PhD Defence Erik Postma | Protein Capture in Electric Fields | Catch Control and Release Using Antifouling Polymer Brushes

Protein Capture in Electric Fields | Catch Control and Release Using Antifouling Polymer Brushes

Erik Postma is a PhD student in the department Molecules & Materials. (Co)Promotors are dr.ir. S.J.A. de Beer & prof.dr. C.G.P.H. Schroën from the faculty of Science & Technology (TNW), University of Twente.

We present an electrically controlled protein separation method that uses an antifouling polymer brush on a conductive surface. Current separation systems typically rely on changes in the salt or pH, processes that are costly and energy-inefficient. Therefore, the development of new separation techniques based on local stimuli, such as electricity, is essential to achieve higher efficiency and greater sustainability.

The novel technique can capture and release lysozyme by applying an electric potential to a modified gold electrode. This was achieved by grafting an antifouling polymer brush on the gold electrode that prevented irreversible adsorption of proteins. We verified that the polymer was resistant to the applied electric potentials by comparing the stability of the anchors. Thiol- and diazonium-based anchors were tested for polyelectrolyte and poly(MeOEGMA) brushes in electric fields. We found that diazonium anchors are less likely to be reduced in negative electric fields compared to thiol anchors.

With quartz crystal microbalance (QCM) we measured the adsorption and desorption of positively charged lysozyme under negative fields. We show that electrically tunable, reversible protein capture is possible by adjusting the polymer brush thickness, electric potential, and salt concentration. Furthermore, we confirmed that negatively charged alpha-lactalbumin is not captured in negative fields. Therefore, this system allows for specific separation of proteins based on their net-charge.

Controlling protein adhesion and release is especially relevant in sensors and in fields where protein fouling reduces the runtime of processes, e.g., in protein separation processes used for food ingredient production, and isolation of biomedical compounds. Our results demonstrate that electrically driven protein separation is a viable and promising method for future food, pharma, and bio-process applications.