Physical Homogenization

By Aimee O'Driscoll, 29 August 2013

Currently, several means of mechanical cell disruption and tissue homogenization are commercially available for processing small samples - typically less than 1 ml, to larger production quantities. Mechanical methods of lysing do not introduce chemicals or enzymes to the system; however, the energies needed when using these physical methods can be extremely high and destroy the very substances being isolated - especially in the case of RNA or when attempting to extract native-state proteins.

The destruction of cell membranes and walls is done by subjecting the cells: to shearing by liquid flow; to exploding by pressure differences between inside and outside of cell; to collision forces by impact of beads or paddles; or a combination of these forces.

Generally speaking, any of the techniques described here are able disrupt any cells or tissues at some point. For more difficult materials, simply increase the motivation force or time of exposure in order to improve breakage. However, use of excessive force is limited because of the generation of detrimental heat and/or shear that can ruin the desired proteins. Moreover, excess force will accelerate wear and ultimately damage the equipment.

By judicious use of the equipment one can select from a gentle nicking of the cell to release intact organelle up to a vigorous action to release membrane bound proteins. Some methods are suitable to handle tissues only, others for free cells only, and some are suitable for both. Some techniques are capable of processing only small quantities of material whereas others are limited to handling larger amounts.

Tissues that are difficult to break down include heart muscle, lung, intestine, and skin. On the other hand, some fragile mammalian cells can be broken by just a moderate shaking of the suspended cells. Free cells that are difficult to process include those that are extremely small size (below 0.25 micron) bacteria, and the tough yeasts and spores. Plant materials and seeds will need higher energy inputs for proper maceration.

More information on mechanical homogenization will be posted on the upcoming blogs - so keep checking!