A label-free lead(II) ion sensor based on surface plasmon resonance and DNAzyme-gold nanoparticle conjugates
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RESEARCH PAPER
A label-free lead(II) ion sensor based on surface plasmon resonance and DNAzyme-gold nanoparticle conjugates Huanan Wu 1 & Shuokang Wang 1 & Sam Fong Yau Li 2 & Qi Bao 1 & Qiyong Xu 1 Received: 25 May 2020 / Revised: 6 August 2020 / Accepted: 14 August 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Detection of lead(II) (Pb2+) ions in water is important for the protection of human health and environment. The growing demand for onsite detection still faces challenges for sensitive and easy-to-use methods. In this work, a novel surface plasmon resonance (SPR) biosensor based on GR-5 DNAzyme and gold nanoparticles (AuNPs) was developed. Thiolated DNAzyme was immobilized on the gold surface of the sensor chip followed by anchoring the substrate-functionalized AuNPs through the DNAzyme-substrate hybridization. The coupling between the localized surface plasmon (LSP) of AuNPs and the surface plasmon polaritons (SPP) on the gold sensor surface was used to improve the sensitivity. The substrate cleavage in the presence of Pb2+ ions was catalyzed by DNAzyme, leading to the removal of AuNPs and the diminished LSP-SPP coupling. The optimal detection limit was 80 pM for the sensor fabricated with 1 μM DNAzyme, corresponding to two or three orders of magnitude lower than the toxicity levels of Pb2+ in drinking water defined by WHO and USEPA. By tuning the surface coverage of DNAzyme, the sensitivity and dynamic range could be controlled. This sensor also featured high selectivity to Pb2+ ions and simple detection procedure. Successful detection of Pb2+ ions in groundwater indicates that this method has the prospect in the onsite detection of Pb2+ ions in water. Given the variety of AuNPs and metal-specific DNAzymes, this detection strategy would lead to the development of more sensitive and versatile heavy metal sensors. Keywords DNAzyme . Surface plasmon resonance . Gold nanoparticles . Lead(II) ions
Introduction Lead(II) (Pb2+) ions are highly toxic heavy metal ions widely distributed in industrial wastewater, and they are hazardous to human health and environment through water contamination [1]. The maximum concentrations of lead in drinking water set by the World Health Organization (WHO) and the United States Environmental Protection Agency (EPA) are 48 nM and 72 nM, respectively [2]. Detection and analysis of lead Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00216-020-02887-z) contains supplementary material, which is available to authorized users. * Qiyong Xu [email protected] 1
Shenzhen Engineering Laboratory for Eco-Efficient Recycled Materials, School of Environment and Energy, Peking University Shenzhen Graduate School, Shenzhen 518055, Guangdong, China
2
Department of Chemistry, National University of Singapore, Singapore 117543, Singapore
ions are in growing demands, but they are mostly done with sophisticated instruments in laboratories, such as the inductively coupled plasma (ICP) technique integrated with opti
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