Induction of Instability in Water-in-Oil-in-Water Double Emulsions by Freeze−Thaw Cycling

Individual water-in-oil-in-water (W1/O/W2) double-emulsion globules loaded with fluorescently labeled bovine serum albumin (FITC-BSA) were optically monitored within cylindrical capillaries during freeze−thaw cycling. Coalescence of internal aqueous droplets (W1) and external aqueous phase (W2), ter...

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Bibliographic Details
Published in:Langmuir 2007-06, Vol.23 (13), p.6911-6917
Main Authors: Rojas, Edith C, Papadopoulos, Kyriakos D
Format: Article
Language:English
Subjects:
Alkanes - chemistry
Animals
Cattle
Chemistry
Colloidal state and disperse state
Emulsions
Emulsions. Microemulsions. Foams
Exact sciences and technology
Fluorescein-5-isothiocyanate - chemistry
Freezing
General and physical chemistry
Oils - chemistry
Phase Transition
Serum Albumin, Bovine - chemistry
Surface physical chemistry
Water - chemistry
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Summary:Individual water-in-oil-in-water (W1/O/W2) double-emulsion globules loaded with fluorescently labeled bovine serum albumin (FITC-BSA) were optically monitored within cylindrical capillaries during freeze−thaw cycling. Coalescence of internal aqueous droplets (W1) and external aqueous phase (W2), termed external coalescence, was not observed before or during freezing of the oil phase (O). On the other hand, this instability mechanism was readily promoted during thawing. This realization confirms the previously suggested potential of W1/O/W2 double emulsions to trigger release upon oil thawing1 and demonstrates that it is a direct result of globule breakage through external coalescence. The presented results also identified a threshold in the relative W1 droplet size above which instability occurred, while smaller droplets remained unperturbed and therefore indicate that optimization of the delivery can be achieved by tuning the size of W1 droplets. In addition, we propose a possible explanation for the occurrence of instability during oil thawing and its dependence on the size of W1 droplets. Because this alternative globule-breakage mechanism simply uses temperature increase (solid-to-liquid-phase transition) as external stimulus, W1/O/W2 double-emulsion delivery systems can be easily tailored by choosing an oil phase with the appropriate phase-transition temperature.
ISSN:0743-7463
1520-5827
DOI:10.1021/la063533f