nanomaterials (metallic, silica, polymeric and carbon-based) for solid phase extraction and microextraction techniques in speciation analysis of some metals and metalloids (As, Cr, Sb, Se). Emphasis will be placed on the presentation of the most representative works published in the last five years (2015-2019).

Gold nanoparticles: New routes across old boundaries

In recent years, gold nanoparticles have emerged as unique non-invasive drug carriers for targeting drugs to their site of action. Their site specificity has helped in increasing drugs' efficacy at lower dose as well as reduction in their side effects. Moreover, their excellent optical properties and small size offer their utilization as diagnostic tools to diagnose tumors as well as other diseases. This review focuses on various approaches that have been used in last several years for preparation of gold nanoparticles, their characterization techniques and theranostic applications. Their toxicity related aspects are also highlighted. Gold nanoparticles are useful as theranostic agents, owing to their small size, biocompatible nature, size dependent physical, chemical and optical properties etc. However, the challenges associated with these nanoparticles such as scale up, cost, low drug payload, toxicity and stability have been the major impediments in their commercialization. The review looks into all these critical issues and identifies the possibilities to overcome these challenges for successful positioning of metallic nanoparticles in market.