OBJECTIVETo investigate various methods for constructing soybean lecithin (SL)-based vesicles and evaluate the permeation-enhancing effect of SL-based vesicles on the penetration of insulin through buccal mucosa.

METHODSThe ultrasonic method, high speed shear method and high pressure homogenization method were respectively used to prepare the SL-based vesicles, and the particle size of the vesicles was measured with photon correlation spectrometry (PCS). The penetration rate of insulin through porcine buccal mucosa was investigated with the Valia-Chien diffusion cells.

RESULTSThe average particle sizes of 3 formulations of SL-based vesicles were 97.39, 85.60, and 100.60 nm when prepared by ultrasonic method, and were 58.7, 88.7, and 91.9 nm when prepared by high pressure homogenization method. Both vesicles presented good stability. However, the SL-based vesicles prepared by high speed shear method had larger average diameters and were found to be unstable. Transmission electron microscopy showed that SL-based vesicles had a spherical shape and the result accorded with PCS. The permeation flux of insulin of formulation 1 and control solution were 0.0024 and 0.0008 IU x ml(-1) x min(-1), respectively. The accumulative amount of formulation 1 at 180 min was (0.436 +/- 0.010 ) IU x ml(-1), which was 1.46 times higher than the control solution.

CONCLUSIONSThe SL-based vesicles obtained using high pressure homogenization method are characterized by small particle size, narrow distribution, good stability, and powerful permeation-enhancing effect, which enables them to be good carriers for the buccal delivery of insulin.