Exosomes are cell‐derived extracellular vesicles that hold promise for diagnosis and therapy. The surface characteristics of exosomes dictate their biological fate and are therefore important for various applications, however surface modification strategies are generally either limited in scope or require complex equipment or experimental procedures. Herein, we employ a simple and fast method to control the surface properties of exosomes via polydopamine coating. Specifically, the polydopamine coating allowed for tailorable functionalization via secondary reactions, which opens exciting avenues for the application of exosomes.

Exosomes were non‐covalently functionalized using the self‐polymerization of dopamine and subsequent PEGylation via Thiol‐Michael addition. This rapid and versatile exosome coating method improved the colloidal stability of exosomes and endowed them with tunable fluorescence and coating thickness. Collectively, this aggregation‐free non‐covalent coating approach expands the potential of exosomes in various applications without requiring complex equipment or reagents. More information can be found in the Communication by Hirotaka Ejima et al.