Ralph Merkle, a nanotechnology expert at the Georgia Institute of Technology in Atlanta, calls vitrification the greatest advancement in the field of cryonics.
"The preservation that we're able to do today is adequate to preserve the critical information that we believe is important to the human personality and human memory," said Merkle, who is an Alcor board member.
Alcor, which is one of only two cryonics firms in the United States, now uses vitrification to cryopreserve human brains. Skeptics, however, say there is no evidence that such large structures can be successfully vitrified.
About 80 percent of Alcor's "patients" have had only their heads cryopreserved. (The company's most famous patient, Baseball Hall of Fame slugger Ted Williams, has had his head and torso cryopreserved.)
"The brain is what houses your identity. It has your memories, all your stored experiences," Waynick said. "Without the brain, you might as well clone an individual, because you have a completely new person."
Alcor continues to use glycerol-based freezing for patients who have their whole bodies preserved, since vitrification of an entire body is beyond current technical capabilities.
While vitrification circumvents some of the problems associated with freezing, it raises other issues. Scientists must impregnate tissues with high concentrations of cryoprotective chemicals that promote the vitreous state, but these are potentially toxic.
Another concern is the cooling rate needed to vitrify large organs. Some scientists say vitrification requires high cooling rates that are typically not achievable at the center of large objects.
"If you talk about the brain, we can achieve very high cooling rates at the outer surface of the brain, but the cooling rate at the center will be lower than the critical one required for vitrification," said Yoed Rabin, a cryopreservation specialist at Carnegie Mellon University in Pittsburgh, Pennsylvania.
That view is "not strictly correct," contends Brian Wowk, an Alcor advisor and senior scientist at 21st Century Medicine, a California-based company specializing in medical cryopreservation applications. In an e-mail, Wowk said vitrification via very low cooling rates can be achieved, provided the right cryoprotectant solution in sufficient concentration is used.
A third issue with vitrification is that it may lead to fracturing of the brain.
"One major fracture may prevent recovery of the brain as an organ," Rabin said. "We know that vitrification of large objects very frequently involves a huge number of micro-fractures as well."
The chances of cracking and fractures increase with the size of the specimen.
Taylor, the Charleston cryobiologist, contends that vitrification is currently only successful for small tissue samples.
"We are still unable to cryopreserve an intact organ such as a kidney or heart by either a freezing or vitrification approach," he said. "It is inconceivable, therefore, that these techniques will ever permit the long-term preservation of a whole body, especially a dead body."
But cryonics advocates believe that advancements in nanotechnology will ultimately make it possible for scientists to repair any freezing or fracturing damage.
"Being able to manipulate matter at the cellular level will enable us to repair a lot of the damage that occurs to an individual during the cryopreservation process today," Waynick said, "especially those patients that were cryopreserved in the earlier years, where there was a significant amount of ice damage during the freezing process."
In the future, breakthroughs in stem cell research and cellular regeneration may enable scientists to regenerate a new body from a person's existing DNA and attach it to the person's cryopreserved brain, Waynick speculates.
"A cure also has to be found for whatever caused your death in the first place," he said. "If you die of lung cancer or kidney failure, those diseases would need to be conquered, or it wouldn't do much good to revive you."
But Rabin, the Carnegie Mellon professor, said there is another problem with restoring a brain to its original state.
"Even if, by some miracle, all brain cells can be revived, the idea that memories and personality could also be revived is completely not clear," he said.
He uses an analogy from the computer world to describe how the loss of communication between the brain cells affects the memory of the brain.
"Information is lost when the power of a computer is turned off, even if it's only an instantaneous event and even if no harm is done to the memory chips," Rabin said.
"On the other hand we know that harm is done to the memory cells in cryopreservation of biological materials, and we know that the lines of communication between memory cells are devastated and lost," he said.
SOURCES AND RELATED WEB SITES