Is isochoric vitrification feasible? Cycling between modeling, experimental observations, and first principles.

Isochoric cryopreservation is preservation of biological material in a constant-volume container, to benefit from a presumed baroprotective effect. From its inception, the premise for the isochoric approach is that pressure elevation can be achieved by permitting some ice formation in the system. The idea of integrating vitrification into an isochoric chamber followed at a later stage, where vitrification is a century old established approach of ice-free cryopreservation. At face value, the resulting term "isochoric vitrification" encompasses an internal contradiction revolving around ice formation. We have previously shared modeling results pointing to this contradiction and, hence, questioning the feasibility of the process (Cryobiology 2023, 111, 9-15). More recently, Ali et al. (Cryobiology 2024, 116, 104935) claimed to have obtained contradictory experimental evidence while stating that isochoric vitrification is feasible. The objective for this communication is to share our skepticism about this claim with the community of cryobiology.