Evolution of gold nanoparticle clusters in living cells studied by sectional dark-field optical microscopy and chromatic analysis

• Published in: Journal of biophotonics 2016-07, Vol.9 (7), p.738-749
• Main Authors: Wang, Sheng-Hann, Lee, Chia-Wei, Tseng, Fan-Gang, Liang, Kuo-Kan, Wei, Pei-Kuen
• Format: Article
• Language: English
• Subjects: chromatic analysis; Clusters; dark-field image; endocytosis; Endosomes; Fission; Gold; gold nanoparticles; Kinetics; Mathematical analysis; Microscopy; Nanoparticles; Nanostructure; Optical microscopy
• ISSN: 1864-063X; 1864-0648
• DOI: 10.1002/jbio.201500182

The evolution of gold nanoparticle (Au NP) clusters in living cells are studied by using sectional dark‐field optical microscopy and chromatic analysis approach. During endocytosis, Au NP clusters undergo fantastic color changes, from green to yellow‐orange due to the plasmonic coupling effect. Analysis of brightness/hue values of the dark‐field images helps estimate the numbers of Au NPs in the clusters. The Au NP clusters were further categorized into four groups within the endocytosis. As the results, the late endosomes had increased number of large Au NP clusters with time, while clustered numbers in secondary and tertiary groups were first increased and then decreased due to the fusion and fission of the endocytic vesicles. The time constants and cluster numbers for different groups are fitted by using an integrated rate equation, and show a positive correlation with the size of the Au NP cluster. The efficiency of Au NP uptake is only about 50% for normal cells, while 75% for cancer cells. Compared to normal cells, cancer cells show a larger number in uptake, while faster rate in removal. The propose method helps the kinetic study of endocytosed nanoparticles in physiological conditions. The scattering color of gold nanoparticles (Au NPs) are dependent on their aggregated number. Within the endocytosis process, the endosomes contained Au NPs inside would undergo the fission and fusion. Under the dark field illumination, the chromatic analysis of Au NP clusters can be used to refine the kinetics and number of influx and efflux of endosomes with different cell lines.