| Autor: |
Lustig DR; Department of Chemistry, Colorado State University, 200 West Lake Street, Fort Collins, Colorado 80523-1872, United States., Buz E; Department of Chemistry, University of Massachusetts Amherst, 710 North Pleasant Street, Amherst, Massachusetts 01003, United States., Mulvey JT; Center for Complex and Active Materials, University of California, Irvine, Irvine, California 92697-2025, United States.; Department of Materials Science and Engineering, University of California, Irvine, Irvine, California 92697-2025, United States., Patterson JP; Center for Complex and Active Materials, University of California, Irvine, Irvine, California 92697-2025, United States.; Department of Chemistry, University of California, Irvine, Irvine, California 92697-2025, United States.; Department of Materials Science and Engineering, University of California, Irvine, Irvine, California 92697-2025, United States., Kittilstved KR; Department of Chemistry, University of Massachusetts Amherst, 710 North Pleasant Street, Amherst, Massachusetts 01003, United States., Sambur JB; Department of Chemistry, Colorado State University, 200 West Lake Street, Fort Collins, Colorado 80523-1872, United States. |
| Abstrakt: |
Poly(ethylene glycol) (PEG) ligands can inhibit proteins and other biomolecules from adhering to underlying surfaces, making them excellent surface ligands for nanocrystal (NC)-based drug carriers. Quantifying the PEG ligand shell morphology is important because its structure determines the permeability of biomolecules through the shell to the NC surface. However, few in situ analytical tools can reveal whether the PEG ligands form either an impenetrable barrier or a porous coating surrounding the NC. Here, we present a Förster resonance energy transfer (FRET) spectroscopy-based approach that can assess the permeability of molecules through PEG-coated ZnO NCs. In this approach, ZnO NCs serve as FRET donors, and freely diffusing molecules in the bulk solution are FRET acceptors. We synthesized a series of variable chain length PEG-silane-coated ZnO NCs such that the longest chain length ligands far exceed the Förster radius ( R 0 ), where the energy transfer (EnT) efficiency is 50%. We quantified the EnT efficiency as a function of the ligand chain length using time-resolved photoluminescence lifetime (TRPL) spectroscopy within the framework of FRET theory. Unexpectedly, the longest PEG-silane ligand showed equivalent EnT efficiency as that of bare, hydroxyl-passivated ZnO NCs. These results indicate that the "rigid shell" model fails and the PEG ligand shell morphology is more likely porous or in a patchy "mushroom state", consistent with transmission electron microscopy data. While the spectroscopic measurements and data analysis procedures discussed herein cannot directly visualize the ligand shell morphology in real space, the in situ spectroscopy approach can provide researchers with valuable information regarding the permeability of species through the ligand shell under practical biological conditions. |
