Reporting in the January/February issue of Bioconjugate Chemistry, Byron Ballou and colleagues at Carnegie Mellon, in collaboration with the Quantum Dot Corporation, found that the company's quantum dots (Qdot Particles) coated with an amphiphilic polyacrylic acid polymer are stable in vivo. A member of the team, Lauren Ernst, also found that modifying the surface molecules by adding a second polymer coat prolongs the time quantum dots circulate in the body.
"Because uncoated quantum dots are too fragile for most biological studies in vivo, the coating is the most critical step," explained Ballou, research scientist at the Molecular Biosensor and Imaging Center (MBIC) at Carnegie Mellon's Mellon College of Science. "The new coatings allowed us to observe quantum dots much longer than previously demonstrated. We had concerns that the coats might dissolve or be digested away, so we were pleased with the long persistence of fluorescence, as well as the large increase in circulating time caused by increasing the thickness of the outer polymer coat." Both these features enabled the quantum dots to deposit effectively within tissues, Ballou noted.
First commercialized by the Quantum Dot Corporation in 2002, Qdot Particles are nanosized crystalline particles composed of a few hundred to a few thousand atoms of a semiconductor material (typically cadmium selenide). Quantum dots emit light in a variety of colors, depending on size. Unlike traditional fluorescent markers used in research and medicine, quantum do
Contact: Lauren Ward
Carnegie Mellon University