Preparation of dual temperature/pH-sensitive polyampholyte gels and investigation of their protein adsorption behaviors

Dual temperature/pH-sensitive polyampholyte gels were developed for use as adsorbents and carriers that deal with organic electrolytes such as proteins. NIPA-co-DMAPAA-co-AA gels were prepared by copolymerizing N-isopropylacrylamide (NIPA) as a thermosensitive component with N,N-dimethylaminopropylacrylamide (DMAPAA) as a weakly-basic cation-comonomer, acrylic acid (AA) as a weakly-acidic anion-comonomer, and N,N′-methylenebisacrylamide (MBAA) as a cross-linker, and their thermosensitive and pH-sensitive swelling properties and protein adsorption properties were investigated. The gel adsorbed bovine serum albumin (BSA) applied as a model protein at pH values in the range of 4.5–10 and 25 °C as a result of the electrostatic interactions. In addition, the pre-adsorbed BSA was well desorbed from the gel at pH values less than 4 or greater than 11. The pH-sensitivity of the adsorption is found to be based on the protonation of amino groups in DMAPAA and dissociation of carboxyl groups of AA. The BSA adsorption was investigated as a function of MBAA concentration and temperature, and was discussed in terms of the difference in the sizes of the BSA molecule and gel network.

► Preparation of dual temperature/pH-sensitive polyampholyte gels.
► Copolymerizing N-isopropylacrylamide with a weakly-basic cation-comonomer and a weakly-acidic anion-comonomer.
► Adsorption of bovine serum albumin onto the gels.