Autofluorescence is the natural emission of light by biological structures such as
mitochondria and
lysosomes when they have absorbed light, and is used to distinguish the light originating from artificially added fluorescent markers (
fluorophores).[1]
The most commonly observed autofluorescencing molecules are
NADPH and
flavins; the
extracellular matrix can also contribute to autofluorescence because of the intrinsic properties of
collagen and
elastin.[1]
Autofluorescence also occurs in non-biological materials found in many papers and textiles. Autofluorescence from U.S. paper money has been demonstrated as a means for discerning counterfeit currency from authentic currency.[3]
Microscopy
Autofluorescence can be problematic in
fluorescence microscopy. Light-emitting
stains (such as fluorescently labelled
antibodies) are applied to
samples to enable visualisation of specific structures.
Autofluorescence interferes with detection of specific fluorescent signals, especially when the signals of interest are very dim — it causes structures other than those of interest to become visible.
In some microscopes (mainly
confocal microscopes), it is possible to make use of different lifetime of the
excited states of the added fluorescent markers and the endogenous molecules to exclude most of the autofluorescence.
In a few cases, autofluorescence may actually illuminate the structures of interest, or serve as a useful
diagnostic indicator.[1]
For example, cellular autofluorescence can be used as an indicator of
cytotoxicity without the need to add fluorescent markers.[4]
The
super resolution microscopySPDM revealed autofluorescent cellular objects which are not detectable under conventional fluorescence imaging conditions.[7]
^
Kaufmann, R.; Müller, P.; Hausmann, M.; Cremer, C. (2010). "Imaging label-free intracellular structures by localisation microscopy". Micron. 42 (4): 348–352.
doi:
10.1016/j.micron.2010.03.006.
PMID20538472.
^
ab
Georgakoudi, I.; Jacobson, B.C.; Müller, M.G.; Sheets, E.E.; Badizadegan K.; Carr-Locke, D.L.; et al. (2002-02-01). "NAD(P)H and collagen as in vivo quantitative fluorescent biomarkers of epithelial precancerous changes". Cancer Research. 62 (3): 682–687.
PMID11830520.
^
Gallas, James M. & Eisner, Melvin (May 1987). "Fluorescence of melanin-dependence upon excitation wavelength and concentration". Photochemistry and Photobiology. 45 (5): 595–600.
doi:
10.1111/j.1751-1097.1987.tb07385.x.
S2CID95703924.