Use of β-cyclodextrin as enhancer of ascorbic acid rejection in permselective films for amperometric biosensor applications

Interference rejection in amperometric biosensors can be more effective introducing some modifiers during electro-deposition of permselective film. Addition of beta-cyclodextrin (beta CD), a cyclic oligosaccharide composed of seven glucose units, to the ortho-phenylendiamine (oPD) monomer were already demonstrated to provide an enhancement in ascorbic acid (AA) rejection. Here we evaluated the improvement in permselectivity of polyeugenol and poly-magnolol films electro-polymerized in presence of different amounts of beta CD or eugenol-beta CD inclusion complex for amperometric biosensor application. Starting from Pt-Ir wire as transducer several microsensors were covered with polymeric films doped with beta CD-based modifiers through constant potential amperometry. Characterization of modified polymers was achieved by scanning electron microscopy and permselectivity analysis. Poly-magnolol film in combination with beta CD showed a worsening in permselectivity compared to poly-magnolol alone. In contrast, the introduction of beta CD-based modifier enhanced the interference rejection toward the archetypal interferent AA, while slightly affecting permeability toward H2O2 compared to the poly-eugenol without modifier. The AA rejection seems to be influenced by the availability of beta CD cavity as well as film performance due to concentration of beta CD-Eugenol inclusion complex. A poly-eugenol film co-polymerized with 2 mM beta CD-eugenol inclusion complex showed a permselectivity equal to poly-orthophenylendiamine film (PPD), with a lower permeability to AA, likely to be related with a self-blocking mechanism. Based on these results, a biosensor for glutamate was constructed with a poly-eugenol doped with beta CD-eugenol as permselective layer and its permselectivity, stability and lifetime were determined.