Cellular uptake, biodistribution and protection against oxidative damage by Withania somnifera leaf extract-loaded PCL and MPEG-PCL nanoparticles

Withania somnifera (WS) or Ashwagandha is a well-known medicinal plant, cultivated in dry areas of India and Pakistan, where it represents an important resource as a widely used medicinal crop. Because of its anti-inflammatory and immunomodulatory effects, its extract is used, alone or in combination with other herbal extracts, in the treatment of age-related and neurodegenerative disorders. For tapping on the important therapeutic potential of this resource for biomedicine, strategies for controlled delivery and biodistribution improvement are necessary to guarantee treatment efficacy. Pharmacological properties of WS leaf extract (WSE) are mainly attributed to the presence of withanolides. In the present study, WSE was encapsulated in nanoparticles composed of biodegradable polymers as poly-ε-caprolactone (PCL) and methoxy poly-ethylene glycol poly-ε-caprolactone (MPEG-PCL) di-block copolymer. Laser doppler anemometry (LDA), X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) were used to analyze their size and shape. The particle size distribution of WSE-loaded PCL and MPEG-PCL nanoparticles was measured as 214-268 and 30-62 nm, respectively, presenting in both cases a spherical shape. U251 glioma cells, representative of the most common and lethal type of intracranial tumor which is glioblastoma, were exposed to these nanoparticles, demonstrating their efficient uptake. It was showed that MPEG-PCL nanoparticles containing WSE offered better protection to U251 cells against tert-butyl hydroperoxide (tBHP)-induced oxidative damage (95.1%), compared to PCL nanoparticles with WSE (56.4%) and free WSE (39.0%). In vivo distribution of these nanoparticles was further analyzed using zebrafish embryos to validate their biocompatibility in a relevant vertebrate neurodevelopment model.