Covalent immobilization and enhanced electrical wiring of hemoglobin using gold nanoparticles encapsulated PAMAM dendrimer for electrochemical sensing of hydrogen peroxide

Design and development of electrochemical biosensors with improved selectivity, sensitivity and stability is one of the thrust areas of research in analytical and materials chemistry. In the present work, hemoglobin (Hb) was covalently immobilized on polyamidoamine (PAMAM) dendrimer encapsulated with gold nanoparticles (AuNPs), which was further utilized for the electrochemical detection of hydrogen peroxide (H2O2). Third generation PAMAM dendrimers were synthesized and AuNPs were encapsulated within the dendrimer network. Hb was covalently immobilized through glutaraldehyde cross-linking between the free amino groups of Hb and that of the PAMAM dendrimer. Hb/PAMAM-AuNPs was immobilized on a glassy carbon electrode (GCE) and the Hb/PAMAM-AuNPs/GCE modified electrode thus fabricated was characterized with electrochemical impedance spectroscopy and cyclic voltammetry. The Hb/PAMAM-AuNPs/GCE biosensor displayed well resolved redox peaks with anodic peak potential at -0.252 V and cathodic potential at -0.321 V, corresponding to Fe(III)/Fe(II) redox couple of heme active centre. Further, the developed Hb/PAMAM-AuNPs/GCE showed very good electrocatalytic activity for the reduction of H2O2 at a potential of -0.35 V. The Hb/PAMAM-AuNPs/GCE biosensor has shown impressive performance towards H2O2 determination in the concentration range from 20 mu M to 950.22 mu M. The sensitivity of the biosensor was calculated to be 35.07 mu A mu M-1 cm(-2) with a detection limit of 6.1 mu M. Also, the Hb/PAMAM-AuNPs/GCE modified electrode exhibited higher stability and good reproducibility.