Control of Metal Content in Polystyrene Microbeads Prepared with Metal Complexes of DTPA Derivatives

Mass cytometry (MC) is an emerging analytical technique in which an inductively coupled plasma time-of-flight mass spectrometer is employed to analyze the signals of isotopic labels on cell and microbead samples. Bead-based applications in mass cytometry require one to label the microbeads with various metal ions that can be individually identified by MC. This paper describes a novel approach to encoding microbeads with controlled levels of metal ions by introducing polymerizable metal complexes of the structure M(DTPA-VBAm2) in two-stage dispersion polymerization reactions. Using this method, the incorporation of various metal ions is effective and consistent in the investigated concentration range. As a result, this method provides a convenient path for synthesizing microbeads with controlled metal content for mass cytometry applications. As a proof-of-concept experiment, a sample of europium-labeled microbeads was surface-functionalized with a goat anti-mouse IgG antibody and tested by mass cytometry for its ability to detect a Lu-labeled mouse IgG. Surface functionalization involved a thin silica shell to which neutravidin was covalently attached. This experiment demonstrates the potential use of these microbeads as classifier beads for bead-based assays in MC.