Influence of nanoparticles on mammalian reproduction
Nanoparticles (NP) play an increasing role in the daily life of our animals and us, since the addition of NP to food, feed, coatings and consumer products is growing steadily. The ability of NP to cross biological barriers (for example testis, brain) after being introduced to the organism and additionally the possibility to functionalize the NP surface makes them promising prospects for various applications including medical diagnostics and therapies. The developments in nanotechnology and NP production in the last two decades greatly exceed the knowledge about the influences of NP on organisms and cell functions, especially on reproduction and following generations in mammals, which cannot be answered comprehensively so far. The goal of the presented study is to gain reliable information about the effects of NP contact on critical aspects of reproduction. Several experiments have been performed so far with gold NP (AuNP) and silver NP (AgNP) since gold is considered to be biologically inert in contrast to the highly active silver. Additionally gold silver alloy NP (AuAgNP) with varying silver molar fractions were tested. Porcine oocyte in vitro maturation with the different NP present in the maturation medium (10µg/ml) revealed a highly significant effect of AgNP on the nuclear maturation rate (only 12% matured oocytes (control: 77.3%)). Interestingly, while the AuNP seemed to have no effect on the maturation, they were found in large numbers in the oocytes cytoplasm after maturation in contrast to the AgNP, which accumulated in the surrounding cumulus cells. The AuAgNP did not impair maturation up to a silver content of 50%. Higher silver content lead to similar results as pure AgNP. Co-incubation of ejaculated boar spermatozoa with NP for 2h at 37°C did not influence the tested sperm vitality parameters. In vitro fertilization in the presence of AuNP did not result in different pronuclear formation (fertilization rate) or number of 2-cell-stages (cleavage rate). In conclusion, the conducted experiments have shown that reproductive functions can be impaired by NP and especially in vitro oocyte maturation has proven to be a viable tool for reprotoxic screening of NP and to evaluate mechanisms of toxicity and possible effects on following generations.