Enhanced Entrapment of Isopropamide Iodide in Liposomes by Ion-Pairing with Sodium Taurodeoxycholate

A study was carried out to determine the effect of sodium taurodeoxycholate (TDC) on the encapsulation efficiency of isopropamide iodide(IPM) in large unilamellar liposomes prepared by reverse phase evaporation method. The apparent partition coefficient of IPM between n-octanol and phosphate buffer (pH 7.4) was approximately zero, but it was increased by addition of TDC below CMC(1×l0 −2M). The increased partitioning of IPM into n-octanol seemed be due to ion-pair complex formation between IPM and TDC. The encapsulation efficiency of IPM by the liposome, which was determined by equilibrium dialysis method, was increased from 21% to 62% by the presence of TDC(1x10 −2M). It may be due to the solubilization of the ion-pair in the phospholipid bilayer of the liposome.