A carbohydrate-antioxidant hybrid polymer reduces oxidative damage in spermatozoa and enhances fertility

Gamete-gamete interactions are critically modulated by carbohydrate-protein interactions that rely on the carbohydrate-selective recognition of polyvalent carbohydrate structures(1,2). A galactose-binding protein has been identified in mammalian spermatozoa(3) that has similarity to the well-characterized hepatic asialoglycoprotein receptor(4). With the aim of exploiting the ability of this class of proteins to bind and internalize macromolecules displaying galactose, we designed hybrid carbohydrate-antioxidant polymers to deliver antioxidant vitamin E (alpha-tocopherol) to porcine spermatozoa. Treatment of sperm cells with one hybrid polymer in particular produced large increases in intracellular sperm levels of alpha-tocopherol and greatly reduced endogenous fatty acid degradation under oxidative stress. The polymer-treated spermatozoa had enhanced physiological properties and longer half-lives, which resulted in enhanced fertilization rates. Our results indicate that hybrid polymer delivery systems can prolong the functional viability of mammalian spermatozoa and improve fertility rates, and that our functionally guided optimization strategy can be applied to the discovery of active glycoconjugate ligands.