Structural studies on stabilized microbubbles: development of a novel contrast agent for diagnostic ultrasound

Wheatley, Margaret A.; Singhal, Sarita

doi:10.1016/0923-1137(94)00039-8

Cited by 40 publications

(25 citation statements)

References 10 publications

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“…Results from these experiments suggested that generation of stable microbubbles is possible only by using a mixture of a water-soluble and a non-soluble surfactant such as Tween and Span. This is consistent with the results previously reported by others (e.g., Wheatley et al, 1995). The combination of soluble and non-soluble surfactants stabilizes the microbubbles by forming a solid-condensed monolayer at the gas-water interface.…”

Section: Microbubble Generatorsupporting

confidence: 93%

Sorption of Colloids, Organics, and Metals onto Gas-Water Interfaces: Transport Processes and Potential Remediation Technology

Wan

1999

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Project EXECUTIVE SUMMARYThe knowledge gap on vadose zone colloid transport limits predicting contaminant transport at many DOE sites, and remains an outstanding scientific challenge. Although the process of contaminant sorption at mineral surfaces has received much recognition as a major mechanism controlling contaminant behavior in subsurface environments, virtually little attention has been given to the possibility of contaminant sorption at gaswater interfaces, a major interface in the vadose zone. Moreover, little effort has yet been advanced to optimize such interactions for the purpose of facilitating in-situ remediation. Gas-water interfaces, unlike water-solid interfaces, are mobile. Therefore, associations of contaminants with gas-water interfaces can be very important not only in subsurface contaminant distributions, but also in contaminant mobilization, and potentially in remediation.The first objective of this project was to develop a fundamental understanding of interactions between contaminants and gas-water interfaces.For surface-active molecules, surface excesses can be determined through the Gibbs equation combined with measuring changes in surface tension with respect to changes in their solution concentration. However, for surface-active colloids, surface tension changes are too small to measure. Until initiation of this research project, there were no techniques available for quantifying sorption of colloids at gas-water interfaces. The second purpose of the proposed research, based on improved understanding gained in the first phase studies, was to develop a sorptive microbubble remediation technique, using surfactant stabilized microbubbles (fine gas-bubbles, 1-15 µm in diameters) for subsurface in-situ remediation.. In the saturated zone, both pump-and-treat, and air sparging remediation methods are ineffective at displacing contaminants in zones that are "advectively inaccessible". Stable microbubbles might be able to migrate beyond preferential flow pathways through buoyant rise. Oxygen and nutrient delivery for promoting aerobic degradation of organic contaminants, and surfactant delivery for emulsifying NAPLs are potential benefits of microbubble injection.The work on colloid partitioning at air-water interfaces resulted in the development of the first technique for quantifying this process. With this new ability to measure colloid surface excesses at air-water interfaces, quantitative analyses of a wide variety of environmental colloid processes become possible (Figure 1). Implications of these types of measurements are especially relevant in the vadose zone because this portion of the environment can have high values of air-water interfacial area per unit bulk volume. Due to the common existence of thin water films in the vadose zone, the distribution of surface-active colloids between bulk water and the air-water interface can become significant. The calculated values of colloid distribution at the air-water interface relative to bulk water ranged from about 1 up to 20 for a wide r...

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Section: Microbubble Generatorsupporting

confidence: 93%

Sorption of Colloids, Organics, and Metals onto Gas-Water Interfaces: Transport Processes and Potential Remediation Technology

Wan

1999

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“…ST68 was manufactured using a method developed in our laboratory (Wheatley et al 1994; Wheatley and Singhal 1995; Wheatley et. al 2006).…”

Section: Methodsmentioning

confidence: 99%

Preserving enhancement in freeze-dried contrast agent ST68: Examination of excipients

Solis

Forsberg

Wheatley

2010

International Journal of Pharmaceutics

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The perfluorcarbon (perfluorobutane) ultrasound contrast agent ST68, composed of sonicated mixtures of non-ionic surfactants, is stable in solution for only a few weeks at 4°C. Freeze-drying critically diminished ST68’s ability to reflect ultrasound (its echogenicity). A method of incorporating specific lyoprotectants before lyophilization was investigated. Reintroduction of perfluorobutane to the protected freeze-dried sample, followed by reconstituting with preserved echogenicity. Glucose, trehalose, sucrose, and mannitol were tested at 100 mM and in vitro echogenicity data was collected from samples with dose concentrations of 50 µl/l to 300 µl/l. Glucose was found to be the best lyoprotectant providing an average (n=3) maximum peak enhancement of 23.2 ± 1.2 dB in vitro, measured at 5 MHz, 684 kPa, and a pulse repetition frequency (PRF) of 100 Hz (p<0.05 over freeze-dried ST68 control) and 20.8 ± 0.8 dB in vivo in New Zealand white rabbits at 5 MHz and a PRF of 6.7 kHz. Pulse inversion harmonic US images of a rabbit kidney, pre- and post-contrast injection (0.1 ml/kg), showed excellent enhancement and clear vascular delineation, similar to that of the original agent. For the first time this contrast agent can be successfully freeze-dried yielding a longer self-life without the need for refrigeration.

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“…Surfactant encapsulated microbubble has been reported by several researches to act as contrast agents [10][11][12]. Like other encapsulated microbubbles, the nonlinear response of such encapsulated microbubble in an acoustic field is strongly influenced by the shell viscoelastic properties that are determined by the shell composition and thickness.…”

Section: Introductionmentioning

confidence: 99%

Optimal design and experimental investigation of surfactant encapsulated microbubbles

et al. 2006

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Structural studies on stabilized microbubbles: development of a novel contrast agent for diagnostic ultrasound

Cited by 40 publications

References 10 publications

Sorption of Colloids, Organics, and Metals onto Gas-Water Interfaces: Transport Processes and Potential Remediation Technology

Sorption of Colloids, Organics, and Metals onto Gas-Water Interfaces: Transport Processes and Potential Remediation Technology

Preserving enhancement in freeze-dried contrast agent ST68: Examination of excipients

Optimal design and experimental investigation of surfactant encapsulated microbubbles

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