Synthetic polymers enable non-vitreous cellular cryopreservation by reducing ice crystal growth during thawing

Polyvinyl alcohols (PVA) (CAS no. 9002-89-5) are synthetic polymers used in a wide range of industrial, commercial, medical and food applications. The purpose of this review, this critical evaluation of the available information on PVA, is to support the safety of PVA as a coating agent for pharmaceutical and dietary supplement products. All the available information on PVA gleaned from a comprehensive search of the scientific literature were critically evaluated. Orally administered PVA is relatively harmless. The safety of PVA is based on the following: (1) the acute oral toxicity of PVA is very low, with LD(50)s in the range of 15-20 g/kg; (2) orally administered PVA is very poorly absorbed from the gastrointestinal tract; (3) PVA does not accumulate in the body when administered orally; (4) PVA is not mutagenic or clastogenic; and (5) NOAELs of orally administered PVA in male and female rats were 5000 mg/kg body weight/day in the 90-day dietary study and 5000 mg/kg body weight/day in the two-generation reproduction study, which was the highest dose tested. A critical evaluation of the existing information on PVA supports its safety for use as a coating agent for pharmaceutical and dietary supplement products.

The technique of cryopreservation (maintenance of biological samples in a state of 'suspended animation' at cryogenic temperatures), its potential use in tissue engineering applications and current obstacles to the development of effective cryopreservation methods for tissues are reviewed. A didactic overview of the principles of cryobiology and the methodology of cryopreservation is given, with emphasis on the processes of injury to cells during freezing and thawing, and how these are related to the physicochemical and biophysical changes occurring during cryopreservation. Critical issues relevant to the application of cryopreservation methods to tissues are then addressed, including heat and mass transfer limitations in these bulk systems, intrinsic differences between isolated and cultured cells, and mechanisms of freezing injury unique to tissue systems.