A new piezo-driven ultrasonic cell microinjection system

Over the past decade, the rapid development of biotechnologies such as gene injection, in-vitro fertilization, intracytoplasmic sperm injection (ICSI) and drug development have led to great demand for highly automated high precision equipment for microinjection. Recently a new cell injection technology using piezo-driven pipettes with a very small mercury column was invented and successfully applied in ICSI to a variety of mammal species. Although this technique significantly improves the survival rates of the ICSI process, shortcomings such as the toxicity of mercury, the damage to the cell membrane due to the lateral tip oscillations of the injector pipette may limit its application. In this paper, a new cell injection system for automatic batch injection of suspended cells is developed. A new design of the piezo-driven cell injector is proposed for automated suspended cell injection. This new piezo-driven cell injector design centralizes the piezo oscillation power on the injector pipette which eliminates the vibration effect on other parts of the micromanipulator. A small piezo stack is sufficient to perform the cell injection process. Harmful lateral tip oscillations of the injector pipette are reduced to a satisfying degree even without the help of mercury column. Furthermore, ultrasonic vibration micro-dissection (UVM) theory is utilized to explain the piezo-driven cell injection process, and the source of the lateral oscillations of the injector pipette is investigated. From preliminary experiments of automatic cell injection of zebrafish embryos, the injector pipette can easily pierce through the cell membrane with much low injection speed and almost no deformation of the cell wall. This new injection approach shows good potential for precision injection with less damage to the injected cells.