Currently, most non-viral nucleic acid vectors are in the form of colloidal suspensions administered primarily parenterally. This type of formulation and the mode of administration impose strong constraints such as the size of the administered vectors or the production of sterile preparations. The tablet form provides access to easy oral administration, well accepted by patients, it is also an advance for the stability of the nucleic acids vectors, since it is a dry form.Using an optimized lipid-based small interfering RNA delivery system, we studied the tabletability of a liquid suspension of these vector. We optimized the conditions of freeze-drying by choosing excipients and process, allowing for the conservation of both the gene silencing efficacy of the formulated siRNAs and the supramolecular structure of the lipid particulate system. Gene silencing efficacy was assayed on luciferase-expressing cells and the structure of the siRNA vector in freezedried and tablet forms was examined using SAXS Synchrotron radiation. The freeze-dried powders were then mixed with excipients necessary for the good progress of the compression by allowing for a regular supply of the matrix and the reduction of friction. The compression was carried out using a rotary press simulator that allow for complete monitoring of the compression conditions. After compression, formulated siRNAs retained more than 60% of their gene silencing efficacy. Within the tablets, a specific SAXS signal was detectable and the lamellar and cubic phases of the initial liquid suspension were restored after re-suspension of siRNA vectors by disintegration of the tablets. These results show that the bilayer lipid structures of the particles were preserved despite the mechanical constraints imposed by the compression. If such a result could be expected after the freeze-drying step, it was never shown, to our knowledge, that siRNA delivery systems could retain their efficacy and structure after mechanical stress such as compression. This opens promising perspectives to oral administration of siRNA as an alternative to parenteral administration.

Since the possibility of silencing specific genes linked to retinal degeneration has become a reality with the use of small interfering RNAs (siRNAs), this technology has been widely studied to promote the treatment of several ocular diseases. Despite recent advances, the clinical success of gene silencing in the retina is significantly reduced by inherent anatomical and physiological ocular barriers, and new strategies are required to achieve intraocular therapeutic effectiveness. In this study, we developed lipoplexes, prepared with sodium alginate as an adjuvant and strategically coated with hyaluronic acid (HA-LIP), and investigated the potential neuroprotective effect of these systems in a retinal light damage model. Successful functionalization of the lipoplexes with hyaluronic acid was indicated in the dynamic light scattering and transmission electron microscopy results. Moreover, these HA-LIP nanoparticles were able to protect and deliver siRNA molecules targeting caspase-3 into the retina. After retinal degeneration induced by high light exposure, in vitro and in vivo quantitative reverse transcription-PCR (RT-qPCR) assays demonstrated significant inhibition of caspase-3 expression by HA-LIP. Furthermore, these systems were shown to be safe, as no evidence of retinal toxicity was observed by electroretinography, clinical evaluation or histology.