Hemin/G-Quadruplex Dnazyme for Electrochemical Biosensing

Review Article

Austin J Biosens & Bioelectron. 2015;1(2): 1009.

Hemin/G-Quadruplex Dnazyme for Electrochemical Biosensing

Yanping Gao*, Lin Liu and Ning Xia*

College of Chemistry and Chemical Engineering, Anyang Normal University, China

*Corresponding author: Ning Xia, College of Chemistry and Chemical Engineering, Anyang Normal University, Anyang, Henan 455000, People’s Republic of China

*Corresponding author: Yanping Gao, College of Chemistry and Chemical Engineering, Anyang Normal University, Anyang, Henan 455000, People’s Republic of China

Received: February 20, 2015; Accepted: March 29, 2015; Published: March 31, 2015

Abstract

Guanine quadruplex (G-quadruplex) can bind tightly with hemin to form the hemin/G-quadruplex that displays robust peroxidase activity. Acting as a peroxidase-mimicking DNAzyme, hemin/G-quadruplex has been considered as a promising artificial enzyme for biosensing because of its low cost, high thermal stability as well as easy preparation and modification in the laboratory. Recently, hemin/G-quadruplex–based electrochemical biosensors have been successfully used for the detection of proteins, DNA, metal ions and small molecules. In this short review, we highlighted the recent advances of the design of strategies for the fabrication of hemin/G-quadruplex–based electrochemical biosensors.

Keywords: Electrochemical biosensors; Guanine quadruplex; Hemin; DNAzyme

Abbreviations

G-quadruplex: Guanine quadruplex; HRP: Horseradish Peroxidase; GOx: Glucose Oxidase; PSA: Prostate Specific Antigen; FR: Folate Receptor; Fc: Ferrocene; MB: Methylene Blue; RCA: Rolling Circle Amplification; HCR: Hybridization Chain Reaction; EXPAR: Exponential Amplification Reaction; miRNA: microRNA; AuNPs: Gold Nanoparticles; [email protected]: [email protected] Nanowires; PdNPs: Pd Nanoparticles; rGO: reduced Gaphene Oxide; SWPN.b: Pebrine disease related Spore Wall Protein of Nosemabombycis; ADH: Alcohol Dehydrogenase; TBA: Thrombin Binding Aptamer; HPtCoNCs: PtCo Nanochains; FeTe NRs: iron Telluride Nanorods; PtNTs: Platinum Nanotubes; GDH: Glucose Dehydrogenase

Introduction

In recent years, enzyme-amplified electrochemical biosensors have attracted considerable attention and have emerged as viable alternatives to conventional spectrophotometric enzyme affinity assays for detection of trace amounts of biomarkers in biological studies, clinical diagnostics, and treatment. Commonly, peroxidase and phosphatase are the used enzyme labels in connection to electrochemical monitoring of the biocatalytic reaction product. The enzymatic reaction may follow two strategies: one in which the current is the electro catalytic response of a redox couple serving as a substrate to a redox enzyme label and another in which an electrochemically active product of the enzyme label is detected. Guanine-rich nucleic acid sequence can fold into Guanine quadruplex (G-quadruplex) that is found to complex tightly with hemin to form the hemin/G-quadruplex. Under physiological conditions, the hemin/G-quadruplex displays robust peroxidase activity. Recently, the hemin/G-quadruplex peroxidase-mimicking DNAzyme has been considered as a promising artificial enzyme for biosensing due to its low cost, high stability and simple preparation procedure in the laboratory. In this short review, we highlighted the recent advances of the design of strategies for the fabrication of hemin/G-quadruplex– based electrochemical biosensors.

Hemin/G-quadruplex–based electrochemical biosensors

Willner’s group, for the first time, demonstrated that the hemin/ G-quadruplex Horseradish Peroxidase (HRP)-mimicking DNAzyme on electrode exhibited bioelectrocatalytic functions toward the electro catalyzed reduction of H2O2 [1]. The electro catalytic properties of the DNAzyme were then used to develop electrochemical sensing platforms for analyzing the activities of enzymes and their substrates, DNA-sensors and aptasensors. The simplest methodology was to attach Glucose Oxidase (GOx) to the electrode surface through a nucleic acid sequence able to form a G-quadruplex structure in the presence of hemin (Figure 1) [1]. The GOx mediated the glucose oxidation to gluconic acid and H2O2 and the resulting H2O2 was analyzed through its electro catalyzed reduction by the DNAzyme. The success of the initial efforts provides good motivation for further manipulation of kinds of hemin/G-quadruplex–based electrochemical biosensors for detection of DNA [1], proteins (e.g. thrombin, recombinant human IFN-g) [2,3] and metal ions [4,5]. The most common strategy consists on modification of the gold electrode by a hairpin nucleic acid oligonucleotides that contains both a sequence capable to form G-quadruplex and an aptamer able to specifically bind the analyte. In the presence of the analyte and hemin, the hairpin structures were opened, the analyte bound to the aptamer part, and hemin/G-quadruplex structures were formed on the electrode surface. Furthermore, sandwich-like electrochemical biosensors with single hemin/G-quadruplex DNAzyme or hemin/Gquadruplex DNAzyme wires containing many units of hemin/Gquadruplex DNAzyme as the signal tags have also been developed for detection of Prostate Specific Antigen (PSA) and telomere [6], cisplatin (a cytotoxic and antineoplastic metallodrug) [7] as well as Folate Receptor (FR) [8]. In the DNAzyme electrochemical assays, redox reporters such as Ferrocene (Fc) and Methylene Blue (MB) could be used as the electron-transfer mediators for the DNAzyme to improve the sensitivity [9-11].