A amperometric biosensor for hydrogen peroxide by adsorption of horseradish peroxidase onto single-walled carbon nanotubes

Development of a highly sensitive nanostructured electrochemical biosensor based on the integrated assembly of horseradish peroxidase (HRP) and single-walled carbon nanotubes (SWNTs) is described. In this study, we describe the use of a sodium cholate suspension-dialysis method to adsorb the horseradish peroxidase (HRP) onto single-walled carbon nanotubes (SWNTs). We demonstrate that HRP–SWNTs conjugates can be assembled into amperometric biosensors which l-cysteine were assembled on a gold electrode through the covalent bond of S–Au and was used as a substrate for the immobilization of enzymes. Direct electron transfer of HRP is realized at SWNTs, and both anodic and cathodic currents of the redox reaction at the l-cysteine–HRP–SWNTs-modified gold film upon electrocatalysis are amplified. Meanwhile, experimental results reveal that HRP is stably immobilized onto the SWNTs and maintains inherent enzymatic activity toward H2O2. The modified electrode shows high sensitivity toward H2O2. A linear response to hydrogen peroxide measurement is obtained over the range from 1.0 × 10−12 to 1.0 × 10−11 M and an amperometric detection limit of 2.1 × 10−13 M due to its bioelectrocatalytic reduction based on direct electron transfer between gold electrode and the active site of the HRP. The biosensor displays excellent operational, storage stability and highly sensitive. The excellent performance validates the integrated assembly as an attractive sensing element for the development of a new hydrogen peroxide amperometric biosensor.

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► A low detection limit and novel nanostructured electrochemical biosensor based on the integrated assembly of HRP and SWNTs is described.
► SWNTs dispersed with sodium cholate adsorbed HRP using noncovalent method by dialysing suspension and the benefit of noncovalent immobilization is what allows for the electronic structures and the geometric structures of the SWNTs to be retained.
► Direct electrical contacting of redox proteins to electrodes has been accomplished through self-assembling layers and noncovalent conjugates which provide electron-conducting pathways between the protein and the electrode.