3D dynamic observation of human sperm by parallel phase-shifting digital holographic microscopy based on pixelated polarization

Abstract

Morphology and motility are essential criteria for assessing sperm viability. However, the human sperm head is small (∼3–4 μm) and requires a relatively high-magnification microscope objective, while the sperm flagella (∼45 μm) are poorly visible with complex 3D properties. Microscopic dynamic observation of intact sperm in 3D is challenging. Conventional inspection methods with a limited depth of field are inadequate for this issue. To provide a solution to this critical need, we develop pixelated polarization-based parallel phase-shifting digital holographic microscopy for the 3D dynamic observation of human sperm. Compared to conventional holographic imaging, this approach can effectively separate the object wavefront and avoid image quality degradation while fully exploiting the spatial bandwidth of the camera. We propose the use of the Stokes parameter reconstruction method to reconstruct the object wavefront and investigate the effect of the sampling interval on the system resolution by spectral analysis. The methodology achieves the retrieval of the 3D trajectory and motion parameters of sperm and reconstructs the sperm head orientation and the thin, highly-dynamic flagellum. The system allows for more comprehensive information on sperm motility and morphology, which is significant for male reproductive research. It also has significant potential for 3D dynamic observation of micro-organisms.

Exploring altered bovine sperm trajectories by sperm tracking in unconfined conditions

“…Regarding the acquisition chambers, it is recommended to use a depth of 10 – 20 μm which is considered optimal for motility evaluation ( 27 ). However, such confined geometry could limit the observation of the native three-dimensional (3D) motility of sperm, confining their motion vertically, given that sperm head is wide and the flagellum is long ( 28 , 29 ). To date, also deeper chambers - having a depth of 100 μm - have been developed to evaluate possible azoospermia condition which requires a larger volume to accurately assess sperm count ( 30 ).…”

Snapshot Polarization-Sensitive Holography for Detecting Microplastics in Turbid Water

“…One of the main reasons is that the features employed for MP classification are relatively limited. To obtain more meaningful information and extract more distinguishable features about environmental samples, a promising approach is the integration of holographic imaging and polarization imaging. − Consequently, the specificity of the detection system can be considerably enhanced. There are notable examples that have explored the implementation of polarization imaging through holographic approaches, − highlighting the potential for combining these two imaging modalities.…”