Photo (L-R): Assistant Professor John Ho and Professor Zhang Yong/ Credit: NUS

Photo (L-R): Assistant Professor John Ho and Professor Zhang Yong/ Credit: NUS

NUS researchers develop novel approach to expand use of light-induced precision cancer treatment method

Researchers at the National University of Singapore have developed a novel approach for using a powerful light-induced cancer treatment for inner organs of the body. The method is often limited to surface cancers due to the low penetration of light through biological tissue.

Photodynamic therapy (PDT) uses a light sensitive drug, called a photosensitiser, that is triggered by a specific wavelength of light, to produce a form of oxygen that kills nearby cells. This provides a precision approach to cancer therapy, avoiding many of the whole-body side effects of classical drugs such as chemotherapy. In addition to directly killing cancer cells, PDT shrinks or destroys tumours by damaging blood vessels in the tumour, preventing the cancer cells from receiving necessary nutrients. PDT may also activate the immune system to attack the tumour cells.

Traditional light sources such as light-emitting diodes (LEDs) or lasers may be used for surface tumours, such as skin cancer, but the low penetration of light through tissue limits the depth to less than a centimetre. An endoscope – a thin, lighted tube used to look at tissues inside the body – can be used to insert a fibre optic cable into the inner lining of some organs, such as the oesophagus. But for organs such as the brain or liver, the organ must be exposed by surgery before PDT can be used.

The new wireless approach of light delivery enables PDT to be used on the inner organs of the body with fine control.

The study, supported by the Singapore Ministry of Education’s Tier 3 grant, was led by Professor Zhang Yong and Assistant Professor John Ho, who are from the Department of Biomedical Engineering and Department of Electrical and Computer Engineering at NUS Faculty of Engineering, respectively. The findings of the study were published in the scientific journal Proceedings of the National Academy of Sciences (PNAS) on 29 January 2018. 

The NUS team’s approach involves the insertion of a tiny wireless device at the target site, extending the spatial and temporal precision of PDT deep within the body. 

The miniaturised device, which weighs 30 mg and is 15 cubic mm in size, can be easily implanted, and uses a wireless powering system for light delivery. A specialised radio-frequency system wirelessly powers the device and monitors the light-dosing rate after the device has been implanted at the target site. 

The team demonstrated the therapeutic efficacy of this approach by activating photosensitisers through thick tissues – more than three centimetres – which are inaccessible by direct illumination, and by delivering multiple controlled doses of light to suppress tumour growth. 

Asst Prof Ho said, “Our approach of light delivery will provide significant advantages for treating cancers with PDT in previously inaccessible regions. Powered wirelessly, the tiny implantable device delivers doses of light over long time scales in a programmable and repeatable manner. This could potentially enable the therapies to be tailored by the clinician during the course of treatment.” Asst Prof Ho is also a Principal Investigator at the Biomedical Institute for Global Health Research and Technology (BIGHEART) at NUS.

“This novel approach enables ongoing treatment to prevent reoccurrence of a cancer, without additional surgery. The application of the technology can also be extended to many other light-based therapies, such as photothermal therapy, that face the common problem of limited penetration depth. We hope to bring these capabilities from bench to beside to provide new opportunities to shine light on human diseases,” said Prof Zhang.

The team is now working on developing nanosystems for targeted delivery of photosensitisers. They are also coming up with minimally invasive techniques for implanting the wireless devices at the target site and looking into integrating sensors to the device to monitor the treatment response in real-time.  

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