Gelatin Microcartridges for Onboard Activation and Antioxidant Protection of Sperm

Sperm-driven micromotors are promising devices for developing autonomous, noninvasive diagnostic and therapeutic tools, specifically in reproductive biology and medicine. In this article, we present template-based microstructures fabricated from gelatin for sperm capture, activation, and antioxidant protection. The cartridge-like structures with one closed end-capture single bovine sperm cells and are propelled by the sperm's flagellum. We demonstrate the pH-dependent release of heparin from the gelatin microcartridges to induce capacitation, a crucial maturation process prior to fertilization. Further, the gelatin cartridges exhibit a protection against oxidative stress, one of the main causes for sperm damage. Finally, we investigate the stability and degradability of the microstructures in various physiological environments, such as endometrial cell culture, different pH, and in the presence of proteases. Overall, we prove that these gelatin spermbots display great potential for the development of noninvasive theranostic tools in reproductive biology and medicine for the protection and activation of sperm, especially useful for studying sperm migration. We present their beneficial features which comprise not only biocompatibility and biodegradability but also pH response, loading stability, and antioxidant protection.