Nano-Winter Is Coming for Sperm Cryopreservation: Advanced Approaches for Life in Ice: A Review

Cryopreservation (CP) can negatively impact sperm quality, but recent studies have shown promising results using nanoparticles (NPs) as cryoprotectants. This review examines the potential of various NP types, including metallic, magnetic, polymeric, and lipid-based, in improving post-thaw sperm characteristics across different species, not only humans. The unique surface properties of NPs and their ability to inhibit ice formation are believed to mitigate freezing and thawing damage. A comprehensive literature review of over 40 recent studies revealed that multiple NP types, such as curcumin, cerium oxide, gold, silver, zinc oxide (ZnO), and soy lecithin, demonstrated cryoprotective properties. These NPs generally enhanced post-thaw sperm quality metrics, including motility, viability, chromatin integrity, mitochondrial activity, acrosome reaction, and antioxidant status. Proposed mechanisms of action include reducing freezing damage, oxidative stress, and apoptosis. However, some studies also revealed potential toxicity with long-term exposure. While NPs offer a promising platform for optimizing sperm CP protocols in assisted reproductive technology (ART) and reproductive management, further research is needed. Key areas for investigation include standardizing methodologies, understanding biological interactions, reducing cytotoxicity, and extending preservation strategies to diverse species. The development of cost-effective formulations applicable to all human ejaculates, along with a thorough investigation of bio-interactions, toxicity, and reproductive impacts, is crucial for advancing this field. Rational NP design and comprehensive assessments could lead to safer and more effective fertility preservation techniques, but optimization is still required to realize the potential of NPs in sperm CP fully.