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Abstract
To examine gold nanoparticle reprotoxicity, bovine spermatozoa were challenged with ligand-free or oligonucleotide-conjugated gold nanoparticles synthesized purely without any surfactants by laser ablation. Sperm motility declined at nanoparticle mass dose of 10 µg/ml (corresponding to ∼14 000 nanoparticles per sperm cell) regardless of surface modification. Sperm morphology and viability remained unimpaired at all concentrations. Transmission electron microscopy showed an modification dependant attachment of nanoparticles to the cell membrane of spermatozoa, but provided no evidence for nanoparticle entrance into sperm cells. A molecular examination revealed a reduction of free thiol residues on the cell membrane after nanoparticle exposure, which could explain the decrease in sperm motility. Sperm fertilising ability decreased after exposure to 10 µg/ml of ligand-free nanoparticles indicating that agglomerated ligand-free nanoparticles interfere with membrane properties necessary for fertilisation. In conclusion, nanoparticles may impair key sperm functions solely by interacting with the sperm surface membrane.
Acknowledgements
We acknowledge the skilful assistance of Patrick Aldag, Annabel Bergman, Antje Frenzel, Julia Heinzmann, Andre Mittag, Ronald Wittig, Rolf Poppenga and Hans-Georg Sander.
Declaration of interest
No authors have affiliations or financial involvement with any organization or entity with a direct financial interest in the subject matter or materials discussed in the manuscript. The authors declare that they have no competing interests.
The work was generously supported by Masterrind GmbH Verden, the German Research Foundation (Priority Program SPP1313 and BA3580-10-1 with RA898-8-.1) and the Excellence Cluster REBIRTH.
Supplementary material available online
Supplementary Figures S1–S3