A new approach for paper-based analytical devices with electrochemical detection based on graphite pencil electrodes

The present work describes for the first time the coupling of graphite pencil electrodes with paper-based analytical devices (μPADs) for glucose biosensing. Electrochemical measurement for μPADs using a two-electrode system was also developed. This dual-electrode configuration on paper provides electrochemical responses similar to those recorded by conventional electrochemical systems (three electrode systems). A wax printing process was used to define hydrophilic circular microzones by inserting hydrophobic patterns on paper. The microzones were employed one for filtration, one for an enzymatic reaction and one for electrochemical detection. By adding 4-aminophenylboronic acid as redox mediator and glucose oxidase to the reaction microzone, it was possible to reach low limits of detection for glucose with graphite pencil electrodes without modifying the electrode. The limit of detection of the proposed μPAD was found to be 0.38 μmol L−1 for glucose. Low sample consumption (40 μL) and fast analysis time (less than 5 min) combined with low cost electrodes and paper-based analytical platforms are attractive properties of the proposed μPAD with electrochemical detection. Artificial blood serum samples containing glucose were analyzed with the proposed device as proof of concept.