Ethanol treatment a Non-extrusion method for asymmetric liposome size optimization

Background: siRNA is a new tool for treatment of diseases such as cancer. However, it cannot be used directly due to rapid degradation in body fluid and blood stream; therefore, vectors are necessary for protection of siRNA against RNases and also for its precise delivery to the target cells. Since viral vector causes cancer and immune response in the host, liposomes are more preferable vectors. Liposome size is an important factor for longer circulation time. Extrusion minimizes the liposome size; however, it leads to less liposome encapsulation. Moreover, it changes structure of asymmetric liposomes. Findings: Here, ethanol treatment is introduced as a method of liposome size optimization that significantly decreases the liposome size without any effect on liposome encapsulation and its asymmetric structure formulation. For this, after liposome formation while there is some ether in solution, ethanol was added to fresh liposomes (25 and 30 percent of total liposomes volume) and liposomes were incubated at room temperature with mild agitation for 20 minutes. Finally, the extra ethanol and ether were removed by dialysis. Conclusion: Utilizing this method the liposome size was successfully decreased about 100 nm. The size of optimized liposomes (200 nm) is quite suitable for in vivo target delivery.