(Invited) Assets of Nanodiamonds for Bioapplications

Abstract

Diamond nanoparticles (nanodiamonds, NDs) behave physical and chemical properties expected from bulk diamond. Among these assets, their biocompatibility and their versatile surface chemistry based on carbon make them good candidates for bioapplications [1]. Moreover, the high surface to volume ratio of NDs can be tuned with sizes down to 5 nm depending on their synthesis methods [2]. This nanoscale confers new properties to NDs, often governed by their surface chemistry. This small primary size could also ensure a better elimination for in vivo studies. Lastly, the presence of color centers (NV, SiV) in the diamond lattice allow to use fluorescent NDs as biomarkers [3]. After providing the state of art of the synthesis and the current main applications of NDs, this talk will focus on the intrinsic properties of hydrogenated detonation NDs, from surface chemistry to colloidal behavior in water suspensions. Two hydrogenation methods will be compared in terms of hydrogen grafted or incorporated into NDs via isotope studies (3H) [4]. The hydrogenated NDs revealed an ability to produce reactive oxygen species (ROS) in radioresistant human cancer cells under gamma irradiation. This radiosensitive behavior was in vitro demonstrated, turning these cells into senescence state [5]. The physical and chemical mechanisms involved in the production of radicals were investigated by illuminating aqueous colloids of hydrogenated nanodiamonds under X-rays and gamma-rays. An overproduction of hydroxyl radicals and solvated electrons versus water radiolysis was measured using the 7-OH-coumarin as a fluorescent probe [6]. These results well evidence that NDs can act as active nanoparticles under illumination. The main perspectives of NDs for bioapplications will be discussed.