Detecting Pb 2+ by a ‘turn-on’ fluorescence sensor based on DNA functionalized magnetic nanocomposites

Abstract Sensitive and selective detection of the lead ion (Pb 2+ ) plays an important role in terms of both human health and environmental protection, as the heavy metal is fairly ubiquitous and highly toxic. The highly stable fluorescence biosensor is composed of Fe 3 O 4 @TiO 2 core–shell nanocomposites, functionalized with a carboxyl fluorescein labeled DNA. The morphology, physical and chemical properties of the sensing nanomaterials were studied by transmission electron microscopy, FT-IR spectroscopy (FT-IR), x-ray powder diffraction and vibrating sample magnetometer. UV–visible and fluorescence spectroscopy were used to characterize the fluorescein functionalized magnetic nanoparticles. The performance of Pb 2+ detection displayed an excellent linearity ( R 2 = 0.995) in the range of 10 −10 to 5 × 10 −9 ppm with a detection limit of 10 −10 ppm, based on the optimization of the fabrication process and aptamers’ specification. The fluorescence biosensor has an accurate response, excellent recoveries and high adsorbent capacities. It was successfully applied for the determination of Pb 2+ in contaminated water and serum samples; the detection of limit in both media were 10 −10 ppm. These features ensure the potential use of aptamer functionalized magnetic nanocomposites as a new class of non-toxic biocompatible sensors for biological and environmental applications.