Recently, the use of mammalian target of rapamycin (mTOR) inhibitors, in particular rapamycin (Rp), has been suggested to improve the treatment of neurodegenerative diseases. However, as Rp is a strong immunosuppressant, specific delivery to the brain has been postulated to avoid systemic exposure. In this work, Rp loaded solid lipid nanoparticles (Rp-SLN) stabilized with polysorbate 80 (PS80) were prepared comparing two different methods and lipids. The formulations were characterized by differential scanning calorimetry (DSC), nuclear magnetic resonance (NMR), wide angle X-ray scattering (WAXS), cryo-transmission electron microscopy (cryo-TEM), dynamic light scattering (DLS) and particle tracking. In vitro release and short-term stability were assessed. Biological behavior of Rp-SLN was tested in SH-SY5Y neuroblastoma cells. The inhibition of mTOR complex 1 (mTORC1) was evaluated over time by a pulse-chase study compared to free Rp and Rp nanocrystals. Compritol Rp-SLN resulted more stable and possessed proper size and surface properties with respect to cetyl palmitate Rp-SLN. Rapamycin was entrapped in an amorphous form in the solid lipid matrix that showed partial crystallinity with stable Lbeta, sub-Lalfa and Lbeta’ arrangements. PS80 was stably anchored on particle surface. The SEM and AFM imaging and shape-modeling by the combined DLS-SANS analysis revealed that Rp-SLN with a hydrodynamic radius of ∼46 nm preserve a platelet-like or flat ellipsoidal structure with a thickness of 8–9 nm. These dimensions correlate with a single lipid bilayer, organized in a triclinic Lbeta polymorph, and covered with a 1–2-nm P80 shell. Consistently, FT-IR spectra acquired in the range 52–75◦C, confirmed that the Rp incorporation within the lipid matrix decreases the point of the gel-liquid crystal (Lbeta-Lalfa) phase transition. No drug release was observed over 24 h and Rp-SLN had a higher cell uptake and a more sustained effect over a week. The mTORC1 inhibition was increased with Rp-SLN. Overall, compritol Rp-SLN show suitable characteristics and short-term stability to be considered for further investigation as Rp brain delivery system.
Solid lipid nanoparticle as a tool to deliver mTOR inhibitors
GIOVAGNOLI, Stefano;MAGINI, Alessandro;POLCHI, ALICE;TANCINI, Brunella;EMILIANI, Carla
2016
Abstract
Recently, the use of mammalian target of rapamycin (mTOR) inhibitors, in particular rapamycin (Rp), has been suggested to improve the treatment of neurodegenerative diseases. However, as Rp is a strong immunosuppressant, specific delivery to the brain has been postulated to avoid systemic exposure. In this work, Rp loaded solid lipid nanoparticles (Rp-SLN) stabilized with polysorbate 80 (PS80) were prepared comparing two different methods and lipids. The formulations were characterized by differential scanning calorimetry (DSC), nuclear magnetic resonance (NMR), wide angle X-ray scattering (WAXS), cryo-transmission electron microscopy (cryo-TEM), dynamic light scattering (DLS) and particle tracking. In vitro release and short-term stability were assessed. Biological behavior of Rp-SLN was tested in SH-SY5Y neuroblastoma cells. The inhibition of mTOR complex 1 (mTORC1) was evaluated over time by a pulse-chase study compared to free Rp and Rp nanocrystals. Compritol Rp-SLN resulted more stable and possessed proper size and surface properties with respect to cetyl palmitate Rp-SLN. Rapamycin was entrapped in an amorphous form in the solid lipid matrix that showed partial crystallinity with stable Lbeta, sub-Lalfa and Lbeta’ arrangements. PS80 was stably anchored on particle surface. The SEM and AFM imaging and shape-modeling by the combined DLS-SANS analysis revealed that Rp-SLN with a hydrodynamic radius of ∼46 nm preserve a platelet-like or flat ellipsoidal structure with a thickness of 8–9 nm. These dimensions correlate with a single lipid bilayer, organized in a triclinic Lbeta polymorph, and covered with a 1–2-nm P80 shell. Consistently, FT-IR spectra acquired in the range 52–75◦C, confirmed that the Rp incorporation within the lipid matrix decreases the point of the gel-liquid crystal (Lbeta-Lalfa) phase transition. No drug release was observed over 24 h and Rp-SLN had a higher cell uptake and a more sustained effect over a week. The mTORC1 inhibition was increased with Rp-SLN. Overall, compritol Rp-SLN show suitable characteristics and short-term stability to be considered for further investigation as Rp brain delivery system.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
