Abstract
Magnetic particles have been evaluated for their biomedical applications as a drug delivery system to treat asthma and other lung diseases. In this study, ferromagnetic barium hexaferrite (BaFeO) and iron oxide (FeO) particles were suspended in water or glycerol, as glycerol can be 1000 times more viscous than water. The particle concentration was 2.50 mg/mL for BaFeO particle clusters and 1.00 mg/mL for FeO particle clusters. The magnetic particle cluster cross-sectional area ranged from 15 to 1000 m, and the particle cluster diameter ranged from 5 to 45 m. The magnetic particle clusters were exposed to oscillating or rotating magnetic fields and imaged with an optical microscope. The oscillation frequency of the applied magnetic fields, which was created by homemade wire spools inserted into an optical microscope, ranged from 10 to 180 Hz. The magnetic field magnitudes varied from 0.25 to 9 mT. The minimum magnetic field required for particle cluster rotation or oscillation in glycerol was experimentally measured at different frequencies. The results are in qualitative agreement with a simplified model for single-domain magnetic particles, with an average deviation from the model of 1.7 ± 1.3. The observed difference may be accounted for by the fact that our simplified model does not include effects on particle cluster motion caused by randomly oriented domains in multi-domain magnetic particle clusters, irregular particle cluster size, or magnetic anisotropy, among other effects.
Highlights
Excessive mucus production is a significant cause of airway obstruction and mortality in over 24 million US asthma patients [1]
We showed that the experimentally measured minimum magnetic field needed to oscillate or rotate multi-domain magnetic BaFe12O19 and Fe3O4 particle clusters in glycerol at a given driving frequency was within a factor of five when compared to the predictions of a simplified model for single-domain magnetic particles (given in Equation (3))
We showed that the simplified model given in Equation (3) can estimate the minimum required magnetic field to rotate/oscillate magnetic particle clusters of diameters ranging from 5 to 45 μm in viscous fluids with viscosities up to 1.4 Pa·s within less than an order of magnitude
Summary
Excessive mucus production is a significant cause of airway obstruction and mortality in over 24 million US asthma patients [1]. There are existing drugs that limit excessive mucus production, there is no cure for excessive mucus production in asthma and other chronic lung diseases. This is likely due to the complex mucus structure that forms a physical barrier, preventing drugs from reaching the diseased airway mucosa (epithelium) [2,3,4]. Barium hexaferrite nanoparticles coated with an antiinflammatory drug were pulled by external magnetic forces through the mucosal barrier [6]. These experiments showed that barium hexaferrite nanoparticles can penetrate a ∼100 μm thick mucus layer in a static magnetic field gradient of 360 T/m. The work presented here investigates the magnetic field requirements for particle rotation at given frequencies and fluid viscosities
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