An Introduction to Microinjection

Microinjection is one of the key techniques I will be using during my summer project. It is an incredibly versatile and widely used technique, with applications from ranging from IVF to producing transgenic organisms. Its application during my project will be to introduce the gold nanoparticles (GNPs) into the cells for photothermal imaging.

Although microinjection at its core is simply a case of guiding a glass microcapillary needle to the desired cell and injecting, in practice it is far more difficult and requires a lot of practice (and patience). There are several ways in which successful microinjection can be achieved. The first is passive/constant flow injection which relies on a small, constant amount of flow out of the needle tip, this is achieved by setting the compensation pressure to ensure all of the solution isn’t expelled at once whilst still allowing some leakage. The second is by active/pulsed flow injection where a defined injection volume is delivered into the cells. There are numerous factors that can effect this technique, and even if injection is successful there is no guarantee the injected cells will survive…

As microinjection has a key role within my project, the first two weeks have been spent practicing using fluorescently labelled dextran instead of GNPs.  The benefit of using something that fluoresces is that it makes it very easy to check whether a cell has been successfully injected or not by viewing the cells under UV light. The two images below were taken of some of my own successful microinjections into HeLa cells.

 

HeLa cells successfully injected with fluorescently labelled dextran. Imaged using a Andor iXon 897 Ultra camera.
HeLa cells successfully injected with fluorescently labelled dextran. Imaged using a Andor iXon 897 Ultra camera.

At the Centre for Cell Imaging (CCI) an epifluorescent Zeiss Axio Observer Z.1 microscope is equipped with the micromanipulator and Eppendorf FemtoJet system required for micronjection (more information can be found on the CCI’s website).

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