De Novo synthesis of selenium-doped CeO2@Fe3O4 nanoparticles for improving secondary metabolite biosynthesis in Carthamus tinctorius cell suspension culture

Elicitation is a potent strategy to enhance secondary metabolite yield, and nanoparticle-mediated elicitation offers a compelling alternative to traditional methods. Carthamus tinctorius (C. tinctorius) is rich in bioactive chlorogenic acids (CGAs) within its suspension cells. However, the mechanism by which doped nanoparticles (NPs) stimulate the CGAs biosynthesis in the cells remains unclear. Therefore, this study first elucidated the synthesis and characterization of selenium (Se)-doped CeO₂@Fe₃O₄ NPs and then explored their regulatory effect and mechanism for the CGAs biosynthesis in C. tinctorius cells. Material characterization via TEM, XPS, XRD, and EDX analysis confirmed the successful synthesis of selenium-dopped CeO₂@Fe₃O₄ nanocomposite. Fe₃O₄, CeO₂, Fe₃O₄@CeO₂, and selenium-dopped CeO₂@Fe₃O₄ NP treatments all promoted the biosynthesis of CGAs in the cells. Notably, the group treated with 15 mg L^-1 selenium-dopped CeO₂@Fe₃O₄ NPs showed best effect (37.04 mg g⁻¹, 1.92 times that of control). Finally, metabolome and transcriptome profiling revealed the differential alterations in the content of 45 primary metabolites and differential expression of 83 CGA biosynthesis-related genes. This suggested that selenium-doped CeO₂@Fe₃O₄ NPs up-regulated the expression of CGA biosynthesis-related genes, and consequently enhanced CGAs accumulation in the cells. This study provides the first evidence that selenium-doped CeO₂@Fe₃O₄ acts as nano-elicitors for the biosynthesis of CGAs.