Hydrogen Peroxide Biosensor Based On Au/CeO₂-CS Nanocomposite

ObjectiveThe determination of hydrogen peroxide （H₂O₂） is of great importancein clinical, biological, food, pharmaceutical and environmental analysis. Thethird generation H₂O₂electrochemical biosensors, which are based on thedirect electron transfer （DET） of horseradish peroxidase （HRP）, havingachieved more attention in the key research felds of today electrochemicalbiosensors due to the simplicity, high selectivity and relative low cost.Cerium dioxide nanostructure （nanoCeO₂） is one of the most promisingsemiconductor oxide material for constructing biosensor due to theirexcellent properties, including good biocompatibility, vast surface-to-bulkratio, high chemical stability, nontoxicity, excellent electronic conductivityand high isoelectric point （IEP）. The high isoelectric point of CeO₂（IEP≈9.0） was suitable for the adsorption of a low IEP protein or enzyme via theelectrostatic interactions. Hence, the nanoCeO₂have attracted muchattention for the development of electrochemical biosensors.There are two aims of our work: 1. Au/CeO₂–CS composite was synthesized via a facile one-step directchemical reduction route. The component and properties of thenanocomposite were studied, and the electrochemical characteristics of thehybrid nanomaterial were explored.2． A mediator-free H₂O₂biosensor based on the Au/CeO₂–CScomposite as the HRP immobilization matrix was proposed. Theelectrochemical performances of the biosensor and the optimization ofexperimental condition have been studied. The analytical performance ofbiosensor for hydrogen peroxide was also evaluated.Methods1. Au/CeO₂hybrid material has been synthesized via a facile one-stepdirect chemical reduction route using chitosan as reducing agent. Initially,0.5wt.%CS solution was prepared by dissolving appropriate amount of CSflakes in acetic acid solution，then1mg of CeO₂NPs were added in1mL ofabove CS solution and sonicated for2h, a high dispersed colloidal solutionwas formed. Subsequently, HAuCl4solution was added into the resultantCeO₂–CS suspension, and the mixture solution was incubated in a hot waterbath at80℃for1h with stirring. The prepared Au/CeO₂–CScompositewascharacterized by transmission electron microscopy （TEM） and UV-visspectra.2. For preparation of enzyme electrode, HRP solution（5mg mL-1）was first prepared with0.1M PBS （pH7.0）. Then an equal volume of as-synthesized Au/CeO₂–CS composite was added to the enzyme solution.The mixture was hand-mixed thoroughly.5.0μL of the above resultedsolution was pipetted onto the surface of pretreated GCE and dried at4℃overnight. The stepwise assembly process and electrochemical performanceof the biosensor were characterized by means of cyclic voltammetry （CV）,electrochemical impedance spectroscopy （EIS） and typical amperometricresponse （i–t curve）.ResultsThe prepared Au/CeO₂hybrid material shows a core/shell-like structure,and a high dispersed colloidal solution of Au/CeO₂–CS composite wasformed. The developed biosensor exhibited excellent response to H₂O₂inthe linear range of0.05～2.5mM （r=0.998）withthedetectionlimitof8μM（S/N=3）. Moreover, the biosensor presented high affinity （Kappm=1.93mM）,good reproducibility and storage stability.ConclusionThe composite exhibited high conductibility, good biocompatibility,and high stability, and the prepared biosensor displayed good performancefor the detection of H₂O₂. The Au/CeO₂–CS composite can provide apromising bio-interface for the biosensor designs and other biologicalapplications.