title: Magnetic switch of permeability for polyelectrolyte microcapsules embedded with Co@Au nanoparticles.
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 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.
authors.affiliation: Institute for Micromanufacturing, Louisiana Tech University, Ruston, Louisiana, USA.
authors.forename: Zonghuan
authors.initials: Z
authors.lastname: Lu
authors.forename: Malcolm D
authors.initials: MD
authors.lastname: Prouty
authors.forename: Zhanhu
authors.initials: Z
authors.lastname: Guo
authors.forename: Vladimir O
authors.initials: VO
authors.lastname: Golub
authors.forename: Challa S S R
authors.initials: CS
authors.lastname: Kumar
authors.forename: Yuri M
authors.initials: YM
authors.lastname: Lvov
mesh_terms: D002214:Capsules / Q000737:chemistry*; D003035:Cobalt / Q000737:chemistry*; D004573:Electrolytes / Q000737:chemistry*; D016650:Fluorescein-5-isothiocyanate; D006046:Gold / Q000737:chemistry*; D008280:Magnetics; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure; D010539:Permeability; D013057:Spectrum Analysis; D013696:Temperature
chemical_list: D002214:Capsules; D004573:Electrolytes; D003035:Cobalt; D006046:Gold; D016650:Fluorescein-5-isothiocyanate