Structural transitions in TPGS micelles induced by trehalose as a model cryoprotectant

Sugar-based Cryoprotectants Stabilize Liposomal Vesicles by Exhibiting a Cholesterol-like Effect

Liposomal vesicles tend to fuse and aggregate during lyophilization. To avoid these events, cryoprotectants are added to the dispersion before lyophilization. Herein, we have compared the effect of three commonly used cryoprotectants (mannitol, MTL; trehalose, THL; and β-cyclodextrin, β-CD) upon structural characteristics of liposomes. The formulation was prepared using ethanol injection method, and cryoprotectants were tested at three dose levels (2, 6, and 10 mM). We have elucidated their effect on soy lecithin (SL) liposomes formulated with and without cholesterol (CHL). Characterizations were performed using scattering, thermal, and spectroscopic techniques. CHL molecules interacted hydrophobically with the SL bilayer. In spite of triggering a noticeable increase in the hydrodynamic diameter (about 30 nm), CHL promoted the stabilization of vesicles. Hydrogen bonding interactions were verified by the shift in -OH stretching over 3300-3500 cm-1. This manifested in an increased phase transition temperature (Tm) of SL liposomes. Tm increased further upon incorporation of cryoprotectants, particularly with β-CD. Enthalpic changes were indicative of an affinity interaction between phospholipids and cryoprotectants, regardless of the presence of CHL. β-CD showed concentration-dependent changes in the energetics of this interaction. The affinity of cryoprotectant-liposome interaction has been ranked as β-CD ≫ THL > MNT.

Enhancing long-term storage and stability of engineered living materials through desiccant storage and trehalose treatment

Engineered living materials (ELMs) have broad applications for enabling on-demand bioproduction of compounds ranging from small molecules to large proteins. However, most formulations and reports lack the capacity for storage beyond a few months. In this study, we develop an optimized procedure to maximize stress resilience of yeast-laden ELMs through the use of desiccant storage and 10% trehalose incubation before lyophilization. This approach led to over 1-year room temperature storage stability across a range of strain genotypes. In particular, we highlight the superiority of exogenously added trehalose over endogenous, engineered production in yielding robust preservation resilience that is independent of cell state. This simple, effective protocol enables sufficient accumulation of intracellular trehalose over a short period of contact time across a range of strain backgrounds without requiring the overexpression of a trehalose importer. A variety of microscopic analysis including µ-CT and confocal microscopy indicate that cells form spherical colonies within F127-BUM ELMs that have variable viability upon storage. The robustness of the overall procedure developed here highlights the potential for widespread deployment to enable on-demand, cold-chain independent bioproduction.