X-Message-Number: 12608
Date: Thu, 21 Oct 1999 09:49:38 -0700 (PDT)
From: Doug Skrecky <>
Subject: microwaves and ethylene glycol

  Jackson TH.  Ungan A.  Critser JK.  Gao D.
  Department of Mechanical Engineering, Purdue University at Indianapolis,
  Indiana, USA.
  Novel microwave technology for cryopreservation of
  biomaterials by suppression of apparent ice formation.
  Cryobiology.  34(4):363-72, 1997 Jun.
  Ice formation inside or outside cells has been proposed to be a factor
  causing cryoinjury to cells/tissues during cryopreservation.
  How to control, reduce, or eliminate the ice formation has been an important
  research topic in fundamental cryobiology. The objective of this study was to
  test a hypothesis that the coupled interaction of microwave radiation and
  cryoprotectant concentration could significantly influence ice formation and
  enhance potential vitrification in cryopreservation media at
  a relative slow cooling rate. Test samples consisted of a series of solutions
  with ethylene glycol (a cryoprotectant)
  concentration ranging from 3 to 5.5 M. A specific microwave resonant cavity
  was built and utilized to provide an intense oscillating electric field.
  Solutions were simultaneously exposed to this electric field and cooled to
  -196 degrees C by rapid immersion in liquid nitrogen. Control samples were
  similarly submerged in liquid nitrogen but without the microwave field. The
  amount of ice formation was determined by analysis of digital images of the
  samples. The morphology of the solidified samples was observed by
  cryomicroscopy. It was found that ice formation was greatly influenced by
  microwave irradiation. For example, ice formation could be reduced by roughly
  56% in 3.5 M ethylene glycol solutions. An
  average reduction of 66% was observed in 4.5 M solutions. Statistical
  analysis indicated that the main effects of microwave and
  ethylene glycol concentration as well as
  the interaction between these two factors significantly (P < 0.01) influenced
  ice formation amount, confirming the hypothesis. This preliminary study
  suggests that a combined use of microwave irradiation and cryoprotectant
  might be a potential approach to control ice formation in cells/tissues
  during the cooling process and to enhance vitrification of these biomaterials
  for long-term cryopreservation.

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