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

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.