Stearic Acid and Glyceryl Monostearate Based Self-Assembled Vesicles: Preparation and In vitro Evaluation

The objective of the present investigation was to study the spontaneous self-assembling behavior of stearic acid in the presence of its monoglyceride and to evaluate its potential to be used as drug delivery vehicle. The interesting feature of this system lies in spontaneous formation of vesicles on hydration of molten mixture of stearic acid (SA) and glyceryl monostearate (GMS) without using any solvent. The 1H NMR spectrum of a sample was devoid of signals from fatty acid side chain protons, suggesting that upon interaction between SA and GMS, it adopts an orientation in which fatty acid side chains exists in hydrophobic domains separated from hydrophilic headgroup. A single endothermic event of optimized formulation was obtained as the inflection point of the jump heat capacity at 57 degrees C. To evaluate its feasibility to be used as drug delivery vehicle, ciprofloxacin HCl (CFn) was chosen as a model drug. The entrapment efficiency of CFn was found to be 13 +/- 3% and 32 +/- 4.2% when the formulation was prepared at pH 5.5 and 9.5, respectively. When viewed through polarizing filter, discernible Maltese cross was observed describing bilayer structure. The viscosity profile demonstrates that the both of the formulation follow Newtonian flow. The size of the vesicles was found to be in the range of 1-3 mu m. In a 24 hours study period the VES-1c and VES-2c formulation released 95.8% and 82.3% of the drug, respectively. The formulation was found to be resistant towards osmotic stress. These formulations were found to be biocompatible when studied against J774 macrophages.