Fluorescent Quantum Dots

Dendrimers can be used to effectively coat and passivate fluorescent quantum dots to make biocompatible surfaces for coupling proteins or other biomolecules. In addition, the ability of dendrimers to contain guest molecules within their three-dimensional structure also has led to the creation of dendrimer-metal nanoclusters having fluorescent properties. In both applications, dendrimers are used to envelop metal or semiconductor nanoparticles that possess fluorescent properties useful for biological detection. 

Testing of G-l, G-2, and G-3 dendrimers in this application provided insight into the density of surface modification needed to passivate completely the particles and prevent aggregation. The G-l dendron was insufficient in this regard, but both the G-2 and G-3 dendron were big enough to create a surface barrier, which resulted in excellent colloidal stability of the particles in solution. 

The broad emission band displayed by these silver/dendrimer constructs actually was found to consist of 5 overlapping fluorescent peaks caused by individual silver/dendrimer complexes. Each of these complexes evidently contained a uniquely sized silver nanocluster, which resulted in an individual emission peak. Therefore, all the silver/dendrimer complexes together in solution presented a combined average of these 5 discrete emission peaks, and thus displayed the broad emission band covering nearly 200 nm in width across the spectrum. 

Lesniak et al. (2005) also describe the preparation and use of similar dendrimer/silver nanoclusters using G-5 PAMAM dendrimers terminated with either amino, hydroxyl, or 

In another example, ligands can be biotinylated with a cleavable biotinylation reagent and then incubated with receptor molecules. The resulting complex can be isolated by affinity chromatography on immobilized (strept)avidin. Final purification of the ligand-receptor can be accomplished by cleaving the biotin modification sites while the complex is still bound to the support. The receptor complex thus can be eluted from the column without the usual harsh conditions required to break the avidin-biotin interaction. 

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Fleischhaker, E Zentel, R. 2005. Photonic crystals from core-shell colloids with incorporated highly fluorescent quantum dots. Chem. Mater. 17 1346-1351. 

Jaiswal JK, Simon SM (2004) Potentials and pitfalls of fluorescent quantum dots for biological imaging. Trends Cell Biol 14 497-504... 

Yum K, Na S, Xiang Y, Wang N, Yu MF (2009) Mechanochemical delivery and dynamic tracking of fluorescent quantum dots in the cytoplasm and nucleus of living cells. Nano Lett 9 2193-2198... 

We were fortunate to have oral and poster presentations given by scientists from 19 countries, as well as active participation from industrial exhibitors. The sessions included luciferase-based bioluminescence, photoprotein-based bioluminescence, fundamental aspects and applications of chemiluminescence, luminescence imaging, fluorescence quantum dots and other inorganic fluorescent materials, phosphorescence and ultraweak luminescence, instrumentation and new methods. 

In addition to molecularly distributed compounds, the material can also be encapsulated as aggregate, crystal, etc., as is the case for the encapsulation of pigments and, for thermally labile azo-components, photoinitiators, and highly fluorescent quantum dots in polymeric nanoparticles by using the miniemulsion process. 

Tu C, Yang Y, Gao M (2008) Preparations of bifiinctional polymeric beads simultaneously incorporated with fluorescent quantum dots and magnetic nemocrystals. Nanotechnology 19 105601... 

The possible use of fluorescent quantum dots as labels in biological environments has made it necessary to devise ways to transfer semiconductor nanocrystals from organic to aqueous medium. Furthermore, the new layer of... 

N. Y. Morgan et al., Real time in vivo non-invasive optical imaging using near-infrared fluorescent quantum dots. Academic Radiology, 12(3), 313-323 (2005). 

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