Magnetic Switch of Permeability for Polyelectrolyte Microcapsules Embedded with Co@Au Nanoparticles

• DOI: 10.1021/la047629q
• Publication Date: 2005-02-22T05:42:09Z
• Authors: Zonghuan Lu; Malcolm D. Prouty; Zhanhu Guo; Vladimir O. Golub; Challa S. S. R. K...; Yuri M. Lvov
• Keywords: Spectrum Analysis; Temperature; Capsules; Cobalt; 02 engineering and technology; Permeability; Nanostructures; Electrolytes; Magnetics; Microscopy, Electron, Transmission; Microscopy, Electron, Scanning; Gold; 0210 nano-technology; Fluorescein-5-isothiocyanate

We explored using a magnetic field to modulate the permeability of polyelectrolyte microcapsules prepared by layer-by-layer self-assembly. Ferromagnetic gold-coated cobalt (Co@Au) nanoparticles (3 nm diameter) were embedded inside the capsule walls. The final 5 mum diameter microcapsules had wall structures consisting of 4 bilayers of poly(sodium styrene sulfonate)/poly(allylamine hydrochloride) (PSS/PAH), 1 layer of Co@Au, and 5 bilayers of PSS/PAH. External alternating magnetic fields of 100-300 Hz and 1200 Oe were applied to rotate the embedded Co@Au nanoparticles, which subsequently disturbed and distorted the capsule wall and drastically increased its permeability to macromolecules like FITC-labeled dextran. The capsule permeability change was estimated by taking the capsule interior and exterior fluorescent intensity ratio using confocal laser scanning microscopy. Capsules with 1 layer of Co@Au nanoparticles and 10 polyelectrolyte bilayers are optimal for magnetically controlling permeability. A theoretical explanation was proposed for the permeability control mechanisms. "Switching on" of these microcapsules using a magnetic field makes this method a good candidate for controlled drug delivery in biomedical applications.