Enhanced DNA sensitized Tb3+ luminescence in organic solvents for more sensitive detection

• The first systematic study of Tb3+ luminescence with DNA in organic solvents.
• Different nucleosides, nucleotides and DNA show very different behavior.
• Most DNA oligonucleotide can further enhance Tb3+ emission in solvents allowing better sensor sensitivity.

DNA-sensitized Tb3+ luminescence spectroscopy is a powerful method for probing nucleic acids and developing biosensors. Its performance in organic solvents has yet to be explored. In this study, Tb3+ luminescence with nucleosides, nucleotides and DNA oligonucleotides in various organic solvents is studied. Tb3+ emission with single nucleotides is quenched up to 88% in dimethyl formamide (DMF), while its emission with nucleosides is enhanced. For the four 15-mer DNA homopolymers, the strongest absolute emission enhancement was achieved with C15. Similar emission properties are observed in other solvents including DMF, DMSO, acetonitrile methanol, ethanol, isopropanol and ethylene glycol. A few DNAzymes are tested as random DNA sequences all showing 1.4–6.9-fold emission enhancement in ethanol. A previously reported optimized sequence in water (G3T)5 is further enhanced by the solvents. Using this sequence, a detection limit of 5.5 nm Hg2+ is achieved in 25% ethanol solution. A similar Hg2+ sensitivity is also observed in a lake water mixed with ethanol. Luminescence lifetime is longer in DMF than in water. This study indicates that DNA-sensitized Tb3+ luminescence can be measured in water miscible solvents and most likely, with even stronger emission than that in water.

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