Arsonoliposomes: Effect of Lipid Composition on Their Stability and Morphology

Abstract

The influence of the lipid composition of arsonoliposomes on their membrane integrity was investigated to evaluate whether it is possible to combine their action with drugs that can be encapsulated in their aqueous interior. This was investigated by measuring the retention of vesicle-encapsulated calcein (100 mM) during incubation, in the absence and presence of serum proteins. Liposomes containing various concentrations of arsonolipid (with the palmitoyl side chain) as well as egg-lecithin (phosphatidylcholine, PC) and cholesterol (lipid/chol 2:1 mol:mol) were prepared. In some experiments, PC was replaced by the synthetic phospholipid DSPC. All PC/arsonoliposomes tested are stable after 24 h of incubation in buffer at 37 degrees C. After incubation in the presence of serum proteins, arsonoliposomes that contain low amounts of arsonolipid (up to 5 mol% of the lipid content without cholesterol) are stable, whereas increased release of calcein is observed when vesicle arsonolipid concentration is raised (from 5 to 15 mol%). Further increase of arsonolipid content results in immediate decrease of calcein latency while the remaining calcein is rapidly released during incubation. DSPC/arsonoliposomes are comparably more stable, and membrane integrity is independent of the vesicle arsonolipid content, in the range investigated (15-40 mol% of the lipid content without cholesterol). Thereby, we conclude that more stable arsonoliposomes that incorporate high arsonolipid concentrations may be produced when PC is replaced by DSPC. The latter arsonoliposomes provide a system that may be used for combining arsonolipid activity with the activity of other drugs.

Does the lipid membrane composition of arsonoliposomes affect their anticancer activity? A cell culture study

“…As seen in Fig. 3, while both types (PEGylated and non-PEGylated PC arsonoliposomes) demonstrate high integrity during incubation in buffer (calcein latency is always higher than 85%) the nonPEGylated PC arsonoliposomes are very unstable during incubation in presence of serum proteins (calcein latency is 65%, after 5 min of incubation and only 15.4% after 24 h), as demonstrated also before [6]. However, PEGylation results in a significant stabilization of these arsonoliposomes, since in the presence of FCS the calcein latency is 70% after 5 min and 55% after 24 h of incubation (Fig.…”

“…Recently it was noticed that arsonoliposomes are sensitive to glutathione and their integrity decreases when they are incubated in glutathione-rich solutions [12]. However, some arsonoliposome types with high integrity (as DSPC-based and PEGylated arsonoliposomes) [6,7] which were lately demonstrated to have better bioavailabity after in vivo injection (compared to arsonoliposomes with low integrity (PC- based)) [9], were not glutathione-sensitive [12]. In order to evaluate if the previously demonstrated anticancer activity of the more leaky PC-based arsonoliposomes [3,4] is not abolished in the case of more stable arsonoliposomes and to study the general effect of arsonoliposome lipid composition on their activity, we investigated herein the anticancer activity of various types of stable arsonoliposomes on different types of cancer cells, in culture.…”

“…As summarized before [2], promising results were obtained with some of the arsonoliposome types prepared, for which a differential toxicity towards cancer and normal cells was demonstrated [3,4] as well as in vitro antiparasitic activity [5]. However, it has been found that the membrane integrity of arsonoliposomes [6,7] and their in vivo distribution (of arsenic) [8,9] are influenced by the lipid composition of the arsonoliposome membrane, and this has been pinpointed as the reason -or at least one of the reasons -for the different antiparasitic activities demonstrated (in vitro and in vivo), by different arsonoliposome types (with different lipid compositions) [10].…”

“…Arsonolipid (Ars)-containing liposomes were prepared as described previously [1,2,6,7]. In brief, lipids (after removing the organic solvents with a nitrogen stream) were mixed with 5 mM phosphate buffer (pH 7.4) and 20 mM NaCl and magnetically stirred vigorously on a hot plate for 4 h at 70 -808C.…”

Incorporation of PEG-lipids in arsonoliposomes results in formation of highly stable arsenic-containing vesicles

“…1016/j.chemphyslip.2005.11.003 towards cancer cells (compared to normal cells incubated under identical conditions) and anti-parasitic activity (in vitro) (Gortzi et al, 2002(Gortzi et al, , 2003Antimisiaris et al, 2003), and are therefore worthy of further exploitation. By changing their lipid composition, arsonoliposome stability in vitro (and possibly in vivo) can be modulated (Fatouros et al, 2001;Piperoudi et al, 2005). As demonstrated in the first in vivo disposition study performed , arsonoliposome circulation time in the bloodstream is inadequate for applications in which prolonged circulation in the bloodstream and/or distribution in tissues other than those of the reticulo-endothelial system (RES), is required.…”