The long-term aim of this project is to investigate the possibility of using amphiphilic block copolymers instead of ion exchange resins in the therapy of bile acid diarrhea and hypercholesterolemia. The polymers investigated are nonionic triblock copolymers of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) or cationic poly(N-isopropylacrylamide) (PNIPAAM) or PEO diblock copolymers. Bile salts are biological surfactants with a rigid four-ring system, not completely hydrophobic because of the presence of some hydroxyl groups, joined to a carboxylic head by an alkyl chain. In this project, physiochemical studies of the interaction between the anionic bile salts, typically sodium glycodioxycholate (NaGDC), and PEO-PPO-PEO copolymers of various block lengths are carried out by means of dynamic and static light scattering (DLS, SLS), small angle X-ray scattering (SAXS) and small angle neutron scattering in combination with differential scanning calorimetry. The experiments reveal that the bile salt interacts with the copolymers forming, at low bile salt concentrations, a large copolymer-rich complex by association of NaGDC monomers to the block copolymer micelle. The micelle disintegrates upon increasing the concentration of bile salt passing different aggregation states. The association aggregates between bile salt and cationic PNIPAAM copolymers are currently being investigated by SAXS, DLS and SLS.

People: Solmaz Bayati, Karin Schillén, Luciano Galantini (University of Rome “La Sapienza”, Italy), Kenneth D. Knudsen (Institute for Energy Technology, Kjeller, Norway), Bo Nyström and Kaizheng Zhu (University of Oslo, Norway).

Contact person: Karin Schillén