Cryoprotectants and dynamics of exclusion zone water

Hydrophilic membranes are integral components in a wide range of applications, particularly in biological systems, where their negatively charged surfaces resemble those of cell membranes and influence processes such as cryopreservation. This study investigates the relationship between the Exclusion Zone (EZ) near a Nafion membrane and its response to thermal changes. In this context, the EZ denotes an extended interfacial water region adjacent to hydrophilic surface, characterized by physicochemical properties differing from those of bulk water. The present work investigates how cryoprotectants such as polyethylene glycols (PEGs) and trehalose affect the EZ near Nafion surfaces across a range of temperatures, aiming to identify potential links between interfacial hydration and cryoprotective efficiency. Our observations showed that PEG and trehalose exhibit distinct effects on the EZ behavior, with trehalose showing milder suppression of the EZ size compared to PEG at the same concentration. Fluorescent tracking of dansyl-labeled cryoprotectants demonstrated their distribution near the EZ, revealing differential long-range interactions of interfacial water with PEG and trehalose. Herein, we provide the first evidence linking cryoprotectant activity to the EZ behavior, suggesting a role in interfacial water stabilization under cooling, with implications for cryopreservation and membrane-associated processes.