Technological and biological characterization of idebenone-loaded solid lipid nanoparticles prepared by a modified solvent injection technique

The possibility of preparing solid lipid nanoparticles (SLN) by means of an alternative technique to the most diffused high pressure homogenization and dilution of micro-emulsion was tested. SLN formulations were therefore prepared by a solvent injection procedure (SI), by changing the lipid component (palmitic or stearic acid) and using the lipophilic antioxidant agent idebenone (IDE) as a model drug. SI-SLN showed a good compatibility with the encapsulated drug and interesting sizes (around 160–180 nm) and a negative surface charge (zeta potential around −30 mV) for systemic administration purposes. This method of preparation allowed to obtain smaller nanoparticles and higher drug encapsulation efficiency than a micro-emulsion procedure. SI-SLN were stable upon storage at room temperature for up to 6 months and can be also successfully freeze-dried. A slow and prolonged drug release was observed in vitro from these systems. A biological assay proved that the incorporation of IDE in the SLN matrix maintained or in some cases increased drug protecting activity against free radical-induced oxidative damage of astrocyte cell cultures.