Interaction of heparin with amphiphile assemblies and biocompatibility of the heparin complexes

Addition of heparin to preformed vesicles of a cationic surface-active compound, dioctadecyldimethylammonium bromide (DODAB), resulted in fast precipitation of the heparin/DODAB complex. On the other hand, heparin stabilized the vesicle composed of dipalmitoyl L-alpha-phosphatidylcholine (DPPC) which is a neutral lipid. However, DPPC precipitated with heparin by the addition of a small amount of stearylamine (SA), which is a cationic substance. Differential scanning calorimetry of the heparin/amphiphile mixtures showed that the heparin/DODAB complex possess a structure different from that of the original DODAB vesicle. The structure of the DPPC vesicle was unaffected by the addition of heparin, while the structure of the heparin/DPPC-SA complex was found to be different from that of the DPPC-SA vesicle. The interaction of heparin with vesicles depended on the nature of amphiphiles. Heparin was solubilized in organic solvent when complexed with DODAB or DPPC-SA vesicles. Polyurethaneurea membranes blended with heparin/DODAB or heparin/DPPC-SA complexes were highly nonthrombogenic, but somewhat cytotoxic.