Nonenzymatic DNA-Based Fluorescence Biosensor Combining Carbon Dots and Graphene Oxide with Target-Induced DNA Strand Displacement for microRNA Detection.

Yuanyuan Gao,Jingjing Tian,Hong Yu,Botao Xiao

doi:10.3390/nano11102608

Abstract

Based on a fluorescence “on-off-on” strategy, we fabricated a simple and highly sensitive DNA-based fluorescence biosensor for the detection of micro (mi)RNA from carbon dots (CDs) and graphene oxide (GO) without complicated and time-consuming operations. CDs were successfully synthesized and conjugated to the end of a single-stranded fuel DNA that was adsorbed onto the surface of GO through π-π stacking, resulting in fluorescence quenching. In the presence of the target miRNA let-7a, the fuel DNA was desorbed from the GO surface, and fluorescence was restored through two successive toehold-mediated strand displacement reactions on double-stranded DNA-modified gold nanoparticles. The target miRNA let-7a was recycled, leading to signal amplification. The concentration of let-7a was proportional to the degree of fluorescence recovery. Under optimal conditions, there was a good linear relationship between the relative fluorescence intensity and let-7a concentration in the range of 0.01–1 nM, with a detection limit of 7.8 pM. With its advantages of signal amplification and high biocompatibility, this fluorescence sensing strategy can be applied to the detection of a variety of target miRNAs and can guide the design of novel biosensors with improved properties.

Highlights

MicroRNAs are a type of noncoding single-stranded small RNA with a length of about 20–24 nucleotides encoded by endogenous genes [1] that participate in the regulation of normal cellular activities, including proliferation, differentiation, and apoptosis, among others [2]
graphene oxide (GO) and AuNPs with a diameter of 15 nm were purchased from XFNANO Materials Tech
In the absence of let-7a, GO adsorbed single-stranded fuel DNA labeled with carbon dots (CDs) through hydrophobic interactions and π-π stacking and completely quenched the fluorescence of CDs through fluorescence resonance energy transfer (FRET)

Summary

Introduction

Micro (mi)RNAs are a type of noncoding single-stranded small RNA with a length of about 20–24 nucleotides encoded by endogenous genes [1] that participate in the regulation of normal cellular activities, including proliferation, differentiation, and apoptosis, among others [2]. MiRNAs show dysregulated expression in many cancers and have both tumor suppressor and proto-oncogenic functions [3]. The miRNA let-7a is a tumor suppressor [4,5]. The characteristics of miRNAs, including a small size [8], low abundance, and high degree of sequence homology among family members, make their detection technically challenging [9]. A variety of approaches are Nanomaterials 2021, 11, 2608.

Methods

Results

Conclusion