Yuan Liang, Wang Xian, Fang Yimin, Liu Chenbin, Jiang Dan, Wo Xiang, Wang Wei, Chen Hong-Yuan
State Key Laboratory of Analytical Chemistry for Life Science and Collaborative Innovation Center of Chemistry for Life Sciences, School of Chemistry and Chemical Engineering, Nanjing University , Nanjing, Jiangsu 210093, China.
Anal Chem. 2016 Feb 16;88(4):2321-6. doi: 10.1021/acs.analchem.5b04244. Epub 2016 Jan 27.
Gold colloid changes its color when the internanoparticle distance changes. On the basis of analyte-induced aggregation or disaggregation behavior of gold nanoparticles (AuNPs), versatile colorimetric assays have been developed for measuring various kinds of analytes including proteins, DNA, small molecules, and ions. Traditional read-out signals, which are usually measured by a spectrometer or naked eyes, are based on the averaged extinction properties of a bulk solution containing billions of nanoparticles. Averaged extinction property of a large amount of nanoparticles diminished the contribution from rare events when the analyte concentration was low, thus resulting in limited detection sensitivity. Instead of measuring the averaged optical property from bulk colloid, in the present work, we proposed a digital counterpart of the colorimetric assay by imaging and counting individual AuNPs. This method quantified the analyte concentration with the number percentage of large-sized AuNPs aggregates, which were digitally counted with surface plasmon resonance microscopy (SPRM), a plasmonic imaging technique recently developed by us and other groups. SPRM was able to identify rare AuNPs aggregates despite their small population and greatly improved the detection sensitivity as demonstrated by two model systems based on analyte-induced aggregation and disaggregation, respectively. Furthermore, besides plasmonic AuNPs, SPRM is also suitable for imaging and counting nonplasmonic nanomaterials such as silica and metal oxide with poor extinction properties. It is thus anticipated that the present digitized assay holds a great potential for expanding the colorimetric assay to broad categories of nonplasmonic nanoparticles.
当纳米颗粒间距离发生变化时，金胶体的颜色也会改变。基于金纳米颗粒（AuNP）在分析物作用下的聚集或解聚行为，人们开发了多种比色分析法来检测包括蛋白质、DNA、小分子和离子在内的各种分析物。传统的读出信号通常通过光谱仪或肉眼测量，基于含有数十亿纳米颗粒的大量溶液的平均消光特性。当分析物浓度较低时，大量纳米颗粒的平均消光特性会削弱稀有事件的贡献，从而导致检测灵敏度有限。在本工作中，我们没有测量大量胶体的平均光学性质，而是通过对单个AuNP进行成像和计数，提出了比色分析法的数字对应方法。该方法通过大尺寸AuNP聚集体的数量百分比来量化分析物浓度，这些聚集体通过表面等离子体共振显微镜（SPRM）进行数字计数，SPRM是我们和其他团队最近开发的一种等离子体成像技术。SPRM能够识别数量稀少的AuNP聚集体，并且如分别基于分析物诱导的聚集和解聚的两个模型系统所证明的那样，极大地提高了检测灵敏度。此外，除了等离子体AuNP外，SPRM还适用于对消光特性较差的非等离子体纳米材料（如二氧化硅和金属氧化物）进行成像和计数。因此，可以预期，目前的数字化分析方法在将比色分析法扩展到广泛类别的非等离子体纳米颗粒方面具有巨大潜力。
