Breaking News
September 22, 2018 - Cardiac MR With Contrast Feasible in Developing World
September 22, 2018 - Daily low-dose aspirin doesn’t reduce heart-attack risk in healthy people
September 21, 2018 - Children with asthma found to be disadvantaged in education and future occupation
September 21, 2018 - Interaction of chemical slurry and ancient shale in fracking wastewater causes radioactivity
September 21, 2018 - Researchers find that sample size is key factor determining accuracy of study results
September 21, 2018 - Study shows how the drive to eat overpowers the brain’s signal to stop
September 21, 2018 - 30 Million Americans Now Have Diabetes
September 21, 2018 - Thousands of breast cancer gene variants engineered and analyzed
September 21, 2018 - The current fellowship interview process is cumbersome — Stanford researchers have a better idea
September 21, 2018 - Progenitor cells for human bone and cartilage have been identified
September 21, 2018 - Study reveals new therapeutic target for pediatric tumor-associated intractable epilepsy
September 21, 2018 - SLU’s College professor receives NIH grant to develop I-TEST project
September 21, 2018 - DermTech completes enrollment in clinical study to assess DNA damage and reversal
September 21, 2018 - Grieving patients treated with talk therapy have lower risk of suicide and psychiatric illness
September 21, 2018 - NIH and FDA call for eliminating involvement of RAC in human gene therapy experiments
September 21, 2018 - New system uses algorithm to convert 2D videos into 3D printed ‘motion sculptures’
September 21, 2018 - Sea squirt model reveals key molecules in dopaminergic neuron differentiation
September 21, 2018 - Effective management of neonatal abstinence syndrome requires coordinated ‘cascade of care’
September 21, 2018 - Refugees seek care for wounds of war
September 21, 2018 - Under the sea, in an octopus’ garden on ecstacy
September 21, 2018 - Eating foods with low nutritional quality ratings linked to cancer risk in large European cohort
September 21, 2018 - Giving kids honest information about water consumption may help them make healthy choices
September 21, 2018 - Horwitz Prize Awarded for Work on Hormones
September 21, 2018 - CHMP issues positive opinion supporting use of Trelegy Ellipta in broader group of COPD patients
September 21, 2018 - Scientists discover new molecules that work together to remove unwanted DNA
September 21, 2018 - Dr. Fenella France to deliver 2019 Plenary Lecture
September 21, 2018 - New research finds that MHC-II molecules have more influence on tumors than MHC-I
September 21, 2018 - Researchers study effects of cardiac cycle in simple learning task
September 21, 2018 - FDA takes new steps to address opioid crisis by approving Opioid Analgesic Risk Evaluation and Mitigation Strategy
September 21, 2018 - Positive Barhemsys Phase 3 Treatment Data Published in Anesthesia & Analgesia
September 21, 2018 - Celiac Disease Screening: MedlinePlus Lab Test Information
September 21, 2018 - Autism linked to egg cells’ difficulty creating large proteins
September 21, 2018 - Tweaking nuclear pores could provide new avenue to battle against cancer
September 21, 2018 - Experts warn health care providers to slow down in allowing smart pill in patient care settings
September 21, 2018 - MoreGrasp reports breakthrough development of grasp neuroprosthetics activated by thought control
September 21, 2018 - Study reveals new way to target HER2-negative metastatic breast cancer
September 21, 2018 - CHMP grants positive opinion for VENCLYXTO plus rituximab for treating relapsed/refractory CLL
September 21, 2018 - Study offers solid link between visceral organs and brain’s reward, motivation system
September 21, 2018 - First U.S. patient treated with innovative gene therapy at Bascom Palmer Eye Institute
September 21, 2018 - New study shows how Ethiopia has managed to achieve extraordinary progress
September 21, 2018 - Choroidal Detachment – The American Society of Retina Specialists
