MicroCryoCrusher

A compact, low cost screw-press primarily designed to pulverize 50-500mg of hard, brittle material such as bone or teeth. The sample is inserted into in the pre-chilled pulverizer 'nut' and then crushed by manually screwing together two screw plungers.  The end result is a sample crushed to a powder.

Fresh, soft tissue can also be pulverized, but the sample must first be frozen in liquid nitrogen or dry-ice to make it hard and brittle. The MicroCryoCrusher is often used as a preliminary step in processing samples for subsequent cell homogenization and extraction. For cryo-pulverization of larger and/or multiple samples of soft or elastic tissue, see BioSpec Products' series of BioPulverizers.

PROTOCOL:**

1. The MicroCryoCrusher consists of an oversized nut and two knobs having threaded "plungers", one long and the other short.
2. Pre-cool the MicroCryoCrusher metal parts in liquid nitrogen. Screw the short plunger 1/2 way into the Nut. Place the pre-frozen sample into the other end of the nut and screw the longer plunger all the way in. The large mass of the cold stainless steel nut should provide ample time to complete step 3 without additional liq.N₂ for cooling.
3. Hand-tighten both plunger knobs to compact and crush the tissue sample. Do not use tools to tighten.  Occasionally some bone splinters may remain uncrushed.  Loosen, but do not remove, one of the plungers, rap the MicroCryoCrusher on the bench to reposition the bone material and retighten.  Repeat 3-4 times.
4. Remove the short threaded plunger (marked with green) and expel the pellet of compacted, pulverized bone by screwing the long threaded plunger further into the nut.
5. Proceed to the next step of homogenization or extraction promptly.  Powdered tissue exposed to room temperature thaws rapidly.

** This protocol is for biological samples that are soft, oily, or compressible.  Naturally Brittle samples that can be shattered with a hammer (e.g., teeth, dried bone) do not require freezing with liquid nitrogen.

For the origin and use of this device, see Preparation of Bone Samples for DNA Extraction: A Nuts and Bolt Approach, M.G. Thomas and L.J. Moore, BioTechniques, Vol.22, p.402 (1997).