Liposomal Encapsulation and Stability of Dideoxyinosine Triphosphate

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Abstract
Dideoxyinosine triphosphate (ddITP) was encapsulated in multilamellar liposomes prepared with various lipid composition. The stability of liposomes in terms of retention of ddITP was measured at 4°, 25° and 37°C. The encapsulation of ddITP was 7.5 times greater in liposomes prepared with dipalmitoylphosphatidylcholine (DPPC) compared to dimyristoylphosphatidyl-choline (DMPC). When equimolar cholesterol (CHOL) was added to DM PC liposomes the encapsulation of ddITP was increased by 4.5 times. The leakage of ddITP was 60% from DMPC liposomes stored at 4° and 25° C after a month and 100% leakage after 16 days when stored at 37° C. The leakage of ddITP from DMPC:CHOL liposomes was only 20% after a month at 4° C, 50% at 25° and 90% at 37° C. These results suggest that the encapsulation of hydrophilic compound such as ddITP can be increased either by increasing the fatty acid chain length (DPPC) or by inclusion of CHOL. However, the optimum encapsulation and retention of ddITP was achieved using DMPC:CHOL liposomes. Retention of ddITP in these liposomes was maximum when stored at 4°c.