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Chemical coupling of thiolated chitosan to preformed liposomes improves mucoadhesive properties

Authors Gradauer, Vonach, Leitinger G, Kolb, Fröhlich E, Roblegg, Bernkop-Schnürch A , Prassl R

Received 17 January 2012

Accepted for publication 22 February 2012

Published 21 May 2012 Volume 2012:7 Pages 2523—2534


Review by Single anonymous peer review

Peer reviewer comments 3

Kerstin Gradauer,1 Caroline Vonach,1 Gerd Leitinger,2,3 Dagmar Kolb,2,3 Eleonore Fröhlich,3 Eva Roblegg,4 Andreas Bernkop-Schnürch,5 Ruth Prassl1,6

1Institute of Biophysics and Nanosystems Research, Austrian Academy of Sciences, Graz, Austria; 2Institute of Cell Biology, Histology, and Embryology, Medical University of Graz, Graz, Austria; 3Center for Medical Research, Medical University of Graz, Graz, Austria; 4Institute of Pharmaceutical Sciences/Pharmaceutical Technology, Karl-Franzens University, Graz, Austria; 5Department of Pharmaceutical Technology, Institute of Pharmacy, University of Innsbruck, Innsbruck, Austria; 6Ludwig Boltzmann Institute for Lung Vascular Research, Graz, Austria

Aim: To develop mucoadhesive liposomes by anchoring the polymer chitosan-thioglycolic acid (chitosan-TGA) to the liposomal surface to target intestinal mucosal membranes.
Methods: Liposomes consisting of phosphatidylcholine (POPC) and a maleimide-functionalized lipid were incubated with chitosan-TGA, leading to the formation of a thioether bond between free SH-groups of the polymer and maleimide groups of the liposome. Uncoated and newly generated thiomer-coated liposomes were characterized according to their size, zeta potential, and morphology using photon correlation spectroscopy and transmission electron microscopy. The release behavior of calcitonin and the fluorophore/quencher-couple ANTS/DPX (8-aminonaphthalene-1,3,6-trisulfonic acid/p-xylene-bis- pyridinium bromide) from coated and uncoated liposomes, was investigated over 24 hours in simulated gastric and intestinal fluids. To test the mucoadhesive properties of thiomer-coated and uncoated liposomes in-vitro, we used freshly excised porcine small intestine.
Results: Liposomes showed a concentration-dependent increase in size – from approximately 167 nm for uncoated liposomes to 439 nm for the highest thiomer concentration used in this study. Likewise, their zeta potentials gradually increased from about –38 mV to +20 mV, clearly indicating an effective coupling of chitosan-TGA to the surface of liposomes. As a result of mucoadhesion tests, we found an almost two-fold increase in the mucoadhesion of coupled liposomes relative to uncoupled ones. With fluorescence microscopy, we saw a tight adherence of coated particles to the intestinal mucus.
Conclusion: Taken together, our current results indicate that thiomer-coated liposomes possess a high potential to be used as an oral drug-delivery system.

Keywords: thiomer, liposome, mucoadhesion, chitosan-thioglycolic acid, oral drug delivery

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