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This cancer treatment gives patients night-vision, and we finally know why

Scientists figured out how a certain treatment for skin cancer gives some patients a visual "superpower."

Photo Credit: Joshua Rodriguez / Unsplash
  • In the early 2000s, it was reported that some cancer patients being treated with chlorin e6 were experiencing enhanced night vision.
  • Using a molecular simulation, researchers discovered that a chlorin e6 injection under infrared light activates vision by changing retinal in the same way that visible light does.
  • Researchers hope that this chemical reaction could one day be harnessed to help treat certain types of blindness and sensitivity to light.


In the early 2000s, it was reported that a certain kind of skin cancer treatment called photodynamic therapy, which uses light to destroy malignant cells, had a bizarre side effect: It was giving patients enhanced night time vision.

An essential component to this therapy is a photosensitive compound called chlorin e6. Some people being treated with chlorin e6 were upset to discover that they were seeing silhouettes and outlines in the dark. Researchers think they might finally know why this happens.

The chemistry of vision

Rods and cones photoreceptors in a human retina.

Photo Credit: Dr. Robert Fariss, National Eye Institute, NIH / Flickr

"Seeing" happens when a series of receptors in the retina, the cones and rods, collect light. Rods contain a lot of rhodopsin, a photosensitive protein that absorbs visible light thanks to an active compound found in it called retinal. When retinal is exposed to visible light, it splits from rhodopsin. This then allows the light signal to be converted into an electrical signal that the visual cortex of our brains interprets into sight. Of course, there is "less light" at night, which actually means that light radiation is not in a domain visible to humans. It's at higher wavelengths (the infrared level) that retinal is not sensitive to. Hence, why we can't see in the dark like many critters can.

But the vision process can be activated by another interaction of light and chemistry. As it turns out, a chlorin e6 injection under infrared light changes retinal in the same way that visible light does. This is the cause of the unforeseen night vision side effect of the treatment.

"This explains the increase in night-time visual acuity," chemist Antonio Monari, from the University of Lorraine in France, told CNRS. "However, we did not know precisely how rhodopsin and its active retinal group interacted with chlorin. It is this mechanism that we have now succeeded in elucidating via molecular simulation."

Molecular simulation

"Molecular simulation" is a method that uses an algorithm that integrates the laws of quantum and Newtonian physics to model the functioning of a biological system over time. The team used this method to mimic the biomechanical movements of individual atoms – that is, their attraction or repulsion to one another – along with the making or breaking of chemical bonds.

"For our simulation we placed a virtual rhodopsin protein inserted in its lipid membrane in contact with several chlorin e6 molecules and water, or several tens of thousands of atoms," Monari explained to CNRS. "Our super-calculators ran for several months and completed millions of calculations before they were able to simulate the entire biochemical reaction triggered by infrared radiation." In nature, this phenomena occurs within fractions of a nanosecond.

The molecular simulation showed that when the chlorin e6 molecule absorbs the infrared radiation, it interacts with the oxygen present in the eye tissue and transforms it into reactive, or singlet, oxygen. In addition to killing cancer cells, "singlet oxygen" can also react with retinal to enable a slightly enhanced eyesight at night, when light waves are at the infrared level.

Future potential

Now that researchers know why the "supernatural" side effect occurs, they may be able to limit the chance of it happening to patients undergoing photodynamic treatment. Thinking further out, the researchers hope for the possibility that this chemical reaction could be harnessed to help treat certain types of blindness and sensitivity to light.

Ultimately, researchers say that this has been a big flex for the power of molecular simulations, which can give us astonishing scientific insights like this.

"Molecular simulation is already being used to shed light on fundamental mechanisms – for example, why certain DNA lesions are better repaired than others – and enable the selection of potential therapeutic molecules by mimicking their interaction with a chosen target," Monari told CNRS.

Don't hold your breath on night vision eyedrops though.

Neom, Saudi Arabia's $500 billion megacity, reaches its next phase

Construction of the $500 billion dollar tech city-state of the future is moving ahead.

Credit: Neom
Technology & Innovation
  • The futuristic megacity Neom is being built in Saudi Arabia.
  • The city will be fully automated, leading in health, education and quality of life.
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Why do people believe in conspiracy theories?

Are we genetically inclined for superstition or just fearful of the truth?

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  • From secret societies to faked moon landings, one thing that humanity seems to have an endless supply of is conspiracy theories. In this compilation, physicist Michio Kaku, science communicator Bill Nye, psychologist Sarah Rose Cavanagh, skeptic Michael Shermer, and actor and playwright John Cameron Mitchell consider the nature of truth and why some groups believe the things they do.
  • "I think there's a gene for superstition, a gene for hearsay, a gene for magic, a gene for magical thinking," argues Kaku. The theoretical physicist says that science goes against "natural thinking," and that the superstition gene persists because, one out of ten times, it actually worked and saved us.
  • Other theories shared include the idea of cognitive dissonance, the dangerous power of fear to inhibit critical thinking, and Hollywood's romanticization of conspiracies. Because conspiracy theories are so diverse and multifaceted, combating them has not been an easy task for science.

COVID-19 brain study to explore long-term effects of the virus

A growing body of research suggests COVID-19 can cause serious neurological problems.

Brain images of a patient with acute demyelinating encephalomyelitis.

Coronavirus
  • The new study seeks to track the health of 50,000 people who have tested positive for COVID-19.
  • The study aims to explore whether the disease causes cognitive impairment and other conditions.
  • Recent research suggests that COVID-19 can, directly or indirectly, cause brain dysfunction, strokes, nerve damage and other neurological problems.
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Sponsored by Charles Koch Foundation

Better reskilling can future-proof jobs in the age of automation. Enter SkillUp's new coalition.

Coronavirus layoffs are a glimpse into our automated future. We need to build better education opportunities now so Americans can find work in the economy of tomorrow.

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