Preparing Injection Pipettes on a Flaming/Brown Pipette Puller

Abstract

INTRODUCTIONThe efficient delivery of exogenous DNA to cells for expression and function studies is an essential technique of modern cell biology, and direct delivery of genetic material by microinjection remains a reliable means of transfection. Needles for microinjection can either be pulled from glass capillaries on a pipette puller or can be purchased premade. When pulling needles, variables such as filament design, heat, pull strength (tension), and delay time between heating and pulling must be addressed. The heat setting affects the length and the tip size of the needle; high heat will typically produce longer needles and finer tips. The pull strength will also affect length and tip size, with greater pull strength producing longer tapered needles with finer tips. Finally, shorter delay times between heating and pulling can result in longer tapers and finer needles. However, if the delay is too short, the glass forms fibers resembling glass wool instead of usable needles. The advantage of pulling needles in the laboratory is that a variety of different needle types can be pulled, depending on the samples and the cells being injected. For laboratories performing even a moderate number of microinjection experiments, a Flaming/Brown-style pipette puller such as the Sutter Instruments P-97 is a cost-effective choice for manufacturing quality micropipettes quickly and reproducibly.