Label-Free DNA Assay by Metal Stable Isotope Detection

The interest in label-free bioassays is increasing rapidly because of their simple procedure and direct information on the interaction between the target molecule and the sensing unit. One of the major obstacles in the application of label-free biosensors is the difficulty to produce stable and reproducible optical, electric, electrochemical, or magnetic properties for the sensitive detection of the target molecules. In this work, we demonstrated a label-free DNA assay, by directly measuring the intrinsic Cu-63 and Cu-65 stable isotopes inside the double-strand DNA-templated Cu nanoparticles. The experimental conditions, including detection of copper by elemental mass spectrometry, the copper nanoparticles formation parameters, the hybrid chain reaction parameters, and analytical performance, were investigated in detail. The Cu-63 signal intensity possesses a linear relation with the concentration of target DNA over the range of 20-1000 pM with a detection limit of 4 pM (3 sigma). The detection limit of this method is among the most sensitive label-free techniques and also comparable to the lanthanides and Au nanoparticles labeled assays by elemental mass spectrometric detection. The proposed label-free bioassay is simple and sensitive and eliminated the need for optical, electric, electrochemical, or magnetic properties of the sensing unit. To our best knowledge, this is the first report of the label-free bioassay by metal stable isotope detection.

无标记生物检测因其操作简单以及能直接获取目标分子与传感单元之间相互作用的信息而迅速受到关注。无标记生物传感器应用的主要障碍之一是难以产生稳定且可重复的光学、电学、电化学或磁学性质，以实现对目标分子的灵敏检测。在这项工作中，我们通过直接测量双链DNA模板铜纳米颗粒内的固有Cu - 63和Cu - 65稳定同位素，展示了一种无标记DNA检测方法。对实验条件进行了详细研究，包括通过元素质谱检测铜、铜纳米颗粒形成参数、杂交链式反应参数以及分析性能。Cu - 63信号强度与目标DNA浓度在20 - 1000 pM范围内呈线性关系，检测限为4 pM（3σ）。该方法的检测限在最灵敏的无标记技术之列，并且与通过元素质谱检测的镧系元素和金纳米颗粒标记检测相当。所提出的无标记生物检测方法简单且灵敏，并且不需要传感单元具有光学、电学、电化学或磁学性质。据我们所知，这是首次通过金属稳定同位素检测进行无标记生物检测的报道。