Resveratrol-loaded nanocarriers: formulation, optimization, characterization and in vitro toxicity on cochlear cells

The present work aimed to investigate the suitability of polymeric nanoparticles (NPs) loaded with resveratrol (RES) for drug delivery to cochlear cells. RES-loaded NPs were prepared by a solvent-diffusion method without surfactant. The Box–Behnken design was used to study the effect of the formulation variables on the particle mean diameter (PMD), polydispersity index (PDI), zeta-potential (ζ), percent drug encapsulation efficiency (EE%), and ratio between NP size before and after freeze-drying (Sf/Si). The physicochemical stability of the RES-loaded NPs during freeze-drying was investigated using four well-known cryoprotectants (i.e., lactose, mannitol, sucrose, and trehalose) at different concentrations. The RES-loaded NPs were also characterized by powder X-ray diffraction (PXRD) and in vitro drug release studies. Finally, the in vitro toxicity of the synthesized NPs was evaluated on two cochlear cell lines: HEI-OC1 and SVK-1 cells. The optimal formulation (desirability: 0.86) had 135.5 ± 37.3 nm as PMD, 0.126 ± 0.080 as PDI, −26.84 ± 3.31 mV as ζ, 99.83 ± 17.59% as EE%, and 3.30 ± 0.92 as Sf/Si ratio. The PMD and PDI of the RES-loaded NPs were maintained within the model space only when trehalose was used at concentrations higher than 15% (w/v). Results from the in vitro cytotoxicity studies showed that blank NPs did not alter the viability of both cells lines, except for concentrations higher than 600 μg/mL. However, the cell viability was significantly decreased at high concentrations of native RES (>50 μM, p < 0.05) in both cell lines. Overall, the results suggested that the RES-loaded polymeric NPs could be a suitable template for cochlea antioxidant delivery and otoproctection.