STABILITY STUDIES OF LIPOSOMES AS A FUNCTION OF LIPID COMPOSITION, LIPOSOMAL TYPE, SURFACE CHARGE AND STORAGE CONDITIONS | ||||
| Zagazig Journal of Pharmaceutical Sciences | ||||
| Article 7, Volume 5, Issue 2, December 1996, Page 41-48 PDF (3.31 MB) | ||||
| Document Type: Original Article | ||||
| DOI: 10.21608/zjps.1996.185014 | ||||
 View on SCiNiTO | ||||
| Author | ||||
Samir Abu-Zaid 
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| Department of Pharmaceutics and Industrial Pharmacy, Faculty of Pharmacy, Zagazig University Egypt. | ||||
| Abstract | ||||
| The effect of lipid composition, liposomal type, surface charge and storage conditions (time and temperature) on their stability was studied. The time course of lipid peroxidation for different liposomal formulations was chemically followed, during different storage conditions, using the thiobarbituric acid assay. Multilamellar and small unilamellar liposomes were prepared from egg lecithin and varying amounts of cholesterol with or without a charge inducing agent. Dicetyl phosphate or stearylamine was used to impart either a negative or a positive surface charge to liposomes. The results showed that, incorporation of cholesterol into the liposomal bilayer structure, generally, reduced the rate of lipid peroxidation and adjusting its content to 33 mole% could provide an appropriate molar ratio for maximum stability of liposomal system. Also, comparing between the two liposomal types of the same charge and storage conditions, small unilamellar liposomes showed significantly higher peroxidation values than multilamellar type Regarding the liposomal surface charge, negatively charged liposomes showed the lowest peroxidation values and neutral liposomes showed the highest values, as compared to others of the same type and storage conditions. Thus, inclusion of charged lipid results in an structral stabilizing effect, which could be attributed to the steric barrier on the liposomal surface presented by this charge. In addition, concerning the effect of storage temperature on lipid peroxidation, liposomes showed higher stability when stored at low temperature than when stored at high temperature. Finally, for choosing the proper storage conditions to optimize liposomal stability freeze-dried and freeze-thawed liposomes were prepared and compared with untreated liposomes. Freeze-dried negatively charged multilamellar liposomes could provide an optimal storage condition for maintaining liposomal stability. In conclusion, it should be stressed that lipsomal lipid composition, type, surface charge and storage conditions can be modified in a variety of ways, and so can potentially be tailored to satisfy the needs of the formulation for solving the stability problems of liposomes. | ||||
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