Effects of gel morphology on the lysozyme adsorption and desorption kinetics of temperature sensitive magnetic gel composites

Tuning the adsorption and desorption rate constant of proteins is a hot topic for broad range of applications in biotechnology and medical science; especially controlled drug delivery and protein separation are the prominent examples in this field. In this study, Gel-MNPs (Poly(N-isopropylacrylamid) PNIPA-Magnetic Nano Particles) composites were synthesized by using different concentrations of monomer and cross-linker to observe the effect of gel morphology on the adsorption and desorption rate constant and kinetics of lysozyme protein. The synthesized composites were characterized by XRD, VSM, SEM and FTIR techniques. The characterization results showed that superparamagnetic Fe₃O₄ nanoparticles were synthesized inside the temperature sensitive PNIPA hydrogels. Fluorescence measurements were performed for monitoring the adsorption and desorption of lysozyme through Gel-MNPs composites. The adsorption process obeyed pseudo first and second order kinetic models at above and below the lower critical solution temperature (LCST) of PNIPA gels. Pseudo first order kinetic indicates physisorption, between the lysozyme and composite material for both adsorption and desorption. The adsorption was effective below LCST, but it was not effective at a temperatures higher than LCST; the adsorption rate constant was found between 0.59 and 0.082 s⁻¹ at 22 °C. On the other side, samples show well desorption ability at the temperature above than LCST; the desorption rate constant was found between 0.080 and 0.092 s⁻¹ at 45 °C. Moreover, the effects of monomer and cross-linker concentration on the adsorption and desorption kinetics are determined and discussed at the end of the manuscript.