Crystal violet–G-quadruplex complexes as fluorescent sensors for homogeneous detection of potassium ion

A novel K+ detection method was reported using a label-free G-quadruplex-forming oligonucleotide and a triphenylmethane fluorescent dye crystal violet (CV). This method is based on the fluorescence difference of some CV/G-quadruplex complexes in the presence of K+ or Na+, and the fluorescence change with the variation of K+ concentration. According to the nature of the fluorescence change of CV as a function of ionic conditions, two K+ detection modes can be developed. One is a fluorescence-decreasing mode, in which T3TT3 (5′-GGGTTTGGGTGGGTTTGGG) is used, and the fluorescence of CV decreases with an increased concentration of K+. The other is a fluorescence-increasing mode, in which Hum21 (5′-GGGTTAGGGTTAGGGTTAGGG) is used, and the fluorescence of CV increases with an increased concentration of K+. Compared with some published K+ detection methods, this method has some important characteristics, such as lower cost of the test, higher concentrations of Na+ that can be tolerated, adjustable linear detection range and longer excitation and emission wavelengths. Preliminary results demonstrated that the method might be used in biological systems, for example in urine.

Graphical abstractA novel K+ detection method was reported in which a label-free G-quadruplex-forming oligonucleotide and a free triphenylmethane fluorescent dye crystal violet (CV) were used. This method can tolerate the presence of high concentration of Na+. According to the nature of the fluorescence change of CV as a function of ionic conditions, two K+ detection modes (fluorescence-decreasing detection mode and fluorescence-increasing detection mode) can be developed.Figure optionsDownload full-size imageDownload as PowerPoint slide