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We report the development of a hydrogel‐based approach to select bull spermatozoa, a crucial step for successful assisted reproductive techniques (ARTs). Hyaluronic acid (HA) semi‐interpenetrated N‐isopropylacrylamide (PNIPAM) co‐20% N‐Tris (hydroxymethyl) methyl acrylamide (HMA) hydrogels were synthetized on glass surfaces and cultured in presence of frozen‐thawed bull spermatozoa. A fraction of motile bull spermatozoa population strongly attached to hydrogels and was partially released by treatment with hyaluronidase. Fifty‐nine (59 ± 7.24) per cent of sperm cells attached to PNIPAM‐HMA‐HA hydrogels and 31.16 ± 4.81% of them were released upon treatment with medium containing hyaluronidase. This attached‐released sperm fraction has acceptable characteristics of progressive motility (50.0 ± 5.0%), vigour (4), high viability (58.7 ± 11.7%) and low percentage of acrosome reacted spermatozoa (23.36 ± 4.1%). Our findings indicate that PNIPAM‐HMA‐HA hydrogels are non‐toxic and allow the selection of high‐quality sperm cells for ART. [ABSTRACT FROM AUTHOR]

The study of living systems in contact with biocompatible synthetic hydrogels is developing. The authors' group is the first to propose use of polymeric materials to accomplish sperm selection process by attachment of bull sperm to hydrogel surfaces, this being a crucial step for successful assisted reproductive techniques (ARTs). Surfaces based on poly(N‐isopropylacrylamide) hydrogels (PNIPAM) and ionic and neutral copolymers are synthetized. Their physicochemical properties in aqueous and culture medium are related to the percentage of attachment and subsequent release of bull spermatozoa from the hydrogel surface. High attaching capacity (30–45%) of sperm on cationic and neutral surfaces is mainly observed, however, sperm detachment from the hydrogel using traditional induction processes (i.e., sperm capacitation) is not significant. Therefore, PNIPAM‐co‐20%‐N‐Tris(hydroxymethyl)methyl acrylamide (PNIPAM‐HMA) hydrogel surface is semi‐interpenetrated with hyaluronic acid (HA). In this case, 50% of spermatozoa are attached to PNIPAM‐HMA‐HA hydrogel and after treatment with hyaluronidase, 47% of them are released. Collected sperm show acceptable characteristics of progressive motility (70% with score 4 for vigor), high viability, and cytoplasmic membrane integrity. Noteworthy, the study of the interaction of hydrogel surface/spermatozoa can be extended to human and other mammalian species, in order to provide advanced alternatives for gamete selection for ARTs. [ABSTRACT FROM AUTHOR]