A Highly Sensitive Hydrogen Peroxide Biosensor Based on Hemoglobin Immobilized on Cadmium Sulfide Quantum Dots/Chitosan Composite Modified Glassy Carbon Electrode

An L-cysteine capped cadmium sulfide-chitosan nanocomposite has been synthesized, characterized and used for surface modification of a glassy carbon electrode. With direct electron transfer, hemoglobin (Hb) adsorbed strongly on the nanocomposite and displayed excellent bioelectrocatalysis for H2O2. The biosensor was capable of reducing H2O2 at -0.35 V, with a detection limit of 3.13 nM, linearity in the range of 15 nM to 10 mu M and a response time of less than 2 s. The Michaelis-Menten constant (K-M) was 0.57 nM, attesting high bioelectrocatalysis of immobilized Hb for H2O2. Reproducibility of the fabrication method was very satisfactory with a relative standard deviation of 5.3%. The biosensor lost only 6.5% of its original response after 7 days when stored in a pH 7.4 PBS at 4 degrees C.