A study of oocyte/embryo manipulation using microfluidics and robotics

Abstract

The efficient micromanipulation for in vitro handling of gametes and embryos is a primary goal in assisted reproductive technologies (ARTs) for the treatment of human infertility. In this thesis, we developed microrobotic technologies that enables the manipulation and characterization of mammalian oocyte/embryo with microscopic resolution.

For continuous and fast cell transport and immobilization, an opened-channel microfluidic technology is presented that enables micromanipulation by the external access of micropipette. A through-hole mechanically punched open-chamber in the vicinity of the cell trapping junction allows a microtool-tip to reach trapped cells and freely operate on them. With simple construction and operating principle, consisting of a double-layer PDMS structure and operating by only hydrodynamic force, the proposed device acts as a microfluidic conveyer belt to sequentially introduce, retain, and collect cells with high efficiency in a continuous manner.

In addition, a robot-assisted micromanipulation using shared control is performed following immobilization, that allows dexterous micro-operative procedures to be performed on oocyte/embryo. Even if there is perfect teleoperation controller providing telepresence in micromanipulation, we still have the limited accuracy of a human operator. The proposed study, providing kinematic constraints to a user by the aid of a haptic feedback, shows superior task performance with high accuracy and time efficiency in micromanipulation tasks.

For the assessment of oocyte/embryo quality, the viscoelastic properties of zona pellucida (ZP), which is an extracelluar coat surrounding the eggs, are evaluated. There are few studies on changes in the ZP mechanical properties during oocyte maturation, fertilization, and early embryo development, and linear pure elastic models currently being used do not satisfy a time-dependent mechanical behavior of the ZP. Here, nonlinear viscoelastic characterization is per...