Influence of cholesterol on liposome stability and on in vitro drug release

Cholesterol plays a strategic role in liposome composition, however the quantity used to achieve an appropriate formulation has not been yet clarified. Therefore, by screening arrange of lipids and cholesterol ratio, the main aim of this study is to investigate the most suitable amount of cholesterol in lipids in order to prepare stable and controlled drug release vehicles. For the preparation of liposomes, DMPC, DPPC and DSPC phospholipids were used and combined with different molar ratios of cholesterol (e.g. 100%, 80-20%, 70-30%, 60-40%, 50-50%). Stability studies were conducted storing the formulations at 37oC and 50oC for 30 days and by analysing them by AFM, DLS and FT-IR. By detecting the two most stable formulations from the stability results, drug encapsulation and in vitro release studies in PBS were performed by encapsulating Atenolol and Quinine. The release results were validated using a simulation model to ensure the reliability and suitable interpretation of the data. The generated model showed a good correlation between the prediction and the in vitro obtained
results. By using 70:30% ratio (known in literature as 2:1), is possible to reach the most stable formulation to guarantee a controlled and reproducible release for drugs with different physicochemical characteristics and pharmaceutical applications.