Development, characterization, and in vitro evaluation of phosphatidylcholine–sodium cholate-based nanoparticles for siRNA delivery to MCF-7 human breast cancer cells

Phosphatidylcholine–sodium cholate (SC)-based nanoparticles were designed, characterized, and evaluated as plausible oligonucleotides delivery systems. For this purpose, formulation of the systems was optimized to obtain low cytotoxic vehicles with high siRNA-loading capacity and acceptable transfection ability. Mixtures of soybean phosphatidylcholine (SPC) and SC were prepared at different molar ratios with 2 % w/v total concentration; distilled water and two different buffers were used as dispersion medium. Nanoparticles below 150 nm were observed showing spherical shape which turned smaller in diameter as the SC molar proportion increased, accounting for small unilamellar vesicles when low proportions of SC were present in the formulation, but clear mixed micellar solutions at higher SC percentages. Macroscopic characteristics along with physico-chemical parameters values supported the presence of these types of structures. SYBR green displacement assays demonstrated an important oligonucleotide binding that increased as bile salt relative content got higher. Within the same molar ratio, nanoparticles showed the following binding efficiency order: pH 7.4 > pH 5.0 > distilled water. siRNA-loading capacity assays confirmed the higher siRNA binding by the mixed micelles containing higher SC proportion; moreover, the complexes formed were smaller as the SC:SPC ratio increased. Considering cytotoxicity and siRNA-loading capacity, 1:2 and 1:4 SPC:SC formulations were selected for further biological assays. Nanoparticles prepared in any of the three media were able to induce dsRNA uptake and efficiently transfect RNA for gene silencing, for the compositions prepared in buffer pH 5.0 being the most versatile.