DNA协助原位构建高密度“热点”可控的SERS基底及其传感检测研究

Surface-enhanced Raman scattering technology (SERS) is a rapid, ultrasensitive and non-destructive detection technique, which is suitable for the detection of biological samples in aqueous system, because it could provide fingerprint information of molecular vibration with high sensitivity, specificity, and the ability of simultaneous multiplex detection. The localizations of “hot spots” in the most of the reported SERS substrate are usually disordered with poor uniformity, leading to weak detection signal without uniformity, precision and reproducibility. Therefore, we devote our efforts to the in situ construction of SERS substrate for the purpose of high density addressable “hot sports” and uniform signal. By developing the strategy of stepwise assembly combined electrostatic interaction and DNA hybridization, the core-satellite nanostructured assemblies could be constructed on substrate over a large area with precise controllability, and high density “hot spots” can be obtained correspondingly, because the newly-formed localized surface plasmonic resonance (LSPR) coupling locations between core and satellite nanoparticles provide electromagnetic field enhanced “hot spots”. In order to fabricate SERS biosensor with controllable “On-off” signal switch, aptamer, which can binding targets specifically, could be introduced into the DNA sequences modified on the surface of building blocks, and the occurrence and disappearance of “hot spots” are controllable due to the assembly and disaasembly of core-satellite nanostructure resulted from the change of DNA conformation. Therefore, the research in this project has important significance for the development of SERS substrate with high density controllable “hot spots”, homogeneous signal and signal switch “On-off” for biosensing application.

表面增强拉曼散射技术（SERS）作为无损、快速的检测技术，适用于水体系及生物样品的分析，可提供分子结构振动的指纹图谱信息，具有高灵敏度、特异性及同时检测多目标的能力。但目前SERS基底存在活性“热点”排列无序、均匀性差的问题，导致检测信号缺乏精准性及重现性差。本项目致力于原位构建具有高密度 “热点”、且“热点”位置可控、信号均匀的SERS基底，通过发展结合静电组装及DNA杂交的原位分步组装策略来实现核-卫星纳米结构组装体在基底的均匀分散及大面积的精准可控构筑。核-卫星纳米粒子之间的表面等离子体共振（LSPR）耦合区域提供了电磁增强的活性“热点”，同时调控拉曼信号分子定位在 “热点”区域，从而实现高密度“热点”的可控构筑及SERS性能的可控增强。进一步将能够与靶分子特异性结合的适配体引入构筑基元表面，通过组装前后构象变化所引起的“热点”的变化，来构建“On-off”信号转换的SERS传感器。

DNA纳米技术目前已被广泛应用于生命分析，临床诊断及环境科学等领域。在本项目中，我们的核心设计理念是利用DNA来协助原位调控纳米颗粒构筑基元的组装，通过将DNA核酸适配体引入组装体系，利用靶标触发的纳米颗粒组装状态变化导致的Plasmonic、SERS或荧光等信号变化来实现相应的传感检测分析。 .（一）基于以上设计，我们首先研究了不同组分、不同尺寸、不同形貌的纳米构筑基元的合成制备及DNA修饰，有Au纳米球、Au纳米棒、Ag纳米颗粒、Ag纳米簇、Pt纳米颗粒、以及碳量子点等， 并对不同颗粒表面DNA接枝密度、修饰 DNA 序列的链长、修饰DNA的特殊二级结构等都进行了系统的研究和优化，以实现纳米颗粒表面DNA的成功可控修饰。目前已可实现Au、Ag纳米颗粒表面DNA修饰密度的调控，以及DNA链段在Au纳米棒侧面和端面等不同位置的可控修饰。（二）为进一步提高DNA调控纳米颗粒组装排布的精确性和可寻址性，我们致力于构建DNA brick和origami纳米结构作为纳米颗粒的精准组装平台，因此在DNA 纳米结构的设计和组装调控制备方面也同时开展了系统的研究工作，已发展了“晶种”和“错位连接”两种新的组装策略，成功实现了不同尺寸、维度的DNA纳米结构的可控组装，为DNA纳米结构的可控制备提供了新的设计策略。（三）将核酸适配体引入到纳米颗粒表面修饰的 DNA 序列中，通过待检靶标同 DNA 核酸适配体结合所引起的空间构象变化，来触发纳米颗粒的组装状态改变，从而构建光学信号响应的传感器。在序列设计中，我们还引入了DNA调控靶标循环的信号放大策略，提高了检测的灵敏度，可实现对多种目标物的快速、灵敏、重复性好的检测分析。.本项目的研究，有助于更精准纳米颗粒的组装排布及对相应材料的plasmonic、SERS信号、荧光信号的调控，为高灵敏度“off-on”信号打开型生物传感器的构建提供重要的指导和帮助。