Assessment by a multi-technique approach of PtNPs' transformations in waters under relevant environmental concentrations and conditions.

Once released to the environment, platinum nanoparticles (PtNPs) can undergo different transformations and are affected by several environmental conditions. An only analytical technique cannot provide all the information required to understand those complex processes, so new analytical developments are demanded. In the present work, the potential of asymmetric flow field flow fractionation hyphenated to inductively coupled plasma mass spectrometry (AF4-ICP-MS) for these studies, has been investigated, and classical dynamic and electrophoretic light scattering (DLS & ELS) have been used as complementary techniques. The role of ionic strength, ionic water composition, and natural organic matter (NOM) in the behaviour of PtNPs of different sizes (5 and 50 nm) has been specifically studied. Dynamic and electrophoretic light scattering have been used to track changes in the hydrodynamic diameters (dh) and polydispersity index (PdI) for 50 nm PtNPs (5 nm cannot be studied by DLS) and Z-potential values (for all sizes) to monitor aggregation. AF4-ICP-MS has been also employed to have a solid insight of aggregation at low environmental concentrations for different sizes of PtNPs simultaneously. The information gathered with those techniques was useful to observe changes as the ionic strength increases, which induces aggregation. Also, it was observed that this aggregation process was attenuated in the presence of organic matter. This approach, based on complementary analytical techniques, is needed for a comprehensive study of such complex interactions of NPs in the environment. AF4-ICP-MS is still under-exploited but shows a great potential for this purpose, especially low size NPs and concentrations.

A simple analytical methodology for platinum nanoparticles control in complex clinical matrices via SP-ICP-MS.

A simple method based on the use of inductively coupled plasma mass spectrometry in single particle mode (SP-ICP-MS) has been proposed, for the first time, for the study of platinum nanoparticles (PtNPs) in complex clinical matrices such as human urine and blood serum. Critical parameters for signal acquisition were optimized to achieve a correct and simultaneous sizing and counting (particle-based in particles L-1 and mass-based in ng L-1) of 50 and 70 nm PtNPs. Different reagents, as tetramethylammonium hydroxide (TMAH) and/or Triton X-100, and concentrations have been tested to ensure an adequate stabilization and extraction of PtNPs. Finally, TMAH at 1% is demonstrated to be the best reagent to extract the NPs guaranteeing their integrity. No heating or any additional treatment was required, which allows sample preparation, and the overall process, to be simple and fast. Good precisions for size (2% RSD) and particle number and mass concentrations (<1% RSD), and limits of detection of 21.6 nm and 1.9 × 105 particles L-1 were reported. The influence of matrix on the determination of PtNP sizes and number- and mass-based concentrations was evaluated. Particle sizes were in all cases in accordance with values determined by TEM or SEM, whereas recoveries of PtNPs in terms of concentration ranged between 92 and 101%. The stability of PtNP characteristics after 24 h was specifically studied in human urine spiked with PtNPs. Statistically significant differences were only reported for the particle number concentrations of 50 nm PtNPs in female urine samples. The present work will be relevant to understand the behaviour of PtNPs in body fluids and to take appropriate actions in future (pre)clinical trials.

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.

Analytical strategy based on asymmetric flow field flow fractionation hyphenated to ICP-MS and complementary techniques to study gold nanoparticles transformations in cell culture medium.

An analytical methodology based on asymmetric flow field flow fractionation (AF4) hyphenated to inductively coupled plasma mass spectrometry (ICP-MS) has been developed to study gold nanoparticles (AuNPs) in cell culture medium (Dulbecco's Modified Eagle Medium, DMEM, containing 10% fetal bovine serum, FBS, and antibiotics) used for in vitro toxicological studies. AF4-ICP-MS separation of AuNPs was performed using a regenerated cellulose membrane (molecular weight cut-off, MWCO, of 10 kDa). The carrier composition and the AF4 separation program were optimized. Under the optimum conditions, AuNPs of different types, i.e. phosphate buffered saline (PBS) and citrate stabilized, and sizes (10, 30 and 40 nm), without and with cell culture medium could be separated. The developed method allowed to detect transformations in AuNPs and dissolved gold species (Au3+) induced by this medium, such as an increase in the hydrodynamic volume and oxidation. Centrifugal ultrafiltration (CU), transmission electron microscopy (TEM) and Ultraviolet-visible (UV-vis) absorption spectrophotometry have been used as complementary techniques to study these processes. This information is of major interest to have a correct interpretation of the in vitro toxicological studies of NPs, which are more and more demanded due to the increasing concerns about the safe use of these materials and their impacts. This work demonstrates the potential of hyphenated techniques based on AF4 to achieve this relevant information.

Methodology for monitoring gold nanoparticles and dissolved gold species in culture medium and cells used for nanotoxicity tests by liquid chromatography hyphenated to inductively coupled plasma-mass spectrometry.

An analytical methodology based on coupling reversed-phase liquid chromatography (HPLC) to an inductively coupled plasma mass spectrometry (ICP-MS) has been developed for the characterization and identification of gold nanoparticles (AuNPs) and gold dissolved species (Au3+) in culture medium (Dulbecco's Modified Eagle Medium, DMEM) and HeLa cells (a human cervical adenocarcinoma cell line) used in nanotoxicity tests. The influence of the culture medium was also studied and the method applied for nanotoxicity tests. It was also observed that AuNPs can undergo an oxidation process in the supernatants and only a small amount of AuNPs and dissolved Au3+ was associated with cells. To evaluate the biological impact of AuNPs, a classical viability assay onto HeLa cells was performed using cellular media DMEM in the presence of increasing dosage of 10nm AuNPs. The results showed that 10nm AuNPs exhibit a slight toxic effect.