Studies On Functional Nucleic Acids Based Fluorescent Biosensors

Nucleic acids play an important role in living organisms because they store andtransmit genetic information and direct the synthesis of proteins. Nucleic acids alsohave the abilities to bind specific targets and catalyze reactions. Simple and practicalsensors can be developed based on high specificity of nucleic acids. In this paper, westudied the interactions between fluorescent ligands and various DNA structures(G-quadruplex and Triplex) using optical methods. Biosensors were designed basedon these specific interactions. More details are given below:First, the interactions between riboflavin and G-quadruplexes were studiedsystematically. PW17、G3T2、AGRO100、G3T and G3T4TT have stronger interactionwith riboflavin and decrease its fluorescence to about10%. Compared with ssDNAand dsDNA, riboflavin, as a new fluorescent ligand, has high specificity withG-quadruplex. Riboflavin has different interaction with various G-quadruplexes andcan not discriminate parallel G-quadruplexes from antiparallel ones. PW17hasstronger affinity to riboflavin than FMN and FAD.Second, high sensitive fluorescence detection of potassium were achieved basedon the interaction between riboflavin and PW17. The level of K+in urine wasdetermined using this fluorescent sensor. The recovery was in the range of84～109%after K+was added in the urine sample. The sensor had a good performance for thedetection in real samples.Third, a label-free fluorescent “OR” logic gate was designed based on DNAtriplex for the first time. Berberine can intercalate DNA triplex structure induced byAg+, resulting in fluorescence enhancement. This phenomenon is similar to that forthe interaction between berberine and DNA triplex in acidic condition. This systemfunctions as an OR logic gate for pH and Ag+. High sensitivity and a linear range0～15μM were achieved for the detection of Ag+.