Event Abstract Back to Event Localized siRNA delivery by collagen sponges Ozgul Tezgel1, 2, Nicholas Distasio1, Anna Szarpak-Jankowska2, Anne-Claude Couffin1, Fabrice Navarro1, Rachel Auzély-Velty2 and Isabelle Texier-Nogues1 1 CEA-LETI, Microtechnologies for Biology and Healthcare, France 2 University Grenoble Alpes, CERMAV-CNRS, France Introduction: Small interfering RNA (siRNA) has received great attention since its discovery as a powerful tool both to study unknown gene functions and as a gene specific therapeutic agent for the treatment of a variety of diseases. The major drawback of using siRNA especially as a therapeutic agent is the lack of efficient carrier systems to overcome the crossing biological barriers, since siRNA has a high negative charge, high stiffness and instability in serum (Whitehead et al., 2009). There are variety of different carriers available for siRNA delivery in the literature such as cationic polymers, liposomes and nanoparticles (Kanasty et al., 2013). Moreover, localized release of siRNA for a prolonged period of time is also highly desirable, since it is a very promising strategy for many medical applications. Many different synthetic or natural matrix materials have been prepared for sustained delivery. Collagen is one of the biomaterials which received increased attention due to its biocompatibility and safety, especially as hemostatic agent and wound coverings (Chvapil, 1977). Therefore, in our studies, we used collagen sponges obtained by a lyophilization method for localized siRNA delivery. Collagen sponges were loaded with naked siRNA or lipid nanoparticle/siRNA complexes. Materials and Methods: Two different cationic lipid nanoparticles were formulated with different surfactants on the shell. The first one was formulated with DOTAP (1,2-dioleoyl-3-trimethylammonium-propan) and PEG (LNP) and the second one was formulated with DOTAP and hydrophobically modified chitosan (chLNP). The ability of nanoparticles to make stable complexes with siRNA was studied using gel electrophoresis. Lipid nanoparticle/siRNA complexes were loaded in collagen gels at a known concentration, stirred for an hour, then the final collagen sponge materials obtained by lyophilization. In vitro release profile of siRNA from collagen sponges were characterized under physiological conditions (in PBS at 37°C) in a time dependent manner. In addition, the transfection efficiency of fluorescently labeled siRNA by collagen sponges loaded with naked siRNA or lipid nanoparticle/siRNA complexes was studied in NIH3T3 cells at different time points. Results and Discussion: Lipid nanoparticles (LNP and chLNP) were successfully formulated and their ability to form stable complexes with siRNA demonstrated using gel electrophoresis. According to the results, both lipid nanoparticles, formulated with DOTAP or DOTAP/chitosan, showed similar stabilities. For siRNA release and cell transfection experiments, collagen sponges were loaded with siRNA-alone, DOTAP-LNP/siRNA and Chitosan-LNP/siRNA. According to both in vitro release studies and cell transfection experiments, collagen sponges loaded with lipid nanoparticle/siRNA complexes provided prolonged release of siRNA and higher transfection efficiency compared to the sponges loaded with naked siRNA. Chitosan-LNP/siRNA complexes (chLNP/siRNA) demonstrated slower release rates and higher transfection efficiencies compared to DOTAP-LNP/siRNA complexes (cLNP/siRNA). Figure 1: siRNA release from collagen sponges and siRNA transfection by collagen sponges in NIH3T3 cells Conclusion: In conclusion, lipid nanoparticle templates could be useful to prolong and promote siRNA delivery from collagen sponges, a material already used for would healing (dressing, surgical implant). In the future, the delivery of wound healing promoting siRNA or pDNA sequences will be explored for the treatment of chronic wounds. The work has been supported by French National Agency, Labex ARCANE (n°ANR-12-LABx-003)