title: Characterization of insulin-loaded liposome using column-switching HPLC.
abstract: We evaluated the drug-encapsulation state of insulin (INS)-loaded liposome using a novel column-switching HPLC system that can automatically separate unloaded drug from encapsulated drug by hydrophobic interaction. When the INS-loaded liposome was dispersed in water (pH 7.4), the encapsulation efficiency (EE) obtained by the column-switching HPLC system was consistent with that obtained by a conventional ultracentrifugation method. However, the INS-loaded liposome dispersed in 0.1% acetic acid (pH 3.3) showed disagreement between the EEs obtained by both methods. Considering the results of particle size, zeta potential, and transmission electron microscope (TEM) observations, we hypothesized that the column-switching HPLC method was able to distinguish INS adsorbed onto the liposome surface from the encapsulated INS, although an ultracentrifugation method precipitated the adsorbed INS onto the liposome surface along with the encapsulated INS. Therefore, the novel column-switching HPLC system may be a more accurate and useful technique for characterization and optimization of the INS-loaded liposome formulation.
authors.affiliation: Pharmaceutical Science & Technology Unit, Eisai Co., Ltd., 1 Kawashimatakehaya-machi, Kakamigahara, Gifu 501-6195, Japan; Laboratory of Pharmaceutical Engineering, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu 501-1196, Japan.
authors.forename: Naozumi
authors.initials: N
authors.lastname: Ohnishi
authors.affiliation: Laboratory of Pharmaceutical Engineering, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu 501-1196, Japan.
authors.forename: Shota
authors.initials: S
authors.lastname: Tanaka
authors.affiliation: Laboratory of Pharmaceutical Engineering, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu 501-1196, Japan.
authors.forename: Kohei
authors.initials: K
authors.lastname: Tahara
authors.affiliation: Laboratory of Pharmaceutical Engineering, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu 501-1196, Japan. Electronic address: takeuchi@gifu-pu.ac.jp.
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Takeuchi
mesh_terms: D002626:Chemistry, Pharmaceutical / Q000379:methods*; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D007004:Hypoglycemic Agents / Q000008:administration & dosage / Q000737:chemistry*; D007328:Insulin / Q000008:administration & dosage / Q000737:chemistry*; D008081:Liposomes; D046529:Microscopy, Electron, Transmission; D010316:Particle Size
chemical_list: D007004:Hypoglycemic Agents; D007328:Insulin; D008081:Liposomes
keywords: Encapsulation; Hydrophobic-interaction; Insulin; Liposome; Solid-phase extraction