Canada's top stories in the chemical sciences and engineering By Tyler Irving Biotechnology
Fatemeh Nazly Pirmoradi
Magnetic implant could halt vision loss Tens of thousands of Canadians suffer from diabetic retinopathy, where unwanted blood vessels permeate the retina and cause vision loss. Currently, these vessels can only be removed with lasers or surgery. But an implantable, magnetic drug delivery device designed at the University of British Columbia could offer a new way of treating this pervasive condition. Recent PhD graduate Fatemeh Nazly Pirmoradi designed the device, which looks like a tiny contact lens. It’s actually a disc-shaped polydimethylsiloxane (PDMS) chamber filled with docetaxel, a chemotherapy drug that inhibits cell division. The top of the chamber is a membrane made of PDMS impregnated with magnetic iron oxide particles, with a tiny laser-drilled hole in it. When fluid fills the chamber, a small amount of the relatively insoluble docetaxel is dissolved. When exposed to a magnetic field, the membrane
A new implantable device deforms in the presence of a magnetic field and could allow for targeted drug delivery without the need for multiple injections.
deforms, squeezing out the docetaxel solution like toothpaste from a tube. The chamber then refills and more docetaxel dissolves for the next dose. “It worked really well,” says Pirmoradi. “I was activating it every day for five weeks and it was a constant dose.” A second test, where the device was activated after sitting unused for seven months, again showed the same dose. So far, the experiments have used permanent magnets to actuate devices
in test tubes; more data on biocompatibility is needed before the device can be tested in vivo. Still, Pirmoradi is optimistic. “It’s very simple. It doesn’t have a battery, wires or electronics, which allows for a smaller device. And by providing the drug locally, we avoid systemic toxicity,” she says. This means the device may be useful not only for diabetic retinopathy but other applications such as cancer treatments. The work is published in Lab on a Chip.
health
Sweetly healthy maple syrup Canadians love maple syrup, but the associated sugar rush can be hazardous to one’s health, especially for those living with diabetes or other metabolic disorders. But thanks to some clever chemical engineering, a new maple syrup product may soon alleviate those concerns. The project is a collaboration between the National Research Council, the University of Guelph Kemptville Campus and Natunola Health Inc., an Ottawa-based supplier of botanical ingredients for both cosmetics and food. The idea was to use natural enzymes to convert sucrose - the main sugar component of maple syrup - to its structural isomer, isomaltulose. Because it has a different shape than sucrose, isomaltulose is not as readily digested by human enzymes, leading to a slower release of sugar into the blood stream and eliminating spikes in blood glucose. In order to convert the sugars, Wie Zou and his team at the NRC relied on two species of bacteria, Erwinia rhapontici and Protaminobacter rubrum. These plant pathogens, harm-
less to humans, produce enzymes that convert sucrose into isomaltulose. The team immobilized these species in gels made of calcium alginate or carageenan and placed them in a bioreactor with concentrated maple sap from the sugar bush at Kemptville Campus. The enzymes did the conversion efficiently and worked even when the bacteria themselves were killed before inoculation. The altered sap was then boiled into syrup in the traditional way. Zou says the new product tastes great. “We made some cookies, butter, maple candy, all kinds of things. If you didn’t know, you wouldn’t be able to tell the difference.” There are still a few hurdles to jump, including approval from the Canadian Food Inspection Agency and tests to determine the glycemic index (GI), a measure of how fast the body metabolizes the sugars in a given food. This past May, Natunola received a grant from the Ontario Ministry of Agriculture, Food and Rural Affairs to help with this process and Zou is hopeful that consumers can be enjoying new, low-GI maple products by 2012.
october 2011 CAnadian Chemical News 9