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What is cryopreservation?
Cryopreservation is the process of freezing and storing cells and other biological material below -80°C to preserve the biological function. When done successfully, cryopreserved cells and biological samples can be stored for decades before being thawed and returned to their normal state.
History
The earliest attempts at cryopreservation began in the late 1800s when researchers experimented with freezing cells to see if they could resume normal activity and function after thawing. The first attempts were often unsuccessful and the discovery of chemical cryoprotective agents (CPAs) brought about the first real breakthroughs in cryopreservation.
It was subsequently discovered that the cooling and thawing rate, combinations of different CPAs and other cell-specific considerations could improve the outcome.
Today, cryopreservation has evolved into an important and fundamental method for biomedical applications such as cell-based therapeutics, assisted reproduction and vaccine storage, as well as being a fundamental part of biomedical research.
Conventional cryopreservation and its drawbacks
Conventional cryopreservation can be divided into two main categories: slow cooling and fast cooling (vitrification).
During slow cooling, the water in the samples has time to form ice crystals that can puncture and kill the cells. This is mitigated by the addition of moderate concentrations of cryoprotective agents (CPAs). On the other hand, vitrification cools the samples so rapidly that the water forms a non-crystalline structure. Vitirification requires the addition of high concentrations of CPAs.
Choosing the appropriate method of cryopreservation depends on the biological material being frozen. While the non-crystalline structure achieved by vitrification is desireable, not all biological samples tolerate the high CPA concentrations required for vitrification.
In cell therapy, the presence of CPAs can present significant clinical, technical, and regulatory challenges. Cell therapy products often need removal of CPA residues prior to administration to protect the patient from serious and harmful side effects. High CPA concentrations can reduce cell survival after thawing, which creates challenges for cell therapy treatments that require precise dosing. Authorities (FDA and EMA) have strict requirements for the use of CPAs, which increases costs and drives the need for CPA-free solutions.
In other applications of cryopreservation, the presence of CPAs may not pose specific difficulties; instead, users may need to focus on minimizing post-thaw loss of cell function or enhancing the throughput of their freezing protocol.
The optimal cryopreservation approach depends on the cell type, with distinct cost–benefit considerations for each.
The need
There is a rapidly growing global demand for safe and efficient cryopreservation methods that are free from CPAs. Across healthcare, research and biotechnology, the focus is on effecient methods that ensure high cell quality without the risks associated with CPAs. The more sophisticated the research and therapies get, the more critical enhanced cryopreservation becomes.