For critical drugs like those used in chemotherapy, getting the dose right for every patient is a challenge: everyone's physiology is different and too much or too little can be dangerous or deadly. A new tool developed at Stanford could cut the guess work and keep the dose just right, using a biosensor to monitor the active drug levels in a patient's bloodstream in real time, and administering extra doses as needed.

The amount of a given drug that one person needs could be enough to kill someone else and not enough to have any effect at all in the next person. A wide range of genetic and metabolic differences in individuals comes into play, so a personalized approach would make administering drugs much safer and more effective. But with current technology it's nigh on impossible to take the multitude of factors into account.


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The Stanford system is designed to constantly regulate the level of a chemo drug in the bloodstream, and inject more as required. It's made up of three parts: a biosensor, a control system and a programmable pump. After a drug is administered to a patient, the biosensor keeps track of the levels of the drug in the bloodstream by way of molecules called aptamers. When they come into contact with a certain drug, these molecules change shape, and the more of the drug that's there, the more they distort.

An electric sensor picks up that signal every few seconds, and running the data through the control system, software is able to determine when more is needed. The pump will then inject just the right amount of the drug to keep the patient at the desired dose.

"This is the first time anyone has been able to continuously control the drug levels in the body in real time," says H. Tom Soh, lead researcher on the study. "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. For example, what if we could detect and control the levels not only of glucose but also of insulin and glucagon that regulate glucose levels? Now that is an exciting future."

Using the chemotherapy drug doxorubicin, the Stanford team tested the system in live animal models, and found that they were able to account for the different needs of individual animals and maintain a constant dosage. To throw a curveball, the researchers then introduced a second drug that messes with doxorubicin levels, and again, the system managed to stabilize the drug to desired levels.

While it's a promising step towards personalized medicine, results in animal models don't always translate to humans. The current prototype sits outside the body, which would make it useful while a patient is undergoing chemotherapy in a hospital, but it's not yet something that diabetics could wear while going about their day. The researchers plan to test its safety and effectiveness before trials begin on humans, and will experiment with different aptamers to see if they can widen the range of drugs the system can detect.

The research was published in the journal Nature Biomedical Engineering.

Source: Stanford University