Abstract
In this work, a novel colorimetric strategy for miRNA analysis is proposed based on hybridization chain reaction (HCR)-mediated localized surface plasmon resonance (LSPR) variation of silver nanoparticles (AgNPs). miRNA in the sample to be tested is able to release HCR initiator from a solid interface to AgNPs colloid system by toehold exchange-mediated strand displacement, which then triggers the consumption of fuel strands with single-stranded tails for HCR. The final produced long nicked double-stranded DNA loses the ability to protect AgNPs from salt-induced aggregation. The stability variation of the colloid system can then be monitored by recording corresponding UV-vis spectrum and initial miRNA level is thus determined. This sensing system involves only four DNA strands which is quite simple. The practical utility is confirmed to be excellent by employing different biological samples.
Highlights
Act as the stabilizer of the colloid system
After HCR initiated by target miRNA, the transformation of fuel strands with single-stranded DNA tails to double-stranded DNA changes the stabilization ability of DNA molecules in AgNPs colloid system, which can be reflected by UV-vis spectrum
Blocker DNA is immobilized on a gold solid interface via thiol-gold interaction[32]
Summary
A well characteristic absorbance peak at the wavelength around 400 nm can be confirmed in the UV–vis spectrum of AgNPs (Fig. 2b). A series of Mg2+ concentrations have been used to check the salt-tolerance of AgNPs. More Mg2+ may lead to the larger decrease of the absorbance peak. In which y is ΔA/A0, x is the concentration of Mg2+, A1 = 0.0204, A2 = 0.6810, x0 = 0.0062, dx = 0.0004, n = 3, R2 = 0.9977 The slope of this fitting curve reaches a maximum value at the point of 0.0062, indicating that AgNPs is most sensitive to the changes of salt when the concentration of Mg2+ is 6.2 mM, which is used for the following colorimetric investigation.
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