Single-Cell Isotope Dilution Analysis with LA-ICP-MS: A New Approach for Quantification of Nanoparticles in Single Cells.

Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) is an emerging method for the analysis of metal nanoparticles (NPs) in single cells. However, two main obstacles, low analytical throughput and lack of commercial reference materials, need to be overcome. In this work, we demonstrated the principles of a new approach termed "single-cell isotope dilution analysis" (SCIDA) to remove the two obstacles. For a proof of concept, macrophage cells were chosen as a model to study the uptake of silver NPs (AgNPs) at a single-cell level. Single cells exposed to AgNPs were placed in an array by a microfluidic technique; each cell in the array was precisely dispensed with a known picoliter droplet of an enriched isotope solution with a commercial inkjet printer; accurate quantification of AgNPs in single cells was done by using isotope dilution LA-ICP-MS. The average Ag mass of 1100 single cells, 396 ± 219 fg Ag per cell, was in good accord with the average of the population of cells determined by solution ICP-MS analysis. The detection limit was 0.2 fg Ag per cell. The SCIDA approach is expected to be widely applied for the study of cell-NP interactions and biological effects of NPs at the single-cell level.

Elemental analysis and imaging of sunscreen fingermarks by X-ray fluorescence.

Chemical composition in fingermarks could provide useful information for forensic studies and applications. Here, we evaluate the feasibility of analysis and imaging of fingermarks via elements by synchrotron radiation X-ray fluorescence (SRXRF) and commercial X-ray fluorescence (XRF). As a proof of concept, we chose four brands of sunscreens to make fingermarks on different substrates, including plastic film, glass, paper, and silicon wafer. We obtained an evident image of fingermarks via zinc and titanium by XRF methods. In addition, the ratios of element concentrations in sunscreen fingermarks were obtained, which were in accordance with the results obtained by acid digestion and ICP-OES analysis. In comparison, commercial XRF offers the most advantages in terms of non-destructive detection, easy accessibility, fast element images, and broad applicability. The possibility to acquire fingermark images simultaneously with element information opens up new avenues for forensic science. Graphical abstract.

Quantitative analysis of Gd@C82(OH)22 and cisplatin uptake in single cells by inductively coupled plasma mass spectrometry.

Cisplatin is a commonly used chemotherapeutic drug in cancer treatment, whereas Gd@C82(OH)22 is a new nanomaterial anti-tumor agent. In this study, we determined intracellular Gd@C82(OH)22 and cisplatin after treatment of Hela and 16HBE cells by single cell inductively coupled plasma-mass spectrometry (SC-ICP-MS), which could provide quantitative information at a single-cell level. The cell digestion method validated the accuracy of the SC-ICP-MS. The concentrations of Gd@C82(OH)22 and cisplatin in cells at different exposure times and doses were studied. The SC-ICP-MS is a promising complement to available methods for single cell analysis and is anticipated to be applied further to biomedical research.

Quantitative analysis of gold nanoparticles in single cells by laser ablation inductively coupled plasma-mass spectrometry.

Single cell analysis has become an important field of research in recent years reflecting the heterogeneity of cellular responses in biological systems. Here, we demonstrate a new method, based on laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS), which can quantify in situ gold nanoparticles (Au NPs) in single cells. Dried residues of picoliter droplets ejected by a commercial inkjet printer were used to simulate matrix-matched calibration standards. The gold mass in single cells exposed to 100 nM NIST Au NPs (Reference material 8012, 30 nm) for 4 h showed a log-normal distribution, ranging from 1.7 to 72 fg Au per cell, which approximately corresponds to 9 to 370 Au NPs per cell. The average result from 70 single cells (15 ± 13 fg Au per cell) was in good agreement with the result from an aqua regia digest solution of 1.2 × 10(6) cells (18 ± 1 fg Au per cell). The limit of quantification was 1.7 fg Au. This paper demonstrates the great potential of LA-ICPMS for single cell analysis and the beneficial study of biological responses to metal drugs or NPs at the single cell level.

Graphene oxide as an anaerobic membrane scaffold for the enhancement of B. adolescentis proliferation and antagonistic effects against pathogens E. coli and S. aureus.

The impact of the gut microbiota on human health is widely perceived as the most exciting advancement in biomedicine. The gut microbiota has been known to play a crucial role in defining states of human health and diseases, and thus becomes a potential new territory for drug targeting. Herein, graphene oxide (GO) interaction with five common human gut bacteria, B. adolescentis, L. acidophilus, E. coli, E. faecalis, and S. aureus, was studied. It was shown that, in bacterial media, GO sheets were able to form effective, anaerobic membrane scaffolds that enhanced the antagonistic activity of B. adolescentis against the pathogens E. coli andS. aureus. Data obtained using bacterial growth measurements, colony counting and 16S rRNA gene sequencing consistently indicated that GO sheets promoted proliferation of gut bacteria, particularly for B. adolescentis. Scanning electron microscopy, atomic force microscopy images, and membrane potential measurements showed that cell membranes maintained their integrity and that no observable variations in cell morphology were induced after interaction with GO sheets, indicating good biocompatibility of GO. These results suggest the possibility of using GO sheets as efficient drug carriers in therapeutic applications to treat diseases related to the gut microbiota.

Rosafuningensis (Rosaceae), a new species from Yunnan, China.

A new species Rosafuningensis and its variant R.funingensisf.rosea, both collected from Yunnan Province, China, are, for the first time, documented and illustrated in this study. Morphological analysis in comparison with two related species in the wild, R.gigantea and R.rubus, presents distinguishable features through leaf surfaces, inflorescences and the shape of styles. R.funingensis leaf surfaces are abaxially villous, purple-red, pale green when mature, adaxially glabrous, dark green; inflorescences solitary or 2-5(7) in corymbose cyme; and styles connate into a column or not, exserted.

Determination of quantum dots in single cells by inductively coupled plasma mass spectrometry.

In order to assess cytotoxicity of quantum dots (QDs), new reliable analytical techniques that can provide comparative information at a single-cell level are required. In this study, a single cell ICP-MS (SC-ICP-MS) method was established to determine intracellular QDs in single cells after exposure. Uptake kinetics of QDs into cells was studied using the established method. The results were compared and validated by flow cytometry and cell digestion methods. In contrast to other methods, SC-ICP-MS can directly detect QDs and their degradation products via elements, and thus is a promising complement to available methods for single cell analysis and is expected to be a critical tool in the future.