Flame-Sprayed Superparamagnetic Bare and Silica-Coated Maghemite Nanoparticles:  Synthesis, Characterization, and Protein Adsorption−Desorption

Superparamagnetic maghemite (γ-Fe2O3) nanoparticles of tunable diameters and silica-coated maghemite (SiO2/γ-Fe2O3) nanoparticles of controllable morphology were successfully synthesized using a one-step flame spray pyrolysis (FSP) technique. The physical, chemical, and magnetic properties of γ-Fe2O3 and SiO2/γ-Fe2O3 nanostructures were characterized and compared with those of silica-coated FSP γ-Fe2O3 produced by a conventional sol−gel method. Bovine serum albumin (BSA) adsorption−desorption was investigated as a model to demonstrate the feasibility of synthesized superparamagnetic nanoparticles for bioadsorption and bioseparation. Protein adsorption was observed to follow the Langmuir isotherm, with the highest binding capacity of 348 mg of BSA/g of particle and a dissociation constant of 0.0159 g/L attainable for FSP γ-Fe2O3 (dXRD = 14 nm) in 10 mM formate buffer. Electrostatically governed BSA orientations were proposed for different particle−buffer systems. Shifting the pH of suspension with K2HPO4 enabled effective recovery of adsorbed BSA.