UNIVERSITY OF UTAH
ELECTRICAL AND COMPUTER ENGINEERING DEPARTMENT
DISSERTATION DEFENSE FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY
Advisor: Bruce Gale
Active Sperm Separation Technique Using An Inertial Microfluidic Device
Microfluidic technology has the unique potential to separate sperm from unwanted debris while improving the effectiveness of assisted reproductive technologies (ART). Current clinical protocol limitations regarding separation of sperm from other cells and cellular debris can lead to low sperm recovery when the sample contains low concentrations of mostly low motility sperm and a high concentration of unwanted cells or cellular debris, such as occurs with surgical testis dissection samples from non-obstructive azoospermia (NOA) patients who went through microsurgical testicular sperm extraction (mTESE), and semen samples from leukospermia patients (high white blood cell (WBC) semen).
Over the years, most sperm separation approaches utilizing microfluidics have relied on sperm motility for separation with added features through which only highly motile sperm can pass. Thus, these techniques can separate only progressive motile sperm from semen samples, but they lose a significant number of sperm cells including viable non-progressive motile and non-motile sperm. Therefore, these techniques are not feasible for use with immature and non-motile sperm that may be the only sperm produced by some patients. To help address this population, this dissertation proposes a passive microfluidic approach utilizing inertial effects that can separate sperm (regardless of their motility state) from other unwanted cells/debris and can provide enhancement of sperm samples without losing non-motile and non-progressive motile sperm.
This dissertation demonstrates label-free separation of sperm from challenging sperm samples using inertial microfluidics. The approach does not require any externally applied forces except the movement of the fluid sample through the instrument. In this way, it is possible to recover not only any motile sperm, but also viable less-motile and non-motile sperm with high recovery rates. The preliminary results show the usefulness of inertial microfluidics to significantly reduce unwanted cells/cellular debris (RBC and WBC) concentrations by flow focusing of debris within a spiral channel flow. The majority (~80%) of sperm cells collect to the designated outlet and ~98% of debris goes to the waste outlet. The estimated sample process time is more rapid (~5minutes) and autonomous than conventional methods that take at least 1 hour for the most basic ones and 10-18 hours when the common practice of manually searching for sperm under the microscope is used. This study also performed viability, toxicity, and recovery tests on the proposed sperm separation method for biocompatibility verification. These tests should provide initial validation of clinical usefulness.
The sperm separation data obtained using the spiral channel shows that the flow focusing of sperm is not as sharp as the flow focusing obtained for red blood cells. The likely cause of this difference is the different shapes of the cells, but there is no good model for demonstrating this effect. To address this issue, this study presents an improved model of sperm cell motion in curved channels based on both 2D COMSOL ® simulations and experimental studies.
Thursday April 27, 2017
Sorenson Molecular Bioengineering Building (SMBB) room 3750
The public is invited