A label-free lead(II) ion sensor based on surface plasmon resonance and DNAzyme-gold nanoparticle conjugates

• Published in: Analytical and bioanalytical chemistry 2020-11, Vol.412 (27), p.7525-7533
• Main Authors: Wu, Huanan, Wang, Shuokang, Li, Sam Fong Yau, Bao, Qi, Xu, Qiyong
• Format: Article
• Language: English
• Subjects: Analytical Chemistry; Anchoring; Biochemistry; Biosensors; Cations, Divalent - analysis; Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Coupling; DNA, Catalytic - chemistry; Drinking water; Food Science; Gold; Gold - chemistry; Groundwater; Heavy metals; Hybridization; Immobilized Nucleic Acids - chemistry; Ions; Laboratory Medicine; Lead; Lead - analysis; Limit of Detection; Metal Nanoparticles - chemistry; Monitoring/Environmental Analysis; Nanoparticles; Onsite; Polaritons; Research Paper; Resonance; Selectivity; Sensitivity; Sensors; Substrates; Surface plasmon resonance; Surface Plasmon Resonance - methods; Toxicity; Water Pollutants, Chemical - analysis
• ISSN: 1618-2642; 1618-2650
• DOI: 10.1007/s00216-020-02887-z

Detection of lead(II) (Pb 2+ ) 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 Pb 2+ 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 Pb 2+ 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 Pb 2+ ions and simple detection procedure. Successful detection of Pb 2+ ions in groundwater indicates that this method has the prospect in the onsite detection of Pb 2+ 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. Graphical abstract