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November 23, 2000 More effective sunscreens are on the way



Photo of Ann English and Tito Scaiano

Ann English and research partner Tito Scaiano of the University of Ottawa

by Janice Hamilton

If you use sunscreen in the belief that it will prevent sunburn, you are quite correct. If, however, you believe that sunscreen is harmless and will prevent skin cancer later in life, you may be wrong. In fact, the data on cancer prevention won’t be available for another 10 years or so, and one ingredient used in some of the newer sunscreen formulations may actually be dangerous.

Now a Concordia researcher is looking for a way to make a new kind of sunscreen that lessens that danger. Chemistry professor Ann English is a member of a research team that has just received a three-year, $356,700 grant from NSERC to develop a sunscreen that would incorporate a barrier between the active ingredient and the skin. The team includes partners from the University of Ottawa and from Spain, Health Canada and private industry.

There are two basic types of sunscreens. Chemical sunscreens use organic molecules to absorb UV light and convert it to heat. Physical sunscreens are solid materials that scatter the light. This project will focus on titanium dioxide, a semi-conductor that has recently been introduced as a physical sunscreen. Its advantages are that it is cheap, and that it scatters both UVA and UVB light.

However, recent studies have shown that when titanium dioxide is exposed to sunlight, it not only scatters the light, it also absorbs it and becomes reactive. In initial experiments, English says, “we have shown that it then causes key protective enzymes to lose their biological functions.”

The team’s intention is to encapsulate the titanium dioxide so that it still scatters the light, but does not have direct contact with the skin and so cannot damage proteins or cells. The researchers will try packaging the sunscreen agent in a zeolite material to create what they call a “supramolecular sunscreen.”

Zeolites are materials that are permeated with cavities of molecular dimensions. The most common zeolites are made of silicon and aluminum, and, although some are found in nature, most are synthesized in the lab. Molecules of other materials can be placed into these cavities so, for example, titanium dioxide or organic light-absorbers could be incorporated in zeolite cavities, like a ship in a bottle.

English says the idea arose while Tito Scaiano, a professor of chemistry at the University of Ottawa and a world-renowned expert on photochemistry, was spending part of his sabbatical leave at her lab earlier this year.

“He is editor-in-chief of the Journal of Photochemistry and Photobiology, a journal that publishes a lot of research on sunscreens,” she explained. “My interest is in proteins and biological molecules, so we decided to pool our interest in this application.” The Concordia lab’s role will be to test the interaction of the supramolecular sunscreen with proteins and various cell types to see how they are modified by different processes.

The other key team member is Dr. Hermenegildo Garcia, an expert on zeolites with the Instituto de Tecnologia Quimica, in Valencia, Spain. The Health Protection Branch of Health Canada will provide guidance on aspects such as sun-protection factors. If the fundamental idea works, industrial partner Atrium Biotechnologies will investigate the development of a consumer product.

“There will be a lot of interesting science to do in terms of how different compounds behave in the zeolites, and on the properties of sunscreens and their effects on cells, since not much has been published in that area,” English said. The researchers say the concept developed here may also have applications in areas such as cosmetics, drug delivery and surface protection of materials.