Microemulsion of seal oil markedly enhances the transfer of a hydrophobic radiopharmaceutical into acetylated low density lipoprotein.

Four different microemulsions differing in their core lipid component (triolein, canola oil, squalene, or seal oil) and containing 1,3-dihydroxypropan-2-one 1,3-diiopanoate (DPIP), a potential radioimaging probe, were prepared by means of ultrasonication. The DPIP microemulsions were incubated with acetylated human low density lipoprotein (AcLDL) and the amount of DPIP transferred into AcLDL was examined. The amount of DPIP in the microemulsions expressed as DPIP/oil (w/w) was dependent on the core lipid component of the microemulsion in the order of seal oil (0.19+/-0.04, mean +/- standard deviation) > squalene (0.15+/-0.02) > canola oil (0.12+/-0.02) > triolein (0.07+/-0.004). With the exception of canola oil, all microemulsions were effective in enhancing the transfer of DPIP into AcLDL in comparison with commonly used methods, i.e., direct diffusion and detergent solubilization. DPIP in seal oil resulted in the highest amount of DPIP transferred into AcLDL [309.16+/-34.82 vs. 203.19+/-64.51 using squalene and 151.31+/-28.54 using triolein (DPIP molecules per AcLDL particle)]. For the first time, oil from harp seals, was studied as a major core lipid component of formulating pharmaceutical microemulsions. DPIP in seal oil resulted in the highest transfer of DPIP into AcLDL which is likely due to the highest DPIP concentration found in this microemulsion as well as the high fluidity of seal oil.