Ultraviolet-Induced Fluorescence of Polydopamine-Coated Emulsion Droplets

Abstract

Polydopamine (PDA), a multifunctional biomaterial with strong adhesion and coating properties, exhibits melanin-like optoelectronic properties but is virtually devoid of intrinsic fluorescence. Herein we disclose the first PDA-based system that can develop fluorescence without chemical manipulation. The polymerization of dopamine in the presence of oil microdroplets results in the formation of smooth PDA-coated core-shell droplets, which develop a bright and persistent fluorescence upon UVA illumination. The fluorescence induction depends on the excitation wavelength, the nature of the oil, and oxidation and buffer conditions, suggesting photo-oxidation of PDA components within the oil matrix, which shields the developing fluorophores from water quenching. Peroxyl radical scavengers enhance the fluorescence, whereas hydrogen peroxide induces quenching. The new system holds potential interest for imaging and tocopherol sensing applications. Fluorescent droplets: The first polydopamine-based system that can develop fluorescence without chemical manipulation is disclosed. The polymerization of dopamine in the presence of oil microdroplets results in the formation of smooth PDA-coated core-shell droplets, which develop a bright and persistent fluorescence upon UVA illumination (see figure).