Validation of Gold and Silver Nanoparticle Analysis in Fruit Juices by Single-Particle ICP-MS without Sample Pretreatment

SI-traceable characterisation of the first reference material for nanoparticle number concentration in suspension to support regulatory compliance

Reference materials (RMs) are increasingly needed to support number-based characterisation of nanomaterials (NM) in a regulatory context for the purpose of method development, validation and measurement quality control. To date, RMs for number concentration in suspension with a directly assigned value that is SI traceable have been rather scarce, being the LGCQC5050 the only material commercialised so far. This could be attributed to the limited availability of metrologically validated measurement methods and stability challenges associated with long-term storage of NM suspensions. This paper describes development and characterisation of the first RM consisting of 30-nm colloidal gold nanoparticles and value assigned for particle number concentration using the dynamic mass flow (DMF) method with single particle ICP-MS (spICP-MS). Special attention is paid to systematic assessment of the DMF method's performance under operating conditions set outside recommendations described in ISO/TS 19590:2024, but that still comply with key requirements of this method (e.g. use of an ICP-MS system in equilibrium, a cooled spray chamber, etc.). The results of such investigations are reported here for the first time. The paper also discusses practical considerations for the production, storage and transport of nano RMs, and provides guidance on best practice for the production and certification of future nano RMs in accordance with ISO 17034:2016.

A review of chitosan role in milk bioactive-based drug delivery, smart packaging and biosensors: Recent advances and developments

Chitosan, a versatile biopolymer derived from chitin, is increasingly recognized in the milk industry for its multifunctional applications in drug delivery, smart packaging, and biosensor development. This review provides a comprehensive analysis of recent advances in chitosan production techniques. These include chemical, biological, and novel methods such as deep eutectic solvents (DES), microwave-assisted approaches, and laser-assisted processes. Surface modification strategies to enhance its functional properties are also discussed. The review highlights the development of various chitosan-based nanocarriers, including nanoparticles, nanofibers, nanogels, and nanocomposites. It emphasizes their stability when combined with milk bioactive ingredients like lipids, peptides, lactose, and minerals. The gastrointestinal fate and safety of chitosan nanoparticles are critically evaluated, showcasing their potential for safe consumption in dairy-related applications. In drug delivery systems, chitosan exhibits excellent compatibility with milk-derived carbohydrates, proteins, and minerals, enabling the development of innovative drug delivery platforms. Additionally, its incorporation into smart packaging materials enhances the shelf-life and quality of dairy products. Chitosan-based biosensors offer precise contaminant detection in the milk industry by enabling precise detection of contaminants such as Bisphenol A, melamine, bacteria, drugs, antibiotics, toxins, heavy metals, and allergens, thus ensuring food safety and quality. Emerging trends, including the integration of artificial intelligence, advanced gene editing, and multifunctional chitosan, are discussed, offering insights into future personalized delivery systems and merging food and drug technologies. The review concludes by highlighting gaps in current research and offering recommendations for future exploration. These suggestions aim to optimize chitosan's unique properties to address key challenges in the milk industry. This article serves as a valuable resource for researchers, industry professionals, and policymakers aiming to innovate within the dairy sector using chitosan-based technologies.

Preparation of Diosgenin-Functionalized Gold Nanoparticles: From Synthesis to Antitumor Activities

