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International audience; Small interfering RNAs (siRNAs) can down-regulate the expression of a target mRNA molecule in a sequence-specific manner, making them an attractive new class of drugs with broad potential for the treatment of diverse human diseases. Here, we report the synthesis of a series of cationic amphiphiles which were obtained by the coupling of amino acids and dipeptides onto a lipidic double chain. The new amphiphiles presenting a peptidic motif on a short hydrophilic spacer group were evaluated for selective gene silencing through RNA interference. Our results show that tryptophan residues boost siRNA delivery in an unexpected manner. The silencing experiments performed with very low concentrations of siRNA showed that the best formulations could induce significant death of tumor cells after silencing of polo-like kinase 1 which is implicated in cell cycle progression. In addition, these Trp containing peptide amphiphiles were highly efficient siRNA delivery vectors even in presence of competing serum proteins.

Despite its considerable interest in human therapy, in vivo siRNA delivery is still suffering from hurdles of vectorization. We have shown recently efficient gene silencing by non-vectorized cationic siRNA. Here, we describe the synthesis and in vitro evaluation of new amphiphilic cationic siRNA. C 12 -, (C 12 ) 2 - and cholesteryl–spermine x –siRNA were capable of luciferase knockdown at nanomolar concentrations without vectorization ( i.e. one to two orders of magnitude more potent than commercially available cholesteryl siRNA). Moreover, incubation in the presence of serum did not impair their efficiency. Finally, amphiphilic cationic siRNA was pre-loaded on albumin. In A549Luc cells in the presence of serum, these siRNA conjugates were highly effective and had low toxicity.

Summary For the elaboration of efficient Agrobacterium -mediated transformation of banana the initial steps in the plant-bacterium interaction were investigated. Chemotaxis of agrobacteria towards tissues was studied using a swarm agar plate system. Excised leaf, rhizome, root and in vitro proliferating tissues from different banana landraces were found to be able to elicit a positive chemotactic reaction of A. tumefaciens that could be enhanced by extensive wounding. Agrobacterium attachment was examined by UV fluorescence microscopy and scanning electron microscopy, which demonstrated the presence of bacteria individually bound or massively attached to the surface of single banana cells and tissues. It can be concluded that at least during the two early steps of interaction A. tumefaciens appears to be compatible with banana, indicating the potential for genetic transformation.

Top of pageAbstract Linear polyethylenimine (L-PEI) is the most used non-viral delivery reagent for gene delivery in animals. Various delivery routes of small size defined PEI polyplexes formulated in a 5% glucose solution can be used (intravenous, intracerebral, intraperitoneal, intracardiac, instillation |[hellip]|). Intravenous injection is the route of choice in many gene therapy applications. Following systemic delivery of PEI polyplexes, a non-specific targeting of lungs occurs where c.a. 90% of transgene expression are found. We have addressed the bolus effect caused with the injection volume of polyplexes solution using jetPEI|[trade]| after the rapid injection (few seconds) into the tail vein of mice. We have shown that injection volume less than 200|[mu]|l leads to lower transgene expression in lungs than volumes comprised between 200 and 400|[mu]|l. When the injection volume of polyplexes is increased to 2-2.5 ml and the injection performed by perfusion, the transgene level is slightly affected in lungs. The optimal effect of bolus is obtained following a rapid injection (c.a. 10 seconds) of 400|[mu]|l of a 5% glucose solution. It is generally demonstrated that highly positive polyplexes (N/P ratio >4) are efficient in the lungs. We have purified polyplexes formulated with various N/P ratios by ultracentrifugation. We have shown that as expected, the amount of free PEI removed increased with the initial N/P ratio used to prepare polyplexes and reached more than 50% at N/P ratio of 10. When the optimal injection conditions were applied with polyplexes made initially with a N/P ratio of 10 and then purified, a 10-fold decrease in gene expression in the lung was observed. Increasing the dose of DNA injected using purified polyplexes increased the transgene level comparable to the optimal conditions obtained with crude complexes. It appears that the presence of free polymer in the optimal crude complexes has a co-helper effect. The role of this free polymer to reach a high transgene level in vivo is not yet identified and needs further investigations.