Graphene dispersed cellulose microfibers composite for efficient immobilization of hemoglobin and selective biosensor for detection of hydrogen peroxide

In the present work, we have investigated the electrochemical behavior and electrocatalysis of hemoglobin (Hb) immobilized on a glassy carbon electrode (GCE) modified with a graphene-cellulose microfiber (GR–CMF) composite. The GR–CMF composite was characterized by scanning electron microscopy, elemental analysis, and Raman and Fourier transform infrared spectroscopy. Well-defined electrochemical redox characteristics of Hb were observed for Hb immobilized on a GR–CMF composite modified GCE, with a formal potential of −0.306 V and a peak to peak separation of approximately 67 mV. Due to the high biocompatibility of the GR–CMF composite, the electrochemical behavior of the Hb heme redox couple (Fe^II/Fe^III) was enhanced for Hb immobilized on the GR–CMF composite when compared to Hb immobilized on pristine GR. The heterogeneous electron transfer constant (k_s) was calculated as 6.17 s⁻¹, and is higher than previously reported for Hb immobilized GR supports. The Hb immobilized GR–CMF composite modified electrode was used for the quantification of H₂O₂ under optimal conditions, and shows a wider linear amperometric response ranging from 0.05 to 926 μM. The limit of detection of the biosensor was 0.01 μM with the sensitivity of 0.49 μA μM⁻¹ cm⁻². The biosensor also showed high selectivity in the presence of the range of interfering compounds and exhibits good operational stability and practicality in the detection of H₂O₂.