Microinjection is a well-accepted method to introduce matter such as sperm, nucleus, or solutes into biological cells for infertility treatment, transgenic and therapeutic cloning, or cryopreservation purposes. Millions of cellular microinjection operations for such applications and relevant biomedical research are conducted in the United States alone every year. The most utilized microinjection process is known as intracytoplasmic sperm injection as a part of the in vitro fertilization operation. The procedure consists of micropipette penetration through the egg cell's periphery including the zona pellucida and the plasma membrane, followed by the delivery of sperm for fertilization. To date, even with the help of piezo-assisted cell piercing device, the yield of microinjection process is undesirably low because the cells are easily damaged during the penetration and substance delivery, and subsequently causing abnormal growth. Furthermore, the success of the operation strongly depends on the operator's skill. Since the operating conditions are selected in an ad-hoc fashion, the results are often irreproducible at different laboratories or for different cells. To remedy these shortfalls, the PiIs team has recently developed a technology called the Rotationally Oscillating Drill which rotates the pipette via a micro-motor at very small angular strokes (e.g., 0.2 degrees) and at high frequencies (e.g., 500 Hz.). This operation is proven to be quite effective in the preliminary studies of the PI's group. This overarching goal cannot be achieved, however, without basic understanding of the complex microinjection process involving small-scale interactions between micropipettes and the soft biological cells in a fluid environment. The PI's objective is to resolve the transient micro-mechanical interfacial dynamics of the microinjection process and to monitor the rheological properties of the membrane of the oocytes. This fundamental understanding will establish scientific basis in determining the ideal operating conditions without lengthy trial-and-error studies.
The research has two scientific thrusts: (i) Modeling the micro-dynamics while biological cells are pierced by highly flexible micropipettes. (ii) Developing optimal control protocols for our Ros-Drill microinjection process based on the insight gained from (i). The PIs will emphasize the basic understanding of small-scale and frequency-dependent material properties, fluid-pipette-membrane interactions, and the integration of nanoscopic capacitive force sensing devices. These crucial knowledge will potentially remove the dependence on human experience.
If successful, the proposed study will introduce a revolutionary tool for cell biologists. This computer controlled microinjection technology (Ros-Drill) will have great potential to reduce the uncertainty and errors caused by human factors. It will increase the success rate (in injection) and reduce the number of tests on various species involved (in artificial insemination, cell surgery, and gene or drug delivery for therapeutic cloning purposes). The system will also integrate microscale force and position sensing devices, through which the experimental biologists will directly benefit from the emerging microelectromechanical systems technology. In addition to such fundamental scientific impact, the PIs plan on immediate dissemination of the findings in professional journals and at conferences. The PIs will also expand on a number of on-going outreach activities in K-12 education, in which we actively participate every year.
