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"The Singlet Oxygen Strategy: sustainable oxidation procedures for applications in material science, synthesis, wastewater treatment, diagnostics and therapeutics"

Final Report Summary - SO2S (The Singlet Oxygen Strategy: sustainable oxidation procedures for applications in material science, synthesis, wastewater treatment, diagnostics and therapeutics)

The SO2S (singlet oxygen strategy) project aimed to further current research into the generation and use of singlet oxygen for medical, diagnostic and environmental applications. Singlet oxygen is a reactive form of oxygen that is produced through activation of oxygen using a specific molecule (a photosensitizer) and light. When this form of oxygen is produced it is very reactive, although it is also short-lived. This means that it can act as a green reagent for chemical synthesis, a powerful and targeted treatment for cancer and an effective method for removing pollutants. These areas of singlet oxygen research, among others, were addressed specifically in the five research work packages which intertwined to make a truly collaborative project.

WP1 looked at the development of photosensitizers (PSs) capable of producing singlet oxygen. With respect to the expertise of the partners involved, the synthesis of porphyrins and phthalocyanines, two different classes of PSs, was the focus. Porphyrins were used for conjugation to other components such as nanoparticles and antibodies to enhance the characteristics of the PS. Alternative metal ions were investigated on Phthalocyanines (Pcs), namely zinc, silicon and ruthenium, together with the effect of peripheral substituents that could vary the electronic characteristics of the PSs. These were then used in other WPs and shared with other partners for further investigations (vide infra).

The use of singlet oxygen for chemical synthesis was the central theme of WP2 and involved the development of new methodologies and new uses for singlet oxygen. New and more efficient routes for natural product synthesis were discovered and optimised using the reaction of singlet oxygen with furan molecules.

In WP3, selected PS were investigated for use within a variety of medical applications. Porphyrins were conjugated to antibodies that recognise specific antigens expressed on various cancer cells, and are currently being investigated for other medical applications. Phthalocyanines were modified with various ligands to improve their ability to be taken up by cells, and for inactivation of bacteria. Selected PSs were used in the investigation of crosslinking oligonucleotides.

WP4 investigated the possibility of using singlet oxygen for environmental applications such as wastewater treatment. Through the use of magnetic nanoparticles decorated with PSs, it has been shown that certain pollutants in water can be broken down. They can also be recovered for multiple cycles of use, increasing their suitability.

Singlet oxygen has also been investigated for use within diagnostic and analytic applications in WP5. The incorporation of a singlet oxygen-reactive chemical moiety to biologically relevant building blocks enables the formation of stable crosslinks which can be used in various applications. Using this methodology it has been possible to produce more stable diagnostic tools for various diseases. The production, or suppression of reactive oxygen species has also been investigated in algae for biosensors that can be used for monitoring hazardous chemicals.

The research results of the project have been communicated through progress reports and minutes of the meetings. The consortium has published ca. 15 publications in high impact journals (with another 15 in the process of being published) and is further expected to produce 11 PhD theses.

As a training network, we have also focussed on providing the fellows with a fully rounded set of skills, not just in research, but all transferable skills that will enable them to work in various environments. With a mixture of academic, industrial and governmental organisations within the network, each partner has contributed to this training. Regular network meetings were organised (7 over the course of the project) in which the fellows were offered scientific skills and transferable skills training.
The truly collaborative nature of this network has given the fellows the opportunity not only to complete a high profile PhD or post-doctoral research project, but to expand their networking skills and adaptability. The results generated by the network will go far beyond the present time frame of the project, and new collaborations have been established that will ensure the future of these technologies.

The socio-economic impacts of this project are numerous arising from the ambitious goals of this project. The preparation of PSs for the purposes addressed above gave rise to long-term benefits in terms of a deeper understanding of the relationship between structure and properties of the PSs and their conjugation with other components. Medium-term benefits stemmed from the preparation of PSs that will be incorporated as active components in areas of photodynamic therapy (PDT) and bacteria photoinactivation (PDI).

Important social and environmental benefits are also expected from the results of this project which aimed to contribute to one of the most important and crucial issues which our world is facing today, namely improving the health condition of people. Moreover, this field, which lies at the interface of chemistry, biology and materials science has provided a unique opportunity for the training of young researchers in multisectoral, interdisciplinary and emerging fields.