A micro injection is an invasive procedure wherein the liquid component of a substance (usually a chemical) is injected into a cell or tissue through a small needle-like device. It is often used in the study of viruses and cells, as well as in cloning organisms. It is also useful in the treatment of male subfertility through intracytoplasmic sperm injection (ICSI, /ksi/ IK-see). It is also widely employed in horticulture, where it has been used to deliver nutrients to specific branches and trees as an alternative to spraying.
Traditionally, cellular and pronuclear microinjection has been performed in a laboratory environment. A technician identifies the target cell and then inserts a needle into it. The needle can vary in size depending on the purpose. Injections can be performed into single cells, into tissues and even whole organisms. In general, microinjection is accomplished using a microscope and two micromanipulators-one to hold the pipette with which the injection is made, and the other to control a needle that penetrates the outer zona pellucida or nuclear envelope of the cell.
Passive microinjection is a highly effective method for introducing foreign DNA into mammalian cells and embryos. This passive system uses a double-emulsion of oil and water to generate a microneedle with which to inject the DNA into a cell or embryo. Four key coefficients control the interaction between the fluid phases, and a proper selection of these is required for successful microinjection.
For example, the value of the coefficient a needs to be carefully harmonized with the resting time of Droplet at the injection station and the velocity u5 that drives the interaction between the microneedle and the injection station. This helps to prevent the damaging effects of intense collisions between the sharp corners of the microneedle and the injection station and ensures the integrity of the double emulsion.
Furthermore, the value of the coefficient b must be carefully tuned to increase the momentum of pulsating flows in order to overcome the frictional force exerted by Current on the Droplet, and to make it possible for u5 to permeate the Droplet without rupturing it. This is crucial for achieving high-throughput microinjections with the same device.
Nikon offers a number of advanced optical systems that are ideal for microinjection applications. The ECLIPSE Ti2 and ECLIPSE Ts2R series of inverted microscopes, and the SMZ18/25 stereomicroscopes, provide robust, vibration-resistant platforms that will support your research.
While traditional methods of microinjection can be used to introduce DNA into oocytes and early embryos, these techniques are costly and time-consuming, demand experienced operators, and have low success rates and productivity. Additionally, these methods are inefficient and difficult to scale up to the throughput needed for high-throughput DNA microinjection of mammalian cells. A new technique that employs microfluidics to perform cellular and pronuclear microinjection into mammalian eggs has been developed. It is capable of delivering viral-free DNA into mammalian oocytes and metaphase-II mouse embryos with over 90% oocyte survival, dramatically increasing experimental confidence and yield.