Photoprotective and cryoprotective effect of the carotenoid bacterioruberin on peripheral blood mononuclear cells

Cell cryopreservation and biological materials are fundamental in biomedical research, from regular sample storage to innovative cell-based treatments. This process ensures that cell banks deliver verified, stable, and uniform cell products. Since the discovery of glycerol and dimethyl sulfoxide (DMSO) as the first cryoprotectants more than 60 years ago (Lovelock and Bishop 1959 ), the search for more and diverse cryoprotectants has continued, as the aforementioned substances are not effective for all cell types, and they are not suitable for every process (Murray and Gibson 2022 ). Traditionally, the improvement of cryopreservation of biological samples has been approached from a physical perspective, with efforts focused on managing and adjusting ice formation/nucleation, osmotic variations, cellular dehydration, or freezing rates to achieve better results (Wowk et al. 2000 ; John Morris and Acton 2013 ; Murray and Gibson 2022 ). However, current research has shifted towards a biochemical perspective, suggesting that cold stress can be reduced by targeting intracellular pathways (Murray and Gibson 2022 ). For example, the addition of a caspase inhibitor to interfere with apoptosis is effective (Baust et al. 2000 ), since it has been widely reported that this programmed cell death process is responsible for late cell death after thawing (Boon et al. 2006 ; Xu et al. 2010 ; Murray and Gibson 2020 ). Recently, carotenoids have emerged as a highly promising option in the development of agents that can reduce cryopreservation-related apoptosis (Gardela et al. 2023 ; Tvrda et al. 2017 ). However, the studies testing the effectiveness of different carotenoids in cryopreservation, such as lycopene, astaxanthin, or ß-carotene (Tuncer et al. 2014 ; Tizkar et al. 2015 ), are focused mainly on sperm cells (Tuncer et al. 2014 ; Tizkar et al. 2015 ; Kinkar et al. 2020 ; Sapanidou et al. 2022 ; Kolyada et al. 2023 ).