Here described are compounds of formula I: wherein R 1 and R 2 is independently selected from a group consisting of C 10 to C 18 alkyl, C 12 to C 18 alkenyl, and oleyl group； wherein R 3 and R 4 are independently selected from a group consisting of C 1 to C 6 alkyl, and C 2 to C 6 alkanol； wherein X is selected from a group consisting of -CH 2 -, -S-, and -O- or absent； wherein Y is selected from -(CH 2 ) n , -S(CH 2 ) n , - O(CH 2 ) n -, thiophene, -SO 2 (CH 2 ) n -, and ester, wherein n = 1-4； wherein a = 1-4； wherein b=1-4； wherein c=1-4； and wherein Z is a counterion； and compounds consisting of the structure (targeting molecule) m -linker-(targeting molecule) n , wherein the targeting molecule is a retinoid or a fat soluble vitamin having a specific receptor on the target cell； wherein m and n are independently 0, 1, 2 or 3； and wherein the linker comprises a polyethylene glycol (PEG) or PEG-like molecule, as well as compositions and pharmaceutical formulations including one or both of these compounds which are useful for the delivery of therapeutic agents； and methods of using these compositions and pharmaceutical formulations.
