Erythrocyte interactions - Comparison of the aggregation power of polymer molecules used in medicine - Not only size does matter

Achieving high intracellular trehalose in hRBCs by reversible membrane perturbation of maltopyranosides with synergistic membrane protection of macromolecular protectants

Trehalose is considered as a biocompatible cryoprotectant for solvent-free cryopreservation of cells, but the difficulty of the current trehalose delivery platforms to human red blood cells (hRBCs) limits its wide applications. Due to cell injuries caused by incubation at 37 °C and low intracellular loading efficiency, development of novel methods to facilitate trehalose entry in hRBCs is essential. Herein, a reversible membrane perturbation and synergistic membrane stabilization system based on maltopyranosides and macromolecular protectants was constructed, demonstrating the ability of efficient trehalose loading in hRBCs at 4 °C. Results of confocal laser scanning microscopy exhibited that the intracellular loading with the assistance of maltopyranosides was a reversible process, while the membrane protective effect of macromolecular protectants on trehalose loading in hRBCs was necessary. It was suggested that introduction of 30 mM poly(vinyl pyrrolidone) 8000 combined with 1 mM dodecyl-β-D-maltopyranoside and 0.8 M trehalose could increase the intracellular trehalose to 84.0 ± 11.3 mM in hRBCs, whereas poly(ethylene glycol), dextran, human serum albumin or hydroxyethyl starch had a weak effect. All the macromolecular protectants could promote the cryosurvival of hRBCs, exhibiting membrane stabilization, and incubation and followed by cryopreservation did not change the basic functions and normal morphology of hRBCs substantially. This study provided an alternative strategy for glycerol-free cryopreservation of cells and the delivery of membrane-impermeable cargos.

Facilitating trehalose entry into hRBCs at 4 °C by alkylated ε-poly(L-lysine) for glycerol-free cryopreservation

Currently, glycerol is a conventional cryoprotectant of human red blood cells (hRBCs), but the time-consuming thawing and deglycerolization processes are essential before transfusion. Much of the research up to now has been conducted on the delivery of impermeable trehalose to hRBCs at 37 °C, but the cryoprotective effect of trehalose and deterioration of cells still remain challenging. Encouraged by the interaction of hydrophobic or cationic groups on cell membranes and osmotic stabilization, herein, we propose a novel cryopreservation system to facilitate trehalose entry into hRBCs at 4 °C and pH 7.4. High intracellular trehalose contents and cryosurvival of hRBCs were achieved with small function variations via the assistance of self-assembled nanoparticles of alkylated ε-poly(L-lysine) (ε-PL) along with poly(vinyl pyrrolidone) (PVP). The effect of amphipathic alkylated ε-PL with various alkyl chains and grafting ratios on membrane perturbation with protection of PVP was systematically investigated. Overall, by the combination of alkylated ε-PL and PVP, the intracellular trehalose could be enhanced to 109.7 ± 6.1 mM and subsequently hRBC cryosurvival reached 91.7 ± 5.5%, significantly higher than those containing trehalose only, 11.9 ± 1.1 mM and 50.0 ± 2.1%, respectively. It was observed that the biocompatible trehalose-loading system could benefit glycerol-free cryopreservation of hRBCs and also provide a feasible way for impermeable biomacromolecule delivery.