Just like humans, liver cells love doughnuts, but these are polystyrene ring “doughnuts”, just a few microns across, and they might give scientists a new way to deliver drugs selectively, potentially eliminating nasty side effects of life-saving treatments such as chemotherapy, according to chemists writing in Chemical Communications.

Mark Bradley and colleagues at the University of Edinburgh, UK, serendipitously made the polymer doughnuts while studying potential drug-carrying microparticles.

While synthesising micro-spheres, the team added a small amount of dioxane to their usual ethanol solvent. To their surprise, the resulting microparticles were regular in size and shape, with a hole through the middle like a doughnut.



SEM images of the micro-doughnuts.

“Their unique and highly uniform structure was immediately interesting to us and we considered the possible applications they may have – one of which was as carrier particles for cellular delivery,” said Bradley.

When they tested the uptake of the doughnuts into different types of cells, the team found they had an overwhelming preference for liver cells.

The high cell specificity these doughnuts showed led the team to conduct extensive in vivo testing in rats. The doughnuts were injected into the tail and within four hours they were detected solely in the liver region (yellow in image), with no adverse effects observed in the animal after the experiment.



Optical whole body image (Kodak FX-PRO Reflectance System using multi-spectral un-mixing software) of Cy7 labelled doughnuts (yellow) in the liver. Food (chlorophyll – green) is shown in the gut.

Bradley believes there are other uses for the micro-doughnuts besides drug delivery, such as filtration or purification devices, but the team will be keen to develop their ability to selectively deliver drugs into cells.