# Resurgence of a Nation's Radiation Science Driven by Its Nuclear Industry Needs
## 3 Exemplar Results
### Applications of Radiation Science to Healthcare  
Radiation chemistry in aqueous systems is an ongoing area of research at DCF which has applications beyond the nuclear industry; healthcare is one example of this wider application. The redox conditions generated during radiation therapy can damage human cells, so investigation is required to understand how healthy cells can be protected. Radiation chemistry also offers a novel approach to studying in vivo processes: many of the free radicals that can be generated radiolytically are also present in vivo during normal metabolic processes and are over-produced during oxidative stress. Work at DCF was inspired by clinical studies of dietary supplementation to help prevent oxidative stress, and subsequent diseases such as cancer, where a pro-oxidant effect could not be explained [43]. Several dietary carotenoids (CAR) have been shown to give protection to human lymphoid cells from damage by \(\gamma\)-radiation, after two weeks of dietary supplementation with 70-90 mg/day of an individual carotenoid [44; 45]. This protective effect declines as the oxygen concentration increases, and the rate of decline depends on which carotenoid is administered. Remarkably, for the carotenoid lycopene (the red pigment in tomatoes), no protection at all was observed at 100% oxygen, falling from 5-fold protection in air and 50-fold protection in the absence of oxygen. It is postulated that the link between oxygen concentration and cell protection is mediated by an initial addition of a hydroxyl radical (OH\({}^{\bullet}\)) to CAR, followed by the addition of oxygen to the radical adduct (CAROH\({}^{\bullet}\)) forming a more damaging peroxyl radical (CAROH-OO\({}^{\bullet}\)). This series of reactions is outlined in Equations (1)-(3) and is known as the oxygen effect. \[\text{CAR}+\text{OH}^{\bullet}\rightarrow\text{CAROH}^{\bullet} \tag{1}\]  
\[\text{CAROH}^{\bullet}+\text{O}_{2}\rightleftharpoons\text{CAROH-OO}^{\bullet} \tag{2}\]  
\[\text{CAROH-OO}^{\bullet}+\text{cell}\rightarrow\text{cell}\text{ death} \tag{3}\]  
Figure 7: A determination of volume change for different glass compositions that have been exposed to Ni ions beams of two different fluxes (ions cm\({}^{-2}\) s\({}^{-1}\)). For each composition, one part of each sample was masked from the ion beam so that a step was produced by the change in volume. To assist in understanding the underlying radical-based mechanisms of the cellular results described above, the effect of gamma radiation on carotenoids in solution has been studied using a total dose of 25 Gy. The dietary carotenoids studied in the cellular work are lipid soluble, so detergent needs to be used to solubilize them in water. Astaxanthin was solubilized in aqueous 2% Triton-X 100 detergent. Crocetin, a water-soluble carotenoid, was also studied to eliminate any effects of the detergent. Damage of the carotenoids is indicated by bleaching, determined using UV-Vis spectroscopy. Radiolysis of air-saturated water generates oxidizing and reducing species, including OH\({}^{\bullet}\) and superoxide (O2\({}^{\bullet-}\)). Bleaching of carotenoids in essentially oxidizing conditions was studied using nitrous oxide to convert electrons generated during radiolysis to OH\({}^{\bullet}\). A separate study of air-saturated formate (NaCO2H) solutions was carried out to investigate the role of O2\({}^{\bullet-}\), since in the presence of air, NaCO2H converts all the primary radicals, e\({}_{\text{ad}}\), OH\({}^{\bullet}\) and H\({}^{\bullet}\), to O2\({}^{\bullet-}\)[46]. Sodium formate was used at a concentration of 0.1 M. The results are shown in Figure 8.  
For the formate systems, Figure 8 shows that there is a small but detectable reduction in absorbance for astaxanthin in air-saturated aqueous Triton-X 100 solution compared to an un-irradiated sample. We obtain similar results for crocetin in water (Figure 8b) which shows that there is no effect of the Triton detergent associated with the rather low reactivity of carotenoids with O2\({}^{\bullet-}\).