Osmium-Labeled Microspheres for Bead-Based Assays in Mass Cytometry

Area of Science:

• Biomedical research
• Immunology
• Analytical chemistry

Background:

• Polystyrene beads are widely used in flow cytometry but lack elemental labels for mass cytometry detection.
• This limitation hinders the implementation of bead-based assays in high-dimensional mass cytometry studies.
• A method is needed to functionalize beads for mass cytometry detection.

Purpose of the Study:

• To introduce stable osmium tetroxide labeling as a universal method for creating mass cytometry-detectable beads.
• To demonstrate the utility of these labeled beads for signal compensation and quantitative antibody-binding assays.
• To apply the method for high-dimensional profiling of peripheral blood mononuclear cells (PBMCs) to assess receptor expression in systemic lupus erythematosus (SLE).

Main Methods:

• Stable osmium tetroxide labeling of polystyrene beads.
• Application of labeled beads for signal spillover compensation in mass cytometry.
• Quantitative antibody-binding capacity assays combined with high-dimensional mass cytometry profiling of human PBMCs.

Main Results:

• Osmium tetroxide-labeled beads are readily detectable by mass cytometry.
• Labeled beads effectively compensate for signal spillover and enable quantitative assays.
• Analysis revealed increased monocytic Siglec-1 in SLE patients and reduced CD4/HLA-DR expression, suggesting impaired immune cell cross-talk.

Conclusions:

• Stable osmium tetroxide labeling provides a universal approach to adapt flow cytometry beads for mass cytometry.
• This method facilitates high-dimensional cell profiling and the discovery of disease biomarkers.
• The findings open avenues for broader implementation of bead-based assays in mass cytometry for biomedical research.