| Summary: | 碩士 === 國立臺灣大學 === 醫學工程學研究所 === 101 === Traditional fluorescent labels can be roughly categorized into two parts. One is fluorescent organic dye, the other is semiconductor nanocrystal. Both of them have advantages and limitations. Organic dye is the most popular fluorescent label due to its small size and good biocompatibility. However, there are some limitations coming out, such as high photobleaching efficiency and worse optical property. Fortunately, semiconductor nanocrystal improves some shortcomings of organic dye, e.g. excellent optical properties, good photo-stability and high quantum yield. However, the most widely used semiconductor nanocrystal is quantum dots (QDs), even though QDs are very toxic due to cadmium ions within their structure. Therefore, QDs are not suitable for long-term development. Besides, organic dye and QDs are down-conversion materials. They all need a high energy light source for excitation, such as ultra-violet. In this case, there are three problems to face including low penetration depth, biomolecules damage and low signal-to-noise ratio. In the last decade, new fluorescent labels started to rising up, called up-conversion nanoparticles (UCNPs). Compared to down-conversion material, UCNPs can transfer lower energy near infrared excitation into higher energy visible light by a nonlinear optical process. Moreover, UCNPs have many advantages such as autofluorescence absence, deeper tissue penetration depth, excellent optical and chemical stability, and low toxicity. However, in most cases, UCNPs are hydrophobic. Besides, research regarding the use of UCNPs as organelle targeting is not abundant. Therefore, in this study, NaYF4:Yb,Er upconversion nanoparticles were synthesized. After silica coating and amino group grafting, NaYF4:Yb,Er up-conversion nanoparticles could be made hydrophilic and later conjugated with biomolecules. For nuclear targeting purpose, nuclear localization signal (NLS) and TAT peptide was used to conjugate with silica coated NaYF4:Yb,Er nanoparticles. Our expectation is that NaYF4:Yb,Er@SiO2-NLS nanoparticles or NaYF4:Yb,Er@SiO2-TAT nanoparticles could be uptaken by cell and act as a nuclear tracker.
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