A novel pulsed-plasma approach for protein immobilization by grafting reactive amine groups on polyurethane-coated biosensors

Reliable surface chemistry is necessary for immobilization of biological recognition molecules on sensor surfaces. A dry and rapid method of pulsed-plasma assisted grafting of amine surface functional groups, using ammonia gas on polyurethane surfaces is successfully demonstrated by using pulse cycle times of 1-180 s (on-off). One cycle of plasma treatment was found to generate higher amine groups as they tend to degrade upon longer exposure to the high-energy radicals. Successful amination of the polyurethane surfaces was demonstrated by Fourier transform infrared spectroscopy (FTIR). To establish the availability of the surface amine groups for reaction, 1 μm carboxylated polybeads were reacted to polyurethane-coated piezoelectric excited millimeter-sized cantilever (PEMC) sensors before and after plasma treatment. Scanning electron microscope micrographs of PEMC sensors exposed to the same concentration of beads show more than four-fold increase in the presence of beads post pulsed-plasma treatment. Application of this method for protein immobilization was established by BSA chemisorption on plasma treated PEMC sensors.