基于Y型DNA结构和磁分离的荧光生物传感器同时检测Pb^(2+)和Cd^(2+)

A fluorescent biosensor for simultaneous detection of Pb^(2+)and Cd^(2+)based on Y-shaped DNA structure and magnetic separation

多种重金属离子共存对人类健康和环境安全构成严重威胁,因此,建立灵敏、快速和可靠的分析方法尤为重要。将靶标识别元件——核酸适配体和DNAzyme与Y型DNA结构以及磁分离相结合,构建了一种能够同时检测食品中Pb^(2+)和Cd^(2+)的荧光生物传感器。核酸适配体和DNAzyme分别对Cd^(2+)和Pb^(2+)具有高度特异性,经巧妙设计所得的Y型DNA结构可实现对双目标物的同时检测,借助磁珠的固载和磁分离能力可进一步提高传感器的灵敏度。基于以上策略,开发了一种操作步骤简单、灵敏度高和稳定性好的新型荧光传感器分析方法,分别在0.5~100μmol/L和0.01~100μmol/L范围内对Pb^(2+)和Cd^(2+)具有线性响应,检出限分别为9.7 nmol/L和0.4 nmol/L。此外,相对标准偏差为3.3%~5.4%,实际样品中Pb^(2+)和Cd^(2+)的回收率为82.33%~107.25%。所制备的荧光生物传感器能够为重金属离子的多重检测提供一种有力的工具。

The coexistence of multiple heavy metal ions poses a serious threat to human health and environmental safety,therefore it is particularly important to establish sensitive,rapid,and reliable analysis methods.Combining the target recognition elements including aptamer and DNAzyme with Y-shaped DNA structure and magnetic separation,a fluorescent biosensor was constructed for simultaneous detection of Pb^(2+)and Cd^(2+).The Pb^(2+) DNAzyme strand labeled with Cy5 was hybridized to the Cd^(2+)aptamer strand modified with FAM to form a stable Y-shaped DNA structure.This structure was anchored to the surface of magnetic beads by the strong binding force between biotin and streptavidin.In the absence of Pb^(2+)and Cd^(2+),the fluorescent groups of Cy5 and FAM remained stable in the Y-shaped DNA structure and were separated from the solution together with MBs by magnetic separation,hence,no significant fluorescence signal can be detected in the supernatant.When Pb^(2+) and Cd^(2+) were introduced,DNAzyme specifically recognizedPb^(2+)and the S-DNA was cleaved to release the ssDNA labeled with Cy5.Meanwhile,Cd^(2+)is competitively bound to the aptamer to separate it from the Y-shaped DNA structure.After magnetic separation,the fluorescence signals of Cy5 and FAM could be detected in the supernatant.Based on the above strategy,a novel fluorescence sensor with simple steps,high sensitivity,and good stability has been successfully developed.Under the optimal conditions,the prepared fluorescence biosensors showed a linear response to Pb^(2+)and Cd^(2+)in the range of 0.5 to 100μmol/L and 0.01 to 100μmol/L,respectively.The limit of detection(LOD)of Pb^(2+)and Cd^(2+)was 9.7 nmol/L and 0.4 nmol/L,respectively.In addition,the RSD was in the range of 3.3%to 5.4%and the recoveries ranged from 82.33%to 107.25%in actual samples.Therefore,the fabricated fluorescent biosensors are capable to provide a powerful tool for the multiplex detection of heavy metal ions.