RESEARCH ARTICLE Integrating Protein Engineering and

Exosomes are small, cell-secreted vesicles that transfer proteins and genetic information between cells. This intercellular transmission regulates many physiological and pathologi-cal processes. Therefore, exosomes have emerged as novel biomarkers for disease diag-nosis and as nanocarriers for drug delivery. Here, we report an easy-to-adapt and highly versatile methodology to modulate exosome composition and conjugate exosomes for intracellular delivery. Our strategy combines the metabolic labeling of newly synthesized proteins or glycan/glycoproteins of exosome-secreting cells with active azides and bioortho-gonal click conjugation to modify and functionalize the exosomes. The azide-integrated can be conjugated to a variety of small molecules and proteins and can efficiently deliver conju-gates into cells. The metabolic engineering of exosomes diversifies the chemistry of exo-somes and expands the functions that can be introduced into exosomes, providing novel, powerful tools to study the roles of exosomes in biology and expand the biomedical poten-tial of exosomes