DNA增强金纳米颗粒过氧化物模拟酶活性检测K~+

许多纳米材料因具有与天然酶类似的催化活性而被应用于过程催化和酶促动力学分析等领域.本研究发现,当单链DNA如核酸适配子包被在金纳米颗粒表面时,金纳米颗粒的过氧化物模拟酶活性被增强,能催化更多的酶底物3,3′,5,5′-四甲基联苯胺(TMB)生成氧化态的蓝色产物,在650 nm处出现特征吸收峰.若进一步加入能与核酸适配子结合的靶物如K+,由于靶物与核酸适配子的特异性结合形成G-4折叠而从金纳米颗粒表面脱离,导致模拟酶活性降低,溶液颜色变浅,650 nm处的吸光度值随之降低.以此为反应基础,建立了靶物K+的可视化检测分析方法.以650 nm处吸收值变化(ΔA650)对K+浓度的自然对数进行拟合,发现在1.5×10-4~2.8×10-3 mol/L范围内有良好的线性关系,相关系数(r)为0.9916.本方法有很好的选择性,同时具有较强的普适性,可应用于其他具有核酸适配体的物质检测.

Enhanced peroxidiase-like activity of gold nanoparticles by DNA for potassium ion detection

Because of the artificial enzyme mimics, kinds of nanomaterials have been attracted much attention in the process of catalytic and enzymatic domain dynamic analysis. It was found that the single stranded DNA, taking an ssDNA aptamer against potassium ion（K＋） as an example, was able to greatly enhance the mimetic peroxidase activity of gold nanoparticles（AuNPs） to catalyze the oxidation of peroxidase substrate 3,3′,5,5′-tetramethylbenzidine（TMB） to form blue product in the presence of H2O2, which presented a characteristic absorbance at 650 nm. In the presence of K＋, the aptamer folded into a four-stranded tetraplex structure（G-4） and detached from the surface of AuNPs, resulting in the correspondingly reduced peroxidase activity of AuNPs, accompanying with the color fading and decrease of absorbance at 650 nm. Based on this, a colorimetric analysis of K＋ was proposed in the range of 1.5 × 10^-4–2.8 × 10^-3 mol/L with the correlation coefficient（r） of 0.9916, which was fitted with the change of absorbance at 650 nm and the natural logarithm of concentration of K＋. This work displayed the high selectivity towards K＋ sensing as well as other targets that possess aptamers.