September 21, 2018 - New clinical trial evaluates aesthetic results of conservative surgery in breast cancer
September 21, 2018 - Discovery of a key protein involved in the development of autism
September 21, 2018 - Air pollution appears to be linked to increased risk of developing dementia
September 21, 2018 - Henry Ford Health System receives $600k grant to study genetic makeup of gliomas
September 21, 2018 - Arthritis common in individuals with varying degrees of depression, finds study
September 21, 2018 - Scientist intends to fight pathogenic bacteria with viruses
September 21, 2018 - New research suggests link between PFAS chemicals and hyperthyroidism in pet cats
September 21, 2018 - Multi-year study data shows impact of new soft contact lens to slow myopia progression in children
September 21, 2018 - Neuroscientists identify circuit for brain’s statistical inference about motion
September 21, 2018 - MILabs’ VECTor6 system wins Commercial Innovation Award at WMIC 2018
September 21, 2018 - Scientists find wild African monkeys infected with bacterium that causes syphilis, yaws in humans
September 21, 2018 - 2006 to 2015 Saw Increase in Severe Maternal Morbidity
September 21, 2018 - Similar changes in the brains of patients with ADHD and emotional instability
September 21, 2018 - Cobalt mining in DR Congo takes a high toll on both creuseurs and environment
September 21, 2018 - Eating fatty fish during pregnancy may boost unborn child’s brain development
September 21, 2018 - Study reveals promising new drug candidate to treat acute renal failure
September 21, 2018 - Neural signal that urges to eat overpowers the one that says to stop
September 21, 2018 - Scientists achieve breakthrough in accelerated diagnosis of multi-resistant hospital pathogens
September 21, 2018 - Researchers simulate how different breast tissues respond to heat from MRIs
September 21, 2018 - Despite red flags at surgery centers, overseers award gold seals
September 21, 2018 - Zapping Airway Nerves May Help COPD Patients Breathe
September 21, 2018 - Researchers find answers as to why some people are at risk of gout
September 21, 2018 - Stars of Stanford Medicine: Genetic counseling and compassion
September 21, 2018 - Researchers use reinforcement learning to train gliders to soar like birds
September 21, 2018 - New federally-funded research project could lead to treatments that extend human lifespan
September 21, 2018 - Health insurance ads have shifted over time due to health plans offered via ACA
September 21, 2018 - Use of transcranial electrical stimulation to bolster creativity has far-reaching implications
September 21, 2018 - Scientists find way to boost efficacy of powerful antimalarial drug with anti-cancer medicines
September 21, 2018 - Weighing the risks and benefits of drug tapering—two patients, two perspectives
September 21, 2018 - The “exposome” revealed: a barrage of bacteria, chemicals, microscopic animals and more
September 21, 2018 - Top three immune boosting recommendations to ward off freshers’ flu
September 21, 2018 - Young children’s oral microbiota could serve as early indicator for obesity
September 21, 2018 - Older individuals with multiple sclerosis report higher quality of life than younger counterparts
September 21, 2018 - LineaRx signs agreement with Takis/Evvivax to develop linear-DNA based anti-cancer vaccines
September 21, 2018 - AbbVie Presents Upadacitinib Longer-Term (32-Week) and Patient-Reported Outcomes Data from Phase 2b Atopic Dermatitis Study at 27th European Academy of Dermatology and Venereology (EADV) Congress
September 21, 2018 - Alzheimer’s drug may stop disease if used before symptoms develop
September 21, 2018 - Human skeletal stem cell can generate cartilage, bone
September 21, 2018 - UK and European research collaborations receive vote of confidence by three major cancer charities
September 21, 2018 - Microbiota in the intestines and cell stress cause colon cancer
Fluorescent dye could allow doctors to obtain better images of blood vessels, tissues

