Dunking Polymer Doughnuts Into Cells

Rather than dunking their doughnuts in coffee, researchers in Scotland have found a way to dunk polymeric doughnuts into cells (Chem. Commun., DOI: 10.1039/b805323e). The doughnut-shaped microparticles, complete with a hole in the middle, selectively cross cell membranes and could be used as cellular tags for imaging or to deliver drugs directly to the affected organ. To create the particles, a team led by Mark Bradley at the University of Edinburgh used a dispersion technique to copolymerize styrene, divinylbenzene, and aminomethylstyrene in ethanol with 5% dioxane. Once the microdoughnuts reached a certain size, they precipitated out of solution. The polymerization produced highly uniform particles that measure about 3.2 μm in diameter with a 1-μm hole in the center. The microdoughnuts retain the amino functional group distributed throughout the structure, which could provide a handle for attaching fluorophores or drugs. The doughnuts were highly selective for human embryonic kidney cells, the researchers found, and during in vivo mouse testing, the doughnuts were exclusively localized to liver cells with no signs of toxicity.