Fluoresenssiimaging

Fluoresenssiimaging, or fluorescence imaging, is an optical imaging modality used to visualize biological structures and processes by detecting light emitted from fluorescent labels excited by light of specific wavelengths. It is widely used in biomedical research and clinical settings to track molecules, cells, and tissues in situ or in prepared samples.

Principle and modalities. A fluorophore absorbs photons at an excitation wavelength and returns to the ground state by emitting photons at a longer emission wavelength. The emitted light is captured using specialized optics and filters to separate it from excitation light, generating contrast based on the location and concentration of the label. Common modalities include widefield fluorescence, confocal microscopy for optical sectioning, and two-photon fluorescence imaging for deeper tissue penetration.

Instrumentation and labels. Fluorescence imaging relies on light sources such as LEDs or lasers, excitation and emission filters, dichroic mirrors, and sensitive detectors (CCD, EMCCD, or sCMOS cameras). Labels include organic dyes, fluorescent proteins (for example GFP and its variants), and quantum dots, which can be targeted to specific molecules using antibodies, genetic tagging, or chemical probes. Fluorescence lifetime imaging and FRET-based approaches extend the technique to measure dynamics and molecular interactions.

Applications and limitations. Fluorescence imaging is used to study cellular localization, protein interactions, gene expression, and disease mechanisms, as well as for surgical guidance and diagnostics. Limitations include autofluorescence of tissues, photobleaching and phototoxicity, limited depth penetration due to light scattering, and challenges in quantitative interpretation without careful calibration and controls.

See also. Fluorescence microscopy, confocal microscopy, and fluorescence lifetime imaging are related techniques often discussed alongside fluoreenssiimaging.