Detection of magnetic iron nanoparticles by single-particle ICP-TOFMS: case study for a magnetic filtration medical device

Enzymatic hydrolysis for pre-treating human serum before titanium dioxide nanoparticles assessment by spICP-MS

The current use of inorganic nanoparticles (NPs) in many industrial sectors, particularly in the food industry, has led to growing concerns about the toxicity of these emerging materials to humans. Therefore, NPs assessment in foodstuff, environmental materials and biological fluids is becoming an important topic, and the development of reliable quantification/characterization analytical methods is needed. The presence of NPs in blood and urine can be expected because of the bioavailability/assimilation of these entities by the organism. However, the determination of NPs in biofluids is a challenge mainly due to the complexity of the sample and the low levels of NPs (basal levels). The research on new methodologies for sample treatment is therefore needed. The possibilities of enzymatic hydrolysis followed by centrifugal ultrafiltration for isolating titanium dioxide nanoparticles (TiO2 NPs) from serum samples have been explored in the current research. Hydrolysis of serum's matrix components was performed with a pancreatin-lipase mixture (0.1 %(w/v) each one) operating at pH 7.4 and 37 °C for 4.0 h under orbital - horizontal shaking at 150 rpm. In addition, centrifugal ultrafiltration (30 kDa molecular weight cutoff (MWCO) membrane) was optimised for removing enzymes residues and other matrix's components. The developed method showed a limit of detection of 6.89 × 103 NPs mL-1, and a limit of detection in size of 36 nm, whereas analytical recovery for spiking assays with 100 nm TiO2 NPs were within the 103-114 % range.

Quantifying platinum binding on protein-functionalized magnetic microparticles using single particle-ICP-TOF-MS

This work describes an analytical procedure, single particle-inductively coupled plasma-time-of-flight-mass spectrometry (SP-ICP-TOF-MS), that was developed to determine the platinum binding efficiency of protein-coated magnetic microparticles. SP-ICP-TOF-MS is advantageous due to its ability to quasi-simultaneously detect all nuclides (7Li-242Pu), allowing for both platinum and iron (composition of magnetic microparticles) to be measured concurrently. This method subsequently allows for the differentiation between bound and unbound platinum. The 1 μm magnetic microparticles were fully characterized for their iron concentration, particle concentration, and trace element composition by bulk digestion-ICP-MS and SP-ICP-TOF-MS. The results of both approaches agreed with the certificate values. Using the single particle methodology the platinum loading was quantified to be to 0.18 ± 0.02 fg per particle and 0.32 ± 0.02 fg per particle, for the streptavidin-coated and azurin-coated microparticles, respectively. Both streptavidin-coated and the azurin-coated microparticles had a particle-platinum association of >65%. Platinum bound samples were also analyzed via bulk digestion-based ICP-MS. The bulk ICP-MS results overestimated platinum loading due to free platinum in the samples. This highlights the importance of single particle analysis for a closer inspection of platinum binding performance. The SP-ICP-TOF-MS approach offers advantages over typical bulk digestion methods by eliminating laborious sample preparation, enabling differentiation between bound/unbound platinum in a solution, and quantification of platinum on a particle-by-particle basis. The procedure presented here enables quantification of metal content per particle, which could be broadly implemented for other single particle applications.