Abstract
The use of archaeal lipids and their artificial analogues, also known as bolalipids, represents a promising approach for the stabilization of classical lipid vesicles for oral application. In a previous study, we investigated the mixing behavior of three single-chain alkyl-branched bolalipids PC-C32(1,32Cn)-PC (n = 3, 6, 9) with either saturated or unsaturated phosphatidyl-cholines. We proved, that the bolalipids PC-C32(1,32C6)-PC and PC-C32(1,32C9)-PC show miscibility with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). In the present work, we extended our vesicle system to natural lipid mixtures using phosphatidylcholine from soy beans, and we investigated the effect of incorporated bolalipids on the integrity of these mixed liposomes (bolasomes) in different gastrointestinal fluids using a dithionite assay and a calcein release assay in combination with particle size measurements. Finally, we also studied the retention of calcein within the bolasomes during freeze-drying. As a main result, we could show that in particular PC-C32(1,32C6)-PC is able to increase the stability of bolasomes in simulated gastric fluid—a prerequisite for the further use of liposomes as oral drug delivery vehicles.
Highlights
Liposomes were discovered in 1965 by Bangham and have become the most successful drug delivery system [1,2]
In the case PC-C32(1,32C9)-PC, these bolasomes are stable in storage at 4 ◦C for at least three weeks, which was checked by dynamic light scattering (DLS) measurements
We investigated three different bolalipid/phospholipid mixtures in order to discover whether bolalipids could increase the integrity of liposomes in gastrointestinal fluids
Summary
Liposomes were discovered in 1965 by Bangham and have become the most successful drug delivery system [1,2]. It is necessary to stabilize liposomes in order to use them for oral administration. For this purpose, various approaches were evolved in recent years including the variation of the lipid composition using phospholipids with high phase transitions and/or cholesterol [15,19,20], surface coating with polymers, proteins and chitosan [4,6,7,21,22,23,24,25], or the incorporation of bile salts into the lipid bilayer [5,26,27,28,29,30]. It is important to find a compromise between the stability of modified liposomes and the effective protection of their cargo, as well as a timely release of the loaded substances
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