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.  Fresh, deformable tissue can also be pulverized, but the sample must be first made hard and brittle by freezing in liquid nitrogen. The end result is a sample crushed to a powder. The device is often used as a preliminary step in processing a sample for subsequent cell homogenization and extraction. For cryo-pulverization of larger and/or multiple samples of soft or elastic tissue, see the BioPulverizer.

PROTOCOL**:

1. The MicroCryoCrusher consists of a oversized nut and two knobs containing threaded plungers, one long and the other short.
2. Precool the MicroCryoCrusher metal parts in liquid nitrogen. Thread the short plunger 1/2 way into the Nut. Place prefrozen sample into the open end and insert the long plunger.  The large mass of the cold stainless steel nut will give you ample time to complete step 3 without adding additional liq.N₂ for cooling.
3. Hand tighten the plunger knobs to compact and crush the tissue sample. Do not use tools to tighten.  Occasionally some bone splinters may remain uncrushed.  Loosen one of the plungers, rap the MicroCryoCrusher on the bench to reposition the bone material and retighten the plunger 3-4 times.
4. Remove the short threaded plunger (marked with green) and expel the pellet of compacted, pulverized bone by screwing down the long screw plunger.
5. Exposed, powdered tissue thaws rapidly, so proceed to the next step of homogenization or extraction promptly.

** This is a protocol for biological samples that are soft, oily, bendable or compressible.  Naturally Brittle samples that can be shattered with a hammer (e.g., teeth, dryed bone) do not require freezing in liq.N₂.

For information on 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).