Phase coexistence in multilayer phospholipid films treated with certain cryoprotectants

Area of Science:

• Biophysics
• Materials Science
• Biochemistry

Background:

• Cryopreservation relies on cryoprotective agents (CPAs) interacting with cell membranes.
• Understanding CPA interactions with complex phospholipid bilayers is vital but understudied.

Purpose of the Study:

• To investigate CPA interactions with mixed phospholipid/cholesterol bilayers.
• To analyze CPA incorporation into coexisting lipid phases using Raman mapping.

Main Methods:

• Raman mapping of multilayer DOPC/DPPC-d62/Chol films.
• Exposure to vapor phase of various CPAs (DMSO, glycerol, PG, EG) and deuterated analogues.
• Analysis of chemical content, lipid conformational ordering, and CPA incorporation.

Main Results:

• DMSO extracted cholesterol, forming co-crystalline phases under dry conditions.
• DMSO induced dehydration in hydrated films; glycerol-treated films resembled hydrated ones.
• Ethylene glycol reduced phase coexistence; propylene glycol further reduced it and increased disorder.
• Disordered lipid domains incorporated more CPA than ordered domains.

Conclusions:

• CPAs significantly influence the organization and properties of complex phospholipid bilayers.
• The specific CPA and lipid phase organization dictate the extent of interaction and structural changes.
• Findings provide insights into CPA behavior crucial for optimizing cryopreservation techniques.