SEOUL, October 27 (AJP) - A wireless chip implanted in the brain has tracked, second by second, how a widely used Alzheimer's drug changes the level of a brain chemical tied to memory. It gives researchers a direct view of a brain drug at work instead of an inference drawn from behavior.
KAIST said Tuesday that a team led by Jang Kyung-in, a professor in its Department of Mechanical Engineering, developed the chip with researchers from the Daegu Gyeongbuk Institute of Science and Technology, the Korea Brain Research Institute and the Korea Research Institute of Bioscience and Biotechnology. Implanted in a minipig, the chip tracked acetylcholine as it rose after a dose of the drug donepezil and then slowly returned to its normal level.
Brain drugs are mostly judged indirectly, through memory and behavior tests or imaging scans. The main direct method, which draws fluid from the brain for analysis, takes several minutes or more per sample, too slow to follow chemical signals that shift within seconds.
Acetylcholine carries messages between nerve cells and plays a central role in memory and learning. Its level falls in Alzheimer's disease, and donepezil works by blocking an enzyme that breaks it down.
The team placed the chip in the minipig's prefrontal cortex, the region behind the forehead that handles judgment and attention. Minipigs have brains closer in size and structure to human brains than rodents do, and readings traveled by Bluetooth, so the animal was not tethered by wires.
Acetylcholine produces no electrical signal of its own, so the chip uses two enzymes to convert it into hydrogen peroxide, which an electrode turns into a measurable current. A sensing layer of porous chitosan, a material from crab and shrimp shells, woven with platinum-coated silver nanowires, speeds up that reaction.
To filter out other brain chemicals that give off similar signals, the probe carries one electrode coated with the enzymes and one left bare. Subtracting one reading from the other isolates acetylcholine.
The probe also holds a tiny light-emitting diode that can switch on nerve cells engineered to respond to light. In a separate experiment on mice, turning on the light raised the acetylcholine signal, showing the same probe can both stimulate brain cells and read their chemical response.
Jang said the work points toward brain interfaces that read the brain's state and adjust stimulation in response, adding chemical signals to the electrical ones such devices read today.
"This study has laid the foundation for moving toward technology that reads changes in the brain and adjusts stimulation according to that response," he said.
The study did not show that the chip treats Alzheimer's disease or improves memory, and the drug tracking and light stimulation were tested in different animals. Before any use in people, researchers must confirm that the chip is safe to leave in the brain long term and that its readings stay reliable, KAIST said.
Enside, a startup Jang founded and leads as chief executive, will pursue commercialization.
Son Ji-eun, Oh Se-hyeok and Ha Jeong-dae of the Daegu Gyeongbuk Institute of Science and Technology (DGIST) were co-first authors, and Jang was the corresponding author. The study was published Oct. 14 in Device, an applied technology journal from Cell Press.
[Reference Information]
Journal/Source: Device
Title: Implantable Neural Chip with Electrochemical Sensing and Optogenetic Stimulation for Monitoring of Cholinergic Pharmacological Responses
Link/DOI: 10.1016/j.device.2026.101329
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