Murphy Jeffrey N, Cheng Alan K H, Yu Hua-Zhong, Bizzotto Dan
Advanced Materials and Process Engineering Laboratory, Department of Chemistry, University of British Columbia, Vancouver, BC, Canada V6T 1Z4.
J Am Chem Soc. 2009 Mar 25;131(11):4042-50. doi: 10.1021/ja808696p.
The creation of gold surfaces modified by single- or double-stranded DNA self-assembled monolayers (SAMs) is shown to produce heterogeneous surface packing densities through the use of electrochemical studies coupled with fluorescence imaging. The modified surfaces created by direct adsorption of thiolate DNA [followed by passivation with mecaptohexanol (MCH)] resulted in regions covered by a monolayer of DNA SAM and other regions that were coated by large particles of DNA. The difference in fluorescence intensity measured from these regions was dramatic. More importantly, a regional variance in fluorescence intensity in response to electrochemical potential was observed: the large aggregates showing a significantly different modulation of fluorescence intensity than the monolayer-coated regions. Electrochemical desorption and detection of the fluorescently tagged DNA provided clear evidence of a complete surface modification. These studies have implications for biosensor/biochip development using DNA SAMs. A modification in the method used to produce the DNA SAMs resulted in a significantly different surface with much fewer aggregates and more significant electromodulation of the fluorescence intensity, though at much lower DNA surface density (ca. 1% of maximum theoretical coverage). This method for forming the modified surfaces has clear advantages over the currently accepted practice and emphasizes the importance of studying the nonaveraged nature of the sensor surface using in situ imaging tools like electrofluorescence microscopy.
通过电化学研究与荧光成像相结合的方法，结果表明，由单链或双链DNA自组装单层膜（SAMs）修饰的金表面会产生不均匀的表面堆积密度。通过直接吸附硫醇盐DNA（随后用巯基己醇（MCH）钝化）形成的修饰表面，会产生被DNA SAM单层覆盖的区域以及被大颗粒DNA覆盖的其他区域。这些区域测得的荧光强度差异很大。更重要的是，观察到荧光强度随电化学电位的区域变化：大聚集体显示出与单层覆盖区域明显不同的荧光强度调制。对荧光标记DNA的电化学解吸和检测提供了表面完全修饰的明确证据。这些研究对使用DNA SAMs的生物传感器/生物芯片开发具有重要意义。用于制备DNA SAMs的方法的改进导致表面明显不同：聚集体少得多，荧光强度的电调制更显著，尽管DNA表面密度低得多（约为最大理论覆盖率的1%）。这种形成修饰表面的方法相对于目前公认的做法具有明显优势，并强调了使用电荧光显微镜等原位成像工具研究传感器表面非平均性质的重要性。
