Effects of a cationic PAMAM dendrimer on photosynthesis and ROS production of Chlamydomonas reinhardtii

Poly(amidoamine) (PAMAM) dendrimers hold great promises for biomedicine. This study sought to examine the toxicity of generation 4 (G4) cationic PAMAM dendrimer to the green microalga, Chlamydomonas reinhardtii, using physiological and molecular biomarkers. Results revealed that the G4 dendrimer at 15 and 25 nM stimulated the photosynthetic process and the production of reactive oxygen species (ROS) in algae. However, the over-production of ROS did not induce the expression of antioxidant enzyme genes, catalase and glutathione peroxidase. In addition, genes encoding light-harvesting proteins (lhca and lhcb), a ferredoxin (fdx) and an oxygen-evolving enhancer protein (psb) involved in photosynthesis were repressed after treatment. Nevertheless, the expression of the lhcbm9 gene, encoding a major light harvesting polypeptide, was increased. These results suggest that the strong modulation of photosynthesis induced by the dendrimer could lead to elevated ROS levels in microalgae.