Abstract
Here, we propose a fully-automated platform using a spiral inertial microfluidic device for standardized semen preparation that can process patient-derived semen samples with diverse fluidic conditions without any pre-washing steps. We utilized the multi-dimensional double spiral (MDDS) device to effectively isolate sperm cells from other non-sperm seminal cells (e.g., leukocytes) in the semen sample. The recirculation platform was employed to minimize sample dependency and achieve highly purified and concentrated (up to tenfold) sperm cells in a rapid and fully-automated manner (~ 10 min processing time for 50 mL of diluted semen sample). The clinical (raw) semen samples obtained from healthy donors were directly used without any pre-washing step to evaluate the developed separation platform, which showed excellent performance with ~ 80% of sperm cell recovery, and > 99.95% and > 98% removal of 10-μm beads (a surrogate for leukocytes) from low-viscosity and high-viscosity semen samples, respectively. We expect that the novel platform will be an efficient and automated tool to achieve purified sperm cells directly from raw semen samples for assisted reproductive technologies (ARTs) as an alternative to density centrifugation or swim-up methods, which often suffer from the low recovery of sperm cells and labor-intensive steps.
Highlights
In 2018, 50–70 million people worldwide were affected by infertility, and about 50% of all infertility cases presented at fertility clinics are caused by male factor infertility and subfertility[1,2]
To achieve higher separation resolution, the second spiral channel was designed to have a trapezoidal cross-section where a stronger Dean vortex is generated at the outer half of the channel, which leads to more effective expulsion of small particles toward the outer wall without affecting the focusing position of large particles near to the inner wall, resulting in a greater difference between their equilibrium positions[33,34]
Sperm cells achieved a lower focusing behavior as expected in the first spiral channel, but we found that the initial focusing in the first spiral channel greatly reduced the particle dispersion and helped the 10-μm beads and sperm cells move to their own equilibrium positions with tightly focused bands in the second spiral channel, with sperm focusing on the outer wall side and 10-μm beads focusing at the inner wall side
Summary
In 2018, 50–70 million people worldwide were affected by infertility, and about 50% of all infertility cases presented at fertility clinics are caused by male factor infertility and subfertility[1,2]. To overcome the technical limitations of the conventional sperm preparation methods, various microfluidic devices have been introduced[9,13,17,18,21,22,26] Many of these microfluidic technologies have the drawback of low throughput for sample preparation, allowing just small quantities of sperm to be processed, in the order of a few μL to less than 500 μL, while the number of sperm capable of being processed depends on the dilution condition required for the operation of each microfluidic technology. To overcome this limitation, some inertial spiral microfluidic devices have recently been applied for sperm isolation and successfully demonstrated leukocyte removal with higher throughput and sperm recovery compared to the conventional m ethodologies[17,18,26,27]. A useful system for clinical applications should demonstrate high performance regardless of the unique properties of a given (semen) sample without any additional washing steps
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