Pd nanoparticle assemblies-As the substitute of HRP, in their biosensing applications for H ₂O ₂ and glucose

The spherical porous Pd nanoparticle assemblies (NPAs) have been successfully synthesized by starch-assisted chemical reduction of Pd(II) species at room temperature. Such Pd NPAs are not simply used to enlarge the surface area and to promote the electron transfer. They also catalyze the reduction of H ₂O ₂ which are regarded as horseradish peroxidase (HRP) substitutes in electron transfer process. By using them as electrocatalysts, as low as 6.8×10 ^-7M H ₂O ₂ can be detected with a linear range from 1.0×10 ^-6 to 8.2×10 ^-4M. Moreover, through co-immobilization of such Pd NPAs and glucose oxidase (GOx), a sensitive and selective glucose biosensor is developed. The detection principle lies on measuring the increase of cathodic current by co-reduction of dissolved oxygen and the in situ generated H ₂O ₂ during the enzymatic reaction. Under optimal conditions, the detection limit is down to 6.1×10 ^-6M with a very wide linear range from 4.0×10 ^-5 to 2.2×10 ^-2M. The proposed biosensor shows a fast response, good stability, high selectivity and reproducibility of serum glucose level. It provides a promising strategy to construct fast, sensitive, stable and anti-interferential amperometric biosensors for early diagnosis and prevention of diabetes.