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Assessing the impact of nanoparticles in living systems implies a proper evaluation of their behaviour at single-cell level. Due to the small size of nanoparticles, their accumulation, transformation and location within single cells is challenging. In this work, the combination of single cell/single particle triple quadrupole inductively coupled plasma mass spectrometry (SC/SP-ICP-TQ-MS) analysis along with X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements has been applied to go deeper into the uptake and biotransformation of tellurium nanoparticles (TeNPs) in two bacterial model organisms, S. aureus and E. coli. The use of SC-ICP-TQ-MS enabled the individual introduction of bacterial cells where tellurium and phosphorous (as constitutive element) were monitored and detected at concentration levels down to femtogram (fg) per cell. S.aureus uptake of TeNPs was 0.5–1.9 fg Te cell−1 and 7–30 fg Te cell−1 in presence of 0.5 and 15 mg Te L−1 of TeNPs, respectively, whereas for E. coli, the amount of Te ranged from 0.08 to 0.88 fg Te cell−1 and from 2 to 36 fg Te cell−1 in presence of 0.5 and 15 mg Te L−1 of TeNPs, respectively. TEM and XRD analysis confirmed the occurrence of TeNPs biotransformation (from nanospheres to nanorods) as the nanoparticles were incorporated into both bacterial strains. Finally, SP-ICP-MS analysis after cell lysis was applied to determine the number of particles/rods per bacteria cell and to perform the dimensional characterization of the rod-shaped TeNPs. The results obtained clearly confirmed high cell-to-cell variability in terms of Te nanorods dimensions and TeNPs uptake. To the best of our knowledge, this is the first time that SC/SP-ICP-TQ-MS along with TEM and XRD analysis have been applied to investigate, quantitatively, nanoparticle uptake in bacterial cells and to estimate the dimensions of biogenic Te nanorods., Spanish Ministry for Science, Innovation and Universities, Community of Madrid, Asturian Foundation for Biosanitary Research and Innovation (FINBA), Depto. de Química Analítica, CAI Ciencias de la Tierra y Arqueometría, TRUE, pub

A method was developed for the precise and accurate determination of ovalbumin labelled with p-hydroxy-mercuribenzoic acid (pHMB) using polyacrylamide gel electrophoresis with ns-laser ablation-inductively coupled plasma mass spectrometry. Following systematic optimisation of the ablation process in terms of detection sensitivity, two different quantification strategies were applied: external calibration using standards of the derivatized protein after 13C+ normalization and, as a proof of concept, label-specific isotope dilution analysis (IDA) using pHMB enriched in the isotope 199Hg. Due to the inhomogeneous distribution of the protein within the gel bands, it could be demonstrated that the IDA approach was superior in terms of precision and accuracy. Furthermore, it permits a reliable quantification, if more complex separation protocols are applied, as typically occurring analyte loss and degradation can be compensated for as soon as complete mixture of spike and sample is achieved. The estimated limit of detection was 160fmol in the case of ovalbumin. In contrast to earlier studies using metals naturally present in proteins, no loss of mercury was observed during separation under denaturing conditions and other sample preparation steps. Using label-specific IDA, the measured isotope ratios in the gel corresponded to recoveries between 95% and 103%