Deposition of functional polymer thin films with tunable morphology using an ambient air-fed microwave plasma jet for the fabrication of biosensor interfaces

Surface modifications that enable the immobilization of bioreceptors on the signal transducer surfaces of biosensors are typically produced via wet-chemical techniques. Such techniques usually require multi-step procedures and hazardous chemicals, with the stability of the resulting interfaces often being a particular challenge. As an alternative, an approach based on plasma polymerization using a compact and cost-effective microwave plasma source operated at atmospheric pressure and fed with ambient air as process gas was evaluated in this study. Plasma exposure of the non-hazardous monomeric precursor Pentaerythritol tetraacrylate (PETA) resulted in the formation of highly stable plasma polymerized thin films (pp-films) presenting carboxyl (COOH) groups for the covalent immobilization of bioreceptors. The morphology of the pp-films was tuned by varying the injection time of the monomer. In this way, the surface area for bioreceptor coupling and the electronic transfer properties of pp-films deposited on screen-printed electrodes (SPEs) were adjusted and optimized. Finally, glucose oxidase was immobilized on the pp-films and subsequently used for the quantification of glucose via an amperometric readout in order to demonstrate the suitability of the concept for biosensing. In this context, glucose was quantified in a concentration range between 1 and 10 mM with a linear working range between 1 and 4 mM.