Fabrication on the microscale: a two-photon polymerized device for oocyte microinjection

PURPOSE: Intracytoplasmic sperm injection (ICSI) addresses male sub-fertility by injecting a spermatozoon into the oocyte. This challenging procedure requires the use of dual micromanipulators, with success influenced by inter-operator expertise. We hypothesized that minimizing oocyte handling during ICSI will simplify the procedure. To address this, we designed and fabricated a micrometer scale device that houses the oocyte and requires only one micromanipulator for microinjection. METHODS: The device consisted of 2 components, each of sub-cubic millimeter volume: a Pod and a Garage. These were fabricated using 2-photon polymerization. Toxicity was evaluated by culturing single-mouse presumptive zygotes (PZs) to the blastocyst stage within a Pod, with several Pods (and embryos) docked in a Garage. The development was compared to standard culture. The level of DNA damage/repair in resultant blastocysts was quantified (γH2A.X immunohistochemistry). To demonstrate the capability to carry out ICSI within the device, PZs were microinjected with 4-μm fluorescent microspheres and cultured to the blastocyst stage. Finally, the device was assessed for oocyte traceability and high-throughput microinjection capabilities and compared to standard microinjection practice using key parameters (pipette setup, holding then injecting oocytes). RESULTS: Compared to standard culture, embryo culture within Pods and a Garage showed no differences in development to the blastocyst stage or levels of DNA damage in resultant blastocysts. Furthermore, microinjection within our device removes the need for a holding pipette, improves traceability, and facilitates high-throughput microinjection. CONCLUSION: This novel device could improve embryo production following ICSI by simplifying the procedure and thus decreasing inter-operator variability. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10815-022-02485-1.