Smart polymers, whose characteristics undergo appropriate changes in response to surrounding environmental conditions, enable control over properties as the transport of molecules, changes in wettability, and the adhesion of different species among others. pH-Responsive mixed charge polymer provide a new avenue to achieve reversible switching between non-fouling and fouling properties. When carboxylic acid is used as the anionic group of mixed-charge polymer, pH-responsive behavior from mixed charge to positive charge with decreasing pH based on the protonation state of the carboxylic acid group can be switched between fouling and non-fouling properties. Anionic carboxylic acid groups used in mixed-charge polymer has relatively lower pKa~5, which is inadequate physiological pH. Therefore, we aimed to shift the pKa~5 value of the anionic group to neutral by changing the pH-responsive anionic monomer and introduction of spacer moiety. We prepared three type of carboxylic acid monomers with different hydrophobicity of side groups, and synthesized pH-responsive mixed-charged polymers (Fig. 1). The pKavalues of polymers were determined by pH titration. As the hydrophobicity of carboxylic acid monomers, and neutral monomers increased, the pKavalues shifted to higher values. In addition, Increasing the composition ratio of neutral monomers, the pKavalues shifted to higher values. Finally, the pKavalue of polymers shifted from 4.6 to 5.8. Switching pH between mixed-charge and positive charge was successfully tuned by changing the anionic monomers, and composition ratio. In addition, we confirmed pH-responsive protein adsorption with using heparin, which is a well-known anionic protein by dynamic light scattering (Fig. 2). These results indicated that pH-responsive characteristic of mixed-charge polymer was successfully tuned by changing the pH-responsive carboxylic acid group and introduction of spacer moiety.

pH-Response tunable mixed-charged polymers for reversible adsorption and desorption of proteins

2019 Fall National Meeting

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