Freeze-thawed electrosprayed everolimus loaded nanoparticles as a potential drug delivery system in brain tumours: Design and characterisation

Freeze-thawing is a method that has proven beneficial to achieve cross-linking without the use of chemicals. In this study, the aim was to evaluate the applicability of our previously electrosprayed polyvinyl alcohol (PVA)- soluplus (SOL®)-everolimus (RAD001) nanoparticles (NP) as a potential drug delivery system in brain tumours post freeze-thawing. The effects of several formulation variables post freeze-thawing (particle size, encapsulation efficiency (EE%) and % drug release) were investigated using the Box-Behnken (BBD) design of experiment. The optimal PVA-SOL®-RAD001 NP formulation contained 2%PVA-14%SOL®-0.6 % RAD001 with a gelation temperature of 37 °C ± 0.1 at pH 5.5. The average particle size, EE%, and release kinetics of the PVA-SOL®-RAD001 NP were (63.99 ± 0.1) nm, 99 %, and 93 % in 8 h respectively. For the in vitro cell viability tests, the NP were treated at 24h and 48h showing a significant reduction in cell viability at the higher dose treatments for the optimized formulation. Additionally, a comparison was made with our previously developed microspheres containing PVA-RAD001 alone, for the cell viability study. Electrosprayed protocol modifications were proposed to produce NP combining smaller particle size (<100 nm) with higher encapsulation efficiency and to ensure the optimum viscosity at body temperature highlighting the novelty of the freeze-thaw technique on the electrosprayed NP.