Polyacrylate guanidine and polymethacrylate guanidine as novel cationic polymers for effective bilirubin binding

The effect of polycationic polymers of polyacrylate guanidine (PAG) and polymethacrylate guanidine (PMAG) on bilirubin absorbance were studied in phosphate buffer (pH 7.4). It was shown that the change in absorbance spectra of bilirubin in the presence of PAG/PMAG can be associated with the formation of a bilirubin-polymer complex and dissociation of tetramers on bilirubin monomers. Also, the organic-inorganic composite materials based on silica gels and guanidine polymers were synthesized via the sol-gel technique. The incorporated guanidine polymers have a big influence on particle size distribution of silica gel due to their high cross-linking ability. The infrared spectroscopy revealed the presence of guanidine polymers inside solid networks of silica gel. The bilirubin adsorption process onto a guanidine functionalized silica surface was investigated. The Langmuir and Redlich-Peterson isotherm models were tested to explain the adsorption mechanism. The analysis of the adsorption isotherms confirms the possibility of electrostatic interactions of bilirubin molecules with guanidine polymers incorporated inside silica matrix. We conclude that cationic guanidine polymers might be effectively applied for bilirubin removal.