The aim of the present study was to study the efficiency of different techniques used\nfor nanosizing liposomes. Further, the aim was also to evaluate the effect of process parameters\nof extrusion techniques used for nanosizing liposomes on the size and size distribution of the\nresultant liposomes. To compare the efficiency of different nanosizing techniques, the following\ntechniques were used to nanosize the liposomes: extrusion, ultrasonication, freeze-thaw sonication\n(FTS), sonication and homogenization. The extrusion technique was found to be the most efficient,\nfollowed by FTS, ultrasonication, sonication and homogenization. The extruder used in the present\nstudy was fabricated using readily available and relatively inexpensive apparatus. Process parameters\nwere varied in extrusion technique to study their effect on the size and size distribution of extruded\nliposomes. The results obtained indicated that increase in the flow rate of the extrusion process\ndecreased the size of extruded liposomes however the size homogeneity was negatively impacted.\nFurthermore, the liposome size and distribution was found to decline with decreasing membrane\npore size. It was found that by extruding through a filter with a pore size of 0.2 �¼m and above,\nthe liposomes produced were smaller than the pore size, whereas, when they were extruded\nthrough a filter with a pore size of less than 0.2 �¼m the resultant liposomes were slightly bigger\nthan the nominal pore size. Besides that, increment of extrusion temperature above transition\ntemperature of the pro-liposome had no effect on the size and size distribution of the extruded\nliposomes. In conclusion, the extrusion technique was reproducible and effective among all the\nmethods evaluated. Furthermore, processing parameters used in extrusion technique would affect\nthe size and size distribution of liposomes. Therefore, the process parameters need to be optimized to\nobtain a desirable size range and homogeneity, reproducible for various in vivo applications.
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