Monday, 23 May 2005 - 9:00 AM

This presentation is part of: Nanoparticles, Microparticles and Vesicles

Encapsulation of Drug Nanoparticles in Self-Assembled Macromolecular Nanoshells

Michael Pishko, Alisar Zahr, and Cheryl Rumbarger. Penn State University, University Park, PA

A layer-by-layer (LbL) self-assembly technique was used to encapsulate core charged drug particles in a polymeric nanoshell. This approach provides a new strategy in the development of polymeric vehicles for controlled release and targeting to diseased tissues and cells specific to human illness, such as cancer. A nanoshell composed of two biopolymers, poly-L-lysine and heparin sulfate, were assembled stepwise onto core charged drug nanoparticles. The exterior surface of the nanoshell was functionalized with biocompatible and targeting functional moieties, poly(ethylene glycol) (PEG) and folic acid, respectively. Drug nanoparticles of dexamethasone, taxol, and 5-fluorouracil were fabricated using a modified solvent evaporation technique, producing particles within a range of 314.0 to 154.7 nm. Surface morphology of the encapsulated drug nanoparticles were viewed by TEM and SEM. TEM images indicated that the nanoshell was approximately 5 nm, and composed of two polyelectrolyte layers. Characterization of surface chemistry and charge of the nanoshell required the use of XPS and zeta potential, respectively. XPS data collected for PEG modified drug nanoparticles confirmed that the peak at 286 eV represented the repeat unit in a PEG molecule. Zeta potential results re-confirmed PEG's presence at the surface. Chemisorption of PEG molecules neutralizes the surface of the nanoshell and this was illustrated by the measured neutral zeta potential of the drug particles. Preliminary biocompatibility studies to study phagocytosis of PEG modified drug particles were performed using a flow cytometric assay and suggested that the neutral charge of the nanoshell results in decreased phagocytosis after 24 hours of incubation.

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