Improved glucose label-free biosensor with layer-by-layer architecture and conducting polymer poly(3,4-ethylenedioxythiophene)

Layer-by-layer (LbL) self-assembly has been used for the development of a new glucose label-free biosensor. Glucose oxidase (GOx) was incorporated in a multilayer film on a gold electrode, previously modified with a film of the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT), by electropolymerization, for better conductivity. Multilayer films, containing the enzyme and nitrogen doped graphene (NG) dispersed in the biocompatible positively-charged polymer chitosan {chit+(NG + GOx)}, together with the negatively charged polymer poly(styrene sulfonate), PSS−, were assembled. Cyclic voltammetry and electrochemical impedance spectroscopy were used for characterization of the biosensor architectures. The LbL film growth was monitored by Surface Plasmon Resonance Spectroscopy in order to evaluate the interactions involved in the biomolecule immobilization. Atomic force microscopy and scanning electron microscopy imaging show the morphological structure of the multilayer film modified electrode. The analytical properties of the glucose biosensor were determined by fixed potential amperometry and showed a substantial improvement in biosensor sensitivity in the presence of PEDOT. The biosensor operates at a low potential of −0.2 V vs. Ag/AgCl, with a sensitivity of 237 μA cm−2 mM−1 and a detection limit of 41 μM. The biosensor applicability was evaluated by measuring glucose content in wines obtained from Romanian grapes (Vitis vinifera).