Biology subjects

Abbaspourrad, A.

Publications and source records attributed to Abbaspourrad, A..

2 recordsLinked to original sources

bioRxiv2020

Progressive Sperm Separation Using Parallelized, High-Throughput, Microchamber-based Microfluidics

Motility is one of the most important factors in sperm migration toward egg. Therefore, sperm separation based on motility increases the chance of the best sperm selection in the process of infertility treatments. Unfortunately, it is now vastly done by conventional procedures which lack certain delicacy and precision and increase the risk of damage to sperm cells. Microfluidic systems, on the other hand, can sort sperm in a less intrusive way. However, microfluidic techniques have yet to receive widespread adoption in clinical settings, not only due to their relatively cumbersome operation, but also their extremely low outcome, leaving them inefficient in practice. Here we propose a microchamber-based microfluidic platform that can separate progressive motile sperm from nonviable sperm and debris as well as trapped nonprogressive sperm in the microchambers. Our platform is operated in a short period of time (<10 min) with an excellent degree of controllability, without any prior sample preparation. Our results show that the microchambers depth does not affect the residence time of motile sperm. Therefore, we are able to inspect high sample volumes (1 mL) within the same time. Furthermore, we maximize the concentration of the collected sperm by tuning the washing medium flow rate above the sperm rheotactic threshold. We foresee that our microfluidic platform may provide a facile solution for high-throughput, robust, and easy-to-modify for collection of progressive sperm needed for assisted reproductive technologies (ARTs). Significance StatementAssisted Reproductive Technologies require efficient, minimally invasive, and fast methods of sperm separation. Centrifugation methods used in clinics and biological research labs, fall short in these aspects as they are low-yield, intrusive to sperms DNA, and time consuming. We have developed a microchamber-based microfluidic platform for high-throughput separation of progressive motile sperm from undiluted raw semen samples. The method was further optimized to increase the concentration of collected samples. Higher concentration of collected samples combined with higher motility of the separated sperm compared to those in raw semen, make it a suitable choice in clinical applications, fertility diagnostics, and fundamental research.

bioengineering↗

bioRxiv2020

Effect of flagellar beating pattern on sperm rheotaxis and boundary-dependent navigation

The study of navigational mechanisms used by mammalian sperm inside a microenvironment yields better understanding of sperm locomotion during the insemination process, which aids in the design of tools for overcoming infertility. Near- and far-field hydrodynamic interactions with nearby boundaries and rheotaxis are known to be some of the steering strategies that keep sperm on the correct path toward the egg. However, it is not known how the beating patterns of sperm may influence these navigational strategies. In this study, we investigate the effect of flagellar beating pattern on navigation of sperm cells both theoretically and experimentally using a two-step approach. We first isolate bovine sperm based on their rheotactic behavior in a zone with quiescent medium using a microfluidic system. This step ensures that the swimmers are able to navigate upstream and have motilities higher than a selected value, even though they feature various flagellar beating patterns. We then explore the flagellar beating pattern of these isolated sperm and their subsequent influence on boundary-dependent navigation. Our findings indicate that rheotaxis enables sperm to navigate upstream even in the presence of circular motion in their motility, whereas boundary-dependent navigation is more sensitive to the circular motion and selects for progressive motility. This finding may explain the clinical importance of progressive motility in semen samples for fertility, as the flow of mucus may not be sufficiently strong to orient the sperm cells throughout the process of insemination. SignificanceFinding the egg and moving toward it while traversing the complex structure of the female reproductive tract is necessary for mammalian sperm. Previous studies have shown how sperm use navigational steering mechanisms that are based on swimming upstream (i.e. rheotaxis) and along the boundaries of the female reproductive tract. We demonstrate that the performance of theses navigational mechanisms is associated with the primary characteristics of sperm motility. In fact, sperm rheotaxis is more sensitive to the motility and thus average velocity of sperm while navigation via rigid boundaries is more sensitive to the flagellar beating pattern and selects for symmetric beating. Our results can be expanded to other autonomous microswimmers and their subsequent navigation mechanisms.

biophysics↗