Abstract
Nucleic acid stability and structure, which are crucial to the properties of fluorescent DNA-templated silver nanoclusters (DNA-Ag NCs), significantly change in ionic liquids. In this work, our purpose was to study DNA-Ag NCs in a buffer containing the hydrated ionic liquid of choline dihydrogen phosphate (choline dhp) to improve fluorescence for application in DNA detection. Due to the stabilisation of an i-motif structure by the choline cation, a unique fluorescence emission—that was not seen in an aqueous buffer—was observed in choline dhp and remained stable for more than 30 days. A DNA-Ag NCs probe was designed to have greater fluorescence intensity in choline dhp in the presence of a target DNA. A turn-on sensing platform in choline dhp was built for the detection of the BRCA1 gene, which is related to familial breast and ovarian cancers. This platform showed better sensitivity and selectivity in distinguishing a target sequence from a mutant sequence in choline dhp than in the aqueous buffer. Our study provides new evidence regarding the effects of structure on properties of fluorescent DNA-Ag NCs and expands the applications of fluorescent DNA-Ag NCs in an ionic liquid because of improved sensitivity and selectivity.
Highlights
Ionic liquids (ILs), a type of eco-friendly solvents, have garnered interest in recent years because of their unique physicochemical properties such as non-volatility, non-flammability, and good conductivity [1]
C-rich sequences are widely used as templates for the synthesis of DNA-Ag NCs
A-T base pairs are more stable than C-G base pairs in choline dhp, and i-motif structures are greatly stabilised [9]
Summary
Ionic liquids (ILs), a type of eco-friendly solvents, have garnered interest in recent years because of their unique physicochemical properties such as non-volatility, non-flammability, and good conductivity [1]. Nucleic acids are popular building blocks for the design and synthesis of nanomaterials, owing to special base pairing interactions. Unique interactions between nucleic acid and ILs make remarkable differences compared with aqueous conditions [3,4]. Our previous works have revealed different behaviours of nucleic acids in choline dhp [8]. The stability of Watson–Crick and Hoogsteen base pairs is greatly changed in choline dhp [9], in which non-canonical structures such as a triplex and the i-motif are stabilised [10,11]. ILs have been reported to be good storage media for biomolecules with enhanced stability and activity [12]. Uses of ILs for the Molecules 2018, 23, 2889; doi:10.3390/molecules23112889 www.mdpi.com/journal/molecules
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