What’s inside a nanosensor?

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.