Analytical Sciences

Detection of Gold Nanoparticles Aggregation Using Light Scattering for Molecular Sensing

Yuki YANO,*1 Masamichi NISOUGI,*2 Yuki YANO-OZAWA,*1 Tsuyoshi OHGUNI,*3 Atsushi OGAWA,*4 Mizuo MAEDA,*5 Tsuyoshi ASAHI,*2 and Tamotsu ZAKO*1,*3

*1 Department of Chemistry and Biology, Graduate School of Science and Engineering, Ehime University, 2-5 Bunkyo, Matsuyama, Ehime 790-8577, Japan
*2 Department of Materials Science and Biotechnology, Graduate School of Science and Engineering, Ehime University, 3 Bunkyo, Matsuyama, Ehime 790-8577, Japan
*3 Department of Chemistry, Faculty of Science, Ehime University, 2-5 Bunkyo, Matsuyama, Ehime 790-8577, Japan
*4 Proteo-Science Center, Ehime University, 3 Bunkyo, Matsuyama, Ehime 790-8577, Japan
*5 Bioengineering Laboratory, RIKEN Cluster for Pioneering Research, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan

Gold nanoparticles (AuNPs) have been commonly used in molecular sensing, in the form of observation of the color change from red to blue of the AuNP solution, caused by target-molecule-induced AuNP aggregation. In this work, the changes in absorbance and scattering spectra caused by AuNP aggregation were studied using thrombin-induced AuNP aggregation as a model. We demonstrated for the first time that scattering spectra is more sensitive to the changes owing to AuNP aggregation than absorbance spectra. Moreover, a digital color analysis of darkfield images using dark field microscopy (DFM) facilitated a simple method for detection of AuNPs aggregation without the use of spectroscopic analysis. Furthermore, we demonstrated that DFM is useful for detecting AuNPs aggregation in a colored solution, in which the color change by AuNPs aggregation is not visible.

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