Nanotechnology-based approach for safer enrichment of semen with best spermatozoa

Advances in nanotechnology have permitted molecular-based targeting of cells through safe and biocompatible magnetic nanoparticles (MNP). Their use to detect and remove damaged spermatozoa from semen doses could be of great interest. Here, MNP were synthesized and tested for their ability to target apoptotic (annexin V) and acrosome-reacted (lectin) boar spermatozoa, for high-throughout retrieval in a magnetic field (nanoselection). The potential impacts of nanoselection on sperm functions and performance of offspring sired by sperm subjected to nanoselection were determined. Fresh harvested and extended boar semen was mixed with various amounts (0, 87.5, and 175 μg) of MNP-conjugates (Annexin V-MNP or Lectin-MNP) and incubated (10 to 15 min) for 37 °C in Exp. 1. In Exp. 2, extended semen was mixed with optimal concentrations of MNP-conjugates and incubated (0, 30, 90, or 120 min). In Exp. 3, the synergistic effects of both MNP-conjugates (87.5 μg - 30 min) on spermatozoa was evaluated, followed by sperm fertility assessments through pregnancy of inseminated gilts and performance of neonatal offspring. Sperm motion, viability, and morphology characteristics were evaluated in all experiments.

Transmission electron microscopy, atomic force microscopy, and hyperspectral imaging techniques were used to confirm attachment of MNP-conjugates to damaged spermatozoa. The motility of nanoselected spermatozoa was improved (P < 0.05). The viability of boar sperm, as assessed by the abundance of reactive oxygen species and the integrity of the acrosome, plasma membrane, and mitochondrial membrane was not different between nanoselected and control spermatozoa. The fertility of gilts inseminated with control or nanoselected spermatozoa, as well as growth and health of their offspring were not different between (P > 0.05).

The findings revealed the benefit of magnetic nanoselection for high-throughput targeting of damaged sperm, for removal and rapid and effortless enrichment of semen doses with highly motile, viable, and fertile spermatozoa. Therefore, magnetic nanoselection for removal of abnormal spermatozoa from semen is a promising tool for improving fertility of males, particularly during periods, such as heat stress during the summer months.