In a study published in Small, the researchers said their waterproof biosensor includes an “unprecedented combination of features” that may allow it to detect changes in the concentrations of various chemicals in the body and send the results to researchers in real time.
The chip is said to be flexible and thinner than a human hair, making it minimally invasive for use in the brain.
In a statement, study co-author Jinghua Li, assistant professor of materials science and engineering at Ohio State said: “We have a long way to go from our tests in the lab, but these findings were very encouraging.”
The biosensor could have many potential uses, but Li and her co-authors were particularly focused on how it could be used to monitor patients with traumatic brain injuries (TBI).
After TBI, secondary damage can occur that can be detected by changes in sodium and potassium ion concentrations in the brain’s cerebrospinal fluid, said Li, who is a member of Ohio State’s Chronic Brain Injury (CBI) Program.
The researchers tested the biosensor in an artificial solution they created to mimic cerebrospinal fluid and found that it could accurately detect changes in potassium and sodium ion levels that are important in TBI.
In addition to the tests with the artificial cerebrospinal fluid, the team also tested the biosensor in human blood serum, in which they successfully monitored pH levels.
The chip features field-effect transistors that, upon sensing the chemical of interest, produce an electrical signal that can be detected and analysed outside the body. Importantly, the researchers developed calibration standards to address crosstalk.
“When we create a biochemical sensor, we want to make sure that the device only responds to the specific chemicals we are interested in, and ignores the crosstalk from other biomarkers,” Li said. “That is difficult to do in a complex system like our body.”
While a biosensor has to be able to detect changes in the fluids in the brain, the electronics in the chip must be protected from these same fluids, Li said.
A waterproof encapsulation made from a thin film of silicon dioxide – forged in temperatures above 1,000 degrees Celsius – provided high structural integrity as barrier materials in a fluid environment, the study found.
Tests included placing the biosensor in heated fluids and in substances with different pH levels. The findings suggest the waterproof encapsulation with a thickness of several hundreds of nanometres could last at least a few years at body temperature and possibly much longer, Li said.
The biggest issue right now is with the chemical sensing elements, which the study suggests would work for only up to a few weeks.
Li said other issues need to be resolved before the biosensor is ready to be tested in animal models and humans. The response of biotissues to the sensor over extended period needs further study. There are still issues with crosstalk to be resolved, considering the complexity of the biosystem, and questions of how to mass produce the sensors.
The study does, however, provide more evidence that the sensors have a future in health care, she said.
Li said she believes biosensors could be used to analyse not only ions and neurotransmitters, as in this study, but possibly peptides, proteins, nucleotide acids and other chemicals in the body. It could be a breakthrough not only for TBI, but for other chronic diseases such as Parkinson’s and Alzheimer’s disease.