Exploring the full potential of sperm function with nanotechnology tools

Abstract

Sperm quality is essential to guarantee the success of assisted reproduction. However, selecting high-quality sperm and maintaining it during (cryo)preservation for high efficiency remains challenging in livestock reproduction. A comprehensive understanding of sperm biology allows for better assessment of sperm quality, which could replace conventional sperm analyses used today to predict fertility with low accuracy. Omics approaches have revealed numerous biomarkers associated with various sperm phenotypic traits such as quality, survival during storage, freezability, and fertility. At the same time, nanotechnology is emerging as a new biotechnology with high potential for use in preparing sperm intended to improve reproduction in livestock. The unique physicochemical properties of nanoparticles make them exciting tools for targeting (e.g., sperm damage and sexing) and non-targeting bioapplications. Recent advances in sperm biology have led to the discovery of numerous biomarkers, making it possible to target specific subpopulations of spermatozoa within the ejaculate. In this review, we explore potential biomarkers associated with sperm phenotypes and highlight the benefits of combining these biomarkers with nanoparticles to further improve sperm preparation and technology.

Keywords: biomarkers; functional genomics; nanoparticles; spermatozoa.

Figure 1. Structure of a typical nanoparticle. Metal nanoparticles (MNPs) have a metal core and a shell. The core can be made of an inorganic metal (zinc, iron, silver, gold, etc.) or metal oxide (Aluminum, copper, magnesium, titanium, zinc, silica, iron oxides, etc.). The shell can be made of an organic (e.g., polymers) or inorganic material (e.g., gold), or metal oxide (e.g., silane). Nanoparticles made of metallic cores surrounded by oxide shells, also known as metal oxide core-shell nanoparticles, have become popular due to their unique properties and high stability. Diverse metal-oxide interactions in metal oxide core-shell nanoparticles enable tuning their electronic structure (shape and size), spectroscopic properties, and surface reactivity for bioapplications (e.g., sensing, drug/gene delivery, and targeted imaging and selection).

Figure 2. Overview of commonly used inorganic and organic nanoparticles. The presented inorganic nanoparticles can be coated with single or multiple layers of organic or inorganic materials before biofunctionalization for bioapplications. Among the organic nanoparticles, liposomes are the most widely used for bioapplications, such as targeted bioimaging, drug delivery (hydrophobic and hydrophilic), and drug and nucleic acid intracellular delivery. The possibility of coating the external surface of nanoparticles with polyethylene glycol (PEG), or PEGylation, increases nanoparticle’s stability and decreases immunogenicity during in vivo delivery.

Figure 3. Schematic representation of a biofunctionalized nanoparticle. Ready-to-use nanoparticles for bioapplications include a (nano)core surrounded by single or multiple coating layers providing stability and decreasing immunogenicity and an outer surface layer functionalized based on planned unimodal (e.g., imaging) or multimodal (e.g., imaging and drug administration) applications.