Rotary tissue slicer

Contributed by Dejan Vučinić

Preparing living mammalian brain tissue for study in vitro is a delicate task. In most physiology labs brain slicing is performed on a vibratome, such as a Leica VT1000S, which is a very complex device, costs as much as a small car, and cuts very slowly, prolonging the time tissue spends under highly stressful conditions. Moreover, the typical procedure for affixing the brain to the vibratome stage in preparation for slicing is to glue it down onto an aluminum plate using common cyanoacrylic superglue! Surely this can't be good for the tissue.

The rotary slicer described here I first saw in the laboratory of Dejan Zečević at Yale, who in turn picked up this trick from Wei Chen.

The enabling technology are the circular blades of high precision, sold by http://www.specialtyblades.com/, made from zirconia ceramic. Several different sizes are available; use the smallest ones that are deep enough to cut through the thickness of tissue required. The SBIZ45 model is a good size to cut through the entire rat brain, for instance. These blades cost about fifty bucks apiece, significantly less than sapphire blades for vibratomes, and don't seem to ever get dull. They will break if bent, however, so make sure not to touch the edge with forceps for instance.

Marko Popović pointed out that steel rotary blades are also available. You can buy these from Amazon.

The slicer is very simple and inexpensive to build. A slow-turning motor (about one revolution per second, depending on the size of the blade) is affixed to a sturdy aluminum frame so the axle holds the blade vertically. It is important that the axle has very little play so the blade edge doesn't wobble. Two translation stages are bolted together with a little (ferrous) horizontal stage and placed under the blade. The lateral translation stage has a micrometer that is used to set slice thickness, whereas the vertical one is very coarse so the entire cut can be made with a single twist of the wrist.

A bath can be constructed from half a pipette tip box and a refrigerator magnet glued to its bottom. The magnet serves to keep the bath from sliding on the platform during slicing.

The bath is partly filled with 5-7% agar, thick enough to support little pins (such as these from Carolina) which are used to hold the tissue in place. The agar can be reused for several days if the bath is kept wet in a Ziploc bag in a refrigerator. Do not freeze the agar.

The bath is then filled with iced sucrose-based solution into which the brain is extracted. Note that the tissue spends at most a few seconds outside liquid, unlike the superglue procedure with a vibratome. The tissue can be coarsely cut by hand to the desired shape while in the bath, and pinned down for slicing. If the slices desired need to be cut at an angle to a brain surface, a channel can be cut into the agar at the required angle and the tissue pinned down inside the channel; this way the angle is highly repeatable from day to day.

The entire bath is then transferred onto the stage and positioned by hand so the blade is near the tissue.

Slices are made by advancing the micrometer the desired distance, then raising the stage with the bath slowly. As the blade cuts through the tissue and into the agar the slices gently float away.

It takes some practice to achieve the smooth movement required to get good-looking slices, but it is well worth the effort. A practiced operator can finish the entire procedure, from decapitation to incubation, in under four minutes. The speed of the procedure, as well as the much reduced mechanical stress, results in slices that are, in my limited experience, superior to the ones produced by a vibratome. ~~DISCUSSION:off~~