Graphene oxide affects in vitro fertilization outcome by interacting with sperm membrane in an animal model

We realized the exposure of boar spermatozoa to graphene oxide (GO) at concentration of 0.5, 1, 5, 10 and 50 μg/mL in an in vitro system able to promote the capacitation, i.e. the process that allows sperm cells to became fertile. Interestingly, we found that the highest GO concentration (5, 10 and 50 μg/mL) are toxic for spermatozoa, while the lowest ones (0.5 and 1 μg/mL) seem to significantly increase the sperm cells fertilizing ability (p >.05) in an in vitro fertilization experiment. To explain this finding, we investigated the effect of GO on sperm membrane structure (atomic force microscopy) and function (confocal microscopy and flow cytometry, substrate adhesion). As a result, we found that GO is able to interact with spermatozoa membranes and, in particular, it seems to be able to extract the cholesterol, which is a key player in spermatozoa physiology, from plasma membrane of boar spermatozoa incubated under capacitation conditions. In our opinion, these results are very important because they allow identifying either a plausible mechanism of GO toxicity on spermatozoa and new strategies to manage sperm capacitation.