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 wont 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
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 teams 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 labs
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
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
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.