autofluorescen

Autofluorescence, also encountered as autofluorescen in some spellings, is the natural emission of light by biological or inorganic materials after they absorb light, without the need for external fluorescent dyes. It results from endogenous fluorophores and structural components that re-emit photons as fluorescence when excited by appropriate wavelengths.

In biological tissues, common sources include metabolic cofactors such as NADH and NADPH, the oxidized form of flavin adenine dinucleotide (FAD), and the pigment lipofuscin; structural proteins such as collagen and elastin; and porphyrins from heme breakdown. In plant tissues, chlorophyll and related pigments produce characteristic autofluorescence. The spectral properties vary by source and excitation wavelength, with excitation in the ultraviolet to blue range often yielding emission from blue-green to red.

Autofluorescence has several uses, particularly in label-free imaging. It can aid in histology, in vivo tissue assessment, dermatology, and plant biology by revealing tissue architecture, metabolic state, or pigment distribution. Imaging modalities include wide-field fluorescence, confocal and multiphoton microscopes, and newer techniques like fluorescence lifetime imaging (FLIM), which distinguishes signals based on decay time rather than color alone.

Challenges arise because autofluorescence can appear as background or confounding signal when studying targeted fluorescent probes. Its intensity and spectral profile depend on tissue type, age, metabolic condition, and illumination. To address this, researchers employ spectral unmixing, time-gated or lifetime-based discrimination, selective excitation strategies, and computational post-processing to separate autofluorescent components from signals of interest.