In nature, water-bears and some species of frog can survive in very cold temperatures by replacing the water in their bodies with anti-freezing agents, such as glucose.
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In laboratory settings, humans have used specialized preparation methods and extreme cold to preserve cells and tissues for various scientific reasons, but these methods only keep a sample viable for a relatively short period.
Significant interest in cryogenics has been driven by developments in medicine and biology, as well as growing clinical needs. A variety of cell types, including stem, embryonic, genetically-modified, cancer and adult stromal cells are all regularly cryopreserved for both study and clinical reasons. The range of cryopreservation applications includes uses for fertility, cell therapies, regenerative medicine, stem cell study and the handling of organs ahead of transplantation. Along with these applications, long-term preservation of animal and plant cells along with the genetic material of endangered species are also cryopreserved.
While there has been considerable progress in bio-preserving many cell types, the current procedures trigger cryo-injury, like dehydration, loss of cell membrane integrity, loss of functionality by possible disturbance of the cytoskeleton or disruptions in the extracellular matrix qualities of tissues. Improving the quality of cryopreservation results means overcoming some of the existing limitations. This may be accomplished by a greater understanding of what occurs at the micro- and nano-scales during the cryogenic process.
One potential solution is the modification of cells encapsulating nanolitre droplets on super-hydrophobic nano-textured surfaces, as nominal volume technologies offer proposed solutions to existing cryogenics challenges. High-contact angles between surfaces and droplets could allow for greater control of droplet form, improving bio-preservation.
Bio-inspired techniques in cryopreservation could also result in the development of solutions found nature, like those used by extremophilic microorganisms.
Preserving cryogenic tissue with ‘nano-warming.’
The long-term cryopreservation of tissue can currently be used only on small specimens. A technique, known as vitrification, cools specimens in solution to between -160 and -196 degrees Celsius, so they are maintained in an ice-free, glass-like state. The bigger the sample, however, the more susceptible it is to crystallization and failure when rewarmed.
To address this problem, a team of American scientists has created a new technique for thawing frozen tissue that may allow long-term storage and subsequent usability of tissues and organs. The novel technique, known as nano-warming, can prevent tissue damage during a rapid thawing sequence.
According to a March 2017 study, the US scientists showed how a bath containing evenly-distributed and magnetized iron-oxide nanoparticles could be warmed with electromagnetic waves to rapidly and non-destructively thaw bigger volumes of solution and tissue that had been possible. The study authors said their technique if further refined, could revolutionize organ storage for transplants.
To warm their samples without damaging them, the study team used modified MRI equipment that included copper capable of creating an alternating magnetic field within and encompassing the sample. The electromagnetic waves produced in the device had limited impact on tissue and cells but activated and heated the nanoparticles dispersed throughout the sample. The heated nanoparticles, in turn, warmed the sample. To make produce usable tissues, then the iron-oxide particles had to be washed from the sample.
The study team said the primary objective of their technology is to save lives by expanding transplant capabilities. In the United States alone, at least 100,000 patients are waiting for organ transplants at any given time, and many more could reap the benefits of transplanted organs or tissue. The brief preservation time currently possible significantly limits screening and transplantation possibilities. Long-term preservation processes would allow for screening that could help transplant personnel discover optimal matches for donated organs that would lessen transplantation risks, like organ rejection.
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