Lensless imaging for simultaneous microfluidic sperm monitoring and sorting

Abstract

5.3 million American couples of reproductive age (9%) are affected by infertility, among which male factors account for up to 50% of cases, which necessitates the identification of parameters defining sperm quality, including sperm count and motility. In vitro fertilization (IVF) with or without intra cytoplasmic sperm injection (ICSI) has become the most widely used assisted reproductive technology (ART) in modern clinical practice to overcome male infertility challenges. One of the obstacles of IVF and ICSI lies in identifying and isolating the most motile and presumably healthiest sperm from semen samples that have low sperm counts (oligozoospermia) and/or low sperm motility (oligospermaesthenia). Microfluidic systems have shown potential to sort sperm with flow systems. However, the small field of view (FOV) of conventional microscopes commonly used to image sperm motion presents challenges in tracking a large number of sperm cells simultaneously. To address this challenge, we have integrated a lensless charge-coupled device (CCD) with a microfluidic chip to enable wide FOV and automatic recording as the sperm move inside a microfluidic channel. The integrated system enables the sorting and tracking of a population of sperm that have been placed in a microfluidic channel. This channel can be monitored in both horizontal and vertical configuration similar to a swim-up column method used clinically. Sperm motilities can be quantified by tracing the shadow paths for individual sperm. Moreover, as the sperm are sorted by swimming from the inlet towards the outlet of a microfluidic channel, motile sperm that reach the outlet can be extracted from the channel at the end of the process. This technology can lead to methods to evaluate each sperm individually in terms of motility response in a wide field of view, which could prove especially useful, when working with oligozoospermic or oligospermaesthenic samples, in which the most motile sperm need to be isolated from a pool of small number of sperm.

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

“…Using this device, sperm motility and trajectories of motile sperm could be recorded. Subsequently, a lens-free, shadow-based, charge-coupled device (CCD) imaging system with a microfluidic chip was reported in 2011, and oligozoospermic and oligospermaesthenic cases were detected using trajectory analyses and sperm sorting with this system [31]. In 2015, Im et al developed a smartphone-based optical device that exploits diffraction patterns generated by microbeads following binding to biological targets, and detected human papillomavirus DNA.…”

“…Thus, low-cost, portable devices for quantitative sperm analysis have been developed during the last decade [28][29][30][31][32][33][34]. Optical systems using these devices in sperm motility analyses are presented in Figure 2.…”

“…Hence, lens-free imaging systems are preferred for low-cost, lightweight POC systems ( Figure 2A, 2B, and 2C). Comparison of optical systems for optical sperm imaging systems; (A) Lens-free holographic on-chip microscope [29], (B) 3D tracking system for human sperm [30], (C) Lens-free shadow-based CCD imaging system [31], (D) Mobile or smartphone-based clinical microscopic system to detect fluorescence from samples [28], (E) Smartphone-based optical device using diffraction patterns [32], (F) Smartphone-based sperm observation system using a single ball lens [33].…”

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

“…A minimal image platform is desired to enable compactness, ease-of-use, minimized footprint, and portability to monitor sperm motility by a preclinical assay at home. Some researchers have developed a microfluidic chip that can be used by an individual himself at home on convenient moments to check his semen quality [56][57][58][59]. For example, if a person finds that his semen quality is low or that there are no motile sperm in his semen, he can opt for ICSI for his fertility treatment.…”

“…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.…”