Na⁺-Complexed Dendritic Polyglycerols for Recovery of Frozen Cells and Their Network in Media

In this study, a novel phenomenon is identified where precise control of topology and generation of polyglycerol induce the retention of Na⁺ ions in biological buffer systems, effectively inhibiting ice crystal growth during cryopreservation. Unlike linear and hyperbranched counterparts, densely-packed hydroxyl and ether groups in 4th-generation dendritic polyglycerol interact with the ions, activating the formation of hydrogen bonding at the ice interface. By inhibiting both intra- and extracellular ice growth and recrystallization, this biocompatible dendritic polyglycerol proves highly effective as a cryoprotectant; hence, achieving the cell recovery rates of ≈134-147%, relative to those of 10% dimethyl sulfoxide, which is a conventional cryoprotectant for human tongue squamous carcinoma (HSC-3) cell line and human umbilical vein endothelial (HUVEC) cells. Further, it successfully recovers the network-forming capabilities of HUVEC cells to ≈89% in tube formation after thawing. The Na⁺ ion retention-driven ice-growth inhibition activity in biological media highlights the unique properties of dendritic polyglycerol and introduces a new topological concept for cell-cryoprotectant development.