In biological applications, near-infrared (NIR) light is a safe as opposed to ultraviolet light, which could cause damage to cells. NIR can also penetrate deeper into tissues to target tumours. Graphic by Muthu Kumara Gnananasammandhan

Led
by Associate Professor Zhang Yong, a team at the National University of
Singapore believes their latest work has proven that nanoparticle
technology could inhibit tumour growth and control gene expression in
mice. This, they say,  is a world’s first for the use of nanoparticles
for non-invasive photodynamic therapy of deep cancer.

The team’s findings were published online in Nature Medicine on Monday, 17 September 2012.

How
does the technology work? The team has discovered a way to control gene
expression by using nanoparticles which are able to convert
near-infrared (NIR) light to visible or ultraviolet (UV) light. These
nanoparticles can be introduced into target sites of the patient, to do
their good work.

Genes
release certain proteins in our body to ensure that our internal
“machinery” works well and we remain healthy. However, sometimes, the
process can go awry and cause our body to malfunction, leading to
various diseases. But doctors can put this right by manipulating the
process of gene expression by using UV light. However, UV light may
cause more harm than good.

Assoc
Prof Zhang, the team leader, said: “NIR, besides being non-toxic, is
also able to penetrate deeper into our tissues. When NIR reaches the
desired places in the body of the patient, the nanoparticles which we
have invented, are able to convert the NIR back to UV light
(up-conversion) to effectively activate the genes in the way desired—by
controlling the amount of proteins expressed each time, when this should
take place, as well as how long it should take place.”

Their findings from this study were earlier published in the Proceedings of the National Academy of Sciences in May 2012.

As
the up-conversion nanoparticles can also be used to produce visible
light, the team has extended its application to other light-based
therapies. Conventional light therapy for treating tumours uses visible
light to activate light sensitive drugs that can kill cancer cells.
However, such visible light is not penetrative enough to reach
deep-seated tumors. The team’s method of employing NIR is able to
penetrate much deeper.

Their
novel use of nanoparticles made news in 2010. Coated with mesoporous
silica, these particles are each tasked to conduct “up-conversion”.
Their paper “Multicolour Core Shell-Structured Up-conversion Fluorescent
Nanoparticles” was published in Advanced Materials in December 2008. It
was one of the most highly-cited papers because of its relevance in
today’s science.

Wide range of applications

“By
using our nanoparticles, drugs can be activated by NIR light which is
safe. The light is also able to penetrate deeper into tissues to treat
diseased cells,” said Zhang.

Co-author
of the paper, PhD student Mr Muthu Kumara Gnananasammandhan added that
what they have developed is a platform technology which can be
customised for a wide range of applications. For example, in addition to
photodynamic therapy, their innovation can also be used for bioimaging
where the nanoparticles can be attached to biomarkers, which will then
attach to cancer cells, allowing for better imaging of tumours and
cancerous cells.

The
six-member team comprises researchers from the faculties of Engineering
and Science, as well as the NUS Yong Loo Lin School of Medicine.

The
team is currently in collaboration with researchers at the National
Cancer Centre Singapore to pursue a project funded by the Agency for
Science, Technology and Research (A*STAR) that will assess the safety
and efficacy of the technology to pave the way for pilot clinical trials
in the future.

The
team has also embarked on several other projects that make use of the
up-conversion nanoparticle for point-of-care diagnostics for diseases.
They have received the proof-of-concept (POC) grants from the Biomedical
Engineering Programme (BEP) which is funded by the Science and
Engineering Research Council (SERC) at A*STAR and the National Research
Foundation, to develop these point-of-care diagnostic kits for rapid
detection of bacteria and biomarkers.

In vivo photodynamic therapy using upconversion nanoparticles as remote-controlled nanotransducers

Source: National University of Singapore