By modifying the surface of tiny, fluorescent crystals called quantum dots, Carnegie Mellon University scientists have enabled them to circulate for hours in animals and to provide fluorescent signals for at least eight months, the longest that anyone has observed quantum dot fluorescence in a living animal. This technological feat overcomes a major limitation, making quantum dots finally practical for long-term studies in mammals.
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 companys 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 Mellons 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.
Lauren Ward | EurekAlert!
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