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Abstract
The present study involved design of dexamethasone-sodium phosphate (DEX) loaded mucoadhesive
chitosan nanoparticles for topical ocular delivery to improve its precorneal retention
and corneal permeability. The chitosan-sodium tripolyphosphate nanoparticle (CS-NPs)
was developed through ionotropic-gelation technique. The developed CS-NPs were coated
with hyaluronic-acid (HA) to make discrete, free-flowing NPs and to improve their
mucoadhesive characteristics. The particle-size, zeta-potential and polydispersity-index
were determined by Malvern-Zetasizer. The average size of the CS-NPs ranged from 305.25±14.29nm
(without HA-coating and before freeze-drying) to 400.57±15.23nm (HA-coated and after
freeze-drying). Due to the polyanionic nature of HA, reversing of zeta-potentials
from +32.55±4.15 to -33.74±3.45 was observed. Polydispersity-indices varied from 0.178±0.067
(before freeze-drying of HA-coated F2) to 0.427±0.028 (after freeze-drying of HA-coated
F2). The encapsulation and loading capacity of around 72.95% and 14.51% respectively
were found in optimized CS-NPs. In simulated tear fluid 75.84% cumulative amount of
released drug was detected and the in-vitro release results suggested the mechanism
of drug release was Fickian-diffusion type. The clarity, pH, refractive index, surface
tension and viscosity of the suspensions of DEX-CS-NPs were found promising for ocular
use. Stability study on nanoparticles revealed no significant changes were observed
in particle-size, encapsulation, drug release and physicochemical characteristics
at 25°C for 3-months storage.