Preparation and characterization of perfluorocarbon emulsions for biomedical applications.
Item
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Title
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Preparation and characterization of perfluorocarbon emulsions for biomedical applications.
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Identifier
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AAI9417469
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identifier
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9417469
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Creator
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Habif, Stephane Samuel.
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Contributor
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Adviser: Henri L. Rosano
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Date
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1994
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Language
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English
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Publisher
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City University of New York.
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Subject
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Chemistry, Physical | Engineering, Biomedical
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Abstract
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Considerable interest in perflubron (perfluorooctylbromide, PFOB) emulsions has arisen from their numerous potential biomedical applications, such as imaging solutions and oxygen-carrying solutions, i.e., red blood cell substitutes. The objective of the present research was to determine the factors involved in the stability of PFOB/saline emulsions with egg yolk phospholipids (EYP) as emulsifiers. Experimentation yielded an optimal emulsion preparation method based on high pressure homogenization (microfluidization), in which the phospholipids are first dispersed in the aqueous phase as vesicles at a temperature above their phase transition temperature. The vesicles are then broken down by high mechanical stress, resulting in the monomolecular adsorption of the emulsifier at the PFOB/saline interface. The emulsion obtained consists of both PFOB droplets (250 nm in diameter) encapsulated in a phospholipid monolayer, and PFOB-free phospholipid vesicles (80 nm in diameter). Since EYP has a complex and variable composition and is very sensitive to oxidation, either decaglyceroldioleate (10-2-O) or phospholipon 90H (PL), a hydrogenated phospholipid, was substituted for EYP in simpler model systems used in subsequent investigations. Phospholipids and 10-2-O are virtually insoluble in both PFOB and saline, but if by the application of a large amount of mechanical work, for example through microfluidization, they can be made to adsorb monomolecularly at the o/w interface, they will reduce the interfacial free energy and provide a film capable of keeping its ordered structure under high stress and high temperature conditions. This in turn yields an emulsion capable of withstanding heat sterilization. But PL and 10-2-O provide no electrostatic charge at the droplet surface, and yield flocculated PFOB/saline emulsions but stable PFOB/saccharide solution emulsions. Furthermore, studies of PFOB/saline emulsions using a combination of PL and a charged surfactant showed that a negatively-charged interface results in a stable system while a positively-charged interface--with the same zeta-potential amplitude--results in flocculation. We may infer that EYP systems are probably stabilized against flocculation by a combination of both electrostatic and hydration forces due to the presence of minor components in the EYP mixture, which provide a negative charge and a strong hydration shell around the emulsion droplets.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
