Ion-exchange purification of proteins using magnetic nanoclusters.

Polymer-coated magnetic nanoclusters were used for recovery and purification of proteins from both model systems and cell-free Pichia pastoris fermentation broth. The nanoclusters exhibited extremely high capacity for proteins, up to 900 mg/mL adsorbent, and were recovered by high gradient magnetic separation (HGMS) at flow rates of up to 3,600 cm(3)/cm(2) h (flow rates up to 15,000 cm(3)/cm(2) h are possible). The nanoclusters were coated with a primary coating of poly(acrylic acid-co-styrenesulfonic acid-co-vinylsulfonic acid), which allowed both electrostatic and hydrophobic interactions with the protein to be used to enhance specificity for targeted products. With this dual mode separation, nearly pure protein could be recovered from complex mixtures, such as fermentation broth, in a few quick steps.