Basu Soumen, Pal Tarasankar
Department of Chemistry, Indian Institute of Technology, Kharagpur 721302, India.
J Nanosci Nanotechnol. 2007 Jun;7(6):1904-10. doi: 10.1166/jnn.2007.739.
Gold nanoparticles of variable sizes have been prepared by reducing HAuCl4 with trisodium citrate by Frens' method. The synthesized gold particles show intense surface plasmon band in the visible region. The optical resonances in the visible are due to the surface plasmon oscillation, which is a function of geometry of the particles. The work reported here describes the interaction between nanoscale gold particles and a biomolecule, glutathione at low pH. Glutathione, which is a major cellular antioxidant and consists of amino acids glutamic acid, cysteine, and glycine, has been used as a molecular linker between the gold nanoparticles. In glutathione, the reactivity of the a-amines (adjacent to -COOH) is found to be pH-dependent. Linking via the a-amines are activated at low pH but suppressed at high pH due to electrostatic repulsive forces between the gold surfaces and the charged carboxylate groups. In colloidal solutions, the colour of gold nanoparticles may range from red to purple to blue, depending on the degree of aggregation as well as orientation of the individual particles within the aggregates. The citrate-functionalized gold nanoparticles with glutathione in variable acidic pH condition produce different but well-ordered aggregates. It is observed that a new peak appearing at a longer wavelength intensifies and shifts further to the red from the original peak position depending on the particle size, concentration of glutathione, and pH of the solution. The aggregates have been characterized by UV/Vis, FTIR, XRD, and TEM. On the basis of the first appearance of a clearly defined new peak at longer wavelength, a higher sensitivity of glutathione detection has been achieved with gold nanoparticles of larger dimension.
通过弗伦斯方法用柠檬酸钠还原氯金酸制备了尺寸可变的金纳米颗粒。合成的金颗粒在可见光区域显示出强烈的表面等离子体带。可见光中的光学共振归因于表面等离子体振荡，它是颗粒几何形状的函数。本文报道的工作描述了纳米级金颗粒与生物分子谷胱甘肽在低pH值下的相互作用。谷胱甘肽是一种主要的细胞抗氧化剂，由氨基酸谷氨酸、半胱氨酸和甘氨酸组成，已被用作金纳米颗粒之间的分子连接体。在谷胱甘肽中，α-胺（与-COOH相邻）的反应性被发现与pH值有关。通过α-胺的连接在低pH值下被激活，但在高pH值下由于金表面与带电荷的羧酸盐基团之间的静电排斥力而受到抑制。在胶体溶液中，金纳米颗粒的颜色可能从红色到紫色再到蓝色，这取决于聚集程度以及聚集体中单个颗粒的取向。在可变酸性pH条件下，具有谷胱甘肽的柠檬酸盐功能化金纳米颗粒产生不同但有序的聚集体。观察到在较长波长处出现的一个新峰随着颗粒尺寸、谷胱甘肽浓度和溶液pH值的变化而增强，并从原始峰位置进一步向红色移动。这些聚集体已通过紫外/可见光谱、傅里叶变换红外光谱、X射线衍射和透射电子显微镜进行了表征。基于在较长波长处首次出现清晰定义的新峰，使用较大尺寸的金纳米颗粒实现了对谷胱甘肽检测的更高灵敏度。
