pH-Responsive near-infrared fluorescent cyanine dyes for molecular imaging based on pH sensing

Abstract

Indocyanine green (ICG) derivatives having nucleophilic substituents were synthesized as pH-responsive near-infrared dyes. pH-responsive dyes 1-C with closed-ring structures smoothly internalized and converted to emissive open-ring structures 1-O in response to relatively low pHs in acidic intracellular compartments of HeLa cells.