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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。
An electrochemical DNA sensing system with methylene blue (MB) as hybridization indicator was constructed. Au-ssDNA was formed by attaching the thiol-modified single-stranded DNA 5 ’end (HS-ssDNA) to the gold electrode by self- When a single-stranded DNA (cssDNA) complementary to Au-ssDNA was added to the detection system, a double-stranded DNA system (Au-dsDNA) was formed. MB was added and the signal changes during hybridization were detected by cyclic voltammetry. The formation of Au-ssDNA and Au-dsDNA was verified. In the range of 4.0 × 10-6 ~ 1.0 × 10-5mol / L, the detection sensitivity increased with the increase of MB concentration, reaching the maximum when the concentration reached 2.0 × 10-5mol / L. The results of differential pulse voltammetry showed that this detection system has a high ability of selective recognition of target DNA and can distinguish the target DNA sequence with single base mismatch. The sensitivity of the detection system to the target DNA increased with the increase of the target DNA concentration and the linearity was within 5.0 × 10-10 ~ 1.8 × 10-9 mol / L. The detection limit of the target DNA was 5.0 × 10- 10mol / L. Lifetime tests showed that after 5 denaturation / hybridization cycles, the detection signal decreased and approached the detection limit.