SYNTHESIS AND CHARACTERIZATION OF LONG-CHAIN ALKYL ACYL CARNITINE ESTERS - POTENTIALLY BIODEGRADABLE CATIONIC LIPIDS FOR USE IN GENE DELIVERY

A series of alkyl acyl carnitine eaters (alkyl 3-acyloxy-4-trimethylam monium butyrate chloride) were synthesized as potential biocompatible cationic lipids for use in gene transfer. The physicochemical properti es of the lipids, :liposomes prepared from them, and their complexes w ith DNA were characterized by differential scanning calorimetry (DSC), particle size, zeta potential, and surface monolayer measurements. Th e transition temperatures and behavior at an air-water interface for t his series are similar to phosphatidylcholines with the same hydrocarb on chain length. The physical properties of the L derivatives were not significantly different from the DL derivatives. At 70 degrees C, the acyl chains were readily hydrolyzed at pH 7. The influence of the ali phatic chain length (n = 12-18) on transfection efficiency in vitro wa s determined using cationic liposomes prepared from these lipids or th eir mixtures with the helper lipids, dioleoylphosphatidyl ethanolamine (DOPE), dioleoylphosphatidylcholine, monooleoylglycerol, and choleste rol (Chol). The mixture of myristyl 3-myristoyloxy-4-trimethylammonium butyrate chloride (MMCE, 4d) with DOPE at a 1:1 molar ratio mediated the highest transfection efficiency in cell culture. The mixture of ol eyl 3-oleoyloxy-4-trimethylammonium butyrate chloride (OOCE, 4f) with Chol at a 1:1 molar ratio gave the highest transfection efficiency aft er intravenous administration in mice. In vivo gene expression using 4 f was comparable to values obtained with the best cationic lipids repo rted to date.