Carbonized Polymer Dots as Versatile Nanocarrier for Bioincompatible Fluorophore Imaging

Fluorophores with excellent emission often come at the cost of cell permeability, and this long-standing dilemma has limited their effective applications in fluorescence bioimaging to some degree. We report a paradigm-shifting discovery that carbonized polymer dots (CPDs) can function as a versatile, noncovalent translocation platform for a vast spectrum of otherwise impermeable fluorophores. Our investigation began with the serendipitous observation that a new molecule, 1-(2-hydroxyethyl)-5-oxo-1,2,3,5-tetrahydroimidazo[1,2-a]pyridine-7-carboxylic acid (HECA), forms a stable, cell-permeable nanocomplex with carbonized polymer dots (CPDs-280) via noncovalent interactions (loading capacity ∼50.8%). This prompted a systematic exploration, which revealed that CPDs-280 possess a remarkable capacity to override the innate targeting signals of diverse organelle-specific dyes, rerouting them to the cytosol and demonstrating a carrier-dominated localization mechanism. The platform's generality was rigorously proven by delivering custom-designed, membrane-impermeable amphiphilic dyes (ESY-Na⁺ and ESY), which remained inert alone but produced intense intracellular luminescence upon noncovalent complexation. This robust, cargo-agnostic delivery capability is rooted in the abundant orthogonal anchor domains on the CPD's surface, enabling multimodal binding without chemical modification. This work unveils a generic strategy to breach biological barriers, instantly unlocking the vast repository of underutilized fluorescent probes for advanced bioimaging and theranostics.