An Ultra-sensitive Electrochemical Aptasensor for Detection of Cd2+
设计了一种基于核酸适配体检测镉离子（Cd2+）的电化学生物传感器，将适配体互补链（CDNA）通过AuS键自组装于金电极表面，并与适配体杂交结合形成双链DNA。由于适配体对Cd2+有特异性结合能力，加入Cd2+后，与互补链竞争结合适配体，使修饰二茂铁基团的适配体从金电极表面脱落，二茂铁的电化学信号显著减小。采用方波伏安法（SWV）进行检测，本传感器对Cd2+的线性检测范围为1.0 nmol/L~10.0 μmol/L，检出限为65.1 pmol/L，线性方程为ΔI=0.2872+0.2327lgC（R2=0.9972），10 s内即可完成检测。实际江水样品中Cd2+的检测结果与石墨炉原子吸收光谱法的检测结果一致，加标回收率为97.1%~99.5%。本方法灵敏度高、检测速度快、特异性强，在镉环境污染监测方面具有良好的应用前景。
An aptamer-based electrochemical biosensor was developed for detection of cadmium ions (Cd2+). Firstly, the mercapto-modified complementary sequence (CDNA) of aptamer was immobilized on the electrode surface via AuS bond. Then, it hybridized with aptamer to form a double-stranded DNA. Due to the specific binding of aptamer and Cd2+, the aptamer labeled with ferrocene was competed off the gold electrode, so that the electrochemical signal of ferrocene decreased significantly. By using square wave voltammetry (SWV) detection and under the optimal conditions, a linear relationship was found between the current signal and logarithm of Cd2+ concentration with an equation of ΔI=0.2827+0.2372lgC (R2=0.9972), where the linearity range was from 1.0 nmol/L to 10.0 μmol/L, with a detection limit of 65.1 pmol/L, and the recoveries in real river samples were 97.1%-97.9%, which was comparable to those measured by graphite furnace atomic absorption spectrometry. The proposed method displayed many advantages such as high sensitivity, fast detection and excellent specificity, and had a good application prospect in monitoring cadmium pollution.