Solid lipid nanoparticles for efficient delivery of capsaicin-rich extract: Potential neuroprotective effects in Parkinson’s disease

Parkinson’s disease (PD) is a debilitant neurodegenerative disease that unveils severe physical, and psychological burdens on patients. To date, there is no effective treatment capable of inverting the disease course, freezing the cognitive impairment, and other non-motor features. Solid lipid nanoparticles (SLNs) can represent a promising approach to provide safe and site-specific delivery of naturally occurring compounds counteracting PD symptoms. In this work, SLNs were purposed for the release of a capsaicin-rich extract (CPS-extract) and investigated for their efficacy in PD pathology. SLNs were prepared by using stearic acid (SA) and Brij 78 as lipid and surfactant, respectively. Different formulation parameters, including drug: lipid ratio and surfactant concentrations were investigated. The selected formulation brings together particle sizes of around 200 nm, high encapsulation efficiency (>80 %), and provides 90 % of CPS release within 24 h, which well fits in the Kosermayer-Peppas model. Differential Scanning Calorimetry (DSC) analysis confirmed the presence of the lipid in the solid crys talline state, while stability studies revealed that CPS-extract SLNs preserve their stability for at least 30 days. Moreover, biological assays, performed on retinoic acid/phorbol 12-myristate 13-acetate (RA/PMA) differenti ated SH-SY5Y neuroblastoma cell line, revealed that CPS-extract SLNs possessed a significant protective effect in reducing reactive oxygen species (ROS) increments induced by the neurotoxic agent H2O2.