November 20, 2008: A nontoxic nanoparticle developed by Penn State researchers is proving to be an all-around effective delivery system for both therapeutic drugs and the fluorescent dyes that can track their delivery.

In a recent online issue of Nano Letters, an interdisciplinary group of materials scientists, chemists, bioengineers, physicists, and pharmacologists show that calcium phosphate particles ranging in size from 20-50nm will successfully enter cells and dissolve harmlessly, releasing their cargo of drugs or dye.

Peter Butler, associate professor of bioengineering, and his students used high-speed lasers to measure the size of fluorescent dye-containing particles from their diffusion in solution. With this method, his group was able to measure the size of the particles and their dispersion in solution, in this case a phosphate-buffered saline that is used as a simple model for blood.

“What we did in this study was to change the original neutral pH of the solution, which is similar to blood, to a more acidic environment, such as around solid tumors and in the parts of the cell that collect the nanoparticles-containing fluid immediately outside the cell membrane and bring it into the cell. When we lower the pH, the acidic environment dissolves the calcium phosphate particle,” he says.

“We can see that the size of the particles gets very small, essentially down to the size of the free dye that was inside the particles. That gives us evidence that this pH change can be used as a mechanism to release any drug that is encapsulated in the particle,” Butler explains.

Although the primary use envisioned for these particles is for targeted cancer therapy, Butler’s group is interested in their ability to deliver various drugs that have been shown to inhibit cell growth associated with vascular disease.

Support for this research was provided by National Science Foundation, NASA, Keystone Nano Inc. and NIH-NHLBI.