Article

High-throughput lensfree 3D tracking of human sperms reveals rare statistics of helical trajectories

Electrical Engineering Department, University of California, Los Angeles, CA 90095.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 09/2012; 109(40):16018-22. DOI: 10.1073/pnas.1212506109
Source: PubMed

ABSTRACT

Dynamic tracking of human sperms across a large volume is a challenging task. To provide a high-throughput solution to this important need, here we describe a lensfree on-chip imaging technique that can track the three-dimensional (3D) trajectories of > 1,500 individual human sperms within an observation volume of approximately 8-17 mm(3). This computational imaging platform relies on holographic lensfree shadows of sperms that are simultaneously acquired at two different wavelengths, emanating from two partially-coherent sources that are placed at 45° with respect to each other. This multiangle and multicolor illumination scheme permits us to dynamically track the 3D motion of human sperms across a field-of-view of > 17 mm(2) and depth-of-field of approximately 0.5-1 mm with submicron positioning accuracy. The large statistics provided by this lensfree imaging platform revealed that only approximately 4-5% of the motile human sperms swim along well-defined helices and that this percentage can be significantly suppressed under seminal plasma. Furthermore, among these observed helical human sperms, a significant majority (approximately 90%) preferred right-handed helices over left-handed ones, with a helix radius of approximately 0.5-3 μm, a helical rotation speed of approximately 3-20 rotations/s and a linear speed of approximately 20-100 μm/s. This high-throughput 3D imaging platform could in general be quite valuable for observing the statistical swimming patterns of various other microorganisms, leading to new insights in their 3D motion and the underlying biophysics.

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    • "In the present study, we focused on the effect of the viscosity of the oviductal mucus on the sperm motility. Many researchers have conducted rigorous studies on the motion characteristics of sperm from theoretical[4], experimental,[12]and numerical[13][16]standpoints. However, there are few studies that focus on the effect of the surrounding environment of the sperm, i.e., the fluid characteristics of the oviduct, on the sperm motility. "
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    • "Over the last few years, computational lensfree on-chip imaging has emerged and promises to be a versatile, cost-effective, field-portable and yet powerful biomedical imaging tool both in labs and at remote sites89. Based on digital in-line holography, this on-chip imaging technique was shown to be an alternative tool for various clinical and telemedicine applications, addressing diagnosis of diseases such as malaria10, automated cell counting11, water quality monitoring12, blood analysis13 as well as imaging cytometry141516. In this work, we demonstrate that lensfree on-chip imaging can provide a solution to wide-field cell motility tracking that can overcome many of the above outlined shortcomings of lens-based optical microscopy methods. "
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    • "From the decade of the 1980 designing sperm imaging systems, tracking algorithms, and computerized analysis became center of attention broadly and valuable works were published in this area as well [2]-[4]. Some of them dealt with supplementary tools like acoustic device [3], piezo-electric device [5] and lens-free on-chip imaging technique [6] to provide 3D trajectory of sperm. Some others utilized optical tweezers to measure both sperm motility and energy [7] [8]. "
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