Carbon quantum dot priming alleviates salt stress and boosts growth and carotenogenesis in Dunaliella salina

This study investigated the effects of pretreatment with nitrogen-doped (N-CQDs) and sulfur-doped (S-CQDs) carbon quantum dots on the growth and physiology of the microalga Dunaliella salina under salinity stress. The algae were exposed to various concentrations of CQDs (0, 0.5, and 2.5 mg/mL) under either salinity stress (2.5 M NaCl) or control conditions. Growth and physiological parameters, including pigment concentration, proline content, antioxidant enzyme activities, and malondialdehyde (MDA) content, were measured. The results indicated that increasing CQD concentrations generally enhanced algal growth compared to the CQD-free control. Furthermore, CQD pretreatment alleviated the negative effects of salinity stress. Specifically, a higher concentration of CQDs led to a greater decrease in MDA content under stress conditions. Activities of ascorbate peroxidase and catalase, along with proline content, were also elevated in CQD-treated algae. Multivariate hierarchical clustering analysis confirmed that the most favorable physiological profile, integrating enhanced growth, antioxidant defense, and carotenoid accumulation, was uniquely associated with the combined treatment of salinity and high-concentration CQDs. These findings suggest that carbon quantum dots can act as effective priming agents to improve salinity stress tolerance and direct metabolic output in D. salina , highlighting their potential as a novel nano-tool for enhancing productivity in algal biotechnology systems.