Development and Evaluation of Donepezil loaded PEGylated Dendrimers for the treatment of Alzheimer’s Disease

Abstract

Aim and objectives: Now days, it is major challenge for researchers and physicians to achieve maximum concentration of the therapeutic in CNS targeting for management of Alzheimer’s disease, with greatest bioavailability. Thus, there is an indeed need of stable, biocompatible, potent drug delivery system which can offer maximum bioavailability of therapeutic agents for management of Alzheimer’s disease. The present study was aimed to develop donepezil loaded PEGylated Polypropylenimine dendrimers administered through olfactory route for improving bioavailability of donepezil HCl in brain. Material and methods: The PPI dendrimers were synthesized by divergent method and characterized by IR, NMR and microscopically. The synthesized dendrimers were PEGylated with MPEG 5000 and were characterized by IR, NMR and microscopically. The PEGylated dendrimers were evaluated for their biocompatibility and safety with acute toxicity studies on Wistar albino rats, including haematological, biochemical, histopathological parameters. PEGylated 3.0G, 4.0G and 5.0 G were evaluated for their entrapment efficiency of donepezil HCl. The donepezil loaded PPI dendrimers were characterized by IR, NMR and TEM microscopy and then evaluated for In-vitro release studies, stability, drug leakage, storage and haemolytic activity. Ex-vivo study was performed on goat nasal mucosa to check nasal diffusion capacity of the developed formulation followed by nasal histopathology to check the bio-safety of developed formulation on nasal mucosa. In-vivo pharmacokinetic and Pharmacodynamicstudies were carried out using Wistar Albino rats.. Pharmacokinetic estimation included study of bioavailability, Cmax, Tmax, T1/2, AUC and MRT. Pharmacodynamic studies included testing of neurobehavioural parameters of animals on Y- maze and fear conditioning. Results: The synthesis of different generations of PPI dendrimers was confirmed by IR, NMR and microscopy studies. The TEM data indicated 50 nm size ranges of synthesized dendrimers.PEGylation of different generations of PPI dendrimers were confirmed by IR and NMR spectroscopic data. The PEGylated G4 and G5 PPI dendrimers indicated statistically insignificant difference haematological parameters including RBC count, WBC count, HCT values, haemoglobin (Hb) percentage, and platelets count and levels of SGOT, SGPT and LDH of as compared to the values of normal control group at mild (2.5mg/kg) and moderate (25 mg/kg) dose. Histopathological studies displayed an insignificant change in tissue samples of brain, liver, kidney, lung and heart after 24 hours and 15 days. Equilibriumdialysis technique was applied to encapsulate donepezil inside the dendrimer. The drug loading capacity was found 24.33 ± 0.56%, 40.12 ± 0.62% and 60.4 ± 0.6%, for PEGylated G3, G4, and G5 PPI dendrimers respectively. In the in vitro release study, higher generations of dendrimer indicated a higher intensity of controlled release in comparison to lower dendrimeric generations. Data obtained from Ex-vivo nasal diffusion studies, G5PPID indicated 47% and 10% enhancement in drug diffusion as compared to pure donepezil HCl and G4PPID respectively through nasal mucosa. In vivo pharmacokinetic studies revealed thatintranasally administered PEGylated PPI donepezil HCl dendrimeric formulation (Cmax: 98.7±4.89μg/ml) indicated 1.8 and 1.6 times greater concentration of donepezil HCl in the brain as compared to oral donepezil HCl (Cmax: 53±4.21μg/ml) and intranasal API donepezil HCl (Cmax: 62.85±1.4μg/ml). Pharmacodynamic study established greater effect of developed dendrimeric formulation for transportation of donepezil HCl through olfactory route and recovery from memory loss.