title: Proton-Resistant Quantum Dots: Stability in Gastrointestinal Fluids and Implications for Oral Delivery of Nanoparticle Agents.
abstract: Semiconductor quantum dots (QDs) have shown great promise as fluorescent probes for molecular, cellular and in-vivo imaging. However, the fluorescence of traditional polymer-encapsulated QDs is often quenched by proton-induced etching in acidic environments. This is a major problem for QD applications in the gastrointestinal tract because the gastric (stomach) environment is strongly acidic (pH 1-2). Here we report the use of proton-resistant surface coatings to stabilize QD fluorescence under acidic conditions. Using both hyperbranched polyethylenimine (PEI) and its polyethylene glycol derivative (PEG grafted PEI), we show that the fluorescence of core-shell CdSe/CdS/ZnS QDs is effectively protected from quenching in simulated gastric fluids. In comparison, amphiphilic lipid or polymer coatings provide no protection under similarly acidic conditions. The proton-resistant QDs are found to cause moderate membrane damage to cultured epithelial cells, but PEGylation (PEG grafting) can be used to reduce cellular toxicity and to improved nanoparticle stability.
authors.affiliation: Departments of Biomedical Engineering and Chemistry, Emory University and Georgia Institute of Technology, 101 Woodruff Circle NE, Suite 2001, Atlanta, Georgia 30322, USA.
authors.forename: Aaron M
authors.initials: AM
authors.lastname: Mohs
authors.forename: Hongwei
authors.initials: H
authors.lastname: Duan
authors.forename: Brad A
authors.initials: BA
authors.lastname: Kairdolf
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Smith
authors.forename: Shuming
authors.initials: S
authors.lastname: Nie