Hydrophobic Shell Loading of PB-b-PEO Vesicles

We report on the successful encapsulation of hydrophobic substrates into the hydrophobic shell of poly(butadiene)-b-poly(ethylene oxide) vesicles in water and straightforward characterization methods. The hydrophobic fluorescent dye Nile Red was embedded into unilamellar vesicles of PB130-b-PEO66 prepared via different methods leading to different average hydrodynamic radii and distributions but a common hydrophobic shell thickness of similar to 16 nm as determined by transmission electron microscopy (TEM). The combination of cryogenic TEM and fluorescence microscopy studies shows that the self-assembled structure remains unchanged when the hydrophobic dye is incorporated within the vesicle shell. Furthermore, highly fluorescent quantum dots with an average diameter of d = 5.7 +/- 0.6 nm as determined by TEM were selected as hydrophobic model substrates and successfully enclosed into the vesicles, as evidenced by fluorescence correlation spectroscopy (FCS) measurements in combination with dynamic light scattering (DLS). Cryogenic TEM imaging reveals the position of the quantum dots, centered inside the double layer of the vesicle shell.