Micro RNA Sensing with Green Emitting Silver Nanoclusters.

Liam E Yourston,Alexey V Krasnoslobodtsev

doi:10.3390/molecules25133026

Liam E Yourston, Alexey V Krasnoslobodtsev

Open Access

https://doi.org/10.3390/molecules25133026

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Abstract

Micro RNA (miR) are regulatory non-coding RNA molecules, which contain a small number of nucleotides ~18–28 nt. There are many various miR sequences found in plants and animals that perform important functions in developmental, metabolic, and disease processes. miRs can bind to complementary sequences within mRNA molecules thus silencing mRNA. Other functions include cardiovascular and neural development, stem cell differentiation, apoptosis, and tumors. In tumors, some miRs can function as oncogenes, others as tumor suppressors. Levels of certain miR molecules reflect cellular events, both normal and pathological. Therefore, miR molecules can be used as biomarkers for disease diagnosis and prognosis. One of these promising molecules is miR-21, which can serve as a biomarker with high potential for early diagnosis of various types of cancer. Here, we present a novel design of miR detection and demonstrate its efficacy on miR-21. The design employs emissive properties of DNA-silver nanoclusters (DNA/AgNC). The detection probe is designed as a hairpin DNA structure with one side of the stem complimentary to miR molecule. The binding of target miR-21 opens the hairpin structure, dramatically modulating emissive properties of AgNC hosted by the C12 loop of the hairpin. “Red” fluorescence of the DNA/AgNC probe is diminished in the presence of the target miR. At the same time, “green” fluorescence is activated and its intensity increases several-fold. The increase in intensity of “green” fluorescence is strong enough to detect the presence of miR-21. The intensity change follows the concentration dependence of the target miR present in a sample, which provides the basis of developing a new, simple probe for miR detection. The detection strategy is specific, as demonstrated using the response of the DNA/AgNC probe towards the scrambled miR-21 sequence and miR-25 molecule. Additionally, the design reported here is very sensitive with an estimated detection limit at ~1 picomole of miR-21.

Highlights

IntroductionSilver nanoclusters (AgNC) are a novel class of nanomaterials that are only a few atoms in size
Silver nanoclusters (AgNC) are a novel class of nanomaterials that are only a few atoms in size.Cytosine-rich nucleic acid sequences template and stabilize silver nanoclusters limiting their size and modifying their electronic properties
We developed a novel method to detect Micro RNA (miR) sequences with the use of silver nanoclusters

Summary

Introduction

Silver nanoclusters (AgNC) are a novel class of nanomaterials that are only a few atoms in size. Cytosine-rich nucleic acid sequences template and stabilize silver nanoclusters limiting their size and modifying their electronic properties. The continuous density of states, typical for metal structures, breaks up into discrete energy levels in the nanoclusters. AgNCs are more stable in photobleaching than widely used organic dyes, quantum dots, or fluorescent proteins [3,4,5]. These properties make AgNCs suitable for a plethora of practical applications including luminescent labelling, biological imaging, sensing, and catalysis [6,7,8]. Since the precise knowledge of metal nanocluster photophysics is still lacking, further understanding of the energy transfer mechanism

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