Inorganic Metal Nanoparticles in Reproductive Biology: Applications, Toxicities and Future Prospects

The development of inorganic metal and metal oxide nanoparticles (MNPs) has attracted significant attention in diverse biomedical and biotechnological fields including bio-detection, drug delivery, imaging, and theranostics. An emerging field in this context is the use of MNPs for applications in reproductive biology. In this article, we offer a rational review of the development of MNPs employed in the field of reproductive biology by focusing on their interactions with highly delicate and specialized germ cells like spermatozoa, oocytes, and developing embryos. By their unique physicochemical properties, MNPs are versatile and strong candidates for targeted imaging and delivery of various therapeutic molecules to the specific sites of the gametes and reproductive cells. Functionalized MNPs can serve as transfection vectors for the generation of transgenic animals by spermatozoon-supported gene transfer. In addition, MNPs have shown great promise in application fields such as semen collection, nano-purification, cryopreservation, and sex sorting of sperm in the livestock industry. Recently, the potential toxicity of MNPs on maturing oocytes has been investigated, as well as the use of MNPs to preserve fertility by improving cryopreservation and reducing oxidative stress in oocytes. The article further elaborates on the uptake, translocation mechanism, and biocompatibility issues of the MNPs to reproduction-relevant sites on cellular and molecular levels. Based on these promising achievements, the current challenges and prospects for the development of these functionalized MNPs for clinical research in conjunction with the reproductive system will be discussed.