1. Osmotic lysis. The plasma membranes of cells are water-permeable but are impermeable to large molecules and some ions. Thus if cells are placed into water or dilute buffer, they swell due to the osmotically driven influx of water. Since the plasma membrane is not able to stretch very much (the red cell membrane can only stretch by up to 15% of its normal area before disruption), the cell bursts. The method is effective for isolated cells but is not so effective for tissues.
2. Homogenizers.
3. Sonication. This involves the generation of shear forces in a cell sample in the vicinity of a titanium probe (0.5 mm in diameter and 10 cm long) that vibrates at ∼20,000 Hz. The device contains a crystal of lead zirconate titanate that is piezoelectric; i.e., it expands and contracts when an oscillatory electric field is applied to it from an electronic oscillator. The ultrasonic pressure waves cause microcavitation in the sample, and this disrupts the cell membranes, usually in a few seconds.
