以亚甲基蓝为杂交指示剂的DNA电化学传感器

构建了一个以亚甲基蓝(MB)为杂交指示剂的电化学DNA传感体系:通过自组装的方式将巯基改性的单链DNA5′端(HS-ssDNA)连接到金电极表面形成Au-ssDNA,当检测体系中加入和Au-ssDNA互补的目标单链DNA(cssDNA)时,会形成一个双链DNA系统(Au-dsDNA),加入MB并通过循环伏安法检测了杂交过程中的信号变化,验证了Au-ssDNA及Au-dsDNA的形成。在4.0×10-6～1.0×10-5mol/L内,检测灵敏度随MB浓度的增加而升高,当浓度达到2.0×10-5mol/L时接近最大值。示差脉冲伏安法检测结果表明,该检测体系对目标DNA的选择性识别能力高,可区分具有单碱基错配的目标DNA序列。检测体系对目标DNA的检测灵敏度随着目标DNA浓度的增加而增加,在5.0×10-10～1.8×10-9mol/L内呈线性关系,计算所得对目标DNA的检测限为5.0×10-10mol/L。使用寿命检测表明,经过5次变性/杂交循环后,检测信号降低并接近于检测限。

DNA Electrochemical Biosensor with Methylene Blue as Hybridization Indicator

An electrochemical DNA sensing system was constructed and investigated with methylene blue(MB) as hybridization indicator.5'-End-SH modified DNA(HS-ssDNA) probes were firstly self-assembled onto the Au-electrode surface,and then hybridized with the complementary single stranded DNA(cssDNA) to form double-stranded DNA system(Au-dsDNA).The results based on differential pulse voltammetry(DPV) showed that cathodic signals of current system were affected by methylene blue(MB) concentration.Furthermore,a thin film formed on Au electrode surface was successfully identified via DPV measurement.Sensitivity of sensing probe was enhanced when the MB concentration ranged from 4.0×10-6 to 1.0×10-5 mol/L,and the optimum concentration of MB was suggested to be 2.0×10-5 mol/L.Recognizability of a single strand DNA with one mismatch indicated a sensing system with high specificity was achieved.The sensitivity was linear and increased when the target DNA concentration ranged from 5.0×10-10 mol/L to 1.8×10-9 mol/L,and the detecting limitation was estimated to be ca 5.0×10-10 mol/L.Moreover,recycling life of the sensing probe was detected to be 5 times.