Here described is a composition comprising a compound of formula I: wherein R1 and R2 is independently selected from a group consisting of C10 to C18 alkyl, C12 to C18 alkenyl, and oleoyl group; R3 and R4 are independently selected from a group consisting of C1 to C6 alkyl, and C2 to C6 alkanol; X is selected from a group consisting of —CH2—, —S—, and —O— or absent; Y is selected from —(CH2)n, —S(CH2)n, —O(CH2)n—, thiophene, —SO2(CH2)n—, and ester; n=1-4; a=1-4; b=1-4; c=1-4; and Z− is a counterion.