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 β-cyclodextrin (βCD), 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 poly-eugenol and poly-magnolol films electro-polymerized in presence of different amounts of βCD or eugenol-βCD inclusion complex for amperometric biosensor application. Starting from Pt-Ir wire as transducer several microsensors were covered with polymeric films doped with βCD-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 βCD showed a worsening in permselectivity compared to poly-magnolol alone. In contrast, the introduction of βCD-based modifier enhanced the interference rejection toward the archetypal interferent AA, while slightly affecting permeability toward HO compared to the poly-eugenol without modifier. The AA rejection seems to be influenced by the availability of βCD cavity as well as film performance due to concentration of βCD-Eugenol inclusion complex. A poly-eugenol film co-polymerized with 2 mM βCD-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 βCD-eugenol as permselective layer and its permselectivity, stability and lifetime were determined.