A novel method for ICSI: Rotationally oscillating drill, design, control and monitoring

Date of Completion

January 2007

Keywords

Biology, Cell|Engineering, Mechanical

Degree

Ph.D.

Abstract

ICSI (intracytoplasmic sperm injection) procedure is an important assisted reproductive technology (ART), which is one of the commonly used cellular-injection processes. In essence, a drawn glass pipette is used to achieve the piercing and the injection. The process has evolved considerably since its inception. This procedure presently requires a very small mercury column inside a glass pipette which is impulsively forced via a piezo actuator. Despite the toxic mercury, the procedure is commonly utilized in many laboratories. Earlier investigations point out that the occurrence of considerable lateral tip oscillations of the injection pipette as the piezo-electric pulse train is introduced causes adverse effects on the success rate of the injection. The physics of the underlying cellular piercing process is quite complex and presently not fully understood, primarily due the inexistence of appropriate monitoring devices. In this thesis, two aspects of the microinjection procedure are addressed: (a) Development of an efficient and automated technology to prevent the lateral pipette movement during piercing. This technology is based on a rotationally oscillating micro-drill (Ros-Drill©). Ros-Drill© is a mercury-free and minimally invasive device which is designed and built including the peripheral control hardware and software. The experimental results exhibit high survival rate (> 70% of the injected oocytes) and fertilization rate (> 80% of the survived oocytes), and blastocyst formation rates (∼ 50% of the survived oocytes). The blastocysts created by Ros-Drill© ICSI were transferred into the uteruses of pseudopregnant surrogate mothers and healthy pups were born and weaned. (b) Introduction of a novel non-contact sensing mechanism for monitoring the pipette tip motion. In the principle of sensing, properly positioned four photodiodes receive the light which is channeled through the target micro-pipette and create the sense of position. Appropriate electronics and sensitivity enhancement techniques are also utilized and the sensor is shown to have submicron-level motion detection capability already. ^

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