Carbon dots based cascading nanozymes mitigate phytotoxicity in lettuces under imidacloprid stress

Improper pesticide use induces oxidative stress and disrupts detoxification systems in plants. We synthesized CDs with cascading nanozyme activities to mitigate phytotoxicity in lettuces under imidacloprid (IMI) stress. CDs exhibit superoxide dismutase-like (SOD-like) and peroxidase-like (POD-like) activities. Surface modifications and analysis of CDs, the SOD-like activity relies on the -NH2, -COOH, and -OH groups for binding superoxide anions (O2•-), while POD-like activity depends on -COOH and CO groups, also, CO group provides π-system and the electron-deficient structure for electron transfer. Practically, under IMI stress, CDs strengthen multiple defense systems in lettuces, reducing levels of reactive oxygen toxicity (O2•-, H2O2, and MDA, by 26.77 %, 48.52 %, and 13.10 %, respectively). Meanwhile, CDs upregulate detoxification gene expression, resulting in a 42.74 % reduction in IMI residue in lettuces. Moreover, the acceptable daily intake of IMI in lettuces treated with CDs was less than 18.0 % of the reference dose, even at high-concentration IMI. [Display omitted] •We synthesized carbon dots (CDs) with cascading nanozyme (SOD and POD) activities.•CDs could mitigate phytotoxicity in lettuces under imidacloprid (IMI) stress.•CDs strengthen multiple defense systems to reduce ROS toxicity in lettuce cells.•CDs raise detoxification gene expression, reducing IMI residue by 42.74 % in lettuce.•The ADI of IMI for CD-treated lettuce is acceptable even at high exposure levels.