Elsevier

Materials Letters

Volume 282, 1 January 2021, 128703
Materials Letters

The novel immobilization of G-quadruplex aptamer on Cu deposited surface using electrochemical method

https://doi.org/10.1016/j.matlet.2020.128703Get rights and content

Highlights

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    A novel method for AS1411 aptamer trapping on Cu nanoparticles (NPs) surface was exploited.

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    Electrocatalytic activity of surface by deposition of Cu NPs and aptamer was enhanced.

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    The immobilization of G-quadruplex aptamer on electrode via formed guanine based on Cu(111)

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    The Cu concentration for aptamer immobilization (10 µM) was selected 0.03 M.

Abstract

A simple and novel method for immobilization of AS1411 aptamer, on Cu nanoparticles (NPs) electrode has been presented. For the first time, AS1411 aptamer without any functionalization was successfully immobilized on the Cu-NPs coating because of the interaction between guanine and Cu(111). The electrochemical responses determined that the current decreased, due to the strong electrostatic repulsive interaction between the negatively charged phosphate groups in aptamer strands and [Fe(CN)6]3−/4− in the electrolyte solution, leading to less electron transfer efficiency in the system and indicating the absorbance of G- quadruplex aptamer on the surface of Cu-NPs. In this work, 0.03 M was chosen as the Cu concentration, and the optimized aptamer concentration and incubation time on Cu-NPs were determined 10 µM and 20 min, respectively. Finally, the outstanding performance of the immobilized aptamer on the Cu-NPs coated surface was confirmed by quartz crystal microbalance. This study provides a low cost and easy approach for G-quadruplex aptamer trapping on the metal surface without incorporation of any ligand which could be helpful for fast and reliable cancer diagnosis in biomedical researches.

Introduction

In recent years, various methods have been used to modify sensors as biological platforms. Among them, DNA aptamer modified electrodes have been utilized under a variety of conditions for in vitro diagnostics [1], [2], [3]. In order to immobilize aptamer, various strategies have been applied, including target binding-induced aptamer [4], label-free [5] and layer-by-layer [6]. However, most of them suffer from interfering elements which can decline the binding ability of the selected aptamer [7]. Various elements can specifically bind with guanine base in single strand DNA including methylene blue [8] and ions as Ni2+ [9], Cu2+ [10]. Results revealed that G- quadruplex aptamer as a kind of single strand DNA, rich in guanine bases, can be strangely absorbed on these the elements.

Recently, nanomaterials have found widespread applications in biological environments because of the large surface area. Among them, copper surface is a good candidate for DNA immobilization because of guanine and cutosine bases which can be formed on Cu(111) surface [11]. AS1411 aptamer is a 26-mer G-rich oligonucleotide DNA aptamer, applied as a model system in this research [12]. Moreover, as the charge density of G-quadruplex DNA is much higher than single sequence DNA [13], it is expected that its interaction with cations would be much stronger. In the present research, highly-efficient immobilization of AS1411 aptamer on the Cu-NPs electrode was achieved for the first time.

In this regard, G-quadruplex aptamer without any functionalization was applied to interact with Cu-NPs deposited into electrode. A rapid and accurate approach for the immobilization of G-quadruplex aptamer on Cu-NPs coated electrode is reported in the present work in which the formed guanine base on Cu(111) is able to absorb aptamers onto its surface. This interaction can be helpful to develop and modify electrodes.

Section snippets

Materials and methods

The gold electrode was cleaned in sulfuric acid solution (50 nM) by 15 cycles of cyclic voltammetry in a potential range of −400 to 1400 mV (vs. Ag/AgCl) at 100 mV s−1 until a stable cyclic voltammogram was obtained. The electrode was immersed in an electrolyte consisting of 0.03 M CuSO4·5H2O and 1.0 M sulfuric acid solutions at room temperature for potentiostatic deposition of Cu-NPs on the its surface. This process was optimized at the scan rate of 20 mV s−1 for 300 s. Immobilization of the

Results and discussion

The XRD patterns of the annealed specimens at 300 °C indicated the enhancement of the relative intensity ratio of Au(111)/Au(200) compared to that of non-annealed electrode (Fig. 1(A)). In addition, the characteristic peak of Cu(111) was detected at 2θ = 43.30° which could be distinguished from Au(200) (indicated at 2θ = 44.30°), confirming the Cu deposition. Moreover, the relative intensity of Cu(111) peaks enhanced with increasing deposition time, confirming the successful deposition of Cu.

Conclusions

A novel and simple method for the immobilization of AS1411 aptamer on Cu-NPs surface, without any functionalization, was developed. The reaction time, as well as concentration of Cu-NPs and aptamer in the reaction buffer was found to be key parameters affecting the sensitivity of trapping aptamer. Optimum concentration of G- quadruplex aptamer was obtained (10 μM) in presence of 0.03 M Cu-NPs, where the incubation time was 10 min. Results indicated the great potential of Cu-NPs-based platform

CRediT authorship contribution statement

Rana Bagheri: Data curation, Writing - original draft, Conceptualization, Methodology. Fathallah Karimzadeh: Supervision, Writing - review & editing. Ahmad Kermanpur: Supervision, Writing - review & editing. Mahshid Kharaziha: Conceptualization, Methodology, Writing - review & editing.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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