The Effects of Cryopreservation on the Cell Ultrastructure in Aquatic Organisms.

This review provides an update on the current state of cryopreservation studies coupled with ultrastructural observation. Research in these fields has evolved and advanced since its inception in the 1950s. Different techniques have different advantages, but the researcher's technical proficiency is also necessary to derive a sound conclusion. Sperm samples are the most widely studied specimen because they are less sensitive to freezing and have high fluidity in the membrane and low water content. Some studies have also investigated oocytes, embryos, larvae, and algae from aquatic species. Cryopreservation studies have formulated a method applicable to every species of interest to preserve their biodiversity and prevent extinction. However, the avoidance of cryoinjury because of intracellular ice formation is a species-specific challenge. More comprehensive studies on ultrastructural observation can assist in understanding the underlying mechanisms of failed cellular responses to cryopreservation. Thus, optimizing protocols and increasing the survival rates of thawed samples can improve current cryopreservation techniques. Nevertheless, investigations into the effects of freezing on organisms' ultrastructure remain limited, especially regarding aquatic organisms.

Novel Long-Term Cryo-Storage Using Vitrification and Laser Warming Techniques.

Vitrification and laser warming have gained popularity over the traditional convective warming techniques in cryopreservation. Laser warming is rapid with uniform effects, thus preventing ice crystal formation in samples. Contemporary laser warming studies have focused on proof-of-concept experiments. Yet, no protocols or techniques have been developed to address the problem of warming samples from long-term storage. Herein, a new approach to laser warming samples without exposing the samples to ambient temperature is introduced. The new device presented has a mean laser-hitting accuracy of 76% ± 16% and a rewarming rate of 59% ± 25% on samples with <1 µL in volume. Although these rates depend on the choice of vitrification solution and mastery of the technique, the approach described represents a successful first step toward laser warming samples from long-term cryo-storage.