Research Article Quantum Dot-Loaded Liposomes to Evaluate the Behavior of Drug Carriers after Oral Administration

Copyright © 2013 Kohei Tahara et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. We have developed submicron-sized liposomes modified with a mucoadhesive polymer to enhance peptide drug absorption after oral administration. Liposomal behavior in the gastrointestinal tract is a critical factor for effective peptide drug delivery. The purpose of this studywas to prepare quantumdot- (QD-) loaded submicron-sized liposomes and examine liposomal behavior in the body after oral administration using in vivo fluorescence imaging. Two types of CdSe/CdZnS QDs with different surface properties were used: hydrophobic (unmodified) QDs and hydrophilic QDs with glutathione (GSH) surface modifications. QD- and GSH-QD-loaded liposomes were prepared by a thin film hydration method. Transmission electron microscopy revealed that QDs were embedded in the liposomal lipid bilayer. Conversely, GSH-QDs were present in the inner aqueous phase. Some of the GSH-QDs were electrostatically associated with the lipid membrane of stearylamine-bearing cationic liposomes. QD-loaded liposomes were detected in Caco-2 cells after exposure to the liposomes, and these liposomes were not toxic to the Caco-2 cells. Furthermore, we evaluated the in vivo bioadhesion and intestinal penetration of orally administeredQD-loaded liposomes by observing the intestina