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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 contaminate - carbon black - is so inert that its presence in your prep has no effect.  And, it is soon removed upon centrifugation or filtration in the steps that usually follow cell disruption.

Do not acid wash beads.  It is a waste of time and is potentially dangerous. There are better alternatives for cleaning beads.

Clean used glass or ceramic beads for reuse by soaking in a solution of laboratory detergent (the kind used to wash labware).  Now and then, agitate the beads by swirling. Then rinse away all detergent with several changes of tap water and then with RO - or distilled water.  Dry the beads in an open stainless steel or glass tray at 40 to 70ºC.  If the dried beads do not pour freely (i.e., they are caked together), then they were not cleaned or rinsed well enough.  Repeat the cleaning protocol.

Cleaning chrome steel or stainless steel beads requires a modified procedure.  The washing step with detergent must be short...lasting for only a few minutes.  Ditto for the water rinse.  Then, promptly remove all water from the surface of the beads by washing the beads with three changes of absolute (100%) ethanol,(90%) isopropanol, or acetone.  Place the beads in a sterile, shallow stainless or glass tray, cover them with paper towels, and air-dry overnight at RT.  Store the clean, dry beads in a sealed bottle.

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 also completely destroys contaminating nucleic acids (see http://www.ncbi.nlm.nih.gov/pubmed/1571142) and nucleases. Of course, thoroughly rinse the beads with sterile- or RO- water afterward.

All beads can be autoclaved with steam.  But first, make sure that recycled beads are cleaned in detergent.  Note a relatively recent report in Biotechniques (Vol.55, Issue 6, p.296-299, Dec 2013):  The authors report that autoclaving at standard conditions (121º C for 20 min) does not sufficiently destroy the template activity of contaminating DNA.  Autoclaving at 121º C for 80 min is recommended.  Also, the presence of air during autoclaving facilitates nucleic acid decomposition.

Finally, a successful procedure to sterilize and also destroy any residual nucleic acids on clean glass, ceramic or steel beads is baking the beads at 550º F for 2h or 400º F for 4 h.  As mentioned earlier, all recycled beads should first be detergent cleaned.

You can reuse beads about ten times before they wear down to too small a size.

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