Surface functionalisation regulates polyamidoamine dendrimer toxicity on blood-brain barrier cells and the modulation of key inflammatory receptors on microglia

Dendrimers are branched polymers with spherical morphology. Their tuneable chemistry and surface modification make them valuable nanomaterials for biomedical applications. In view of possible dendrimer uses as brain-aimed nanocarriers, the authors studied amine-and lipid-functionalised (G4) polyamidoamine (PAMAM) biocompatibility with cell population forming the blood-brain barrier (BBB). Both amine-PAMAM and lipid-PAMAM dendrimers were able to enter endothelial and primary neural cells. However, only amine-PAMAM damaged cell membranes in a dose-dependent manner. Transmission electron microscopy evidenced the ability of dendrimers to precipitate salts and serum components present in culture medium that slightly increased toxicity of the amine-PAMAM. Amine-and lipid-PAMAM were both able to cross the BBB and differently induced CD11b and CCR2 overexpression on primary CX(3)CR1-GFP murine microglia in vitro. These data emphasise the role of dendrimer surface functionalisation in toxicity and neural immune cell activation, raising concerns about possible neuroinflammatory reactions.