The living light (bioluminescence) emitted by fireflies is used widely in biomedicine as a marker of cells, gene expression and a range of other life or disease processes in living organisms ('in vivo'). Tracking and imaging biological events in vivo is crucial in a wide range biomedical studies. In recent years, the bioluminescence of fireflies has been re-engineered to emit in different colours at far-red to near-infrared (NIR) wavelengths, allowing better imaging in mammals, and bringing new and improved applications in biomedicine
Infraluciferin is a unique colour-shifting far-red to NIR analogue of firefly luciferin (the natural light emitting compound in fireflies). However, bioluminescence generated with infraluciferin is of much longer wavelengths than natural firefly bioluminescence, allowing it to pass much more easily through mammal tissues. As infraluciferin can also emit light of different wavelengths, or 'colours' (depending on the protein sequence of luciferase enzyme it reacts with), it enables the far-red to NIR bioluminescence imaging (BLI) of two things (like 2 types of cell or the expression of 2 different genes – ‘dual parameter’) at the same time in whole living mammals, like mice. Imaging is non-invasive and can be serial and longitudinal. The methyl ester of infraluciferin, as sold by Bioflares, is the version used for cell and animal/ organism imaging, as the stable and cell-penetrating ester is converted into active bioluminescent infraluciferin by cellular esterases. This reacts with firefly luciferase (or engineered variants), cellular adenosine triphosphate (ATP) and oxygen to produce far-red or NIR bioluminescence depending on the colour variant (protein sequence) of the luciferase enzyme (see schematics below, and click the link below the schematics for the literature references section of the website)
For best use, Bioflares also gives researchers access to brighter engineered infraluciferase (iluc) enzyme sequences to best enable dual parameter in vivo BLI (see infraluciferase section of website)
Bioluminescence reaction of D-infraluciferin methyl ester in cells or in vivo:
Schematic illustration of the spectral advantages of using infraluciferin for dual parameter in vivo bioluminescence imaging using infraluciferase (iluc) enzymes:
Dual parameter NIR bioluminescence spectra (red and black lines) at wavelengths beyond blood absorption (oxygenated blood absorption spectrum shown by dotted line)
For selected literature references on infraluciferin click here