title: Understanding the structure and mechanism of formation of a new magnetic microbubble formulation.
abstract: Magnetic nanoparticles and ultrasound contrast agents have both been used as vehicles for therapeutic delivery. More recently, magnetic microbubbles have been developed as a new theranostic agent which combines the advantages of the individual carriers and overcomes many of their limitations. In a previous study of gene delivery using magnetic microbubbles, it was found that a combination of magnetic liquid droplets and non-magnetic phospholipid microbubbles produced higher transfection rates than magnetic microbubbles. The reasons for this were not fully understood, however. The aim of this study was to investigate the hypothesis that conjugation between the droplets and the microbubbles occurred. A combination of optical and fluorescence microscopy and ultrasound imaging studies in a flow phantom were performed. No interaction between magnetic droplets and microbubbles was observed under optical microscopy but the results from the fluorescence and acoustic imaging indicated that magnetic droplets and microbubbles do indeed combine to form a new magnetically and acoustically responsive particle. Theoretical calculations indicate that the driving force of the interaction is the relative surface energy and thus thermodynamic stability of the microbubbles and the droplets. The new particles were resistant to centrifugation, of comparable echogenicity to conventional ultrasound contrast agents and could be retained by a magnetic field (0.2T) in a flow phantom at centre line velocities of ~6 cm s(-1) and shear rates of ~60 s( -1).
authors: Institute of Biomedical Engineering, Department of Engineering Science, University of Oxford, UK.
authors: Joshua
authors: J
authors: Owen
authors: Bin
authors: B
authors: Zhou
authors: Paul
authors: P
authors: Rademeyer
authors: Meng-Xing
authors: MX
authors: Tang
authors: Quentin
authors: Q
authors: Pankhurst
authors: Robert
authors: R
authors: Eckersley
authors: Eleanor
authors: E
authors: Stride
mesh_terms: D060328:Magnetic Phenomena; D045423:Microbubbles; D008856:Microscopy, Fluorescence; D055620:Optical Phenomena; D019047:Phantoms, Imaging; D012212:Rheology; D014465:Ultrasonics
keywords: Microbubbles; magnetic nanoparticles; therapeutic ultrasound
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