A facile route to the synthesis of spherical poly(acrylic acid) brushes via RAFT polymerization for high-capacity protein immobilization

Spherical poly(acrylic acid) brushes were prepared via a facile RAFT polymerization route from silica nanoparticles (SiO2@PAAs). A silane functionalized RAFT chain transfer agent was designed and synthesized by a one-step reaction, and then immobilized onto silica nanoparticles (SiNPs) through its R group to afford RAFT polymerization. Key structural parameters and contents of carboxyl groups of SiO2@PAAs were thoroughly characterized by transmission electron microscopy, dynamic light scattering, gel permeation chromatography, thermogravimetric analysis and conductometric titration. The SiO2@PAAs exhibit excellent dispersity, tunable brush thicknesses (14.6-68.8 nm) and abundant carboxyl groups (0.82-2.37 mmol/g). An ultra-high protein immobilization capacity (2600 μg streptavidin/mg SiO2@PAAs) was realized by virtue of its rich carboxyl groups and spherical brush structure, which opens up new possibilities for biomedical applications.