Formulation Optimization of Metronidazole Loaded Chitosan Microspheres for Wound Management by 3-Factor, 3-Level Box-Behnken Design

Abstract

The aim of present study was to statistically optimize the formulation parameters of metronidazole loaded chitosan microspheres for maximum entrapment and controlled release. A 3-factor, 3-level Box-Behnken design was used to derive a second order polynomial equation and construct 3D surface plots to predict the effect on responses. The independent variables selected were drug (X1), cross linking agent (X2) and chitosan (X3) concentration whereas dependent variables studied were mean diameter (Y1) and entrapment efficiency (Y2) of microspheres. The response surface methodology (RSM) and multiple response optimization were used to select optimal formulation with maximum entrapment and particle size in range. The maximum entrapment (82.56±2.98%) was achieved with 400mg metronidazole, 2% (w/v) tripolyphosphate and 3% (w/v) chitosan. The observed responses coincided well with the predicted values from the RSM optimization technique. The optimal formulation was subsequently characterized in terms of morphology, release kinetics, and antimicrobial activity. Scanning electron microscopy confirmed the smooth spherical microspheres in the size range of 9.65±0.68μm to 22.49±0.79μm. Kinetic models revealed that drug release followed non-Fickian release pattern. Finally, drug bioactivity was found to remain intact after microencapsulation Thus, Box-Behnken design demonstrated the role of the derived equation and 3D surface plots in predicting the values of dependent variables for the preparation and optimization of metronidazole loaded chitosan microspheres. Keywords: Box-behnken design, chitosan, microspheres, metronidazole, wound healing