Pokey patch painlessly monitors drug levels in patients' bloodstreams
There are many orally administered drugs which are very helpful in the right dosage, but quite harmful in larger amounts. A new microneedle patch is designed to help in that regard, by showing exactly how much medication is currently present in a patient's bloodstream.
So first of all, couldn't physicians just be sure to give the correct dosage in the first place?
The problem is, different medications are taken up by different people's systems in different amounts. In other words, even if two people of the same weight, gender and age were given the same dosage of a given pharmaceutical, one of those people would likely end up with more of the drug in their bloodstream than the other.
One method of checking bloodstream medication levels involves drawing and analyzing blood samples. Not only is this unpleasant for the patient, but the analysis may take days to complete. Even then, it will only show what the levels were at the time the sample was taken.
That's where the experimental new patch comes in. Measuring about a quarter of an inch (6 mm) in diameter, the flexible polymer-bodied device is being developed at UCLA by a team led by Assoc. Prof. Sam Emaminejad.
When it's worn against a body part such as the arm, an array of steel microneedles on its underside painlessly penetrate the top layer of skin. They're then exposed to the interstitial fluid which is present in the gaps between the skin cells – medication levels in that fluid correspond to those in the bloodstream.
The tip of each needle is only about a quarter of a millimeter long, and is coated with gold nanoparticles and engineered strands of DNA known as aptamers. One end of each strand is anchored to one of the nanoparticles, while its other end is attached to a methylene blue "signal reporter" molecule.
When the aptamers come into contact with a target molecule – such as a specific medication – they change shape. Their doing so causes the methylene blue molecules to produce an electrochemical signal, which can be externally measured as an electrical current. The strength of that current indicates the amount of medication currently present in the bloodstream.
In lab tests, the patch was used on rats that had received three different dosages of the antibiotic tobramycin. Bloodstream drug level readings delivered by the device were found to match those obtained via traditional blood sample analysis.
Other medications can be targeted and detected, using different aptamers and signal reporter molecules. It is estimated that if the patch were to be commercially manufactured, the materials cost for each one would be less than US$2.
"This biosensing microneedle technology advances many different aspects of personalized medicine," said Emaminejad. "It may allow us to improve treatments by optimizing the drug dosage for each individual, and it’s inexpensive, so everyone could benefit from this solution. Additionally, it may allow us to inform care by measuring not only drug molecules but also naturally occurring molecules in the body that are relevant to health."
A paper on the research was recently published in the journal Science Advances.
And as a side note, UCLA isn't the only institution that's exploring the use of microneedle patches for measuring drug levels in the bloodstream. Scientists at Imperial College London have developed one that uses enzymes which react to pH changes in the interstitial fluid, while a University of British Columbia team has created one that utilizes micro-optical fibers.