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Hugues Girard1

1, CEA LIST, Gif sur Yvette, , France

Detonation nanodiamonds (NDs) behave suitable chemical and physical properties for bio-applications [1]. Well-controlled mass production provides NDs with a primary size of 5 nm made of a diamond-core and a shell-coating containing various surface terminations. Their surface chemistry can be adjusted via wet chemistry and physical treatments (annealing, plasma) [2]. Besides well-identified therapeutic and diagnosis applications of NDs such as drug nanocarriers or biomarkers, we proposed few years ago their use as an active nanoplatform, for which therapeutic effect can be triggered. Indeed, we reported on the radiosensitizing properties of H-NDs to enhance the effect of radiotherapy treatment on radio-resistant cell lines, which were shown to turn into senescence with a stopping of their proliferation [3]. This approach based on a carbon-based material represents a new alternative to metal-based nanoparticles which have not reached yet the clinical trial.
Here, we will summarize the studies conducted these last years in our group to better understand the mechanisms involved behind the reactivity of H-NDs in aqueous suspensions under irradiation. First, we will focus on the hydrogenation of nanodiamonds. Through the use of isotopes of hydrogen, we investigated qualitatively and quantitatively the hydrogenation process on detonation NDs according to the nature of the treatment, i.e. annealing or plasma. Then we will look at the colloidal properties of H-NDs and will report on their stability on short and long term. Finally, we will present our work on the behaviour of NDs suspended in water under ionizing radiations (X- and Gamma-rays). We investigated the production of hydroxyl radicals (HO) and solvated electrons (e-aq) during water radiolysis according to the concentration of H-NDs. We will demonstrate that H-NDs are at the origin of an overproduction of HO and e-aq compared to water radiolysis alone. On the contrary, no effect was measured for oxidized NDs from the same source [4]. The origin of the phenomenon will be discussed.
References
[1] Turcheniuk et al., Nanotechnology 28 (2017) 252001.
[2] Krueger et al., Adv. Funct. Mater. 22 (2012) pp 890
[3] Grall et al., Biomaterials 61 (2015) 290.
[4] Kurzyp et al., Chem. Comm. 53 (2017) 1237.

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