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Tending to wounded soldiers of the Crimean War, pioneering nurse Florence Nightingale famously described fresh air and light as essential tools for improving hygiene and reducing infection. Today, oxygen and light are once again playing a key role in medicine, this time in the fight against cancers.
Photodynamic therapy (PDT) combines light with an organic light-sensitive molecule called a photosensitiser. “When photosensitisers are administrated to a tumour and irradiated with light, they transfer energy to oxygen,” explains OXIGENATED project coordinator Sergio Moya from the Center for Cooperative Research in Biomaterials CIC biomaGUNE in Spain.
“This can induce a series of reactions that cause the destruction of malignant cells and activate the immune system.” These events can lead to the tumour’s eradication.
A key advantage of PDT is that it is highly targeted. By restricting light and photosensitisers to the tumour, collateral damage of healthy tissue in other regions of the body can be largely avoided. For PDT to be successful however, the presence of oxygen is essential.
“The difficulty here is that tumours are often characterised by a limited availability of oxygen,” notes Moya. “If we could increase oxygen availability in the tumour environment for the photosensitiser action, then we could enhance the outcome of photodynamic therapy.”
New ways of transporting oxygen
This has been the key objective of the OXIGENATED project, launched in March 2019 and undertaken with the support of the Marie Skłodowska-Curie Actions programme. “Our goal from the start was to find a new way of transporting both oxygen and photosensitisers to the tumour site,” explains Moya. “We saw that enhancing oxygen availability for initiating oxidation reactions would result in more effective photodynamic therapy.”
To achieve this goal, the project team developed nanoparticles based on haemoglobin, the natural carriers of oxygen in the body present in red blood cells. Unmodified haemoglobin cannot be delivered directly into the body, as it can cause side effects.
“Our work has therefore involved the design, construction and characterisation of nanoparticles with haemoglobin cores,” says Moya. “These could then be used to safely deliver oxygen without any unwanted effects.”
Haemoglobin was successfully trapped in polymeric or protein matrixes. This technique was shown to prevent haemoglobin exposure in the bloodstream, while retaining its capacity to transport and deliver oxygen.
Promoting non-invasive cancer techniques
By improving the effectiveness of PDT in this manner, Moya and his team hope to offer an appealing alternative to chemotherapeutics and other, more invasive methods of cancer therapy. The project, due for completion in August 2024, has already demonstrated that this is eminently possible.
“Until now, experiments have been carried out with in vitro cell cultures,” adds Moya. “In the next phase of the project, we will conduct in vivo experiments as a proof of concept demonstration of the functionality of these nanoparticles.”
Through international exchanges and the involvement of young researchers, the project has sought to ensure that research in this promising field will be continued over the longer term.
“With the easing of COVID restrictions, we have been able to quickly resume researcher exchanges,” says Moya. “In the coming months, more researchers will be able to benefit from working abroad, while tackling the project's main goal of demonstrating the effectiveness of this new technique.”
As well as reducing the financial burden on health systems, effective minimally invasive therapies such as enhanced photodynamic treatment will improve health outcomes and the quality of life of cancer patients. As Florence Nightingale said: “Life is a splendid gift”.