Improving oral bioavailability and pharmacokinetics of liposomal metformin by glycerolphosphate-chitosan microcomplexation

The purpose of this study was to develop a new delivery system capable of improving bioavailability and controlling release of hydrophilic drugs. Metformin-loaded liposomes were prepared and to improve their stability surface was coated with chitosan cross-linked with the biocompatible beta-glycerolphosphate. X-ray diffraction, differential scanning calorimetry, as well as rheological analysis were performed to investigate interactions between chitosan and beta-glycerolphosphate molecules. The entrapment of liposomes into the chitosan-beta-glycerolphosphate network was assessed by scanning electron microscopy and transmission electron microscopy. Swelling and mucoadhesive properties as well as drug release were evaluated in vitro while the drug oral bioavailability was evaluated in vivo on Wistar rats. Results clearly showed that, compared to control, the proposed microcomplexes led to a 2.5-fold increase of metformin T-max with a 40% augmentation of the AUC/D value.