DNA-modified core-shell Ag/Au nanoparticles
DNA-modified core-shell Ag/Au nanoparticles
复制标题
DOI：
10.1021/ja011342n
复制
发表时间：
2001-08-15
影响因子：
15
通讯作者：
Mirkin, CA
中科院分区：
文献类型：
--
作者：
Cao, YW;Jin, R;Mirkin, CA
1996年，我们报道了一种利用生物分子（如DNA）及其分子识别特性来引导用互补识别元件修饰的纳米颗粒构建块组装成功能材料的方法。这些材料在开发高灵敏度和选择性的DNA诊断方法中有着广泛的应用。2这种材料合成方法已经扩展到广泛的生物分子，包括肽和蛋白质，3以及适度的纳米颗粒集合，包括金和半导体量子点。4-9在每种情况下，当设计新的纳米颗粒组合物时，必须开发新的修饰方法以将生物分子固定在感兴趣的颗粒的表面上。这一办法已被广泛采用，但成效有限。用于修饰金纳米颗粒的方法现在已经被优化和推广用于广泛的颗粒尺寸和表面组成，包括球体和棒。1，2，4，10金颗粒特别容易改性，因为它们通常被带电配体（例如柠檬酸盐）的弱结合层稳定，该配体可以被具有比这些配体更强结合其表面的化学官能团（例如硫醇、胺和二硫化物）的分子取代。事实证明，CdSe和CdS量子点更难改性，因为它们具有与其表面非常牢固结合的表面活性剂层，因此很难被取代。5尚未开发出用于产生具有银纳米颗粒的稳定寡核苷酸缀合物的成功途径，主要是因为它们在用于实现DNA杂交的条件下倾向于化学降解。一个主要的进步将是设计一种方法，用于设计具有所选纳米颗粒组合物的物理性质但具有金的表面化学性质的颗粒。在此，我们报告了一种低温方法，用于生成由Ag的核和Au的单层壳组成的核壳颗粒，其可以容易地用寡核苷酸官能化，使用经证实的制备方法用于纯金颗粒寡核苷酸缀合物。此外，我们展示了这种新型纳米颗粒组合物如何用于访问不同于纯金系统的比色检测系统。2a，d Ag纳米颗粒是用于材料合成中的结构单元和作为生物标记物的所需组合物，这有两个重要原因。(1)Ag颗粒表现出在390 nm和420 nm之间的表面等离子体带，这取决于颗粒尺寸; 11这是与Au（520-580 nm）不同的光谱区域。(2)Ag颗粒的表面等离子体激元带的消光系数约为相同尺寸的Au颗粒的消光系数的4倍。因此，用DNA官能化的Ag颗粒不仅提供了定制DNA/纳米颗粒复合结构的光学性质的机会，而且还提供了依赖于表面等离子体带的位置和强度的新诊断系统的途径。（例如基于吸收或散射的比色系统，或SPR和Sers检测系统）。实验上，我们已经确定Ag纳米颗粒不能被烷基硫醇修饰的寡核苷酸有效地钝化，所述烷基硫醇修饰的寡核苷酸使用已建立的用于修饰Au颗粒的方案。2实际上，当在具有实现DNA杂交所需的盐浓度（0.05 M NaCl）的溶液中加热时，通过这种方法制备的Ag颗粒不可逆地聚集。在这里，我们使用核壳方法来克服这个问题。在这种方法中，薄的Au壳生长在Ag纳米颗粒上，形成颗粒。
In 1996, we reported a method for utilizing biomolecules, such as DNA, and their molecular recognition properties to guide the assembly of nanoparticle building blocks modified with complementary recognition elements into functional materials. 1 These materials have found wide application in the development of highly sensitive and selective diagnostic methods for DNA. 2 This material synthesis approach has been extended to a wide range of biomolecules, including peptides and proteins, 3 and a modest collection of nanoparticles, including gold and semiconductor quantum dots. 4-9 In each case, when a new nanoparticle composition is designed, new modification methods must be developed for immobilizing biomolecules on the surface of the particles of interest. This approach has been extensively utilized but with limited success. The methods for modifying gold nanoparticles have now been optimized and generalized for a wide range of particle sizes and surface compositions, including spheres and rods. 1, 2, 4, 10 Gold particles are particularly easy to modify because they are often stabilized with a weakly binding layer of charged ligands (eg, citrate) that can be replaced with molecules with chemical functionalities that bind more strongly (eg, thiols, amines, and disulfides) to their surfaces than these ligands. The CdSe and CdS quantum dots have proven more difficult to modify because they have a surfactant layer that is very strongly bound to their surfaces and, consequently, difficult to displace. 5 No successful routes have been developed for creating stable oligonucleotide conjugates with silver nanoparticles, primarily because they tend to chemically degrade under conditions used to effect DNA hybrization. A major advance would be to devise a method for designing particles with the physical properties of a chosen nanoparticle composition but with the surface chemistry of gold. Herein, we report a low-temperature method for generating coreshell particles consisting of a core of Ag and a monolayer shell of Au that can be readily functionalized with oligonucleotides using the proven preparatory methods for pure gold particle oligonucleotide conjugates. 2d Moreover, we show how this novel nanoparticle composition can be used to access a colorimetric detection system distinct from the pure gold system. 2a, d Ag nanoparticles are desired compositions for building blocks in material synthesis and as biological labels for two important reasons.(1) Ag particles exhibit a surface plasmon band between∼ 390 and 420 nm, depending on the particle size; 11 this is a spectral regime that is distinct from that of Au (520-580 nm).(2) The extinction coefficient of the surface plasmon band for an Ag particle is approximately 4 times as large as that for an Au particle of the same size. 12 Therefore, Ag particles functionalized with DNA would provide not only an opportunity to tailor the optical properties of DNA/nanoparticle composite structures but also routes to new diagnostic systems that rely on the position and intensity of the surface plasmon band (eg colorimetric systems based on absorption or scattering, or SPR and SERS detection systems).Experimentally, we have determined that Ag nanoparticles cannot be effectively passivated by alkylthiol-modified-oligonucleotides using the established protocols for modifying Au particles. 2 Indeed, Ag particles prepared via such methods irreversibly aggregate when heated in a solution with a salt concentration necessary to effect DNA hybridization (0.05 M NaCl). Herein, we use a core-shell approach to overcome this problem. In this approach, a thin Au shell was grown upon an Ag nanoparticle, forming a particle …