Graphene and Co-polymer composite based molecularly imprinted sensor for ultratrace determination of melatonin in human biological fluids

Abstract

A novel molecularly imprinted polymer (MIP) sensor based on a composite of graphene (GR) and a co-polymer of 4-amino-3-hydroxy-1-naphthalenesulfonic acid (AHNSA) and melamine (MM) has been fabricated for detecting melatonin. The MIP film was fabricated by the deposition of a graphene layer on a glassy carbon electrode (GCE) surface followed by electropolymerizing AHNSA and MM in the presence of melatonin. The morphology of the sensor was characterized by using Field Emission-Scanning Electron Microscopy (FE-SEM) and Electrochemical Impedance Spectroscopy (EIS). The electrochemical performance of the imprinted sensor was investigated by using cyclic voltammetry and square wave voltammetry. The electropolymerization conditions, method of template removal, effect of template to monomer ratio and incubation time were optimized. Electrochemical results showed that the oxidation peak current increased linearly with the concentration of melatonin in the range 0.05 to 100 μM L⁻¹. The detection limit of the imprinted electrochemical sensor towards the melatonin determination is calculated to be 60 × 10⁻¹⁰ mol L⁻¹. The suitability of the GR/MIP based sensor has been demonstrated in detecting melatonin in biological samples.