本文采用银染增强金纳米粒子（AuNPs）为信号因子，构建了一种新型的灵敏检测羟基自由基（·OH）的DNA电化学传感器. 首先，巯基化的DNA1通过Au—S键自组装于金基底电极表面. 然后，由Fenton反应产生的·OH可引起电极表面DNA1自组装层的氧化损伤裂解，未损伤的DNA1可与功能化AuNPs上的DNA2杂交. 利用AuNPs对银离子的催化还原反应，将银原子沉积在AuNPs的周围，形成一层银外壳，再用差分脉冲伏安法（DPV）技术对沉积的银进行电化学检测，从而实现·OH的定量分析. 研究结果表明, 在最优实验条件下，该传感器检测·OH的线性范围为0.2 ~ 200 μmol·L^-1，检测下限为50 nmol·L^-1. 该传感器有较好的重复性、选择性，并在抗氧化剂抗氧化能力评估方面具有潜在应用价值.

A novel DNA-based electrochemical sensor has been successfully constructed for sensitive detection of hydroxyl radical (·OH) based on the silver-enhanced gold nanoparticle label. Thiolated DNA1 was firstly immobilized on the gold electrode through Au—S bonds. The ·OH generated from Fenton reaction could induce serious oxidative damage of the DNA1 layer on the electrode surface. Then DNA2-functionalized gold nanoparticles (DNA2-AuNPs) were linked on the electrode through the hybridization between DNA2 and undamaged DNA1. Based on the catalytic reduction of silver ion by AuNPs, a silver layer was formed on the surface of AuNPs. The quantitative assay of ·OH was carried out by differential pulse voltammetry (DPV) detection of the deposited silver. Under the optimization conditions, the developed DNA-based biosensor could detect ·OH quantitatively with wide linear range (0.2 ~ 200 μmol·L^-1) and low detection limit (50 nmol·L^-1), and exhibited satisfactory selectivity and reproducibility. This electrochemical biosensor could have potential application in the evaluation of antioxidant capacity.