Tunable Protein Adsorption by Zwitterionic Spherical Poly(CBAA) Brushes Prepared via Photoemulsion Polymerization

Abstract

Zwitterionic polymer brushes are well-known as excellent hydrophilic and antifouling materials. However, they demonstrate a certain degree of adsorption for proteins and other substances in practical application, and little research has been conducted into this area. Herein, a facile and efficient approach was employed to prepare zwitterionic spherical polymer brushes, polystyrene-poly(2-carboxy-N,N-dimethyl-N-(3′-acrylamidopropyl) ethanaminium inner salt) brushes (PS–PCBAA brushes). Specifically, the preparation process consists of three steps. First, polystyrene (PS) nanospheres were synthesized via conventional emulsion polymerization, and then photoinitiator with terminal double bond was immobilized on the surface of the PS core by copolymerizing with styrene (PS@HMEM). Finally, zwitterionic polymer chains (PCBAA) were grafted onto the surface of PS@HMEM via photoemulsion polymerization. The hydrodynamic diameter and size distribution, morphology, and chemical composition of PS–PCBAA brushes were characterized. The interaction between PS–PCBAA brushes and proteins was investigated by turbidity and size change. The interaction between brushes and proteins was mainly affected by two factors: the electrostatic interaction between polymer chains and proteins, and the transition of zwitterionic polymers from a fouling polymer to a nonfouling polymer. This work provided a simple and environmentally friendly method for constructing zwitterionic materials that showed potential application in the controllable adsorption and desorption of proteins.