Plasmonic Metal–Phenolic Network Nanoprobes for Multiplex Dual-Mode Immunophenotyping

Accurate multiplexed immunophenotyping is essential for understanding cellular heterogeneity. Dual-mode detection strategies, such as surface-enhanced Raman scattering (SERS)-fluorescence, offer synergistic advantages and cross-validation to reduce false positives. We present a method for fabricating dual-mode nanoprobes using metal-phenolic networks (MPNs) as functional coatings on hollow plasmonic nanocapsules. Unlike conventional silica shells, MPNs enable the one-step conjugation of biorecognition elements via metal-phenolic coordination, integrating distinct Raman reporters and fluorescently labeled antibodies within a single probe. These plasmonic MPN nanoprobes achieved multiplex detection of the epidermal growth factor receptor and CD44 in cultured cells using SERS and flow cytometry. Application to mixed HER14 and HEK-293 cultures revealed population distributions of ∼63% HER14 and ∼37% HEK-293 as determined by SERS, corroborated by flow cytometry. This work highlights the potential of dual-mode plasmonic MPNs for accurate, scalable immunophenotyping, offering a robust platform for targeted cell imaging and diagnostics.