Thermally reversible VPBA-NIPAM copolymer gels for nucleotide adsorption

A thermosensitive gel matrix was prepared by free radical copolymerization of N-isopropylacrylamide (NIPAM) with a boronic acid-carrying monomer (i.e. 4-vinylphenylboronic acid, VPBA). The synthesis of the gel was performed at 70 degrees C in an alcohol-water mixture, using azobisisobutyronitrile and methylenebisacrylamide as the initiator and the crosslinker, respectively. To produce thermosensitive gels with a higher diol-binding affinity, an amino-containing comonomer, N-[3-(dimethylamino)propyl]methacrylamide (DMAPM) was included in the gel formation recipe. Thermally reversible VPBA-NIPAM and VPBA-DMAPM-NIPAM gels with different swelling properties were obtained by changing the feed concentrations of VPBA and DMAPM. To test the usability of the produced gels as sorbents in nucleotide adsorption, beta-nicotinamide adenine dinucleotide (beta-NAD) was selected as a model biomolecule. Then the adsorption isotherm for beta-NAD was obtained at +4 degrees C in HEPES buffer medium with a pH of 8.5. The support material was in a highly swollen form under these conditions, due to its thermosensitive character. This property was then used to enhance beta-NAD adsorption onto the gel matrix. Equilibrium adsorption capacities up to 70 mg beta-NAD/g dry gel could be achieved with the thermosensitive support prepared with the 12.9 mol% VPBA feed. The gels produced with higher VPBA and DMAPM feed concentrations exhibited higher equilibrium adsorption capacities for beta-NAD.