Micro RNA Sensing with Green Emitting Silver Nanoclusters

Abstract

<jats:p>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.</jats:p>

DNA-Templated Fluorescent Silver Nanoclusters Inhibit Bacterial Growth While Being Non-Toxic to Mammalian Cells

“…C11 DNA-AgNC also features an extra shoulder of emission at shorter excitation wavelengths. C9, C11, and C13 peaks appear to be elongated featuring red edge emission shift (REES) as reported previously and is common for AgNCs [ 23 , 26 , 27 ]. Interestingly, C7 DNA-AgNC does not have REES-based elongation of the emission peak that is well-pronounced for other samples.…”

“…The search for new therapeutic agents to combat multi-drug resistant bacteria is ongoing. While silver nanoparticles have been recently extensively studied for their use as antibacterial agents [ 31 ], novel silver nanoclusters have been largely overlooked [ 18 ] primarily because most studies have focused on biosensing applications due to the unique optical properties of AgNCs [ 27 , 32 , 33 ]. DNA-AgNCs have several advantages which position them as excellent candidates for antibacterial applications.…”

Hg2+ Detection with Rational Design of DNA-Templated Fluorescent Silver Nanoclusters

“…(1) switch-on (intensity enhancement) [34], (2) switch-off (intensity quenching) [35], (3) fluorescence pattern changes as observed in EEMs [36]. Our designs had the opportunity to provide all three mechanisms.…”

Large-scale investigation of the effects of nucleobase sequence on fluorescence excitation and Stokes shifts of DNA-stabilized silver clusters

“…[2][3][4] Researchers have collectively reported on Ag N -DNAs stabilized by thousands of different DNA strands, representing a diverse palette of fluorescence properties: emission spectra peaked at 450 nm to 1000 nm, 5,6 quantum yields from 3% to 93%, [7][8][9][10][11][12][13] Stokes shifts up to 0.73 eV (5900 cm −1 ), 14 and light-up or color-switching behavior induced by stimuli. [15][16][17][18] These diverse and sequence-tunable fluorescent Ag N -DNAs are promising for applications ranging from sensing [19][20][21][22] and molecular logic schemes 23 to background-free fluorescence microscopy [24][25][26] and nanophotonics. 10,27,28 Recent breakthroughs are rapidly advancing our understanding of the structures of certain Ag N -DNAs, 5,7,14,[29][30][31] , largely due to detailed studies of about 20 different Ag N -DNA species purified by high performance liquid chromatography (HPLC).…”