Cleaning or Sterilizing Your Beads

In most cases, cleaning new glass or ceramic bead media is unnecessary.  Most researchers use them straight out of the bottle.  The only minor contaminant - carbon black - is inert.  And, it is soon removed by centrifugation or filtration in the steps that often follow cell disruption.

Washing beads in acid is a waste of time and potentially dangerous.

Promptly rinse used glass or ceramic beads in tap water and leave them soaking in a beaker containing a diluted solution of laboratory detergent or automatic dishwasher detergent.  Now and then, agitate the beads by swirling them. When you have accumulated enough used beads to work with, rinse away the detergent with several changes of tap water and then with RO - or distilled water.  Dry the beads overnight in an open stainless steel or glass tray at 40 to 70ºC.  If the dried beads do not pour freely from the tray (i.e., some are caked together), then they were not cleaned or rinsed enough.  Repeat the cleaning protocol.

Cleaning chrome steel or stainless steel beads requires a modified procedure.  The washing step must last only a few minutes.  Ditto for the water rinse.  Then, promptly remove all residual water from the surface of the beads by rinsing the beads with three changes of absolute (100%) ethanol, isopropanol, or acetone.  Air dry at RT.

If you are isolating nucleic acids from disrupted cells, an easy alternate cleaning method is to immerse the beads in a 1:10 dilution of ordinary household bleach (Clorox or equivalent) for 5 minutes.  This not only cleans and sterilizes the beads but completely destroys contaminating nucleic acids (see and nucleases. Of course, finish by thoroughly rinsing the beads with sterile or RO water.

All cleaned beads can be autoclaved.  Note that autoclaving at traditional conditions (121º C for 20 min) will not sufficiently destroy the template activity of any contaminating DNA.  Autoclaving at 121º C for 80 minutes is recommended.  The presence of air during autoclaving also facilitates nucleic acid decomposition(see Biotechniques (Vol.55, Issue 6, p.296-299, Dec 2013).

Finally, a successful procedure for both sterilizing and destroying any residual nucleic acids on clean glass, ceramic or steel beads is baking clean beads at 550º F for 2h or 400º F for 4 h.

In general, beads can be recycled about ten times before they wear down to too small a size.