Fluorescent dye could allow doctors to obtain better images of blood vessels, tissues

image_pdfDownload PDFimage_print

Fluorescence imaging is widely used for visualizing biological tissues such as the back of the eye, where signs of macular degeneration can be detected. It is also commonly used to image blood vessels during reconstructive surgery, allowing surgeons to make sure the vessels are properly connected.

For these procedures, as well as others now in clinical trials, such as imaging tumors, researchers use a portion of the light spectrum known as the near-infrared (NIR) — 700 to 900 nanometers, just beyond what the human eye can detect. A dye that fluoresces at this wavelength is administered to the body or tissue and then imaged using a specialized camera. Researchers have shown that light with wavelengths greater than 1,000 nanometers, known as short-wave infrared (SWIR), offers much clearer images than NIR, but there are no FDA-approved fluorescence dyes with peak emission in the SWIR range.

A team of researchers at MIT and Massachusetts General Hospital has now taken a major step toward making SWIR imaging widely available. They have shown that an FDA-approved, commercially available dye now used for near-infrared imaging also works very well for short-wave infrared imaging.

“What we found is that this dye, which has been approved since 1959, is really the best, the brightest fluorophore that we know of at this point for imaging in the short-wave infrared,” says Moungi Bawendi, the Lester Wolf Professor of Chemistry at MIT. “Now clinicians can start to try short-wave imaging for their applications because they already have a fluorophore which is approved for use in humans.”

Imaging this dye with a camera that detects short-wave infrared light could allow doctors and researchers to obtain much better images of blood vessels and other body tissues for diagnosis and research.

Bawendi and former MIT research scientist Oliver Bruns are the senior authors of the study, which appears in the Proceedings of the National Academy of Sciences. The paper’s lead authors are MIT graduate students Jessica Carr and Daniel Franke.

Cutting through the fog

The dye that the researchers used in this study, known as indocyanine green (ICG), fluoresces most strongly around 800 nanometers, which falls within the near-infrared range. When injected into the body, it travels through the bloodstream, making it ideal for angiography (the visualization of blood flowing through vessels). Some robot-assisted surgical systems have incorporated NIR fluorescence imaging to help visualize blood vessels and other anatomical features.

The MIT team discovered ICG’s usefulness for SWIR imaging somewhat serendipitously. As part of a control experiment for another paper, they tested the fluorescence output of quantum dots against the fluorescence output of ICG in the short-wave infrared. They expected that ICG would have no output, but were surprised to discover that it actually produced a very strong signal.

Bawendi’s lab and other researchers have been interested in developing fluorophores for SWIR imaging because SWIR offers better contrast and clarity than NIR. Light with shorter wavelengths tends to scatter off of imperfections in objects that it strikes, but as wavelengths become longer, scattering is greatly reduced.

“In the near-infrared, a lot of the features you see in tissue can look foggy, and once you move into the short-wave infrared, the image clears up and everything becomes sharp,” Bruns says.

Short-wave infrared can also penetrate deeper into tissue, although calculating exactly how far is a complicated process, the researchers say, because it depends on the size of the structure being viewed and the field of view of the microscope. In the new study, the researchers were able to see several hundred micrometers into tissue using a regular fluorescence microscope. Normally, this depth can be reached only with two-photon microscopy, a much more complicated and expensive type of imaging.

“We found that short-wave infrared is particularly useful for imaging small objects that are on top of a large background, so when you want to do angiography of small vessels, or capillaries, that’s significantly easier in the short-wave infrared than in the near-infrared,” Franke says.

A strong signal

In their study, the researchers further explored ICG and showed that it gives a stronger signal than other SWIR dyes now in development. Previous studies of ICG had focused on its emission around 800 nanometers, where it fluoresces the brightest, so no one had observed that the dye also produced a strong signal at longer wavelengths. Though it doesn’t fluoresce efficiently in the shortwave-infrared range, ICG absorbs so much light that if even a small percentage is emitted as fluorescent light, the signal is brighter than that produced by other SWIR dyes.

The researchers also found that ICG is bright enough that it can produce images quickly, which is important for capturing motion.

“If you don’t have a strong enough signal, it slows down how long it takes to take the image, so you can’t use it for imaging motion such as blood flowing or the heart beating,” Carr says.

The researchers also tested another dye that works in the near-infrared. This dye, called IRDye 800CW, is similar to ICG and can be attached to antibodies that target proteins such as those found on tumors. They found that IRDye 800CW also fluoresces brightly in the shortwave-infrared light, thought not as brightly as ICG, and showed that they could use it to image a cancerous tumor in the brains of mice.

To do shortwave-infrared imaging, research labs and hospitals would need to switch from the silicon cameras now used for NIR imaging to an indium gallium arsenide (InGaAs) camera. Until recently, these cameras have been prohibitively expensive, but the prices have been coming down in the past several years.

The research team is now further investigating why ICG works so well for shortwave-infrared imaging, and is trying to identify the optimal wavelength for its use, which they hope will help them determine the best applications for this kind of imaging. They are also working with other labs to develop dyes that are similar to ICG and might work even better.

Source:

http://news.mit.edu/2018/fluorescent-dye-could-enable-sharper-biological-imaging-0406

Tagged with:

About author

Related Articles