Title : Chitosan/?-cyclodextrin-graphene quantum dots composite as a high-performance electrochemical sensing platform for global estimation of fluoroquinolones in food products from animal source
Abstract:
Fluoroquinolone (FQs) antibiotics are broad-spectrum agents widely used to treat a range of infections in the veterinary field or even in human medicine. In recent years FQs have been used in an abusive way within the alimentary industry, leading to the appearance of quinolone resistant microorganisms and reducing so the effectiveness of FQs-based drugs for the treatment of infection diseases at both animal and human levels [1]. In consequence, diverse international organizations have established legislation and regulations regarding the maximum amount of quinolones allowed in food [2]. Hence a new electrochemical approach based on a new designed nanocomposite material modified on screen printed carbon electrodes (SPCE), which is the result of an assembly from graphene quantum dots functionalized gamma cyclodextrins and chitosan (γCDs-GQDs/CHI), has been proposed for the full voltammetric sensing of FQs content in alimentary samples.
Nanostructural and morphological characterization of synthesized composite were assessed by high resolution transmission scanning microscopy (HR-TEM) and dynamic light scattering (DLS). Graphenic structures and correct functionalization of GQDs were confirmed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) respectively. Electrochemical properties of the sensing nanocomposite and involved redox analytes were evaluated by cyclic voltammetry (CV) using potassium ferricyanide as redox probe. The developed sensing system exhibits improved electrocatalytic performance throughout FQs oxidation in terms of relevant electrochemical features as electronic transfer rate (K0), electroactive area (A) and double capacitance layer (Cdl). Electrochemical mechanism of the redox process was also studied on four representative quinolones attending to their distinctive chemical structures, obtaining in all cases the same number of e- (2) and H+ (2) involved in their oxidation process, which suggested a single oxidation mechanism for all FQs, also here elucidated.
Electroanalytical performance features were investigated on mixtures of four FQs selected as representative ones of the electrochemical behaviour for the whole family. Satisfactory results were obtained in terms of linear range (4 – 250 µM) and lower detection limit (LOD = 1.2 µM). The designed sensor allowed the determination of FQs global contain in broths, bouillon cubes and milkshakes at three concentration levels (150, 75 and 37.5 µM) for both equimolar and different FQs ratios in their mixtures, with recoveries ranging from 90 to 106%.
