New Fibers Implanted in the Brain Can Transmit Drugs, Light, and Electrical Signals

The human brain's complexity, with its sheer size and the variety of signaling methods it uses simultaneously, makes it challenging to study. Conventional neural probes are designed to record a single type of signaling, limiting the information that can be derived from the brain at any point in time. Now researchers at MIT may have found a way to change that. By producing complex multimodal fibers that could be less than the width of a hair, they have created a system that could deliver optical signals and drugs directly into the brain, along with simultaneous electrical readout to continuously monitor the effects of the various inputs. In addition to transmitting different kinds of signals, the new fibers are made of polymers that closely resemble the characteristics of neural tissues, allowing them to stay in the body much longer without harming the delicate tissues around them.

Transcript

00:00:14 People have been studying neurons for quite a bit of time actually and two main features that are really important: one, is that device should be small so that it doesn't cause very much damage. And the other one is that it should be bio-compatible so it doesn't damage tissues. We're working to use polymers which is a unique

00:00:29 approach and we're making polymer fibers that are really flexible so when they are put in the brain they don't cause a lot of scarring. So the fabrication method that we use, makes use of a process that is commonly used in the telecommunication industry which is the thermal drawing process. In this process we start with a

00:00:47 large template of what we want the geometry of our neuro-probe, and then by heating it and applying controlled stress we can reduce its dimensions up to 200x. So this allows us to design a geometry in a scale that is easy for us to fabricate and then reduce its dimensions to a useful scale.

00:01:09 So after we thermally draw the fiber it looks like this and it's super flexible but its still a little too thick to be implanted so we're going to selectively etch the outer layer so we can make it smaller and be implanted. We started off with a diameter similar to this one, which is about the diameter of fishing

00:01:26 wire, and then this piece here shows the transition from that thicker, fishing wire, to the diameter closer to the human hair. And then it's this thinner piece that we're going to start using to connect to a board and prepare for implementation. So one of the advantages of this fabrication method is that we can

00:01:45 incorporate many different materials in the same process. And by combining different materials we can achieve different functionalities in our devices. So we can achieve not only re- cording electrodes but also have ways in which we can guide light into the brain or also inject drugs. In this work we show for the

00:02:06 first time that we can modulate the activity in the brain via the injection of drugs while we are stimulating neurons in the brain using light, with a method called optogenetics. And through all this process in which we are stimulating and modulating the response of the neurons we are recording this activity in the

00:02:26 neurons. We hope that these devices we have developed can be useful for other people to do further experiments in the brain so people who are more interested in discovering how the brain works we hope that these tools will be helpful for them in discovering these relationships in the brain.