The use of fine glass microcapillary pipette based techniques for intracellular/extracellular microinjection and perfusion has become a popular procedure in numerous areas of experimental biology research (e.g. In vitro fertilization, transgenics, etc.).
These techniques can best be described as microsurgical procedures that are conducted on a single cell using either a single or multiple barrel glass micropipette, a precision positioning device (micromanipulator), and a microinjector or microperfusor.
The micropipettes used in these procedures are formed using a pipette puller. Capillary glass tubing is heated to its softening point and pulled to create the proper size tip diameter and taper for the desired application.
The small tip diameters (as low as 0.2 µm) of these micropipettes combined with the high precision of the micromanipulator and microinjection/perfusion apparatus, allows for precise and accurate delivery. This precision allows for accurate and repeatable injections down to the sub-picoliter range into or around various types and sizes of cells with accuracy of 0.1 micron.
The process of extruding substances through these micropipettes is accomplished through the use of either direct hydrostatic pressure (pressure injection) or by moving charged ions that are the result of an applied electric field (iontophoresis) without the use of hydraulic flow.
Applications of microinjection range from assisted (in vitro) cell fertilization techniques, to the transport of molecular and cellular elements. These substances are typically injected into the cell to manipulate and/or monitor the fundamental biochemistry of a specific living cell. Substances that can be injected include cellular organelles, kinases, histochemical markers (such as horseradish peroxidase or lucifer yellow), proteins, metabolites, microbeads, ions, antibodies, genes, and molecular biology mRNA and DNA, to name a few.
The precise delivery (microperfusion) of small volumes (picoliter to milliliter) of various agents and drugs to a cell or group of cells for applications such as pharmacological drug testing can also be accomplished using these techniques.