A Microfluidic Platform for Analysis of Beating Characteristics of Sperm Cells

Male infertility contributes to about 50% of infertility cases worldwide. Analyzing the ability of sperm cells to swim progressively to reach and fertilize an oocyte is important in defining new factors that can explain male infertility and its causes. Here, we report a microfluidic platform that enables studying the beating characteristics of sperm cells under different physicochemical conditions. We used microcontact printing to immobilize bovine sperm cells on fibronectin spots on glass slides and inside microchannels. This technique enabled fixing the sperm head while keeping the flagellum free to beat which facilitated studying its beating characteristics more accurately. We used high-speed imaging coupled with machine learning-based keypoint detection to track the sperm flagellum and report the beating frequency and amplitude under different physicochemical conditions. To verify the capabilities of our platform, we used it to study the response of sperm cells to caffeine as a hyperactivation promoter. Our platform reported beating frequencies that are much higher, and more accurate, compared to data reported by regular CASA (computer-assisted sperm analysis) systems. We were also able to characterize the asymmetrical beating of the flagellum after stimulation using caffeine.