Lifetime Studies and Application of Sub-20-nm Fluorescent Nanodiamonds with Different Nitrogen Contents for Biolabeling

• Main Authors: Yu-Tang Chang, 張育唐
• Other Authors: Huan-Cheng Chang
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/38875430496322259124

碩士 === 國立臺灣大學 === 化學研究所 === 101 === Many different kinds of fluorescent nanomaterials have been developed in recent decades. Especially fluorescent nanodiamonds (FNDs), a novel nanocarbon material, is finding its way through various biological applications. The nitrogen-vacancy defect centers (N-V center) in FNDs are produced by high-energy ion beam bombardment and annealing of type Ib diamond. They emit red fluorescence upon illumination by yellow-green light. FND is highly biocompatible, chemically stable, easy to do surface coating, and free from photobleaching and photoblinking, making it suitable for biolabeling and real-time tracking applications. There are many factors affecting the fluorescence intensity of FNDs, including the preparation method, particle size, and nitrogen content. Measuring the fluorescence lifetimes of FND helps us understand better its photophysical properties and thus improve its fluorescence intensity. An increase of the fluorescence intensity with the nitrogen density was observed at nitrogen density of 100 ppm to 200 ppm but failed at larger than 200 ppm because of the reduced fluorescence quantum yield with the increase of nitrogen density. The ratio of negative and neutral N-V centers in FNDs with different nitrogen density is discussed. FNDs with sub-20-nm diameter are well suited for bioimaging applications. The work applies these small FNDs as a biomarker for actin and tunneling nanotubes (TNTs). In order to do biolabeling in cells, we first demonstrate FNDs coated with α-lactalbumin and further coupled with biotin through covalent cross-linkage. These biotinylated FNDs can bind selectively with dye-conjugated streptavidin and subsequently with biotinylated actin and TNTs with different thickness to show colocalization of FNDs and dye in confocal microscopy. With this technique, we achieve high-specificity targeting of TNTs and obtain high-quality fluorescence images of cells.