Self-assembled dipeptide–gold nanoparticle hybrid spheres for highly sensitive amperometric hydrogen peroxide biosensors

Abstract

Novel self-assembled dipeptide–gold nanoparticle (DP–AuNP) hybrid microspheres with a hollow structure have been prepared in aqueous solution by a simple one-step method. Diphenylalanine (FF) dipeptide was used as a precursor to form simultaneously peptide spheres and a reducing agent to reduce gold ions to gold nanoparticles in water at 60°C. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that formed AuNPs were localized both inside and on the surface of the dipeptide spheres. Horseradish peroxidase (HRP) as a model enzyme was further immobilized on the dipeptide–AuNP hybrid spheres to construct a mediate H2O2 amperometric biosensor. UV–vis spectroscopy showed that the immobilized HRP retained its original structure. Cyclic voltammetry characterization demonstrated that the HRP/dipeptide–AuNP hybrid spheres modified glassy carbon electrode showed high electrocatalytic activity to H2O2. The proposed biosensor exhibited a wide linear response in the range from 5.0×10−7 to 9.7×10−4M with a high sensitivity of 28.3µAmM−1. A low detection limit of 1.0×10−7M was estimated at S/N=3. In addition, the biosensor possessed satisfactory reproducibility and long-term stability. These results indicated that the dipeptide–AuNP hybrid sphere is a promising matrix for application in the fabrication of electrochemical biosensors due to its excellent biocompatibility and good charge-transfer ability.