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
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 Molecular Pharmaceutics.
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
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.