Bioluminescence imaging
Encyclopedia
Bioluminescence imaging (BLI) is a technology
developed over the past decade that allows for the noninvasive study of ongoing biological processes in small laboratory animals. Recently, bioluminescence tomography (BLT) has become possible and several systems have become commercially available.
Bioluminescence
is the process of light emission in living organism
s. Bioluminescence imaging utilizes native light emission from one of several organisms which bioluminesce. The three main sources are the North American firefly
, the sea pansy
(and related marine organisms), and bacteria like Photorhabdus luminescens
and Vibrio fischeri
. The DNA
encoding the luminescent protein is incorporated into the laboratory animal either via a viral vector
or by creating a transgenic animal
.
Systems derived from the three groups above differ in key ways:
While the total amount of light emitted from bioluminescence is typically small and not detected by the human eye, an ultra-sensitive CCD camera can image bioluminescence from an external vantage point.
Common applications of BLI include in vivo studies of infection (with bioluminescent pathogens), cancer progression (using a bioluminescent cancer cell line), and reconstitution kinetics (using bioluminescent stem cell
s).
Researchers at UT Southwestern Medical Center have shown that bioluminescence imaging can be used to determine the effectiveness of cancer drugs that choke off a tumor’s blood supply. The technique requires luciferin to be added to the bloodstream, which carries it to cells throughout the body. When luciferin reaches cells that have been altered to carry the firefly gene, those cells emit light.
The BLT inverse problem of 3D reconstruction of the distribution of bioluminescent molecules from data measured on the animal surface is inherently ill-posed. The first small animal study using BLT was conducted by researchers at the University of Southern California
, Los Angeles
, USA in 2005. Following this development, many research groups in USA and China have built systems that enable BLT.
Technology
Technology is the making, usage, and knowledge of tools, machines, techniques, crafts, systems or methods of organization in order to solve a problem or perform a specific function. It can also refer to the collection of such tools, machinery, and procedures. The word technology comes ;...
developed over the past decade that allows for the noninvasive study of ongoing biological processes in small laboratory animals. Recently, bioluminescence tomography (BLT) has become possible and several systems have become commercially available.
Bioluminescence
Bioluminescence
Bioluminescence is the production and emission of light by a living organism. Its name is a hybrid word, originating from the Greek bios for "living" and the Latin lumen "light". Bioluminescence is a naturally occurring form of chemiluminescence where energy is released by a chemical reaction in...
is the process of light emission in living organism
Organism
In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...
s. Bioluminescence imaging utilizes native light emission from one of several organisms which bioluminesce. The three main sources are the North American firefly
Firefly
Lampyridae is a family of insects in the beetle order Coleoptera. They are winged beetles, and commonly called fireflies or lightning bugs for their conspicuous crepuscular use of bioluminescence to attract mates or prey. Fireflies produce a "cold light", with no infrared or ultraviolet frequencies...
, the sea pansy
Sea pansy
The Sea pansy is quite frequently found washed ashore on northeast Florida beaches following northeasterly winds or rough surf conditions. It also can often be found living intertidally completely buried in the sand. Its predator is the striped sea slug, Armina tigrina.The Sea pansy is a...
(and related marine organisms), and bacteria like Photorhabdus luminescens
Photorhabdus luminescens
Photorhabdus luminescens is a Gammaproteobacteria, belonging to the family Enterobacteriaceae, and is a lethal pathogen of insects....
and Vibrio fischeri
Vibrio fischeri
Vibrio fischeri is a gram-negative rod-shaped bacterium found globally in marine environments. V. fischeri has bioluminescent properties, and is found predominantly in symbiosis with various marine animals, such as the bobtail squid. It is heterotrophic and moves by means of flagella. Free living...
. The DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
encoding the luminescent protein is incorporated into the laboratory animal either via a viral vector
Viral vector
Viral vectors are a tool commonly used by molecular biologists to deliver genetic material into cells. This process can be performed inside a living organism or in cell culture . Viruses have evolved specialized molecular mechanisms to efficiently transport their genomes inside the cells they infect...
or by creating a transgenic animal
Genetically modified organism
A genetically modified organism or genetically engineered organism is an organism whose genetic material has been altered using genetic engineering techniques. These techniques, generally known as recombinant DNA technology, use DNA molecules from different sources, which are combined into one...
.
Systems derived from the three groups above differ in key ways:
- Firefly luciferase requires D-luciferin to be injected into the subject prior to imaging. The peak emission wavelength is about 560 nm. Due to the attenuation of blue-green light in tissues, the red-shift (compared to the other systems) of this emission makes detection of firefly luciferase much more sensitive in vivo.
- Renilla luciferase (from the Sea pansySea pansyThe Sea pansy is quite frequently found washed ashore on northeast Florida beaches following northeasterly winds or rough surf conditions. It also can often be found living intertidally completely buried in the sand. Its predator is the striped sea slug, Armina tigrina.The Sea pansy is a...
) requires its substrate, coelenterazine, to be injected as well. As opposed to luciferin, coelenterazine has a lower bioavailability (likely due to MDR1 transporting it out of mammalian cells). Additionally, the peak emission wavelength is about 480 nm. - Bacterial luciferase has an advantage in that the lux operonOperonIn genetics, an operon is a functioning unit of genomic DNA containing a cluster of genes under the control of a single regulatory signal or promoter. The genes are transcribed together into an mRNA strand and either translated together in the cytoplasm, or undergo trans-splicing to create...
used to express it also encodes the enzymes required for substrate biosynthesis. Although originally believed to be functional only in prokaryotic organisms, where it is widely used for developing bioluminescent pathogens, it has been genetically engineered to work in mammalian expression systems as well. This luciferaseLuciferaseLuciferase is a generic term for the class of oxidative enzymes used in bioluminescence and is distinct from a photoprotein. One famous example is the firefly luciferase from the firefly Photinus pyralis. "Firefly luciferase" as a laboratory reagent usually refers to P...
reaction has a peak wavelength of about 490 nm.
While the total amount of light emitted from bioluminescence is typically small and not detected by the human eye, an ultra-sensitive CCD camera can image bioluminescence from an external vantage point.
Common applications of BLI include in vivo studies of infection (with bioluminescent pathogens), cancer progression (using a bioluminescent cancer cell line), and reconstitution kinetics (using bioluminescent stem cell
Stem cell
This article is about the cell type. For the medical therapy, see Stem Cell TreatmentsStem cells are biological cells found in all multicellular organisms, that can divide and differentiate into diverse specialized cell types and can self-renew to produce more stem cells...
s).
Researchers at UT Southwestern Medical Center have shown that bioluminescence imaging can be used to determine the effectiveness of cancer drugs that choke off a tumor’s blood supply. The technique requires luciferin to be added to the bloodstream, which carries it to cells throughout the body. When luciferin reaches cells that have been altered to carry the firefly gene, those cells emit light.
The BLT inverse problem of 3D reconstruction of the distribution of bioluminescent molecules from data measured on the animal surface is inherently ill-posed. The first small animal study using BLT was conducted by researchers at the University of Southern California
University of Southern California
The University of Southern California is a private, not-for-profit, nonsectarian, research university located in Los Angeles, California, United States. USC was founded in 1880, making it California's oldest private research university...
, Los Angeles
Los Ángeles
Los Ángeles is the capital of the province of Biobío, in the commune of the same name, in Region VIII , in the center-south of Chile. It is located between the Laja and Biobío rivers. The population is 123,445 inhabitants...
, USA in 2005. Following this development, many research groups in USA and China have built systems that enable BLT.