Analytical Sciences

Abstract − Analytical Sciences, 33(12), 1369 (2017).

A Novel Biosensor Based on Terminal Protection and Fluorescent Copper Nanoparticles for Detecting Potassium Ion
WenJing DENG, Chang LIU, YanLei HU, RuQin YU, TingTing CHEN, and Xia CHU
State Key Laboratory of Chemo/Bio-Sensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, P. R. China
A novel biosensor for sensitively detecting potassium ion (K+) has been developed based on fluorescent copper nanoparticles (Cu NPs). In our design, we employ a label-free single-strand DNA (ssDNA) that contains two parts. One is 3′-terminus structure-switching aptamers (SSAs) that can fold into G-quadruplex after binding with its target K+. The other is 5′-terminus poly thymine (polyT) which works as a template to construct fluorescent Cu NPs. After incubating with K+, the part SSAs go through target-induced conformational changes. Benifiting from the exceptional digestion ability of exonuclease I (Exo I), the G-quadruplexes display effective resistance to nuclease digestion, so that 5′-terminus polyT remains and the in situ formation of Cu NPs provides a turn-on fluorescent signal that is used to evaluate the concentration of K+. The recovery of the fluorescence intensity is linearly correlated with the K+ concentration in the range of 0.05 to 1 mM with a detection limit of 0.05 mM. Compared with some methods, this assay is cost-effective and facile with high specificity. Meanwhile, this excellent strategy shows a great potentiality in other sensing approaches that can study the interaction between similar SSAs and different specific targets.