Screening of sperm velocity by fluid mechanical characteristics of a cyclo-olefin polymer microfluidic sperm-sorting device

Abstract

The microfluidic sperm-sorting (MFSS) device is a promising advancement for assisted reproductive technology. Previously, poly(dimethylsiloxiane) and quartz MFSS devices were developed and used for intracytoplasmic sperm injection. However, these disposable devices were not clinically suitable for assisted reproduction, so a cyclo-olefin polymer MFSS (COP-MFSS) device was developed. By micromachining, two microfluidic channels with different heights and widths (chip A: 0.3 × 0.5 mm; chip B: 0.1 × 0.6 mm) were prepared. Sorted sperm concentrations were similar in both microfluidic channels. Linear-velocity distribution using the microfluidic channel of chip B was higher than that of chip A. Using confocal fluorescence microscopy, it was found that the highest number of motile spermatozoa swam across the laminar flow at the bottom of the microfluidic channel. The time required to swim across the laminar flow was longer at the bottom and top of the microfluidic channels than in the middle because of the low fluid velocity. These results experimentally demonstrated that the width of microfluidic channels should be increased in the region of laminar flow from the semen inlet to the outlet for unsorted spermatozoa to selectively recover spermatozoa with high linear velocity.

Recent advances in microfluidic diagnostic and treatment systems for assisted reproductive technologies in developing countries

“…Among LOC devices, microfluidic sperm sorting (MFSS) chips have been developed and marketed for motile sperm sorting and use two gravity-driven laminar flows across a microfluidic channel of 50-200 µm [52][53][54][55][56][57][58][59][60][61]. Fluids flowing through the semen inlet (A) and the medium inlet (B) move parallel to each other and exit through respective outlets (A→D and B→C) [53].…”

“…Sperm are then sorted on the basis of their ability to swim across the streamline into the medium stream, and only motile sperm are recovered from outlet C. Using MFSS devices, embryologists can perform a 1-step sorting protocol without centrifugation, and processing can be completed within 30 min [40,[57][58][59][60][61]. Moreover, DNA fragmentation was reduced and sperm with high linear velocities (LV) were effectively sorted [58,60]. Hence, commercialized MFSS devices can be used with clinical semen processing protocols for efficient ICSI and IVF.…”

Use of Silicone Elastomer-Based Microfluidic Devices and Systems in Reproductive Technologies

“…Within the last decade, studies using PDMS microfluidic channels or funnels have suggested novel solutions for oocyte manipulation, sperm sorting, and embryo culture . Microfluidic systems that mimic oviductal structures and functions for use in RT are divided into those used for sperm motility control or monitoring [50][51][52][53][54][55][56][57][58][59][60], regulation of chemical gradients for in vitro fertilization and embryo culture [61][62][63][64][65][66][67][68][69], and applying mechanical stimuli to the developing embryo [70][71][72][73][74]. Although the unique characteristics of elastomers have been exploited for microstructure fabrication and/or micro-pumping, mechanical deformation of the elastomer membrane has not been used to produce new devices for RT.…”

“…Some procedures may take up to 2 h for semen processing by conventional protocols, such as density gradient centrifugation and subsequent swim-up [75]. To reduce treatment times and physical damage induced by centrifugation, microfluidic sperm sorting (MFSS) chip devices have been developed for selecting motile sperm for use in ART [50][51][52][53][54][55]. As shown in Figure 3A, two gravity-driven laminar flows within the microfluidic channel are important for sperm selection.…”

“…Schulte et al previously reported that DNA fragmentation was significantly decreased in MFSS-treated sperm [53]. Technologies that facilitate the identification and selection of sperm with high motility should increase the ART success rate, and the linear velocities (LV) of sperm separated using an MFSS device have been shown to increase compared with those of untreated sperm [54,55]. On the basis of these results, an MFSS device can be used in clinical semen processing protocols for efficient ICSI and IVF.…”