Engineering the surface properties of microbubbles for biomedical applications

<p>Surfactant coated microbubbles are widely used as contrast agents (UCA) in medical ultrasound imaging, due to their high echogenicity and non-linear response to acoustic excitation. Controlling the stability of microbubbles in vivo represents a considerable challenge. Understanding the char...

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Main Author: Mohamedi, G
Other Authors: Stride, E
Format: Thesis
Language:English
Published: 2014
Subjects:
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author Mohamedi, G
author2 Stride, E
author_facet Stride, E
Mohamedi, G
author_sort Mohamedi, G
collection OXFORD
description <p>Surfactant coated microbubbles are widely used as contrast agents (UCA) in medical ultrasound imaging, due to their high echogenicity and non-linear response to acoustic excitation. Controlling the stability of microbubbles in vivo represents a considerable challenge. Understanding the characteristics of the bubble surface and how they change with production method, composition and environment is key to addressing this problem. The aim of this thesis is to investigate viscosity, bubble dissolution, and acoustic response as functions of their composition, manufacturing method and environment.</p> <p>Bubbles were made using combinations of phospholipid and an emulsifier in different molar ratios. Adding the emulsifier decreased both the size and the surface viscosity of the bubbles and caused changes in the scattered pressure amplitude of bubbles under ultrasound.</p> <p>To increase microbubble stability, solid inorganic nanoparticles were adsorbed on to the microbubble surface. These particles behaved as Pickering stabilisers, and deterred Ostwald ripening. The nanoparticles also enhanced the nonlinear behaviour of bubbles at low acoustic pressures.</p> <p>Three manufacturing methods (sonication, cross-flow and flow focusing) were investigated in order to verify stability differences. Sonication produced bubbles with surface viscosities hundreds of centipoise greater than those produced by microfluidics. Both pressure amplitude and harmonic content for sonicated bubbles were found to be much larger due to a higher liposomal adhesion rate at the surface.</p> <p>Solution temperature and bubble age were also investigated. When the solutions were heated above the phospholipid gelling temperature, microfluidic bubbles showed an increased surface viscosity, due to increased liposome adhesion caused by the increased temperature.</p> <p>Bubble composition, manufacturing method and environment were found to vary the surface characteristics of the microbubbles. Further investigations into the affects of the filling gas, <em>in vitro</em> studies, and low temperature TEM characterisation should be conducted to produce a microbubble with the full range of desired characteristics.</p>
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spelling oxford-uuid:e68f2010-19b6-45af-b238-da8e2d29b2702022-03-27T10:32:03ZEngineering the surface properties of microbubbles for biomedical applicationsThesishttp://purl.org/coar/resource_type/c_db06uuid:e68f2010-19b6-45af-b238-da8e2d29b270FoamingInterfacial fenomenaAdvanced materialsSurfacesEnglishOxford University Research Archive - Valet2014Mohamedi, GStride, E<p>Surfactant coated microbubbles are widely used as contrast agents (UCA) in medical ultrasound imaging, due to their high echogenicity and non-linear response to acoustic excitation. Controlling the stability of microbubbles in vivo represents a considerable challenge. Understanding the characteristics of the bubble surface and how they change with production method, composition and environment is key to addressing this problem. The aim of this thesis is to investigate viscosity, bubble dissolution, and acoustic response as functions of their composition, manufacturing method and environment.</p> <p>Bubbles were made using combinations of phospholipid and an emulsifier in different molar ratios. Adding the emulsifier decreased both the size and the surface viscosity of the bubbles and caused changes in the scattered pressure amplitude of bubbles under ultrasound.</p> <p>To increase microbubble stability, solid inorganic nanoparticles were adsorbed on to the microbubble surface. These particles behaved as Pickering stabilisers, and deterred Ostwald ripening. The nanoparticles also enhanced the nonlinear behaviour of bubbles at low acoustic pressures.</p> <p>Three manufacturing methods (sonication, cross-flow and flow focusing) were investigated in order to verify stability differences. Sonication produced bubbles with surface viscosities hundreds of centipoise greater than those produced by microfluidics. Both pressure amplitude and harmonic content for sonicated bubbles were found to be much larger due to a higher liposomal adhesion rate at the surface.</p> <p>Solution temperature and bubble age were also investigated. When the solutions were heated above the phospholipid gelling temperature, microfluidic bubbles showed an increased surface viscosity, due to increased liposome adhesion caused by the increased temperature.</p> <p>Bubble composition, manufacturing method and environment were found to vary the surface characteristics of the microbubbles. Further investigations into the affects of the filling gas, <em>in vitro</em> studies, and low temperature TEM characterisation should be conducted to produce a microbubble with the full range of desired characteristics.</p>
spellingShingle Foaming
Interfacial fenomena
Advanced materials
Surfaces
Mohamedi, G
Engineering the surface properties of microbubbles for biomedical applications
title Engineering the surface properties of microbubbles for biomedical applications
title_full Engineering the surface properties of microbubbles for biomedical applications
title_fullStr Engineering the surface properties of microbubbles for biomedical applications
title_full_unstemmed Engineering the surface properties of microbubbles for biomedical applications
title_short Engineering the surface properties of microbubbles for biomedical applications
title_sort engineering the surface properties of microbubbles for biomedical applications
topic Foaming
Interfacial fenomena
Advanced materials
Surfaces
work_keys_str_mv AT mohamedig engineeringthesurfacepropertiesofmicrobubblesforbiomedicalapplications