Wireless implant sends out light to treat cancer

Japanese scientists develop a new device for metronomic photodynamic therapy to facilitate a minimally-invasive as well as effective cancer treatment in delicate organs.

Writer: Sara Maria Majernikova
Editor: Chelsea K Tripp
Artist: Lucie Gourmet

Conventional photodynamic treatment (PDT) is accomplished by a photodynamic response caused by the excitation of a photosensitizer exposed to light. Raab et al. were the first to report on this phenomenon in 1990. Some skin and eye disorders, as well as some forms of cancer, may be treated with it. PDT uses light-sensitive drugs and a light source to kill cancerous cells by utilising photosensitizing chemicals accumulating in tumours and activating when exposed to a certain wavelength of light. The gadget might be especially effective for treating cancer in sensitive organs, where surgery or radiation would be dangerous.

Low-dose, long-term photodynamic treatment (mPDT) has shown promise in treating malignancies of the internal organs in recent years. The issue with mPDT is that because the light intensity is so low (1/1000 of the conventional method), the antitumor effect cannot be produced if the light source changes even slightly away from the tumour, rendering the illumination inadequate. Thus, Waseda University, the National Defense Medical College, and the Japan Science and Technology Agency collaborated to create a novel bioadhesive, wirelessly driven light-emitting gadget that might help cure tumours in sensitive organs, like the brain and pancreas. 

Yamagishi and colleagues developed an implantable and wirelessly powered mPDT device. It consists of near-field-communication-based light-emitting-diode chips and bioadhesive and stretchable polydopamine-modified poly(dimethylsiloxane) nanosheets. This optoelectronic device adheres to the inner animal tissue surface allowing continuous, local light delivery to the tumour. The nanosheets have been modified with the mussel adhesive protein-inspired polymer polydopamine, which can hold the device in place on animal tissue for more than 2 weeks without the use of surgical suturing/medical glue. If clinically applied, the implant could be beneficial for cancer patients seeking minimally invasive treatment, helping them live longer and improve their quality of life.

Near-field communication technology is used to power the device’s light-emitting diode chips remotely. To assess its efficacy, tumour-bearing mice implanted intradermally with the device were injected with a photosensitizing chemical (photofrin) and subjected to red and green light at a 1,000-fold lower intensity than current PDT techniques for 10 days. Red or green light treatments after being given the medication photofrin to sensitise their cells to light. The investigation revealed that tumour development was greatly decreased overall, particularly under green light, and the tumour was totally eliminated in certain animals. Green light had a much bigger impact, reducing their tumours.

Yamagishi’s team established the therapeutic effectiveness of this strategy by activating photosensitisers through thick tissues; more than three centimetres thick that are unreachable by direct illumination, as well as by providing several regulated doses of light to prevent tumour development. This technology has the potential to simplify treatment for difficult-to-detect micro-tumours and deeply placed lesions that are difficult to reach with regular phototherapy, without the danger of injuring healthy tissues due to overheating. Furthermore, because the device does not require surgical suturing, it is appropriate for treating cancer near important nerves and blood arteries, as well as delicate, changing form, or actively moving organs such as the brain, liver, and/or pancreas. One issue is if the tumour is in a moving organ, like the oesophagus or the lung, the lighting is uneven, making it difficult to manage the dosage. The therapy will not work if the dosage is too low, and if it is too high, it might destroy good tissue by overheating it.

This innovative technique allows for continued therapy to prevent cancer recurrence without the need for extra surgery. The technology’s use may also be expanded to many other light-based treatments, such as photothermal therapy, which have the same issue of limited penetration depth. Researchers seek to transfer these talents from the bench to the field, opening up new avenues for shedding light on human disorders. The team is now working on nanosystems for targeted delivery of photosensitisers. They are also developing minimally invasive ways for implanting wireless devices at the target location, as well as investigating the incorporation of sensors inside the device to monitor the therapy response in real time.

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