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KMID : 0369820040340050369
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Jorunal of Korean Pharmaceutical Sciences
2004 Volume.34 No. 5 p.369 ~ p.377
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Patterns of Protein Leaching to Dispersion Medium during W/O/W Double Emulsion-Based Microencapsulation Processes
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조미현/Cho MH
최수경/사홍기/Choi SK/Sah HK
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Abstract
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The objective of this study was to investigate the patterns of protein leaching to an external phase during an ethyl acetate-based, double emulsion microencapsulation process. An aqueous protein solution (lactoglobulin, lysozyme, or ribonuclease; W₁) was emulsified in ethyl acetate containing poly-d,l-lactide-co-glycolide 75:25. The W₁/O emulsion was transferred to a 0.5% polyvinyl alcohol solution saturated with ethyl acetate (W₂). After the double emulsion was stirred for 5, 15, 30, or 45 min, additional 0.5% polyvinyl alcohol (W₂) was quickly added into the emulsion. This so-called quenching step helped convert emulsion microdroplets into microspheres. After 2-hr stirring, microspheres were collected and dried. The degree of protein leaching to W₂ and/or W₃ phase was monitored during the microencapsulation process. In a separate, comparative experiment, the profile of protein leaching to an external phase was investigated during the conventional methylene chloride-based microencapsulation process. When ethyl acetate was used as a dispersed solvent, proteins continued diffusing to the W₂ phase, as stirring went on. Therefore, the timing of ethyl acetate quenching played an important role in determining the degree of protein microencapsulation efficiency. For example, when quenching was peformed after 5-min stirring of the primary W₁/O emulsion, the encapsulation efficiencies of lactoglobulin and ribonuclease were 55.1 ± 4.2 and 45.3 ± 7.6%, respectively. In contrast, when quenching was carried out in 45 min, their respective encapsulation efficiencies were 39.6 ± 3.2 and 29.9 ± 11.2%. By sharp contrast, different results were attained with the methylene-chloride based process: up to 2 hr-stirring of the primary and double emulsions, less than 5% of a protein appeared in W₂. Afterwards, it started to partition from W₁ to W₂/W₃, and such a tendency was affected by the amount of PLGA75:25 used to make microspheres. Different solvent properties (e.g., water miscibility) and their effect on microsphere hardening were to be held answerable for such marked differences observed with the two microencapsulation processes.
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KEYWORD
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Poy(d,l-lactide-co-glycolide), Microspheres, Protein delvery, Ethyl acetate, Microencapsulation
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