Design Expert® supported optimization and predictive analysis of selegiline nanoemulsion via the olfactory region with enhanced behavioural performance in Parkinson's disease

Selegiline is a monoamine oxidase B (MAO-B) inhibitor and is used in the treatment of Parkinson's disease. The main problem associated with its oral administration is its low oral bioavailability (10%) due to its poor aqueous solubility and extensive first pass metabolism. The aim of the present research work was to develop a nanoemulsion loaded with selegiline for direct nose-to-brain delivery for the better management of Parkinson's disease. A quality by design (QbD) approach was used in a statistical multivariate method for the preparation and optimization of nanoemulsion. In this study, four independent variables were chosen, in which two were compositions and two were process variables, while droplet size, transmittance, zeta potential and drug release were selected as response variables. The optimized formulation was assessed for efficacy in Parkinson's disease using behavioural studies, namely forced swimming, locomotor, catalepsy, muscle coordination, akinesia and bradykinesia or pole test in Wistar rats. The observed droplet size, polydispersity index (PDI), refractive index, transmittance, zeta potential and viscosity of selegiline nanoemulsion were found to be 61.43 +/- 4.10 nm, 0.203 +/- 0.005, 1.30 +/- 0.01, 99.80 +/- 0.04%, -34 mV and 31.85 +/- 0.24 mPas respectively. Surface characterization studies demonstrated a spherical shape of nanoemulsion which showed 3.7 times enhancement in drug permeation as compared to drug suspension. The results of behaviour studies showed that treatment of haloperidol induced Parkinson's disease in rats with selegiline nanoemulsion (administered intranasally) showed significant improvement in behavioural activities in comparison to orally administered drug. These findings demonstrate that nanoemulsion could be a promising new drug delivery carrier for intranasal delivery of selegiline in the treatment of Parkinson's disease.