Exploring Nanoparticle-based Approaches to Improve Semen Freezability in Domestic Animals

Abstract

Semen cryopreservation is an indispensable tool in animal reproductive biotechnology, supporting long-term genetic conservation, artificial insemination, selective breeding and livestock improvement programmes. However, the freeze-thaw process can induce substantial cryoinjury in spermatozoa through oxidative stress, osmotic imbalance, membrane destabilisation, mitochondrial dysfunction and DNA damage, thereby reducing post-thaw sperm quality and fertilising capacity. Conventional cryoprotectants and antioxidants incorporated into extenders before processing provide partial protection, but their efficacy may be limited by low stability, inadequate cellular penetration, batch variability and inconsistent responses among species. Nanotechnology has therefore emerged as a complementary strategy for improving antioxidant delivery, membrane protection and controlled release of bioactive compounds during semen preservation. This review summarises the mechanisms of sperm cryoinjury and evaluates nanoparticle-based approaches used to mitigate freeze-thaw-induced damage in domestic animals. The discussion is restricted to evidence presented in the manuscript and focuses on reproductive applications relevant to semen freezability. Reported nanoparticle systems include selenium, zinc oxide, cerium oxide, iron oxide, gold and silver nanoparticles, nano-emulsions, liposomes, nano-lecithin, polymeric carriers and phytochemical-based nano-formulations. These additives have been associated with improvements in sperm motility, viability, membrane integrity, acrosome status, mitochondrial activity, antioxidant balance and, in selected studies, fertility-related outcomes. Species-specific responses in bovine, caprine, ovine, equine, canine and swine spermatozoa are also considered, as variations in membrane composition and antioxidant capacity influence freezability and nanoparticle efficacy. The review further discusses dose-dependent nanotoxicity, biosafety concerns, reproductive risks and the need for careful physicochemical characterisation. Current evidence indicates that nanoparticle-assisted cryopreservation has practical potential, provided that protocols are optimised for each species and supported by long-term safety and fertility validation.