Abstract
Lead (II) is regarded as one of the most hazardous heavy metals, and lead contamination has a serious impact on food chains, human health, and the environment. Herein, a colorimetric aptasensor based on the graphene/Fe3O4-AuNPs composites with enhanced peroxidase-like activity has been developed to monitor lead ions (Pb2+). In short, graphene/Fe3O4-AuNPs were fabricated and acted as an enzyme mimetic, so the color change could be observed by chromogenic reaction. The aptamer of Pb2+ was decorated on the surface of the amine magnetic beads by streptavidin–biotin interaction, and the complementary strands of the aptamer and target Pb2+ competed for the binding Pb2+ aptamer. In the presence of Pb2+, aptamers bonded the metal ions and were removed from the system by magnetic separation; the free cDNA was adsorbed onto the surface of the graphene/Fe3O4-AuNPs composites, thus inhibiting the catalytic activity and the color reaction. The absorbance of the reaction solution at 652 nm had a clear linear correlation with the Pb2+ concentration in the range of 1–300 ng/mL, and the limit of detection was 0.63 ng/mL. This assay is simple and convenient in operation, has good selectivity, and has been used to test tap water samples, which proves that it is capable for the routine monitoring of Pb2+.
Highlights
Lead contamination is an increasingly important issue accompanied by the wide use of lead in industry sectors such as batteries [1], gasoline [2], metallurgies [3], and paints [4]
The biotin-labeled Pb aptamer was connected and the magnetic beads are separated by magnetic adsorption
Fe3 O4 NPs and AuNPs were grown on the graphene to form graphene/Fe3 O4 -AuNP composites, which served as an enzyme mimetic of peroxidase to catalyze a color reaction
Summary
Lead contamination is an increasingly important issue accompanied by the wide use of lead in industry sectors such as batteries [1], gasoline [2], metallurgies [3], and paints [4]. Lead poses a serious threat to food chains [5], human health [6], and the environment as a whole through chemical waste, soil, and water [7]. Even low levels of lead can pose serious threats for the central nervous system of infants and children, affecting their growth and development and leading to mental retardation [9,10]. Long-term intake of lead-contaminated food or water may result in various health disorders such as anemia [11], hypertension [12], diabetes [13], and reproductive dysfunctions [14].
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