An overview of the role of metallic and nonmetallic nanoparticles and their salts during sperm cryopreservation and in vitro embryo manipulation.

The cryopreservation of spermatozoa and the embryo production are valuable tools used in a variety of species, including humans, livestock, fish, and aquatic invertebrates. Sperm cryopreservation has been used to maintain or increase the genetic diversity of threatened species. Reactive oxygen species (ROS) are molecules derived from oxygen, being formed as byproducts of cellular metabolism. During cryopreservation of sperm and other manipulations of oocytes and embryos, ROS production is dramatically increased. In cells, low, medium, and high levels of ROS lead to different outcomes, apoptosis, auto-phagocytosis, and necrosis, respectively. ROS produced by cells can be neutralized by intracellular antioxidant systems, including enzymes as well as non-enzymatic antioxidants. Free radicals and oxidative stress can be major factors influencing manipulations. In this review, we discuss the role that metallic and nonmetallic nanoparticles and their salts play in the modulation of oxidative stress during embryo production and cryopreservation of sperm.