Graphene–PEDOT:PSS on screen printed carbon electrode for enzymatic biosensing

• Enyzmatic glucose biosensor is made from GOD/PEDOT-PSS/SPCE.
• Sensor is formed by one-step electrolytic exfoliation and enzyme linking with glutraldehyde.
• Quasi-reversible direct electrochemistry of GOD at GP/PEDOT:PSS/SPCE is observed.
• Graphene inclusion gives 13 times sensitivity increase in GOD/PEDOT:PSS/SPCE.
• High sensitivity (7.23 μA/mM) and low detection limit (0.3 μM) are achieved.

In this work, a highly sensitive enzyme-based biosensor is developed based on graphene–poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid (GP-PEDOT:PSS) modified screen printed carbon electrode (SPCE) for electrochemical detection of glucose. GP-PEDOT:PSS nanocomposite synthesized by one-step electrolytic exfoliation is drop-coated on SPCE and glucose oxidase (GOD) enzyme is then immobilized on GP-PEDOT:PSS by glutaraldehyde cross linking. Electron microscope characterization confirms the presence of multi-layer graphene sheets and the appearance of smooth and long microstripe structure of GOD on the electrode surface. Direct electrochemistry of GOD at the GP/PEDOT:PSS electrode is observed by cyclic voltammetry and graphene plays the main role in a quasi-reversible redox process. GOD/GP-PEDOT:PSS electrode exhibits a high amperometric sensitivity of 7.23 μA/mM, which is about 13 times higher than that of GOD/PEDOT:PSS but has a relatively narrow linear dynamic range of ∼20–900 μM. Moreover, GOD/GP-PEDOT:PSS offers a very low detection limits (3S/N) of ∼0.3 μM which is better or comparable to other recent reports of highly sensitive glucose biosensors. Furthermore, the sensor has good stability with only 30% loss of enzyme activity after 30 days.