title: Improving drug retention in liposomes by aging with the aid of glucose.
abstract: This paper describes a novel method to improve drug retention in liposomes for the poorly water-soluble (lipophilic) model drug asulacrine (ASL). ASL was loaded in the aqueous phase of liposomes and the effects of aging conditions and drug loading levels on drug retention were investigated using an in vitro bio-relevant drug release test established in this study. The status of intra-liposomal drug was investigated using differential scanning calorimetry (DSC) and cryo-transmission electron microscopy (cryo-TEM). Pharmacokinetics and venous tolerance of the formulations were simultaneously studied in rabbits following one-hour intravenous infusion via the ear vein. The presence of glucose during aging was found to be crucial to accelerate drug precipitation and to stabilize the liposomal membrane with high drug loading (8.9% over 4.5% w/w) as a prerequisite. Although no drug crystals were detected, DSC showed a lower phase-transition peak in the glucose-assisted aged ASL-liposomes, indicating interaction of phospholipids with the sugar. Cryo-TEM revealed more 'coffee bean' like drug precipitate in the ASL-liposomes aged in the glucose solution. In rabbits, these liposomes gave rise to a 1.9 times longer half-life than the fresh liposomes, with no venous irritation observed. Inducing and stabilizing drug precipitation in the liposome cores by aging in the presence of sugar provided an easy approach to improve drug retention in liposomes. The study also highlighted the importance of bio-relevance of in vitro release methods to predict in vivo drug release.
authors.affiliation: School of Pharmacy, The University of Auckland, Auckland 1142, New Zealand; China Pharmaceutical University, Nanjing 210009, PR China.
authors.forename: Wenli
authors.initials: W
authors.lastname: Zhang
authors.affiliation: School of Pharmacy, The University of Auckland, Auckland 1142, New Zealand; School of Pharmacy, Pharmacy Australia Centre of Excellence, University of Queensland, Brisbane, QLD 4102, Australia.
authors.forename: James R
authors.initials: JR
authors.lastname: Falconer
authors.affiliation: Auckland Cancer Society Research Centre, The University of Auckland, New Zealand.
authors.forename: Bruce C
authors.initials: BC
authors.lastname: Baguley
authors.affiliation: School of Pharmacy, The University of Auckland, Auckland 1142, New Zealand.
authors.forename: John P
authors.initials: JP
authors.lastname: Shaw
authors.affiliation: School of Pharmacy, The University of Auckland, Auckland 1142, New Zealand.
authors.forename: Manju
authors.initials: M
authors.lastname: Kanamala
authors.affiliation: School of Pharmacy, The University of Auckland, Auckland 1142, New Zealand.
authors.forename: Hongtao
authors.initials: H
authors.lastname: Xu
authors.affiliation: China Pharmaceutical University, Nanjing 210009, PR China.
authors.forename: Guangji
authors.initials: G
authors.lastname: Wang
authors.affiliation: China Pharmaceutical University, Nanjing 210009, PR China. Electronic address: jianping1293@163.com.
authors.forename: Jianping
authors.initials: J
authors.lastname: Liu
authors.affiliation: School of Pharmacy, The University of Auckland, Auckland 1142, New Zealand. Electronic address: z.wu@auckland.ac.nz.
authors.forename: Zimei
authors.initials: Z
authors.lastname: Wu
mesh_terms: D000677:Amsacrine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000737:chemistry; D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage* / Q000737:chemistry; D002152:Calorimetry, Differential Scanning; D011232:Chemical Precipitation; D002626:Chemistry, Pharmaceutical / Q000379:methods; D065546:Drug Liberation; D005947:Glucose / Q000737:chemistry*; D006207:Half-Life; D007262:Infusions, Intravenous; D008081:Liposomes; D046529:Microscopy, Electron, Transmission; D044367:Phase Transition; D011817:Rabbits; D012995:Solubility
chemical_list: D000970:Antineoplastic Agents; D008081:Liposomes; D000677:Amsacrine; D005947:Glucose; C042315:asulacrine
keywords: Active loading; Aging; Drug retention; Glucose; Liposomes