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Research Article

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

Zonghuan Lu,^† Malcolm D. Prouty,^† Zhanhu Guo,^‡ Vladimir O. Golub,^§ Challa S. S. R. Kumar,*^‡ and Yuri M. Lvov*^†

Institute for Micromanufacturing, Louisiana Tech University, Ruston, Louisiana; Center for Advanced Microstructures & Devices, Louisiana State University, Baton Rouge, Louisiana; and Institute of Magnetism, National Academy of Sciences of Ukraine, Kiev, Ukraine

Langmuir, 2005, 21 (5), pp 2042–2050

DOI: 10.1021/la047629q

Publication Date (Web): January 26, 2005

†

Louisiana Tech University.

‡

Louisiana State University.

National Academy of Sciences of Ukraine.

In papers with more than one author, the asterisk indicates the name of the author to whom inquiries about the paper should be addressed.

Abstract

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 μm 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.

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