Silica-supported carboxylated cellulose nanofibers for effective lysozyme adsorption: Effect of macropore size

Engineering hierarchical macro/mesoporous structures that offer an abundance of accessible binding sites are highly desirable in protein adsorption processes. However, numerous significant challenges remain. Herein, cellulose nanofiber (CNF)-loaded macroporous silica (CNF-MPS) particles were success-fully synthesized with a high degree of accessible binding sites by tuning the macropore size of the silica
particles and loading a highly carboxylated CNF via smart and rational design. The as-prepared CNF-MPS
particles exhibited a high negative charge (~�59 mV) and excellent protein adsorption ability (>1000 mg/g) in <5 min. Furthermore, tuning the macropore size influenced the CNF deposition either to the external surface or penetrating within the pores. As a result, the optimum macropore successfully enhances the adsorption capability to >1500 mg/g as a result of improved interconnectivity between the channels.
Here exposed macropores of >100 nm allows ingress of protein to the interior structure that houses an abundance of binding sites comprising the dispersed CNF. Additionally, the adsorption kinetics, thermo-dynamics, and isothermal parameters were studied to analyze the mechanism of lysozyme adsorption.
The adsorption process is confirmed to occur spontaneously at any temperature with a pseudo-second-order model describing the kinetic model, and CNF deposition affecting the heterogeneity of the binding sites.