EFFECT OF ADDITIVES ON DISSOLUTION AND SWELLING OF SOYBEAN LECITHIN MICROCAPSULES PREPARED USING THE WURSTER PROCESS

Microcapsules whose membranes contained soybean lecithin (SL), cholest erol (CH), stearic acid (SA) and polyvinylpyrrolidone (PVP) at various compositions were prepared, Then, dissolution and swelling behaviors of the microcapsules in a 0.9% saline solution were studied to be rela ted to the phase diagram of three components containing 42% of PVP in anhydrous state, In the aqueous solution, when an anhydrous microcapsu le membrane was composed of SL not saturated with both CH and SA, the microcapsules showed rapid release of carbazochrome sodium sulfonate ( CCSS, a model drug), poor particle-swelling and spouting of droplets c ontaining CCSS. Long-delayed release of CCSS and drastic particle-smel ling with no spouting of droplets were observed when the anhydrous mem brane was composed of SL saturated with both CH and SA and the composi tion was not close to the two-component Line, CH-SA, or to the saturat ion line, The spouting of droplets would be attributable to the CH and /or SA-poor SL phase and to the SL phase which dissolved CH and SA, bu t contained either CH or SA only in a small amount, and the delayed re lease would be due to the CH and SA-rich SL phase dissolving a great a mount of CH and SA formed by hydration, The degree of release suppress ion and particle-swelling depended on the SL content, At 20-45% of SL content, the prolonged-release, great particle-swelling and no spoutin g of droplets at the early stage were observed only when the CH and SA -rich SL phase formed by hydration contained a high content of CH and SA.