Research creates nanoparticles perfectly formed to tackle
6 June 2011
Researchers from the University 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.
< Dr Ross Boyle
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 – from the University of Hull’s Department of
Chemistry - 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 the current issue of
The nanoparticles have also been designed to
be the perfect size and shape to penetrate easily into the tumour,
as lead researcher, Dr Ross Boyle, explains.
“Small cancer tumours get nutrients and oxygen
by diffusion, but once tumours 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 tumour 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 tumour, 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.