Microsensor Could Help Scientists Better Understand How Cocaine Affects Adolescent Brains

Jan 23, 2018

There's evidence to suggest that cocaine is more addictive for adolescents than adults. Scientists believe that at least part of this has to do with biological mechanisms in the brain, but they're not sure exactly what those mechanisms are.

A special sensor being developed at the University of Pittsburgh could help give them a better understanding.

Pitt bioengineering professor Tracy Cui is interested in a part of the brain called the ventral tegmental area, or VTA, which is part of the brain's reward center and produces large amounts of the neurotransmitter dopamine. Dopamine helps keep human brains healthy, but it also makes the body feel good.

"Different parts of the brain respond to cocaine differently, [and] this particular region of the brain is highly responsive to cocaine," said Cui.

She's trying to figure out whether, in adolescents, the neurons that release dopamine in the VTA somehow respond differently to cocaine than those in adults, or if given the same dosage, proportionally more cocaine is somehow ending up in the VTA of adolescents than adults and producing a stronger response.

To that end, Cui is building a special micro-sensor.

"The device itself is actually kind of like a computer chip," she said. "It's a tiny device that contains multiple very, very small electrodes."

Those electrodes can measure the electrical activity created when neurons release dopamine. A synthetic DNA sequence called an aptamer, which "recognizes" cocaine by binding to it, is then placed on the surface of the sensor. By measuring how the aptamer molecules reconfigure during this binding, the sensor can detect concentration levels of cocaine.

Cui said she is putting these sensors into the brains of adult and adolescent rats to see if she can observe a difference in real time.

In the past, she said scientists have mostly tried to measure cocaine levels in the rodents by removing large chunks of their brain tissue and measuring an overall concentration, which she said makes it hard to study any particular area of the brain.

But there's a challenge to putting these sensors in rat brains.

"They have a rejection reaction when you put a foreign body in them," said Cui.

Currently, the signal from the sensor will begin to fail after just a few hours, as inflammatory cells begin to encapsulate the sensor and block its measurement, or proteins from the brain begin to line the surface of the sensor, creating a similar effect. 

Cui said a major focus of her lab's work is finding a way to effectively "trick" the brain into accepting the sensor in order to delay rejection and allow the sensor more time to collect data.

One promising option could include coating the sensor with a special kind of polymer molecule that has a high affinity for binding with water, which is abundant in the brain. In theory, she said a layer of water would form over the aptamer, and that layer of water would be more agreeable to the surrounding tissue than the surface of the sensor, which is metallic.