Lecithin-Based Microemulsion of a Peptide for Oral Administration: Preparation, Characterization, and Physical Stability of the Formulation

Abstract

The objective of our study was to prepare and characterize a stable microemulsion formulation for oral administration of a peptide, e.g., rh-insulin. The microemulsions were prepared using Labrafil M 1944 CS, Phospholipon 90G (lecithin), absolute alcohol, and bidistilled water. Commercially available soybean lecithins (namely, Phospholipon 80, phosphatidylcholine purity 76 +/- 3%, and Phospholipon 90G, phosphatidylcholine purity 93 +/- 3%) were used in the study. The results showed that the phase diagram obtained using a low purity lecithin was not similar to that obtained with a high purity lecithin. We observed that the microemulsion area was wider at the phase diagram obtained with the higher purity lecithin. We found that the extent of the microemulsion region depended upon both the purity of the lecithin and the surfactant/co-surfactant (s/co-s) mixing ratios (K(m)). The rheological studies showed that microemulsions followed a Newtonian behavior. Such physical characteristics as viscosity, turbidity, density, conductivity, refractive index, droplet size, physical appearance, and phase separation of the microemulsion were measured at different temperatures (4 degrees C, 25 degrees C, and 40 degrees C) during 6 months. The results indicated that the physical characteristics of the developed microemulsions did not change under different storage temperatures (p > 0.05).

Benzyl Benzoate-Loaded Microemulsion for Topical Applications: Enhanced Dermatokinetic Profile and Better Delivery Promises

“…The refractive index values were of the studied formulations and were found to range between 1.418 and 1.450 against water. The consistency in RI values of all developed formulations is an indication of regular microemulsion structure (44).…”

“…The relationship between the phase behavior of a mixture and its composition can be established with the aid of a phase diagram (44). Figure 2 shows the obtained phase diagrams from all the S mix compositions.…”

Intestinal permeation enhancers for oral peptide delivery

“…Provalis (UK) developed a w/o microemulsion (Macrulin TM ) to improve oral delivery of insulin. Macrulin TM is composed of an external oil phase (Labrafil® M1944CS) with an aqueous disperse phase stabilised with lecithin and alcohol [297]. The optimised dispersion exhibited physical stability for at least six months at 4°C, 25°C and 40°C, although pseudo-ternary phase diagrams prepared during the preparation of the microemulsion clearly indicate the destabilising effect of water [297].…”

Preparation and Evaluation of Topical Microemulsion System Containing Metronidazole for Remission in Rosacea

“…In the pseudo-ternary phase diagram, the presence and extent of the microemulsion region depends on the partition coefficient of co-surfactant and the surfactant/ co-surfactant ratio. 38,[40][41][42]46) The butanol used in this study has medium level water solubility; its affinity to the IPM used in Before treatment: baseline (initial assessment). After treatment: at the end of the study (at 6th week, final assessment).…”