Abstract
Sperm selection is crucial to assisted reproduction, influencing the success rate of the treatment cycle and offspring health. However, in the current clinical sperm selection practices, bypassing almost all the natural selection barriers is a major concern. Here, we present a biomimicry microfluidic method, inspired by the anatomy of the female reproductive tract, that separates motile sperm based on their rheotaxis behavior to swim against the flow into low shear rate regions. The device includes micropocket geometries that recall the oval-shaped microstructures of the female fallopian tube to create shear protected zones for sperm separation. Clinical tests with human samples indicate that the device is capable of isolating viable and highly motile sperm based on their rheotaxis responses, resulting in a separation efficiency of 100%. The device presents an automated alternative for the current sperm selection practices in assisted reproduction.
Highlights
Sperm selection is crucial to assisted reproduction, influencing the success rate of the treatment cycle and offspring health
The success rate of the Assisted reproductive technologies (ART) treatment cycle and embryo development rate are both directly correlated with the quality of selected s perm[6]
Due to the unique capability of microfluidics in controlling and manipulating fluidic microenvironments, rheotaxis has been used in microfluidics to isolate motile sperm[34], including recent developments with diffuser type micro geometries that create favorable low shear rate zones to select motile sperm[35,36]
Summary
Sperm selection is crucial to assisted reproduction, influencing the success rate of the treatment cycle and offspring health. We present a biomimicry microfluidic method, inspired by the anatomy of the female reproductive tract, that separates motile sperm based on their rheotaxis behavior to swim against the flow into low shear rate regions. Swim-Up (SU) and Density Gradient Centrifugation (DGC) are the two most commonly used clinical methods for selecting high-quality sperm[7,8,9] These methods are time-consuming, labor-intensive, highly subjective, and they introduce sperm DNA damage due to centrifugation while resulting in relatively low recovery rates[6,7,8,9]. It is crucial to develop new methods for rapid, automated, and non-invasive selection of high-quality sperm by mimicking the natural selection process in vivo, improving the ART outcome. We present a physiologically relevant approach, inspired by the mucosal flow through the oval-shaped microgrooves in the female fallopian tube, for rheotaxis-based separation of highly motile sperm (Fig. 1).
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