Facile Synthesis of Trialkylamine Oxide-Modified Platinum Polymer Probes for Mass Cytometry

Mass cytometry is a powerful, high-throughput single-cell analysis technique that uses metal-tagged antibodies detected via inductively coupled plasma time-of-flight mass spectrometry. Current reagents use metal-chelating polymers (MCPs) for hard metal ions, but expanding to soft metal ions could significantly improve multiplexing. However, high nonspecific binding and poor water solubility have been challenges for polymer reagents, with chelators for soft metal ions. To address this, we synthesized a polyacrylamide polymer with dipicolylamine (DPA) pendant groups by reacting poly(pentafluorophenyl acrylate) with a lysine-based DPA chelator. To enhance the water solubility of Pt²⁺-loaded poly(DPA), we modified DPA units with trialkylamine amine oxide (TAAO) molecules. Further treatment with glutathione to displace the Pt–Cl bond yielded polymers with enhanced water solubility and low nonspecific binding to peripheral blood mononuclear cells in mass cytometry analyses. We also prepared a water-soluble TAAO polymer through postpolymerization modification of poly(dimethylaminoethyl methacrylate), synthesized via reversible addition–fragmentation chain transfer polymerization (RAFT). The oxidation reaction simultaneously cleaved the trithiocarbonate end group and introduced the TAAO functionality. The resulting polyTAAO was conjugated to poly(DPA) through an amine end group, producing a highly soluble polymer, even without glutathione modification. Pt polymers modified with polyTAAO exhibited ultralow nonspecific binding in mass cytometry. A polyTAAO-modified Pt probe was conjugated to an anti-CD20 antibody and used for labeling peripheral blood mononuclear cells. This probe demonstrated effective cell population identification comparable to that of commercial Maxpar reagents. This work advances zwitterionic materials for biological applications and develops novel MCPs for next-generation mass cytometry reagents.