Elemental Analysis in Yeast Cells and Selenium Enriched Yeast Cells by ICP-MS with Automated Micro-Flow Sample Introduction

Significance of the Topic

Single-cell and nanoparticle elemental analysis by ICP-MS provides high sensitivity and specificity for detecting trace elements within individual cells or particles. This capability is increasingly important for fields such as nanotoxicology, cellular biology, drug delivery research, and quality control in biotechnology industries. By resolving element distributions at the single-cell level, researchers can gain insight into cellular heterogeneity, metal uptake pathways, and the efficacy of enrichment protocols.

Objectives and Study Overview

The primary aim of this study was to demonstrate a fully automated micro-flow ICP-MS approach for elemental analysis of nanoparticles and Saccharomyces cerevisiae cells, including selenium-enriched strains. Key objectives included:

• Optimization of sample introduction to preserve intact single cells or clusters
• Validation of instrument settings for reliable multielement detection
• Comparison of regular and Se-enriched yeast cells to confirm selenium uptake at the single-cell level

Methodology

Samples of nanoparticles and dried yeast (3–5 µm) were prepared by serial dilution in deionized water. Yeast cells underwent three wash cycles (shake, centrifuge, decant) to remove extracellular contaminants before final dilution to 50 mL. An ESI microFAST autosampler delivered samples at 10 µL/min through a 100 µL loop, ensuring low dispersion and high throughput. Rapid multi-element acquisition mode on the ICP-QQQ allowed simultaneous monitoring of Fe, Cu, Zn, C, P, and Se signals as discrete pulses corresponding to single cells or particles.

Instrumentation Used

• ESI microFAST autosampler Sample injection rate 10 uL/min Loop size 100 uL Nebulization efficiency >80%
• Agilent 8900 ICP-QQQ Plasma power 1550 W Sampling depth 8 mm Nebulizer gas 0.63 L/min Makeup gas 0.2 L/min Reference material Pt NP 50 nm

Main Results and Discussion

Single cells and nanoparticles produced characteristic pulse signals for target elements (Zn, Mg, Au). In regular yeast samples, element distributions for C, P, and Fe showed consistent frequency patterns without detectable Se signals. In contrast, Se-enriched yeast displayed clear Se pulses in addition to C, P, and Fe, confirming successful incorporation of selenium at the cellular level. Quantitative comparison of detected cell counts revealed strong agreement for C, P, and Fe between sample replicates and a distinct Se signal only in enriched samples. Signal distribution plots highlighted shifts in elemental responses, demonstrating the method’s capability to resolve multielement profiles in heterogeneous populations.

Benefits and Practical Applications

• High-throughput, automated analysis reduces hands-on time and increases lab productivity
• Single-cell resolution enables study of population heterogeneity and metal uptake mechanisms
• Applicable to quality control in food, pharmaceutical, and biotechnology sectors
• Minimal sample preparation preserves cell integrity and reduces contamination risk

Future Trends and Possibilities

Advancements in microfluidic sample introduction and cell sorting promise further sensitivity improvements and integration with imaging techniques. Coupling scICP-MS with mass cytometry or single-cell genomics could provide comprehensive multimodal cellular profiles. Expansion to other cell types, nanoparticles, and environmental samples will broaden applications in biomedical research, nanomedicine, and environmental monitoring.

Conclusion

The automated micro-flow ICP-MS workflow demonstrated here offers a robust platform for rapid, multiplexed elemental analysis of individual cells and nanoparticles. The method reliably distinguished Se-enriched yeast from controls and yielded reproducible counts for multiple elements. Its high throughput and sensitivity make it well suited for diverse research and industrial applications requiring single-cell elemental resolution.

Reference

• Theiner S et al 2020 Single-cell analysis by use of ICP-MS Journal of Analytical Atomic Spectrometry 35(9) 1784-1813