Since I arrived, I’ve heard a lot of talk about Heather Clark’s nano-sensors around campus. I finally got the chance to meet her this morning and learn more about her work. By now, most of the Northeastern community is familiar with the smart-phone app that a couple of Clark’s grad students designed to help people monitor their blood sugar levels. She gave me an insider’s look at what’s actually going inside the particles that glow in varying intensity based on the glucose concentration in a person’s blood*.
The particles are made out of a biocompatible polymer and an “oily” plasticizer. All the normal plastic things we’re familiar with have some amount of plasticizer in them, more rigid materials have less; materials with more plasticizer are, well, more “plastic,” or flexible. Since Clark’s nanoparticles are so rich in the stuff, they’re rather dynamic. Molecules in the surrounding solution can pulled into the particle under the right conditions.
Inside the particle, there is a fluorescent dye and a molecule called boronic acid. The boronic acid, which likes to bind with glucose, pulls the molecule inside. The binding of glucose to boronic acid activates the dye. So, the more glucose, the more bound boronic acid; the more bound boronic acid, the more fluorescence!
Clark is also developing sodium sensing particles that can detect differences in the way healthy and unhealthy cardiac cells beat (yes, the cells themselves actually beat.…super cool, right?!). In this case the particle contains a neutralizer, which keeps the particle at a constant neutral charge. When the positively charged sodium ion busts on the scene, the particle must lose a proton somewhere else in order to maintain neutrality. Detection of that lost proton affords the sensing capacity this time.
*Don’t worry, it doesn’t happen spontaneously! You have to shine light on the area of the particle injection in order for the glowing to occur.
Photo by Heather Clark.