Table 1.

Examples and characteristics of the most common cryoprotective agents.

CPA	Source and Examples	Classification	Reference
Sulfoxides	Synthesized from dimethyl sulfide (the prototypal CPA of this category is dimethyl sulfoxide)	Penetrating	[17]
Diols	Propylene glycol (or 1,2-propanediol) is the prototypical agent of this category of CPA that is produced via hydration of propylene oxide; other diols are methylene glycol and ethylene glycol	Penetrating	[17]
Synthetic and semisynthetic polymeric agents	Synthetic resins obtained from hydrolysis of polyvinyl acetate (such as polyvinyl alcohols), and copolymers and semisynthetic polymers of different origin, including polyampholytes (such as carboxylated poly-ʟ-lysine and others)	Nonpenetrating	[18,19,20,21]
Saccharides	Fungi, plants, invertebrate animals (examples are: sucrose and trehalose)	Nonpenetrating	[22,23]
Proteins	Animals (antifreeze proteins)	Nonpenetrating	[24]