Cancer ranks among the top causes of illness and death globally. Nanotechnology holds considerable promise for enhancing the effectiveness of therapeutic and diagnostic approaches in cancer treatment. Our study presents a promising strategy for applying thiocompound nanomedicine in cancer therapy. Our first study aimed to investigate the biological properties of a new compound thiodiosgenin (TDG)-a new derivative of diosgenin-a natural compound with known antioxidant and anticancer properties. Our current second study aimed to compare the therapeutic efficacy of a new diosgenin-functionalized gold nanoparticles-with its precursor on prostate cancer (DU-145) cell lines. Moreover, the safety of the new thio-derivative and new conjugates was tested against the human epithelial line PNT-2. New advanced analytical techniques were developed for the characterization of nanomaterials using methods such as SP-ICP-MS, UV-Vis, TEM, NMR, FT-IR ELS, and TGA. Our synthetic approach was based, on the one hand, on the ligand exchange of citrates to thiodiosgenin (TDG) on gold nanoparticles, and on the other hand, on the attachment of DG through an ester bond to the linker, which was 3-mercaptopropionic acid (MPA) on gold nanoparticles. Initial in vitro studies indicate that TDG shows greater cytotoxic effects on cancer cells but poses risks to normal prostate epithelial cells (PNT-2). It was demonstrated that all the conjugates produced exhibited significant cytotoxic effects against cancer cells while being less harmful to normal prostate epithelial cells (PNT-2) compared to TDG itself. All the obtained conjugates showed antitumor properties; however, for targeted transport, the system referred to as AuNPs-MPAm1-DG is promising, due to the size of the nanoparticles of 53 nm, zeta potential of -30 mV, and loading content of 27.6%. New methods for synthesizing conjugates with diosgenin were developed and optimized for medical applications. Advanced new analytical methodologies were developed to characterize new conjugates, particularly the use of SP-ICP-MS, to solve existing differences in the shape and morphology of the surface of new conjugates.

Advancing Simultaneous Extraction and Sequential Single-Particle ICP-MS Analysis for Metallic Nanoparticle Mixtures in Plant Tissues

Engineered nanoparticles (ENPs) have been increasingly used in agricultural operations, leading to an urgent need for robust methods to analyze co-occurring ENPs in plant tissues. In response, this study advanced the simultaneous extraction of coexisting silver, cerium oxide, and copper oxide ENPs in lettuce shoots and roots using macerozyme R-10 and analyzed them by single-particle inductively coupled plasma-mass spectrometry (ICP-MS). Additionally, the standard stock suspensions of the ENPs were stabilized with citrate, and the long-term stability (up to 5 months) was examined for the first time. The method performance results displayed satisfactory accuracies and precisions and achieved low particle concentration and particle size detection limits. Significantly, the oven drying process was proved not to impact the properties of the ENPs; therefore, oven-dried lettuce tissues were used in this study, which markedly expanded the applicability of this method. This robust methodology provides a timely approach to characterize and quantify multiple coexisting ENPs in plants.

Determination and Characterization of Gold Nanoparticles in Liquor Using Asymmetric Flow Field-Flow Fractionation Hyphenated with Inductively Coupled Plasma Mass Spectrometry

The EU has approved the usage of gold as a food additive (E175) and it has been applied in numerous foods for coloring and decoration purposes. Different from the general assumption that edible gold is mainly present in the form of flakes or external coating in foods, this work demonstrated that gold nanoparticles (Au NPs) can be released from gold flakes and extracted under optimized conditions. To support future risk assessment associated with the exposure of Au NPs to human health, an effective approach was established in this study for both size characterization and mass determination of Au NPs released in a commercial gold-containing liquor using Asymmetric Flow Field-flow Fractionation (AF4) hyphenated with Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Our results showed that no Au NPs were detected in the original liquor product and only after ultrasonication for several minutes did Au NPs occur in the ultrasound-treated liquor. Particularly, Au NPs released in the liquor can be well extracted after 100-fold enrichment of gold flakes and the subsequent ultrasonication for 25 min. Size characterization of Au NPs was conducted by AF4-ICP-MS under calibration with Au NP standards. The gold particle sizes detected ranged from 8.3-398.0 nm and the dominant size of the released Au NPs was around 123.7 nm in the processed liquor. The mass concentration of gold particles determined in the liquor sample with gold flakes concentrated and subsequently sonicated was 48.1 μg L-1 by pre-channel calibration and the overall detection recoveries ranged over 82-95%. For the comparison control samples without ultrasonication, there was no detection of Au NPs. The established method was demonstrated to be useful for monitoring Au NPs in liquor and is possibly applied to other similar foodstuffs.

