Preparation of stable polymer-liposome complexes by a novel approach employing a one-pot method

The purpose of this study was to prepare stable polymer-liposome complexes using a new, improved one-pot method. Complexes prepared by the conventional method were used as reference. The one-pot method combines the vesicle formation and complexation with the polymer in a single step allowing for fewer steps compared to the conventional thin-film method followed by coating. This has the possibility of complexing the polymer on the surface and within the aqueous core of the liposomes. Soya phosphatidylcholine (SoyPC) in combination with different amounts of either dioleoyl trimethylammoniumpropane (DOTAP, positively charged) or egg phosphatidylglycerol (Egg PG, negatively charged) were complexed with alginate or chitosan, respectively. All the alginate-liposome complexes were larger compared to the naked liposomes and the zeta potential changed from positive to negative after complexation with the polymer. Polydispersity index (PDI) analysis showed narrow size distributions implying homogenous populations.

The best stability was obtained by employing 20 mol% DOTAP in the membrane. This formulation was stable during the whole four months period when the stability test was performed. The chitosan-liposome complexes were generally difficult to extrude and were larger than the alginate-liposome complexes due to the need for a larger pore size in the membrane during extrusion. Based on these results, the one-pot method can be used for preparing stable alginate-liposome complexes. For the chitosan-liposome complexes alternative methods for size reduction should be investigated.

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Materials

Phosphatidylcholine from soyabean (SoyPC, Lipoid S PC, Approximate Mw = 787 Da, >98% phosphatidylcholine) was a kind gift from Lipoid GmbH (Ludwigshafen, Germany). Dioleoyl trimethylammoniumpropane (DOTAP) a cationic lipid and phosphatidylglycerol (Egg PG) an anionic lipid, were purchased from Avanti Polar Lipids, Inc. (Alabaster, USA). Chitosan hydrochloride (Protasan UPCL 213, Novamatrix DD = 83%, Mw = 3.1 ×10⁵ Da) was purchased and sodium alginate (Protanal LF 10/60, Mw = 1.47 ×10⁵ Da) was a gift, from FMC Biopolymer AS (Sandvika, Norway). Sodium dihydrogen phosphate monohydrate, disodium hydrogen phosphate dihydrate and chloroform of analytical grade were purchased from Merck (Darmstadt, Germany).

Joseph Azumah, Gro Smistad, Marianne Hiorth,
Preparation of stable polymer-liposome complexes by a novel approach employing a one-pot method,
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2022, 129924, ISSN 0927-7757,
https://doi.org/10.1016/j.colsurfa.2022.129924.