Cryopreservation of Large Biological Systems
G.M. Fahy*
Naval Medical Research Institute
This is an abstract
for a talk to be given at the
Fifth
Foresight Conference on Molecular Nanotechnology.
There will be a link from here to the full article when it is
available on the web.
Large biological systems represent a challenge to
cryobiologists because of their diverse cell populations, the
inability to apply high cooling and warming rates, and the
requirement for preservation not only of cells but also of
extracellular connective tissue and cell-matrix and cell-cell
connections. Examples of complex biological systems that tolerate
massive distortion by ice exist, and even some mammalian organs
have survived and functioned after extensive ice formation, but
the general experience and concensus is that the best option for
the cryopreservation of large systems is generally metastable or
quasi-stable vitrification as introduced by Fahy in the early
1980's. With increasing size, vitrification becomes increasingly
difficult on statistical grounds, but the volume fraction of the
sample that undergoes injury from random heterogeneous nucleation
may be small. Both the problem of rare nucleation events during
cooling and the problem of devitrification on warming can be
approached by the design of solutions that maximize biological
viability but minimize ice crystal nucleation and ice crystal
growth. Molecular design techniques can play a role in addressing
these issues. As of this writing, it is probably possible to
vitrify rabbit kidneys with preservation of viability in the
vitrified state, but we do not yet have the technology to restore
these kidneys to active function. However, in the future, it
should be possible to warm these kidneys sufficiently quickly to
demonstrate viability.
*Corresponding Address:
Gregory M. Fahy, Ph.D., Organ, Inc., c/o Naval Medical Research
Institute, Building 29, Bethesda, MD 20889, email: [email protected]
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