We demonstrate that synthetic soft materials can extend the utility of natural vesicles, from predominantly hydrophilic reservoirs to functional colloidal carriers that facilitate the biomedical application of large aqueous-insoluble compounds. Near-infrared (NIR)-emissive polymersomes (50-nm-to 50-m-diameter polymer vesicles) were generated through cooperative self assembly of amphiphilic diblock copolymers and conjugated multi(porphyrin)-based NIR fluorophores (NIRFs). When compared with natural vesicles comprised of phospholipids, polymersomes were uniquely capable of incorporating and uniformly distributing numerous large hydrophobic NIRFs exclusively in their lamellar membranes. Within these sequestered compartments, long polymer chains regulate the mean fluorophore-fluorophore interspatial separation as well as the fluorophore-localized electronic environment. Porphyrin-based NIRFs manifest photophysical properties within the polymersomal matrix akin to those established for these high-emission dipole strength fluorophores in organic solvents, thereby yielding uniquely emissive vesicles. Furthermore, the total fluorescence emanating from the assemblies gives rise to a localized optical signal of sufficient intensity to penetrate through the dense tumor tissue of a live animal. Robust NIR-emissive polymersomes thus define a soft matter platform with exceptional potential to facilitate deep-tissue fluorescence-based imaging for in vivo diagnostic and drug-delivery applications.porphyrin ͉ vesicles ͉ nanoscale ͉ diblock copolymer S upramolecular self assembly has revolutionized soft materials research by enabling the efficient and high-throughput fabrication of complex multicomponent nanostructures (1-3). For decades, self-assembled vesicles comprised of phospholipids (liposomes) or small-molecule surfactants (4) have been used for sequestering high concentrations of hydrophilic compounds (5) and controlling their temporal release and distribution for maximal therapeutic efficacy (6). More recently, amphiphilic peptides and polymers have been shown to form very elaborate architectures (7-9) and serve as useful nanocontainers in aqueous solution (10). In particular, self-assembled materials are ideal for carrying promising imaging and therapeutic agents whose biomedical utility has hitherto been hampered by inadequate aqueous solubility (11). Here, we demonstrate the unique ability of synthetic amphiphiles to assemble into functional vesicles that membrane-disperse numerous large hydrophobic fluorophores and enable their specialized application for deeptissue fluorescence-based in vivo imaging.Although visible probes enable exquisite imaging of live animals by intravital microscopy (12), their utility is significantly limited at greater than submillimeter tissue depths as a result of extensive light scattering and optical absorption. Because light scattering diminishes with increasing wavelength, and hemoglobin electronic and water vibrational overtone absorptions approach their nadir over the near-infrared (N...

Dendritic cells (DCs) play a pivotal role in both immune tolerance and the initiation of immunological responses. The ability to track DCs in vivo is imperative for the development of DC-based cellular therapies and to advance our understanding of DC function and pathophysiology. Here, we conjugate a cell permeable peptide, Tat, to near-infrared (NIR) emissive polymersomes in order to enable efficient intracellular delivery for future DC tracking with these optical probes. NIR imaging allows quantitative, repetitive, in vivo detection of fluorophore-laden cells, at centimeter tissue depths without disturbing cellular function. Flow cytometry and confocal microscopy results indicate that Tat-mediated polymersome delivery to DCs is concentration and time dependent, resulting in punctate intracellular localization. Further, loading cells with Tat NIR emissive polymersomes does not interfere with cytokine-induced DC maturation and has modest effects on DC viability, but has a significant effect on mature DC-induced activation of naive T cells. We observe significant uptake of NIR emissive polymersomes when conjugated to the peptide, with a lower detection limit of 5000 labeled DCs. The extent of polymersome delivery is estimated as 70 000 +/- 10 000 vesicles/cell, equivalent to 0.7 +/- 0.1 fmol of NIR fluorophore. Our studies will enable future in vivo tracking of ex vivo labeled DCs by NIR fluorescence based imaging.