Application of Single Particle ICP-MS for the Determination of Inorganic Nanoparticles in Food Additives and Food: A Short Review

Due to enhanced properties at the nanoscale, nanomaterials (NMs) have been incorporated into foods, food additives, and food packaging materials. Knowledge gaps related to (but not limited to) fate, transport, bioaccumulation, and toxicity of nanomaterials have led to an expedient need to expand research efforts in the food research field. While classical techniques can provide information on dilute suspensions, these techniques sample a low throughput of nanoparticles (NPs) in the suspension and are limited in the range of the measurement metrics so orthogonal techniques must be used in tandem to fill in measurement gaps. New and innovative characterization techniques have been developed and optimized for employment in food nano-characterization. Single particle inductively coupled plasma mass spectrometry, a high-throughput nanoparticle characterization technique capable of providing vital measurands of NP-containing samples such as size distribution, number concentration, and NP evolution has been employed as a characterization technique in food research since its inception. Here, we offer a short, critical review highlighting existing studies that employ spICP-MS in food research with a particular focus on method validation and trends in sample preparation and spICP-MS methodology. Importantly, we identify and address areas in research as well as offer insights into yet to be addressed knowledge gaps in methodology.

Detection, Identification and Size Distribution of Silver Nanoparticles (AgNPs) in Milk and Migration Study for Breast Milk Storage Bags

The engineered silver nanoparticles (AgNPs) have been widely used in various food contact materials (FCMs) based on their antibacterial properties. This widespread use of nanosilver has, however, increased the risk of exposure of AgNPs to human due to their migration from FCMs causing a potential hazard present in foods. Therefore, it is important to establish a reliable and practical method for the detection of AgNPs in food matrices to support risk assessment on AgNPs exposure. Taking the examples of milk and AgNPs-containing breast milk storage bags, this study established an approach for size characterization and quantification of AgNPs in milk and evaluated the relevant silver migration, based on enzymatic digestion and the analysis by asymmetric flow field–flow fractionation (AF4) hyphenated with inductively coupled plasma mass spectrometry (ICP-MS) and single particle inductively coupled plasma mass spectrometry (SP-ICP-MS). No migration of AgNPs was found from breast milk storage bags under various simulated storage conditions as well as extreme scenarios. The suitability and reliability of this method were also validated by the determination of multiple parameters, including accuracy, repeatability, limit of detection (LOD), limit of quantification (LOQ), and recovery, for AF4-ICP-MS and SP-ICP-MS, respectively, with good and overall acceptable evaluation results obtained for all. The established and validated approach was demonstrated to be suitable for the characterization and quantitation of AgNPs in milk as well as the analysis of their migration from breast milk storage bags.

Food and Beverage Ingredients Induce the Formation of Silver Nanoparticles in Products Stored within Nanotechnology-Enabled Packaging

Nanotechnology-based packaging may improve food quality and safety, but packages manufactured with polymer nanocomposites (PNCs) could be a source of human dietary exposure to engineered nanomaterials (ENMs). Previous studies showed that PNCs release ENMs to foods predominantly in a dissolved state, but most of this work used food simulants like dilute acetic acid and water, leaving questions about how substances in real foods may influence exposure. Here, we demonstrate that food and beverage ingredients with reducing properties, like sweeteners, may alter exposure by inducing nanoparticle formation in foods contacting silver nanotechnology-enabled packaging. We incorporated 12.8 ± 1.4 nm silver nanoparticles (AgNPs) into polyethylene and stored media containing reducing ingredients in packages manufactured from this material under accelerated room-temperature and refrigerated conditions. Analysis of the leachates revealed that reducing ingredients increased the total silver transferred to foods contacting PNC packaging (by as much as 7-fold) and also induced the (re)formation of AgNPs from this dissolved silver during storage. AgNP formation was also observed when Ag⁺ was introduced to solutions of natural and artificial sweeteners (glucose, sucrose, aspartame), commercial beverages (soft drinks, juices, milk), and liquid foods (yogurt, starch slurry), and the amount and morphology of reformed AgNPs depended on the ingredient formulation, silver concentration, storage conditions, and light exposure. These results imply that food and beverage ingredients may influence dietary exposure to nanoparticles when PNCs are used in packaging applications, and the practice of using food simulants may in certain cases underpredict the amount of ENMs likely to be found in foods stored in these materials.

