Graphenic Nanoparticles from Combustion Sources Scavenge Hydroxyl Radicals Depending Upon Their Structure Emanuele Carella & Mara Ghiazza & Michela Alfè & Elena Gazzano & Dario Ghigo & Valentina Gargiulo & Anna Ciajolo & Bice Fubini & Ivana Fenoglio Published online: 14 February 2013 # Springer Science+Business Media New York 2013 Abstract Graphenic nanomaterials like fullerenes, carbon nanotubes (CNT), and carbon black (CB) are known to scavenge free radicals. This antioxidant activity makes these materials promising in all applications where radical reac- tions need to be controlled. Therefore, CNT and fullerenes has been proposed as stabilising additives for composites and in medicine to prevent free-radicals-mediated diseases. CB has been used for more than a century as a stabilising filler in rubbers. The mechanisms responsible of the scav- enging activity and the role of the nanoparticles structure in the antioxidant potency are still poorly known. In the present study, two samples of very pure soot having different struc- ture were prepared as model of graphenic nanoparticles and tested for their capability to scavenge hydroxyl radicals by means of electron paramagnetic resonance (EPR)/spin trap- ping technique. The mechanism of the reactions occurring between the soot samples and the free radicals was evaluated by EPR spectroscopy of the dry powder while the possible introduction of oxygenated acidic functionalities during the reaction was evaluated by titration and confirmed by mea- suring the variation in ζ-potential of particles. The results indicate that soot persistently scavenge hydroxyl radicals through a reaction leading to the introduction of acidic functionalities at the surface. The scavenging activity was found to depend upon the bulk/surface structure of soot. When tested on alveolar macrophages MH-S cells, both samples did not induce cell damage (lactate dehydrogenase leakage) and oxidative stress (intracellular GSH depletion), suggesting a possible safe use of graphenic nanoparticles. Keywords Toxicity . Soot . ROS . EPR/spin trapping . Scavenging . Antioxidant 1 Introduction The human exposure to nanoparticles (or ultrafine particles) has considerably heightened over the last few decades due to combustion-derived air pollution. Moreover, the current development of nanotechnology has also been generating new type of engineered nanoparticles that are employed in several fields, such as medicine, food, clothes, personal care products industries, and construction [1]. The concern on possible adverse effects elicited by nanoparticles is related to their small size which increases the chance of transfer from the airways to other organs via circulation system [2]. However, the behaviour and the effects of nanoparticles within living systems cannot be foreseen without taking into account their physico-chemical features [3]. Graphenic nanoparticles are a heterogeneous group of nanomaterials mostly composed by elemental carbon par- tially or totally organised in graphenic/graphitic structures. They include combustion-generated nanoparticles and engi- neered nanomaterials like carbon nanotubes (CNT), carbon black (CB), graphene, and fullerenes. The majority of airborne fine and ultrafine particles (par- ticulate matter (PM) of less than 2.5 and 0.1 μm, respec- tively) are combustion-generated or combustion-derived particles. Combustion-generated particles include a E. Carella : M. Ghiazza : B. Fubini : I. Fenoglio (*) Department of Chemistry, Interdepartmental Center for Studies on Asbestos and other Toxic Particulates “G. Scansetti” and Interdepartmental Centre for Nanostructured Interfaces and Surfaces, University of Torino, Turin, Italy e-mail: ivana.fenoglio@unito.it M. Alfè : V. Gargiulo : A. Ciajolo Istituto di Ricerche sulla Combustione-C.N.R, Naples, Italy E. Gazzano : D. Ghigo Department of Oncology, Interdepartmental Center for Studies on Asbestos and other Toxic Particulates “G. Scansetti”, University of Torino, Turin, Italy BioNanoSci. (2013) 3:112–122 DOI 10.1007/s12668-013-0077-6