Radiotherapy is one of the most effective forms of cancer treatment and is used as part of treatment plans for approximately 50% of patients. Huge strides have been made in the last few decades in improving accuracy of ionizing radiation dose, increasing the precision of deposition of dose to tumours whilst reducing the overall dose delivered to healthy tissues. Despite these recent improvements, tumours of similar size, stage, grade and delivered doses will sometimes recur, whilst some will not. This is owed to biological factors determining treatment success and has led to a recent surge of interest in complementary agents for drug assisted radiotherapy. Photodynamic therapy (PDT) is a therapeutic technique of neoplastic tissues employing a photosensitiser and visible light to create reactive oxygen species (ROS) triggering cell death by necrosis and apoptosis. A limitation of PDT has always been the transmission of the light used through tissue being only a few millimetres, leading to the need for the more invasive use of optical fibres when trying to employ PDT for anything other than topical uses.<br/>Ionizing radiation interacts with nano-scintillator crystals which can attenuate the energy and in turn, luminesce visible light, by a process known as scintillation. The crystals respond to both X-rays and gamma rays, giving emission spectrums with a maximum wavelength at 450 nm and light outputs relative to NaI(Tl). This emission spectrum overlaps with the absorption spectra of porphyrins, the most abundant clinically approved PDT agents. These systems have therfore been combined into a single agent capable of generating singlet oxygen when irradiated with X-rays to give a combined treatment or so called PDT assisted radiotherapy.<br/>We investigate several suitable non-hydroscopic, non-toxic and biocompatible scintillation crystals and conjugated them to porphyrin based photosensitisers by both previously known as well as novel and unique conjugation methodologies. A library of conjugates has been synthesised and tested for singlet oxygen production is ongoing, to determine the best system of energy transfer from ionising radiation to photocytotoxic singlet oxygen production.

Scintillating possibilities of a drug assisted radiotherapy

253rd National Meeting (2017)

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