Intelligent poly(N-isopropylacrylamide)-carboxymethyl cellulose full interpenetrating polymeric networks for protein adsorption studies

Poly(N-isopropyl acrylamide) (PNIPAm)–carboxymethyl cellulose (CMC) full interpenetrating polymeric networks (IPNs), based on PNIPAm and CMC, were prepared and investigated for adsorption of biomolecules utilizing a model protein, bovine serum albumin (BSA). N-isopropyl acrylamide monomers were polymerized in the presence of a natural polymer, e.g., carboxymethyl cellulose sodium salt. N,N′-methylenebisacrylamide (CL) was used to crosslink PNIPAm and CMC chains and IPN formed simultaneously. Spectroscopic and thermal characterization of the hydrogels were done with IR spectroscopy and thermogravimetric analysis. The swelling properties of PNIPAm and PNIPAm–CMC hydrogels were investigated as functions of the medium pH, temperature, ionic strength, and BSA. It was observed that the adsorption of protein molecules onto the hydrogels was mainly dependent on temperature and pH of the environment during the experiments. The maximum adsorption capacity (X) was observed at pH 4.7 which is the isoelectric point of BSA and at 40 °C for both hydrogels; and introducing CMC to PNIPAm increased the protein adsorption of the hydrogel. Adsorbed amounts of BSA were 26.70 mg g⁻¹ (4 °C) and 38.70 mg g⁻¹ (40 °C) for PNIPAm–CMC full IPN hydrogels. Adsorbed BSA (up to 80%) was eluted in the elution medium containing 0.1 mol dm⁻³ NaSCN at pH 8.0. Synthesized cylindrically shaped PNIPAm–CMC full IPN hydrogels can be used for adsorption studies related to the removal of proteins in pH- and temperature-sensitive biotechnological areas.