A new light-emitting device that can be implanted in the body could be used to treat cancer.
Photodynamic therapy, which is already used to treat some cancers, involves the patient taking a drug that makes cells vulnerable to light. Doctors then shine a light on the tumour for around 10 to 45 minutes, using a flexible tube called an endoscope if the tumour is inside the body,
One difficulty is that if the tumour is located in an organ that moves, such as the oesophagus or the lung, the illumination is irregular, which makes it hard to control the dose. If the dose is too small, the treatment won’t work, and if it’s too high, it can damage healthy tissue by overheating it.
To overcome this problem, some researchers have tried to develop ways to deliver light at a lower intensity for a longer period of time by implanting optical fibres inside the body. But keeping the light source in the right place is challenging: surgical sutures can’t be used on fragile organs such as the brain and liver, or organs that move like the skin and intestines.
Now Toshinori Fujie at Waseda University, Japan, and colleagues have developed a device that is sandwiched between two thin, sticky sheets that attach it to the body. These sheets are covered in a sticky polymer based on proteins found in mussels’ feet.
Shrinking tumours
The device consists of an LED chip powered wirelessly by NFC – the technology used in contactless payment terminals – so there is no need for batteries to be implanted in the body.
When the team implanted the device under the skin of mice that had been given tumours, it was held in place by the sticky nanosheets. This allowed them to shine light onto tumours for up to 10 days, using light 1000 times less intense than is usually used in photodynamic therapy.
The mice were treated with the drug photofrin to sensitise their cells to light and then given red or green light therapy. Tumour growth was greatly reduced in mice given red light therapy, compared to mice given no light therapy. Green light had an even stronger effect, shrinking their tumours.
Fujie says the device could be particularly useful for treating cancer in delicate organs such as the brain and pancreas, where surgery or radiotherapy is risky.
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