title: Direct Fluorescent Detection of Blood Potassium by Ion-Selective Formation of Intermolecular G-Quadruplex and Ligand Binding.
abstract: G-quadruplex analogues have been widely used as molecular tools for detection of potassium ion (K(+)). However, interference from a higher concentration of sodium ion (Na(+)), enzymatic degradation of the oligonucleotide, and background absorption and fluorescence of blood samples have all limited the use of G-quadruplex for direct detection of K(+) in blood samples. Here, we reported, for the first time, an intermolecular G-quadruplex-based assay capable of direct fluorescent detection of blood K(+). Increased stringency of intermolecular G-quadruplex formation based on our screened G-rich oligonucleotide (5'-TGAGGGA GGGG-3') provided the necessary selectivity for K(+) against Na(+) at physiological ion level. To increase long-term stability of oligonucleotide in blood, the screened oligonucleotide was modified with an inverted thymine nucleotide whose 3'-terminus was connected to the 3'-terminus of the upstream nucleotide, acting as a blocking group to greatly improve antinuclease stability. Lastly, to avoid interference from background absorption and autofluorescence of blood, a G-quadruplex-binding, two-photon-excited ligand, EBMVC-B, was synthesized and chosen as the fluorescence reporter. Thus, based on selective K(+) ion-induced formation of intermolecular G-quadruplex and EBMVC-B binding, this approach could linearly respond to K(+) from 0.5 to 10 mM, which matches quite well with the physiologically relevant concentration of blood K(+). Moreover, the system was highly selective for K(+) against other metal ions, including Na(+), Ca(2+), Mg(2+), Zn(2+) common in blood. The practical application was demonstrated by direct detection of K(+) from real blood samples by two-photon fluorescence technology. To the best of our knowledge, this is the first attempt to exploit molecular G-quadruplex-based fluorescent sensing for direct assay of blood target. As such, we expect that it will promote the design and practical application of similar DNA-based sensors in complex real systems.
authors: State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Molecular Science and Biomedicine Laboratory, Hunan University , Changsha 410082, P. R. China.
authors: Le
authors: L
authors: Yang
authors: School of Chemistry and Biological Engineering, Changsha University of Science and Technology , Changsha 410004, P. R. China.
authors: Zhihe
authors: Z
authors: Qing
authors: State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Molecular Science and Biomedicine Laboratory, Hunan University , Changsha 410082, P. R. China.
authors: Changhui
authors: C
authors: Liu
authors: State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Molecular Science and Biomedicine Laboratory, Hunan University , Changsha 410082, P. R. China.
authors: Qiao
authors: Q
authors: Tang
authors: State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Molecular Science and Biomedicine Laboratory, Hunan University , Changsha 410082, P. R. China.
authors: Jishan
authors: J
authors: Li
authors: School of Chemistry and Biological Engineering, Changsha University of Science and Technology , Changsha 410004, P. R. China.
authors: Sheng
authors: S
authors: Yang
authors: State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Molecular Science and Biomedicine Laboratory, Hunan University , Changsha 410082, P. R. China.
authors: Jing
authors: J
authors: Zheng
authors: State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Molecular Science and Biomedicine Laboratory, Hunan University , Changsha 410082, P. R. China.|School of Chemistry and Biological Engineering, Changsha University of Science and Technology , Changsha 410004, P. R. China.
authors: Ronghua
authors: R
authors: Yang
authors: State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Molecular Science and Biomedicine Laboratory, Hunan University , Changsha 410082, P. R. China.
authors: Weihong
authors: W
authors: Tan