An investigation into the role of surfactants in controlling particle size of polymeric nanocapsules containing penicillin-G in double emulsion

Preparation, characterization and drug release behavior of loaded polybutyl adipate (PBA) nanocapsules with penicillin-G are described here. The nanocapsules were produced using a double emulsion solvent evaporation technique, using dichloromethane as an organic solvent and Tween and Span as surfactants. In this process, a mixture of glycerin and water was used instead of the traditional stabilizer system in the preparation of double emulsion. The influence of surfactants on the property of nanocapsules was discussed in detail. The effects of Span and Tween to modify the size of the nanocapsules were different. The mean diameters of penicillin-G loaded nanocapsules ranged from 75 nm to 638 nm, and were dependent on the types and content of the surfactants. The encapsulation efficiencies and drug release rates were also affected by the surfactants in the preparation process. It was found that the encapsulation efficiencies of penicillin-G enhanced up to 76.8% with the increase in Span and Tween contents. Increasing Span concentration as an inner surfactant results in the remaining of penicillin-G mostly sealed in the inner aqueous phase and increasing Tween concentration as the outer surfactant enhanced the viscosity of external water phase, which decreased the rate of penicillin-G diffusion from the inner water phase to the outer water phase. Interestingly, the in vitro drug release profiles exhibited a significant burst release, followed by a lag phase of little or no release. Penicillin-G loaded nanocapsules with low concentrations of both surfactants tend to have higher burst release. Under optimum formulation conditions, the encapsulation of penicillin-G can reach up to 60% and the burst release can also fall below 45%. In this case, the fact that the nanocapsules have only 130 nm diameter will be important. (C) 2008 Elsevier Masson SAS. All rights reserved.