Fluorescence Imaging with Quantum Dot Nanocrystals

Oct 31, 2023 by IDEX Health & Science

Quantum dot nanocrystals are fluorophores that absorb photons and then re-emit longer-wavelength photons nearly instantaneously. However, there are some important differences between quantum dots (e.g., Qdot nanocrystals made by Thermo Fisher Scientific) and traditional fluorophores including organic dyes and naturally fluorescing proteins. Quantum dots are nanometer-scale clusters of semiconductor atoms, typically coated with an additional semiconductor shell and then a polymer coating to enable coupling to proteins, oligonucleotides, small molecules, etc., which are then used for direct binding of the quantum dots to targets of interest.

Nanocrystals are extremely bright and highly photostable, making them ideal for applications that require high sensitivity with minimal label interference, as well as long-term photostability, such as live-cell imaging and dynamic studies. Their excellent photostability also means they are fixable and archivable for permanent sample storage in pathology applications. Because there is a direct relationship between the size of a nanocrystal and the wavelength of the emitted fluorescence, a full range of nanocrystals can be made – each with a narrow, distinct emission spectrum and all excited by a single blue or ultraviolet wavelength. Thus nanocrystals are ideal for dense multiplexing. Some important nanocrystal features that may limit certain applications include their fairly large physical size and long lifetime.

To take advantage of nanocrystal features, it is important to use properly optimized filters. Semrock offers BrightLine^® filter sets specially optimized for the most popular quantum dot imaging applications. A universal set with a long-wave-pass emitter enables simultaneous imaging of multiple quantum dots by eye or with a color camera. Additionally, filter sets tailored to individual quantum dots are also available (see filter sets above). Best of all, these filters share the incredible “no burn-out” reliability of all BrightLine filters, an ideal match for highly photostable quantum dot nanocrystals!