Materials for the delivery of biologically-active material to cells

A lipid of general formula (I) or (II):

• wherein
• X1 and X2 are —O—;
• R1 and R2 for formula I are the same or different and are straight or branched, saturated or unsaturated C7 to C24 hydrocarbyl groups which are unsubstituted or substituted by one or more substituents selected from the group consisting of hydroxy, halogen and OR′, wherein R′ is a C1 to C6 hydrocarbyl group and
• R1 and R2 for formula II are the same or different and are straight or branched unsaturated C7 to C24 hydrocarbyl groups or straight or branched saturated C18 to C24 hydrocarbyl groups, which are unsubstituted or substituted by one or more substituents selected from the group consisting of hydroxy, halogen and OR′, wherein R′ is a C1 to C6 hydrocarbyl group;
• R5 is —N+(R3)2—R6;
• R6 is either:
• (a) -[A-Y]nR4 wherein:
• each Y is the same or different and is —N+(R4)2—;
• each A is the same or different and is a C1-20 alkylene group which is unsubstituted or substituted by one or more substituents selected from the group consisting of hydroxy, halogen, —OR′, —C(O)OH, —CN, —NR′R″, and —C(O)R′ wherein R′ and R″ are the same or different and are C1-6 hydrocarbyl;
• and
• n is an integer of from 1 to 10;
• or
• (b) —[B—O]mB-Q wherein:
• each B is the same or different and is a C1-10 alkylene group which is unsubstituted or substituted by one or more substituents selected from the group consisting of hydroxy, halogen, —OR′, —C(O)OH, —CN, —NR′R″ and —C(O)R′ wherein R′ and R″ are the same or different and are C1-6 hydrocarbyl;
• m is an integer of from 1 to 10;
• and
• Q is selected from the group consisting of —N+(R3)3, —OH, —OR′, —OC(O)R′ and halogen, wherein R′ is as defined above;
• and
• each R3 and each R4 is the same or different and is a straight or branched, saturated or unsaturated C1 to C10 hydrocarbyl group which is unsubstituted or substituted by one or more substituents selected from the group consist of hydroxy, halogen, —OR′, —C(O)OH, —CN, —NR′R″, and —C(O)R′ wherein R′ and R″ are the same or different and are C1 to C6 hydrocarbyl.