Nano particles as sensor in the brain

Roberto Saracco July 2, 2018 Blog 1,031 Views

Magnetic calcium-responsive nanoparticles (dark centers are magnetic cores) respond within seconds to calcium ion changes by clustering (Ca+ ions, right) or expanding (Ca- ions, left), creating a magnetic contrast change that can be detected with MRI, indicating brain activation. (High levels of calcium outside the neurons correlate with low neuron activity; when calcium concentrations drop, it means neurons in that area are firing electrical impulses.) Blue: C2AB “molecular glue” Credit: MIT

Many feel that the next decade will be the one of the brain, reaching a tipping point where we will eventually understand how the brain works. A number of mega-projects are active each one following a slightly different approach. All of them require more raw data on what it is actually going on to reverse engineer the processes and associate to each of the specific brain structure.

So far we haven’t been able to find a method that can provide the resolution we are seeking (that for some would require to go down at synaptic level, well beyond the neurone level), the breath required to monitor parallel activities (we know for sure that brain neurones and neural circuits influence -it goes beyond interact!- one another, hence to see them all is important) and the time sensitivity that let understand what is cause and what is the result.

A high resolution image of the portion of the brain involved in the formation of memories. This kind of images are created by a computer using slices of the brain. They provide resolution at the level of a single neurone but there is not functional information associated since the brain is “dead”. Credit: HKU and Imperial College

Neurons in the hippocampus flash on and off as a mouse walks around with tiny camera lenses on its head. One can visualise what is going on but resolution is not accurate. Click on the image to see the animation. Credit: The Rockefeller University

Scientists have found a way to look at synaptic level to see the activity in a precise spot of the brain. However, this very accurate resolution does not allow the visibility of what is going on in nearby neurones and even less in other parts of the brain. Illustration: An astrocyte (green) interacts with a synapse (red), producing an optical signal (yellow). Credit: UCLA/Khakh lab

These three axis have to be present at the same time and we don’t have a technology, a monitoring approach that can deliver that (actually none is in sight yet and scientists are pursuing each of them independently and then are trying to reconstruct by simulation what is going on).

Finding new methods for monitoring the brain is crucial and here is where the news from MIT makes sense.

Neuroscientist researchers at MIT have announced a new method, and technology, to monitor the brain activity by observing the use of calcium molecules by the neurones.

Calcium molecules (ions) are at the root of the firing mechanisms of neurones, hence the ability of tracking them provide much more accurate information on what is going on. The researchers are using iron oxide nanoparticles that binds to synaptotagmin, a protein in the brain that attaches to calcium ions. The iron oxide nano particles can be detected through fMRI (Functional MRI) to detect the concentration of calcium ions that in turns is a good and precise indicator of neuronal activity.

The experiments so far have involved rats. Researchers have been able to observe the neuronal activity in the striatum, a part of the brain. The detection is not instantaneous, there is a delay of a few seconds and researchers are working to decrease the delay.

As I mentioned we are still missing a silver bullet, and we might never have one, but we keep growing our brain sensing capability and the goal of understanding the brain workings by 2040 seems reachable.