Uniform Superparamagnetic Fe3O4/CMCS Composite Nanospheres for Lysozyme Adsorption.

In this study, uniform superparamagnetic Fe3O4/carboxymethyl chitosan composite nanospheres with high saturation magnetization were successfully synthesized via a modified inverse emulsion crosslinking approach, using genipin as a cross-linking agent. These nanospheres were then characterized, and their protein adsorption capacity was further investigated under various conditions. The implementation of a sonication treatment of a mixture containing Fe3O4 nanoparticles and carboxymethyl chitosan before the emulsion process significantly promoted the homogeneity of Fe3O4 nanoparticles in an aqueous phase system. The Fe3O4/carboxymethyl chitosan composite nanospheres were of uniform spherical structure, were approximately 230 nm in size, and possessed superparamagnetic characteristics with a mean saturation magnetization as high as 35 emu g(-1), corresponding to a magnetite content of 43%. Lysozyme was then employed as a model protein to investigate the effects of pH, incubation time and ion strength on the protein adsorption capacity of the as-synthesized composite nanospheres. The as-obtained composite nanospheres could serve as a promising candidate for fast and efficient protein adsorption.

Polyacrylic acid brushes grafted from P(St-AA)/Fe3O4 composite microspheres via ARGET-ATRP in aqueous solution for protein immobilization.

Recently, the atom transfer radical polymerization (ATRP) of acrylic monomers in many reaction systems has been successfully accomplished. However, its application in aqueous solution is still a challenging task. In this work, polyacrylic acid (PAA) brushes with tunable length were directly grafted from P(St-AA)/Fe3O4 composite microspheres in aqueous solution via an improved method, activators regenerated by electron transfer atom transfer radical polymerization (ARGET-ATRP). This reaction was carried out in environment-friendly solvent. As well, this method overcame the sensitivity of the catalyst. Due to the strong coordination interaction of carboxyl groups, PAA brushes were employed for immobilizing gold nanoparticles, which were prepared via the in situ reduction of chloroauric acid. The PAA brushes modified magnetic composite microspheres decorating with gold nanoparticles were efficient for specific immobilization and separation of bovine serum albumin (BSA) from aqueous solution under the external magnetic field.