Researchers from the Univ. of Hull
have discovered a way to load up nanoparticles with large numbers of
light-sensitive molecules to create a more effective form of photodynamic
therapy (PDT) for treating cancer.
Photodynamic therapy uses molecules which, when
irradiated with light, cause irreparable damage to cells by creating toxic
forms of oxygen, called reactive oxygen species.
Most
PDT works with individual light-sensitive molecules—but the new nanoparticles
could each carry hundreds of molecules to a cancer site.
A
number of different light-sensitive molecules—collectively known as
photosensitisers—are used in PDT and each absorbs a very specific part of the
light spectrum. The research team placed one kind of photosensitiser inside
each nanoparticle and another on the outside, which meant that far more
reactive oxygen species could be created from the same amount of light. The
findings are published in Molecular Pharmaceutics.
The
nanoparticles have also been designed to be the perfect size and shape to
penetrate easily into the tumor, as lead researcher, Dr Ross Boyle, explains.
“Small
cancer tumors get nutrients and oxygen by diffusion, but once tumors reach a
certain size, they need to create blood vessels to continue growing,” he says. “These new blood vessels, or neovasculature, are ‘leaky’ because the vessel
walls are not as tightly knit as normal blood vessels. Our nanoparticles have
been designed so the pressure in the blood vessels will push them through the
space between the cells to get into the tumor tissue.”
The
nanoparticles are made from a material that limits the leaching of its contents
while in the bloodstream, but when activated with light, at the tumor, the toxic
reactive oxygen species can diffuse freely out of the particles; meaning that
damage is confined to the area of the cancer.
The
researchers tested the nanoparticles on colon cancer cells, and while they were
able to penetrate the cells, they also found that the nanoparticles could still
be effective when near—rather than inside—the cancer cells.
“Some
types of cancer cell are able to expel conventional drugs, so
if we can make this kind of therapy work simply by getting the nanoparticles
between the cancer cells, rather than inside them, it could be very
beneficial,” says Dr Boyle.
