Theoretical consideration behind liposome formation by broad spectrum of methods.There is a lot in common(current status) 8 MLV 米 H88 e DI参8 IPATION OF能N月信￥ ⑤ 言 w2988 LUV pid re ao dire from pre using templ Functional Classification of Liposomes(1) Liposome Plasma clearance Plasma clearance for type Main features for large liposomes small liposomes High accessibility to interact with factors from extraliposomal medium Medium(tk~>1h)） Conventional (ie., opsonins,enzymes,low Fast (t.<30 min) liposomes molecular mass agents).high RES Saturation dependent Saturation dependent uptake.For um size range,high lung Extravasation is feasible uptake Slow (t%>8h) Sterically Low accessibility to extraliposomal Slow (t >5 h) Saturation independent stabilized factors due to grafted steric barrier. Saturation liposomes low RES uptake independent Extravasation into tumors and sites of inflammation Vesicular to non vasicular transition upon contact with agent or medium components:(a)cationic liposomes- nucleic acid interaction induce lipoplex Actisomes formation.The lipoplexes when Very fast(t min exemplified injected i.v.accumulate in the lung range)Saturation Fast(t.-min range) by: where maximum transfection occurs. dependent Saturation dependent (b)pH sensitive liposomes,which fuse and release their content as a result of exposure to acidic pH(Drummond et al.2000). Based on Barenholz,1998.6 Theoretical consideration behind liposome formation by broad spectrum of methods. There is a lot in common (current status) Functional Classification of Liposomes (1) Plasma clearance for small liposomes Plasma clearance for large liposomes Main features Liposome type Medium (t½ ~> 1h) Saturation dependent Extravasation is feasible Fast (t½ < 30 min) Saturation dependent High accessibility to interact with factors from extraliposomal medium (i.e., opsonins, enzymes, low molecular mass agents), high RES uptake. For µm size range, high lung uptake Conventional liposomes Slow (t½ > 8 h) Saturation independent Extravasation into tumors and sites of inflammation Slow (t½ >5 h) Saturation independent Low accessibility to extraliposomal factors due to grafted steric barrier, low RES uptake Sterically stabilized liposomes Fast (t½-min range) Saturation dependent Very fast (t½~ min range) Saturation dependent Vesicular to non vasicular transition upon contact with agent or medium components: (a) cationic liposomes– nucleic acid interaction induce lipoplex formation. The lipoplexes when injected i.v. accumulate in the lung where maximum transfection occurs; (b) pH sensitive liposomes, which fuse and release their content as a result of exposure to acidic pH (Drummond et al., 2000). Actisomes exemplified by: aBased on Barenholz, 1998