An optical method for the detection of potassium ion based on the conformational change of aptamer and fluorescent probe thiazole orange (TO) was reported. Anti-K+ aptamer was hybridized with its complementary strand which has a single base mutation and is shorter than aptamer. TO exhibited stronger fluorescence when it interacted with the double-strand DNA mentioned above. The fluorescence emission intensity of TO decreased when double-strand DNA was dehybridized due to the formation of G-quadruplex structure and single strand DNA in the presence of K +. The influences of TO concentration, temperature and time on the sensing of K+ were investigated. Under the optimum reaction conditions, a good linear relationship was found between the fluorescence decreasing ratio (IOF -IF)/IOF and the potassium ion concentration in the range of 1.0 × 10-6 -2. 0 × 10-4 moL/L, and a sensitive detection limit of 3.3 × 10-7 mol/L was obtained. Contrast experiments with other ions such as Li + , Na + , Ca2+ , Mg2+ and NH4+ showed that this method was label-free, simple and eeonomical, and could be used for the determination of K + in potassium penicillin-V tablets with good sensitivity and specificity for K +. The results obtained by this method were in agreement with those from atomic absorption spectrophotomertic analysis.%建立了一种基于核酸适体(Aptamer)构象效应和荧光探针噻唑橙(TO)为荧光分子开关进行钾离子检测的光学方法.室温下钾离子可与Aptamer结合形成G-四面体结构,使双链解链变为四面体结构和单链,从而导致TO荧光强度降低.考察了TO浓度、反应温度及反应时间的影响.在最佳实验条件下,钾离子浓度在1.0×10-6 ～2.0×10-4 mol/L范围内与荧光强度降低比率(I0F-IF)/I0F呈良好的线性关系,检出限达3.3×10-7 mol/L;对Li+、Na+、Ca2+、Mg2+、NH+4离子进行对照实验的结果表明,该方法不仅具有较好的灵敏度和选择性,且无需荧光标记,操作简单、成本低.将该方法用于药品中钾离子含量的测定,其结果与原子吸收法一致.
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