Selective separation of proteins with pH-dependent magnetic nanoadsorbents

Two kinds of unique pH-dependent magnetic nanoadsorbents based on silica coated magnetic nanoparticles (SMNPs) and amino-silica coated magnetic nanoparticles (ASMNPs) have been exploited for selective separation of proteins. With different isoelectric points, silica coated magnetic nanoadsorbents (SMNAs) and amino-silica coated magnetic nanoadsorbents ( ASMNAs) can respectively adsorb proteins with different charges. The interactions between proteins and magnetic nanoadsorbents changed with the solution pH. Thus, the adsorption or desorption between proteins and magnetic nanoadsorbents can be controlled by changing the solution pH according to the charge of the proteins. And the magnetic nanoadsorbents can be separated and recycled simply with a magnet. As model adsorbates, Cyt-c and BSA are selectively separated from simple protein mixtures with SMNAs and ASMNAs respectively. Cyt-c was adsorbed on SMNAs at pH 8.0 at 0.160 mg mg(-1). And BSA was adsorbed on ASMNAs at pH 5.0 at 0.142 mg mg(-1).