Ultra-High-Throughput Discovery of Multifunctional Polyphenolic Coatings on Droplet Microarrays

This ultra-high-throughput workflow enabled the rapid identification of hundreds of previously unknown fluorescent coatings, including over 225 strong green-, blue-, or red-emissive PaPp materials. Systematic redox screening revealed more than 100 highly active metal-reducing coatings, dominated by PaPp combinations containing galloylated or catecholic structures, with the ternary compositions Pa2Pp43Pp44 and Pa2Pp43Pp45 emerging as the strongest reducers.

Antibacterial screening uncovered seven PaPp coatings with reproducible activity against Pseudomonas aeruginosa, and subsequent validation on macroscale substrates confirmed up to <1 log CFU reduction against P. aeruginosa and E. coli. Importantly, five coatings exhibited multiple functionalities, including Pa2Pp3, Pa2Pp6, Pa6Pp3, Pa8Pp18, and Pa9Pp18, which combined surface stability, intrinsic fluorescence, metal-reducing activity, antibacterial effects, and compatibility with adherent human cells.

Several additional coatings were identified as fluorescent–redox dual-functional materials (e.g., Pa2Pp7, Pa6Pp33, Pa8Pp9, etc.), or redox-active but cell-compatible surfaces, expanding the design space for optically traceable, redox-responsive, or bioactive interfaces. Together, this UHT approach yields the first comprehensive functionality map of polyamine–polyphenolic coatings, revealing previously inaccessible multifunctional materials and demonstrating a scalable strategy for the discovery of surface chemistries with tailored optical, redox, and biological properties.