Protein valves formed through click-reaction grafting of poly(N-isopropylacrylamide) onto electrospun poly(2,6-dimethyl-1,4-phenylene oxide) fibrous membranes

In this study a thermo-sensitive switching membrane was prepared through grafting, using a click reaction, of an N-isopropylacrylamide (NIPAAm) derivative onto an electrospun poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) fibrous membrane (EPFM). The PPO was first electrospun into a fibrous membrane, then brominated and reacted with NaN3 to generate the azido-terminated EPFMs. A propargyl-terminated poly(N-isopropylacrylamide) (PNIPAAm) was synthesized and grafted onto the azido-terminated EPFMs. The surface roughness of PPO fibers was increased due to the presence of PNIPAAm grafts, such that the thermoresponse of the static water contact angle (SWCA) of PNIPAAm-grafted EPFMs between 25 and 45 °C was significantly greater than that of the same PNIPAAm grafted on a flat surface. Thermo-sensitive affinity of the membrane with water resulted the average pore dimension responded to temperature changes. Taking advantage of this temperature-responsive affinity, we applied the membranes as protein valves that blocked and released an antibody. At 25 °C, the collection efficiency was 90% for antibody concentrations of up to 5 ng/mL. Increasing the temperature to 45 °C caused the collection efficiency to decrease abruptly, to 7.5%, when the antibody concentration was greater than 1.5 ng/mL. Accordingly, this system of PNIPAAm-grafted PPO fibers functioned as a protein valve, allowing the blocking and release of proteins.