LED dye-linked silica nanoparticles with tunable size for imaging applications.
- Incorporation of a naphthalimide derivative greatly enhances photostability and increases pH tolerance.
- Large size range and easily tunable.
- Excited by visual light, 450-495 nm (blue) & emits visual wavelength, 545 nm (green).
- Particle can be excited and viewed by non-UV light, which reduces additional risk to the patient from UV exposure associated with fluorescent particles.
Fluorescein is one of the most widely-used green fluorescent labeling dyes in biomedical research because it has spectral properties that are favorable in aqueous media. However, due to its low photostability and steep pH-dependence, it is not ideal for a number of biological studies, in particular those using single-molecule fluorescence. In addition, fluorescein can exist in four different prototropic forms (monoanion, dianion, neutral, and cation), each with significantly different absorption and emission properties, that is dependent on the pH of the solution. pH stability is important in biomedical applications as imaging material can be exposed to low pH conditions in either the intracellular environment or systemically in the stomach. Because synthesized particles often have many OH groups, the change of pH might result in protonation which could affect fluorescent intensity and be detrimental to fluorescence labeling.
Emory researchers have generated LED dye-linked silica nanoparticles that incorporate a naphthalimide derivative. This derivative enhances photostability and pH tolerance of the dye. After 31 days exposure of various pH conditions, a change in morphology was not observed, their size and shape were the same as initial measurements, and no aggregations was observed in solution. A potential application of this particle is for medical imaging. For example, the particle could be used to identify changes in skin cells to a melanoma phenotype by conjugating targeting moieties to the surface. Because the nanoparticle can be excited and viewed by non-UV light, unlike fluorescent particles for imaging, UV exposure and its associated risks would be reduced in the patient.
Nanoparticles have been synthesized and characterized. They can be excited by commercial blue LED chips without any modification.