Quantification of titanium dioxide nanoparticles in human urine by single-particle ICP-MS

The increasing use of titanium dioxide nanoparticles in daily use consumer products such as cosmetics, personal care products, food additives, and even medicine has led to growing concerns regarding human safety. It would be ideal to track exposure to this emerging nanopollutant, for example through bioassays, however, so far nanoparticle assessment in biological matrices such as urine remains challenging. The lack of data is mainly due to the limitations of the current metrology, but also to the low expected concentration in human samples. In this study, a quantification method for titanium dioxide nanoparticles in urine has been developed and validated following the ISO/CEI 17025:2017 guidelines. The detection limit for titanium dioxide nanoparticle mass concentration by single-particle inductively coupled plasma mass spectrometry (SP-ICP-MS) was 0.05 ng mL^-1. The particle size limit was determined using three different approaches, with the highest calculated limit value approaching 50 nm. Repeatability and reproducibility of 14% and 18% respectively were achieved for particle mass concentration, and 6% for both parameters for particle size determination. Method trueness and recovery were 98% and 84%, respectively.

Continued Efforts on Nanomaterial-Environmental Health and Safety Is Critical to Maintain Sustainable Growth of Nanoindustry

Nanotechnology is enjoying an impressive growth and the global nanotechnology industry is expected to exceed US$ 125 billion by 2024. Based on these successes, there are notions that enough is known and efforts on engineered nanomaterial environmental health and safety (nano-EHS) research should be put on the back burner. However, there are recent events showing that it is not the case. The US Food and Drug Administration found ferumoxytol (carbohydrate-coated superparamagnetic iron oxide nanoparticle) for anemia treatment could induce lethal anaphylactic reactions. The European Union will categorize TiO2 as a category 2 carcinogen due to its inhalation hazard and France banned use of TiO2 (E171) in food from January 1, 2020 because of its carcinogenic potential. Although nanoindustry is seemingly in a healthy state, growth could be hindered for the lack of certainty and more nano-EHS research is needed for the sustainable growth of nanoindustry. Herein, the current knowledge gaps and the way forward are elaborated.

Estimation of the Uncertainties Related to the Measurement of the Size and Quantities of Individual Silver Nanoparticles in Confectionery

E174 (silver) is a food additive that may contain silver nanoparticles (AgNP). Validated methods are needed to size and quantify these particles in a regulatory context. However, no validations have yet been performed with food additives or real samples containing food additives requiring a sample preparation step prior to analysis. A single-particle inductively coupled plasma mass spectrometry (spICP-MS) method was developed and validated for sizing and quantifying the fraction of AgNP in E174 and in products containing E174, and associated uncertainties related to sample preparation, analysis and data interpretation were unraveled. The expanded measurement uncertainty for AgNP sizing was calculated to be 16% in E174-containing food products and increased up to 23% in E174 itself. The E174 food additives showed a large silver background concentration combined with a relatively low number of nanoparticles, making data interpretation more challenging than in the products. The standard uncertainties related to sample preparation, analysis, and challenging data interpretation were respectively 4.7%, 6.5%, and 6.0% for triplicate performances. For a single replicate sample, the uncertainty related to sample preparation increased to 6.8%. The expanded measurement uncertainty related to the concentration determination was 25-45% in these complex samples, without a clear distinction between additives and products. Overall, the validation parameters obtained for spICP-MS seem to be fit for the purpose of characterizing AgNP in E174 or E174-containing products.

Silver nanoparticles assessment in moisturizing creams by ultrasound assisted extraction followed by sp-ICP-MS

Advances on nanometrology require reliable sample pre-treatment methods for extracting/isolating nanomaterials from complex samples. The current development deals with a discontinuous ultrasonication (60% amplitude, 15 cycles of ultrasound treatment for 59 s plus relaxing stage for 59 s, 20 mL of methanol) method for a fast and quantitative extraction of silver nanoparticles (Ag NPs) from moisturizing creams. Possibilities offered by modern inductively coupled plasma mass spectrometry (ICP-MS) which allow 'single particle' assessment (sp-ICP-MS) have been used for Ag NPs assessment (Ag NPs concentration and Ag size distribution). The relative standard deviation (RSD) of the over-all procedure (Ag NPs concentration in eleven extracts from a same cream) was found to be 5%; whereas, the analytical recovery for spiking experiments with Ag NPs of 20, 40, and 60 nm was found to be within the 90-109% range. The limit of quantification in Ag NPs concentration was established at 8.25 × 10⁵ Ag NPs g^-1; whereas, the limit of detection in size was found to be within the 5-13 nm (several equations were used for calculation). Finally, moisturizing creams prescribed for atopic dermatitis and also regular moisturizing creams were analyzed for total Ag, and for Ag NPs characterization (Ag NPs concentration and Ag NPs size distribution) by sp-ICP-MS. Electronic microscopy was also used for comparative (qualitative) purposes.

