Development of lipid A-imprinted polymer hydrogels that selectively recognize lipopolysaccharides.

Abstract To remove lipopolysaccharide (LPS) from pure water, we developed polymer hydrogels that selectively recognize LPS. A molecular imprinting technique was used to prepare the polymer hydrogels. We prepared the polymer hydrogels with LPS-binding sites by using acryloyllysine and acryloylphenylalanine as functional monomers and used lipid A as a template because it is the biologically active part of LPS and contains two phosphate groups. Co-existence of n-octane during the polymerization process was highly effective in promoting the formation of LPS-accessible sites on the surface of the hydrogels. Both an electrostatic and a hydrophobic interaction between the lipid A portion of LPS and the recognition site of the imprinted hydrogel are necessary for LPS recognition. The adsorption isotherm of LPS to the lipid A-imprinted hydrogels was Langmuir-type; the saturated adsorption capacity and the adsorption constant, calculated by applying an equation for Langmuir-type adsorption isotherms, were 1.0×10 –11  mol/cm 2 and 2.5×10 5  M −1 , respectively. The imprinted hydrogels selectively recognized toxic LPS in a competition experiment in which two other kinds of LPS with similar chemical structures to that of the LPS of E. coli (toxic LPS) were adsorbed to the lipid A-imprinted hydrogels.