'Smart Petri Dish'

Researchers at the University of California, San Diego have developed a "Smart Petri Dish' that could be used to rapidly screen new drugs for toxic interactions or identify cells in the early stages of cancer circulating through a patient's blood.

Their invention, described in the June 20 issue of Langmuir, a physical chemistry journal published by the American Chemical Society, uses porous silicon crystals filled with polystyrene to detect subtle changes in the sizes and shapes of the cells.

"One of the big concerns with any potential new drug is its toxicity," says Michael Sailor, a professor of chemistry at biochemistry at UCSD who headed the research team. "Since the liver is the organ that cleans up the blood, liver cells are particularly susceptible when a toxin is introduced to the body. Pharmaceutical companies want to know early on the effect a drug has on the liver. But it's very expensive to screen every potential candidate on living animals, typically rats. So if you can use just a few cells from the liver rather than the entire animal, you can perform many more thorough tests."

"You could also in principle use this to identify metastatic cancer cells circulating in a patient's blood," Sailor adds, "by putting blood samples from a patient onto the crystal and comparing them to normal blood samples."

The scientists constructed their Smart Petri Dish by first fabricating silicon crystals with nanometre-sized holes. This enabled them to produce a photonic crystal, capable of controlling light within the structure analogous to the way that semiconductors transmit electricity through computer chips. By attaching rat liver cells to the polystyrene within the crystals and measuring the scattering of light with a sensitive spectrometer, they were able to detect small changes in the shapes of the cells as they reacted to toxic doses of cadmium chloride and acetaminophen.

The design of the new device builds on a previous development in the UCSD laboratories of Sailor and Bhatia that allowed the scientists to maintain fully functioning liver cells in culture.