Biomedical subjects

Jaclyn M Nascimento

Publications and source records attributed to Jaclyn M Nascimento.

5 recordsLinked to original sources

PubMed2007

High-throughput sorting and analysis of human sperm with a ring-shaped laser trap.

Sperm motility is an important concept in fertility research. To this end, single spot laser tweezers have been used to quantitatively analyze the motility of individual sperm. However, this method is limited with throughput (single sperm per spot), lacks the ability of in-situ sorting based on motility and chemotaxis, requires high laser power (hundreds of milliWatts) and can not be used to dynamically monitor changes in sperm swimming behavior under the influence of a laser beam. Here, we report a continuous 3-D ring-shaped laser trap which could be used for multi-level and high-throughput (tens to hundred sperm per ring) sperm sorting based on their motility and chemotaxis. Under a laser power of only tens of milliWatts, human sperm with low to medium velocity are slowed down, stopped, or forced to change their trajectories to swim along the ring due to the optical gradient force in the radial direction. This is the first demonstration of parallel sperm sorting based on motility with optical trapping technology. In addition, by making the sperm swimming along the circumference of the ring, the effect of laser radiation, optical force and external obstacles on sperm energetics are investigated in a more gentle and quantitative way. The application of this method could be extended to motility and bio-tropism studies of other self-propelled cells, such as algae and bacteria.

Cell Separation↗

PubMed2006

Size tunable three-dimensional annular laser trap based on axicons.

A three-dimensional (3D) ring-shaped laser trap has been built using axicons. The diameter of this laser trap ranges from 70 to 140 mum and is adjusted by simply changing the position of one axicon in the optical path. Parallel 3D trapping of 5 mum silica microspheres and 3D confinement of cells along the ring are demonstrated. In this system the special optical properties of axicons are used to create a continuous annular trap with high power efficiency and a constant numerical aperture. This new approach, without any mechanical scanning, offers significant potential for applications in cell motility analysis and biotropism studies.

Equipment Design↗

PubMed2006

Dynamically adjustable annular laser trapping based on axicons.

To study the chemotactic response of sperm to an egg and to characterize sperm motility, an annular laser trap based on axicons is designed, simulated with the ray-tracing tool, and implemented. The diameter of the trapping ring can be adjusted dynamically for a range of over 400 microm by simply translating one axicon along the optical axis. Trapping experiments with microspheres and dog sperm demonstrate the feasibility of the system, and the power requirement agrees with theoretical expectation. This new type of laser trapping could provide a prototype of a parallel, objective, and quantitative tool for animal fertility and biotropism study.

Animals↗

PubMedDate not supplied

Analysis of sperm motility using optical tweezers.

This study examines the use of optical trapping as a quantitative measure of sperm motility. The effects of laser trap duration and laser trapping power on sperm motility are described between sperm swimming force, swimmimg speed, and speed of progression (SOP) score. Sperm (SOP scores of 2-4) were trapped by a continuous-wave 1064 nm single-point gradient laser trap. Trap duration effects were quantified for 15, 10, and 5 seconds at 420 mW laser power. Laser power effects were quantified at powers of 420 mW, 350 mW, 300 mW, and 250 mW for five seconds. Swimming force, swimming speed, and SOP score relationships were examined at a trap duration and trapping power shown to minimally affect sperm motility. Swimming forces were measured by trapping sperm and subsequently decreasing laser power until the sperm escaped the trap. Swimming trajectories were calculated by custom-built software, and SOP scores were assigned by three qualified sperm scoring experts. A ubiquitous class of sperm were identified that swim with relatively high forces that are uncorrelated to swimming speed. It is concluded that sperm swimming forces measured by optical trapping provide new and valuable quantitative information to assess sperm motility.

Animals↗

PubMedDate not supplied

Computer-based tracking of single sperm.

This paper describes a robust single sperm tracking algorithm (SSTA) that can be used in laser optical trapping and sperm motility studies. The algorithm creates a region of interest (ROI) centered about a sperm selected by the user. SSTA contrast enhances the ROI image and implements a modified four-class thresholding method to extract the tracked sperm as it transitions in and out of focus. The nearest neighbor method is complemented with a speed-check feature to aid tracking in the presence of additional sperm or other particles. SSTA has a collision-detection feature for real or perceived collision or near-miss cases between two sperm. Subsequent postcollision analysis employs three criteria to distinguish the tracked sperm in the image. The efficacy of SSTA is validated through examples and comparisons to commercially available computer-aided sperm tracking systems.

Algorithms↗