In situ investigation of lysozyme adsorption into polyelectrolyte brushes by quartz crystal microbalance with dissipation

Abstract

A well understanding about protein adsorption into charged polymer brushes is of importance in the elucidation of mechanism and important phenomena (such as “chain delivery” effect) in protein adsorption on polymer-grafted ion exchange adsorbents. In this work, quartz crystal microbalance with dissipation (QCM-D) was introduced to in situ investigate lysozyme adsorption on QCM sensors grafted with poly(3-sulfopropyl methacrylate) ( p SPM) via atom transfer radical polymerization. It was achieved by analyzing frequency ( f ) and energy dissipation ( D ) shift simultaneously on p SPM-grafted sensors. The result showed that an initial decrease in Δ D was typical of lysozyme adsorption on p SPM-grafted sensor and more significant with an increase of chain length and grafting density. It was attributed to significant water release in the hydration layer of protein and polymer chains in lysozyme adsorption into p SPM brushes. On p SPM-grafted sensors with long and dense chains, furthermore, lysozyme transitioned from monolayer to multilayer adsorption and the maximum adsorbed amount was obtained to be 374.0 ng·cm −2 among all p SPM-grafted sensors in this work. The results in D - f plot further revealed that lysozyme adsorption into p SPM brushes increased the rigidity of adsorbed layer and little structure adjustment of adsorbed lysozyme. It was unfavorable for “chain delivery” effect for facilitated transport of adsorbed protein. This work provided valuable insight into protein adsorption in p SPM brushes and outlined a feasible approach to increasing mass transport in polymer-grafted ion exchange adsorbents.