May 22, 2019 | Updated: 08:18 AM EDT

New biological sensor can help diagnose cancer and epilepsy better

Mar 15, 2019 03:49 PM EDT

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LLNL or Lawrence Livermore National Laboratory researchers developed a biological sensor to better diagnose illnesses such as cancer and epilepsy. These biological sensors can monitor tiny molecules, ions and protons and they are important as a medical diagnostic. Even the signals of the simplest form like the intracellular pH level, can give vital information for the medical professionals. A sample stated is when the acidification of tumors occur because of the glucose uptake that are elevated and the lactic acid that is released is a biomarker of cancer cells. In the same instance, acidification of fluid that is extracellular is one of the major processes during seizures, for those with epilepsy. 

But manmade biosensors have limits like biocompatibility and fouling. Biological systems are made in separating and protecting important components of biological machinery that has semipermeable membranes that most of the time contains the defined gates and pores to prevent transmembrane transport to specific species. 

The LLNL team, led by Aleksandr Noy, made a pH sensor by integrating silicon nanoribbon transistor sensors with an antifouling lipid bilayer coating that has CNTP or proton-permeable carbon nanotube porin channels and showed robust pH detection using those sensors in a wide range of complex biological fluids.

"Our device is a versatile platform for real-time, label-free, highly sensitive detection of disease biomarkers, DNA mismatches and viruses," said Xi Chen, a UC Merced graduate student, a UC-National Lab In-residence graduate fellow at Lawrence Livermore and a first author in a cover article in the journal Nano Letters. He said the biosensor eventually could even be implantable.

To create the pH sensor, the lipid membrane needs to incorporate a robust channel that is highly permeable to protons. Noy's team previously showed that narrow 0.8 nanometer CNTPs have high proton permeability that is higher than proton permeability of bulk water in order of magnitude. Extreme water confinement in the 0.8-nm-diameter nanotube pores is also responsible for making conditions that shows fast proton transport. Small pore size and high proton permeability also ensure that CNTPs can block most of the fouling components effectively of biological mixtures and prevent them from reaching the sensor surface.

"For each of these experiments, we have characterized the ability of our sensor to respond to variations in the solution pH values before and after continuous exposure to the different foulant mixtures," Noy said. "When the lipid bilayer incorporated CNTP channels, the pH response was preserved and showed very little signs of degradation."

In the future, the team could develop the CNTPs to transfer specific ions and small molecules while blocking other biomolecules. This could change the device into a versatile platform-type sensing technology that could be used in applications from genetic screening, drug discovery and disease diagnosis. 

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