Probing the Size Effect of Graphene Oxide Nanosheets on Ice Crystal Regulation and Laser-Assisted Rapid Rewarming

Two-dimensional (2D) nanomaterials have attracted many researchers to explore the effect of ice control and rapid deicing due to their functional groups, large specific surface area, and excellent photothermal properties. However, the impact of size effects on ice crystal formation, growth, and photothermal performance has been rarely explored. Here, graphene oxide nanosheets (GO NSs) with controllable sizes were used as a representative of 2D nanomaterials to probe the effect of size on ice crystal regulation and rapid rewarming in cell cryopreservation. All sizes of GO NSs exhibited notable inhibitory effects on ice crystal size during the recrystallization process. Significantly, when the size of GO NSs was smaller than a certain size (<150 nm), they showed a more significant ice recrystallization suppression effects, which could reduce the ice crystal size to about 17% of that of pure water. Meanwhile, the photothermal experiments also indicated that smaller-sized GO NSs exhibited better photothermal behavior, with 90 nm GO NSs (GO-90) heating to 70 °C in just 1 min induced by an 808 nm laser (2 W/cm 2 ). Furthermore, applying GO-90 (200 μg/mL) to cell cryopreservation, cell viability could reach 95.2% and 93% with a low amount of traditional cryoprotectant (2% v/v DMSO) for A549 cells and HeLa cells after recovery, respectively. With the assistance of a 808 nm laser, the rewarming time was also shortened to 20 s, greatly improving the rewarming rate. Our work associated specific sizes of 2D nanomaterials with their ice growth inhibition behaviors during recrystallization and photothermal properties to synergistically improve cell cryopreservation efficiency, providing guidance for effectively designing novel 2D nanomaterials for collaborative control of ice crystals in cell cryopreservation.