Amplified Surface Plasmon Resonance and Electrochemical Detection of Pb²⁺ Ions Using the Pb²⁺-Dependent DNAzyme and Hemin/G-Quadruplex as a Label

Abstract

The hemin/G-quadruplex nanostructure and the Pb(2+)-dependent DNAzyme are implemented to develop sensitive surface plasmon resonance (SPR) and electrochemical sensing platforms for Pb(2+) ions. A complex consisting of the Pb(2+)-dependent DNAzyme sequence and a ribonuclease-containing nucleic acid sequence (corresponding to the substrate of the DNAzyme) linked to a G-rich domain, which is "caged" in the complex structure, is assembled on Au-coated glass surfaces or Au electrodes. In the presence of Pb(2+) ions, the Pb(2+)-dependent DNAzyme cleaves the substrate, leading to the separation of the complex and to the self-assembly of the hemin/G-quadruplex on the Au support. In one sensing platform, the Pb(2+) ions are analyzed by following the dielectric changes at the surface as a result of the formation of the hemin/G-quadruplex label using SPR. This sensing platform is further amplified by the immobilization of the sensing complex on Au NPs (13 nm) and using the electronic coupling between the NPs and the surface plasmon wave as an amplification mechanism. This method enables the sensing of Pb(2+) ions with a detection limit that corresponds to 5 fM. The second sensing platform implements the resulting hemin/G-quadruplex as an electrocatalytic label that catalyzes the electrochemical reduction of H(2)O(2). This method enables the detection of Pb(2+) with a detection limit of 1 pM. Both sensing platforms reveal selectivity toward the detection of Pb(2+) ions.

Polymerase/nicking enzyme synergetic isothermal quadratic DNA machine and its application for one-step amplified biosensing of lead (II) ions at femtomole level and DNA methyltransferase

“…22,[26][27][28][29] This sensitivity is also much higher than those of several electrochemical and electrochemiluminescence approaches 24,25,30,31 and is even comparable to the surface plasmon resonance-based biosensor. 32 The details are summarized in Table 1.…”

Voltammetry and molecular assembly of G-quadruplex DNAzyme on single-crystal Au(111)-electrode surfaces – hemin as an electrochemical intercalator

“…Electronic conductivity of "non-canonical" DNA forms, quadruplexes in particular have also been addressed, but such reports have only begun to appear much more recently [27][28][29][30][31][32][33] , and with little if any direct approach to interfacial ; (c) surface immobilized G-quadruplexes finally offer perspectives for ultra-sensitive detection of metal ions [40][41][42] , complex biomolecules such as peptides [23][24][25][26][27][28][29][30] , and perhaps other analytes.…”

“…Other recent studies have addressed single-molecule conductivity in situ using direct conductivity approaches 39 . The G-qs structure can be combined with iron (III) porphyrin IX (hemin) through л−л stacking between the porphyrin and the guanine quartet plane 26,40,41 . This "hybrid", known as DNAzyme catalyzes the reduction of dioxygen or hydrogen peroxide similarly to the peroxidase enzyme class.…”

Guanine Quadruplex Electrochemical Aptasensors

“…In comparison with protein peroxidases, the hemin/G4 peroxidase-mimicking DNAzymes have several advantages, such as high chemical stability, low cost and simple synthesis. Hemin/G4 DNAzyme electrochemical biosensors were successfully used for the detection of cells [106,107], proteins [108][109][110] or low molecular weight molecules, such as adenosine monophosphate (AMP) [102,111,112], anticancer drugs [113], gaseous ligands [114], toxins [115,116], pollutant agents [117,118] or metal ions [119,120].…”