New biosensor controls body's drug levels in real time

In a first, Stanford scientists have developed a new biosensor that continuously monitors and delivers lifesaving drugs in the body in real time, ensuring that the patient receives the correct dosage.
As with coffee or alcohol, the way each person processes medication is unique. One person's perfect dose may be another person's deadly overdose, researchers said.
With such variability, it can be hard to prescribe exactly the right amount of critical drugs, such as chemotherapy or insulin.
Researchers led by electrical engineer H Tom Soh and postdoctoral fellow Peter Mage at Stanford University in the US developed the drug delivery tool that could make it easier for people to get the correct dose of lifesaving drugs.

In a study published in the journal Nature Biomedical Engineering, the researchers showed that the technology could continuously regulate the level of a chemotherapy drug in living animals.
"This is the first time anyone has been able to continuously control the drug levels in the body in real time," Soh said.

"This is a novel concept with big implications because we believe we can adapt our technology to control the levels of a wide range of drugs," he said.
The new technology has three basic components: a real- time biosensor to continuously monitor drug levels in the bloodstream, a control system to calculate the right dose and a programmable pump that delivers just enough medicine to maintain a desired dose.

The sensor contains molecules called aptamers that are specially designed to bind a drug of interest. When the drug is present in the bloodstream, the aptamer changes shape, which an electric sensor detects.
That information, captured every few seconds, is routed through software that controls the pump to deliver additional drugs as needed. Researchers call this a closed-loop system, one that monitors and adjusts continuously.
The group tested the technology by administering the chemotherapy drug doxorubicin in animals.
Despite physiological and metabolic differences among individual animals, they were able to keep a constant dosage among all the animals in the study group, something not possible with current drug delivery methods.

The researchers also tested for acute drug-drug interactions, deliberately introducing a second drug that is known to cause wide swings in chemotherapy drug levels.
They found that their system could stabilise drug levels to moderate what might otherwise be a dangerous spike or dip.
If the technology works as well in people as in their animal studies, it could have big implications, Soh said.
For example, the system could detect and control the levels of glucose and insulin in diabetics, he said.
That could allow researchers to create an electronic system to replicate the function of the dysfunctional pancreas for patients with type 1 diabetes.

The team plans to miniaturise the system so that it can be implanted or worn by a patient.