Fluorescein labelled cationic carbosilane dendritic systems for biological studies

Fluorescein-cationic carbosilane dendrimers and dendrons have been synthesized and formation of dendriplexes with siRNA Nef have been studied. The biodistribution assays in a BALB/c mice model showed the relevance of dendriplex formation. [Display omitted] •Synthesis of labelled cationic carbosilane dendrimers and dendrons.•Study of interactions of dendritic compounds with siRNA Nef.•The chromophore did not modify the toxicity of dendrimers and dendriplexes.•The biodistribution assay of a dendrimer and its dendriplex indicate long circulation times. Cationic carbosilane dendrimers and dendrons labelled with one fluorescein unit have been synthesized. For dendrimers (generations 1–3), a random procedure was followed by successive addition of two types of thiol compounds to vinyl terminated derivatives, first one with –NH3Cl and second one with –NMe2HCl functions, subsequent reaction with FITC and finally quaternization with MeI. For dendrons, the use of compounds with a –NH2 group at the focal point and –NMe2 functions at the periphery allowed us to obtain the corresponding fluoresceinated cationic derivatives. The toxicity of these dendritic molecules was studied by MTT and their interaction with siRNA Nef by electrophoresis. Finally, second generation dendrimer and their dendriplexes with siRNA Nef were chosen as a model to analyse their in vivo biodistribution in a BALB/c mouse model. The highest levels for dendriplexes were found in spleen and liver, followed in lymph nodes, while lower levels were found in kidneys. This distribution is in accordance with long circulation times.