Development of nanocatalytic-based assay for the detection of an endocrine disrupting compound in aqueous solution
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Endocrine disrupting compound (EDC) pollutants raise a concern among researchers as these pollutants are implicated in the increasing incidence of testicular, breast and thyroid cancers. Some of these chemicals are widely used for plastics production and discharged into the water system as industrial effluents that could harm the ecosystem as well as plant, animal and human life. Thus, rapid detection and quantification of EDCs in water is desired for screening and investigative purposes. For this purpose, nanoparticle-based methods appear to be potentially efficient, quick and cost-effective techniques to rapidly assess this toxic pollutant. The main focus of this study was to synthesize heterogeneous nanoparticles, iron oxide/gold nanoparticles (IONPs/AuNPs) and to manipulate their synergistic effects for the development of a nanoparticles-based assay, specifically for the EDC compound, 17β-estradiol. As the first step, IONPs and AuNPs were synthesized separately and heterogeneous nanoparticles were formed by a simple electrostatic- self- assembly technique. The unique physiochemical properties of this hybrid nanoparticle were investigated as a supporting material for biomolecules, as well for its intrinsic peroxidase-like activity using a hydrogen peroxidase dependent system. The formation of the IONPs/AuNPs was verified using several characterization tools such as UV-Vis spectrophotometry, Dynamic Light Scattering (DLS), Transmission Electron Microscope (TEM), Energy Dispersive X-ray (EDX) and X-ray Photoelectron Spectroscopy (XPS). The diameter calculated from TEM was 16.1 ± 11.1 nm and EDX confirmed the presence of the Fe and Au elements. From a heterostructural analysis using HRTEM and XPS data, an alloy-like morphology (Fe/Au) was suggested for the heterogeneous nanoparticles, rather than a core-shell structure. The Fe/Au nanoparticles showed good potential for the basis of a colorimetric assay for glucose detection using glucose oxidase immobilized on the Fe/Au surface. In addition, the Fe/Au nanoparticles also showed a significant peroxidase-like activity. A nanocatalytic-based assay was developed by modifying the nanoparticles surface with an aptamer in order to specifically “capture” the target molecule, 17β-estradiol. The formation of a Fe/Au-17β-estradiol complex significantly hampered the peroxidase-like catalytic activity resulting in the development of a unique nanosensor system based on the extent of loss of peroxidase activity. Development of the nanocatalytic-based assay suggests the potential application of Fe/Au nanoparticles to capture, separate and detect a selective target as well as a basis for the development of a rapid, simple and reliable detection tool. The heterogeneous Fe/Au nanoparticles show a remarkable synergistic property for application in nanosensor system. Therefore, some of the work presented here can be extended in certain major directions such as heterostructure formation and optimization of nanocatalytic-based assay.