Cellular imaging and bactericidal mechanism of green-synthesized silver nanoparticles against human pathogenic bacteria

In recent years, silver nanoparticles (AgNPs) have attracted significant attention in medicinal, biomedical, and pharmaceutical research owing to their valuable physicochemical and antibacterial properties. Leaf sap extract (LSE) from Aloe arborescens can be used as an active ingredient for different biological applications, including wound healing. In this study, we have investigated the use of LSE from A. arborescens as a reducing, stabilizing and capping agent to produce AgNPs during the so called "green synthesis" (G-AgNPs). The objective of this study was to prepare, characterize and evaluate the potential of G-AgNPs against human pathogenic bacteria for the intended use as treatment of infected wounds. When the mixture of silver nitrate solution and LSE was exposed to direct sunlight it yielded a rapid color change from colorless to reddish-brown, indicating the formation of G-AgNPs. Physicochemical characterization such as Single particle inductively coupled plasma mass spectrometry, High resolution transmission electron microscopy and surface chemistry studies (Fourier transform infrared spectroscopy and X-Ray diffraction) revealed a small size in the range of 38±2nm, smooth surface and existence of LSE on the G-AgNPs. G-AgNPs possessed good antibacterial activity against both Pseudomonas aeruginosa and Staphylococcus aureus. The flow cytometry study revealed the increased percentage of dead cells treated by G-AgNPs through cell membrane damage, and it was further confirmed by confocal laser scanning microscopy. Thus, the present study reveals that the novel G-AgNPs demonstrated effective antibacterial properties against both Gram-negative and Gram-positive bacterial strains and shows great potential for its use in the treatment of pathogen infected wounds.

Physicochemical and colloidal aspects of food matrix effects on gastrointestinal fate of ingested inorganic nanoparticles

Inorganic nanoparticles, such as titanium dioxide, silicon dioxide, iron oxide, zinc oxide, or silver nanoparticles, are added to some food products and food packaging materials to obtain specific functional attributes, such as lightening, powder flow, nutrition, or antimicrobial properties. These engineered nanomaterials (ENMs) all have dimensions below 100nm, but may still vary considerably in composition, morphology, charge, surface properties and aggregation state, which effects their gastrointestinal fate and potential toxicity. In addition to their intrinsic physicochemical and morphological properties, the extrinsic properties of the media they are suspended in also affects their biotransformation, gastrointestinal fate and bioactivity. For instance, inorganic nanoparticles are usually consumed as part of a food or meal that contains numerous other components, such as lipids, proteins, carbohydrates, surfactants, minerals, and water, which may alter their gastrointestinal fate. This review article provides an overview of the potential effects of food components on the behavior of ENMs in the gastrointestinal tract (GIT), and highlights some important physicochemical and colloidal mechanisms by which the food matrix may alter the properties of inorganic nanoparticles. This information is essential for developing appropriate test methods to establish the potential toxicity and biokinetics of inorganic nanoparticles in foods.

Results of an interlaboratory method performance study for the size determination and quantification of silver nanoparticles in chicken meat by single-particle inductively coupled plasma mass spectrometry (sp-ICP-MS)

Single-particle inductively coupled plasma mass spectrometry (sp-ICP-MS) promises fast and selective determination of nanoparticle size and number concentrations. While several studies on practical applications have been published, data on formal, especially interlaboratory validation of sp-ICP-MS, is sparse. An international interlaboratory study was organized to determine repeatability and reproducibility of the determination of the median particle size and particle number concentration of Ag nanoparticles (AgNPs) in chicken meat. Ten laboratories from the European Union, the USA, and Canada determined particle size and particle number concentration of two chicken meat homogenates spiked with polyvinylpyrrolidone (PVP)-stabilized AgNPs. For the determination of the median particle diameter, repeatability standard deviations of 2 and 5% were determined, and reproducibility standard deviations were 15 and 25%, respectively. The equivalent median diameter itself was approximately 60% larger than the diameter of the particles in the spiking solution. Determination of the particle number concentration was significantly less precise, with repeatability standard deviations of 7 and 18% and reproducibility standard deviations of 70 and 90%.