Sperm Selection by Rheotaxis and Thermotaxis in In-Situ Handmade Microfluidics of Fluidic Walls in the Same ICSI Plate

Overview

Microfluidics technologies are proving their capability to select suitable sperm for ICSI, especially those that take advantage of the rheotaxic properties of sperm migration. In contrast to other sperm preparation methods such as Wash-Swim-Up and Density- Gradients-Centrifugation (DGC), microfluidics disregards washing and centrifugation steps along the procedure. However, microfluidics devices are costly and likely to fail to select motile sperm in dispermic samples. The investigators have recently described a novel approach for sperm selection by In-Situ handmade rheotaxis microfluidics of fluidic walls in the same ICSI plate. This methodology integrates a swim-over based on horizontal migration with a positive rheotaxis zone. The present study aims to deliver an unbiased comparison between two sperm selection techniques: DGC and In-Situ handmade rheotaxis microfluidics of fluidic walls (isM).

Microfluidics technologies stand as the latest sperm selection methodology for ICSI. Increasingly, publications show novel and ingenious microfluidics strategies to integrate sperm biomimicry during in vitro sperm selection while simplifying the IVF workflow. Microfluidics are time-efficient methods which reduce the risks associated with handling, gamete mix-up and ROS production. However, microfluidics devices are costly and likely to fail to select motile sperm in dispermic samples. Aiming to outline the application of microfluidics in ART, the investigators conceived a lab-on-a-chip approach for sperm selection by In-Situ rheotaxis handmade microfluidics of fluidic walls. This microfluidics system allows selecting sperm for ICSI in the same ICSI-dish. Thus, from a microvolume of the raw semen sample, only using microfluidics, disregarding centrifugation, washing, plasticware, other cells, products or materials, and using the same culture medium needed to prepare the rest of the ICSI plate. A previous proof-of-concept study showed that this methodology efficiently selected suitable sperm for ICSI. The investigators also demonstrated that the microfluidic protocol effectively separates at least 20 progressive spermatozoa in less than 15 minutes in a clean microdroplet, free of any remaining seminal plasma. A subsequent non-inferiority study showed that the microfluidic method performs as well as density gradient centrifugation to achieve ICSI outcomes such as fertilization and day-5 blastocyst formation rate, proving that In-Situ handmade rheotaxis microfluidics of fluidic walls are also effective in supporting pre-implantation embryonic development in vitro.