Want to attract media attention by studying the toxicity of a nanomaterial? Then use graphene and study human sperm. There are already several studies that have gone this route. The new study published in Scientific Reports indicates that concentrations between 1 and 25 μg/ml do not affect sperm viability.
Let’s understand it
The new work, which is perhaps seeking an Ig Nobel prize, uses sperm to study cytotoxicity because in humans it is the easiest route. Previous studies in animal models (intravenous administration to mice of doses up to 1 mg/ml) show oxidative stress damage to DNA and cell membrane, accumulation in the testes, causing inflammation, nodules and lesions, and reduced sperm motility.
The new work studies two functionalized carbon-based nanomaterials that have been proposed for biomedical applications. Specifically, carbon nanotubes with a carboxyl group (CNT-COOH) and reduced graphene oxide (rGO).
The article is Waseem Asghar, Hadi Shafiee, …,Utkan Demirci, «Toxicology Study of Single-walled Carbon Nanotubes and Reduced Graphene Oxide in Human Sperm,» Scientific Reports 6: 30270 (19 Aug 2016). Read here
Carbon Nanotubes
Carbon nanotubes and graphene are insoluble in water, so they are functionalized to improve their solubility and binding to certain drugs. Single-layer carbon nanotubes are usually functionalized with a carboxyl group (SWCNT-COOH). To functionalize single-layer graphene sheets, graphene oxide is used, which is partially reduced to improve its electrical conductivity, giving rise to the so-called RGO.
The viability of human spermatozoa in culture with different concentrations of SWCNT-COOH or RGO was quantified after 30 minutes and after 3 hours. For doses below 25 μg/ml, no effects on sperm viability are observed.
Final Note
Signs of possible oxidative stress are observed, which could have adverse effects on male fertility in higher amounts and for longer periods than those studied. Therefore, the authors of the study call for future analyses of the effects of these nanomaterials on spermatozoa.