In-vitro antileishmanial and trypanocidal activities of arsonoliposomes and preliminary in-vivo distribution in BALB/c mice

Synthesis of Novel Arsonolipids and Development of Novel Arsonoliposome Types

Arsonolipids represent a class of arsenic-containing compounds with interesting biological properties either as monomers or as nanostructure forming components, such as arsonoliposomes that possess selective anticancer activity as proven by in vitro and in vivo studies. In this work, we describe, for the first time, the synthesis of novel arsono-containing lipids where the alkyl groups are connected through stable ether bonds. It is expected that this class of arsonolipids, compared with the corresponding ester linked, will have higher chemical stability. To accomplish this task, a new methodology of general application was developed, where a small arsono compound, 2-hydroxyethylarsonic acid, when protected with thiophenol, can be used in an efficient and simple way as a building block for the synthesis of arsono-containing lipids as well as other arsono-containing biomolecules. Thus, besides the above-mentioned arsonolipid, an arsono cholesterol derivative was also obtained. Both ether arsonolipid and arsono cholesterol were able to form liposomes having similar physicochemical properties and integrity to conventional arsonoliposomes. Furthermore, a preliminary in vitro anticancer potential assessment of the novel ether arsonolipid containing liposomes against human prostate cancer (PC-3) and Lewis lung carcinoma (LLC) cells showed significant activity (dose- and time-dependent), which was similar to that of the conventional arsonoliposomes (studied before). Given the fact that novel arsonolipids may be more stable compared to the ones used in conventional arsonoliposomes, the current results justify further exploitation of the novel compounds by in vitro and in vivo studies.

Nanotechnological interventions for treatment of trypanosomiasis in humans and animals

Trypanosomiasis is a parasitic infection caused by Trypanosoma. It is one of the major causes of deaths in underprivileged, rural areas of Africa, America and Asia. Depending on the parasite species responsible for the disease, it can take two forms namely African trypanosomiasis (sleeping sickness) and American trypanosomiasis (Chagas disease). The complete life-cycle stages of trypanosomes span between insect vector (tsetse fly, triatomine bug) and mammalian host (humans, animals). Only few drugs have been approved for the treatment of trypanosomiasis. Moreover, current trypanocidal therapy has major limitations of poor efficacy, serious side effects and drug resistance. Due to the lack of economic gains from tropical parasitic infection, it has always been neglected by the researchers and drug manufacturers. There is an immense need of more effective innovative strategies to decrease the deaths associated with this diseases. Nanotechnological approaches for delivery of existing drugs have shown significant improvement in efficacy with many-fold decrease in their dose. The review emphasizes on nanotechnological interventions in the treatment of trypanosomiasis in both humans and animals. Current trypanocidal therapy and their limitations have also been discussed briefly. Graphical abstract.

Sodium arsenite augments sensitivity of Echinococcus granulosus protoscoleces to albendazole

This study aimed to observe the effects of sodium arsenite (NaAsO₂) on apoptosis of Echinococcus granulosus protoscoleces induced by albendazole (ABZ), and to explore the potential mechanism of NaAsO₂. According to the following final concentrations, the experimental groups were divided into 10 μM NaAsO₂, 20 μM NaAsO₂, 80 μM ABZ, 10 μM NaAsO₂+80 μM ABZ, and 20 μM NaAsO₂+80 μM ABZ. Viability was detected with 0.1% eosin staining. The ultrastructural alterations were visualized by scanning electron microscopy. Caspase-3 activity was assessed with colorimetric assay. Meanwhile, ELISA or WST were applied to detect the activities of antioxidases in NaAsO₂ treatment groups. The maximum protoscolicidal effect was seen with the combination 20 μM NaAsO₂+80 μM ABZ. The ultrastructural damage detected after NaAsO₂+ABZ incubation were greater than those caused by ABZ alone and its primary damage site was the tegument of the parasite. The caspase-3 activity was clearly higher in protoscoleces treated with the combination of NaAsO₂+ABZ than when drugs were used separately. The activities of NQO-1, HO-1, GST, and SOD were significantly lower in protoscoleces incubated with NaAsO₂ than the untreated controls (P < 0.05). According to our results, ABZ could induce protoscoleces apoptosis, and NaAsO₂ could significantly augment sensitivity of protoscoleces to ABZ.

Organic Arsenicals as Functional Motifs in Polymer and Biomaterials Science

Arsenic (As) exhibits diverse (bio)chemical reactivity and biological activity depending upon its oxidation state. However, this distinctive reactivity has been largely overlooked across many fields owing to concerns regarding the toxicity of arsenic. Recently, a clinical renaissance in the use of arsenicals, including organic arsenicals that are known to be less toxic than inorganic arsenicals, alludes to the possibility of broader acceptance and application in the field of polymer and biomaterials science. Here, current examples of polymeric/macromolecular arsenicals are reported to stimulate interest and highlight their potential as a novel platform for functional, responsive, and bioactive materials.

New Approaches to Overcome Transport Related Drug Resistance in Trypanosomatid Parasites

Leishmania and Trypanosoma are members of the Trypanosomatidae family that cause severe human infections such as leishmaniasis, Chagas disease, and sleeping sickness affecting millions of people worldwide. Despite efforts to eradicate them, migrations are expanding these infections to developing countries. There are no vaccines available and current treatments depend only on chemotherapy. Drug resistance is a major obstacle for the treatment of these diseases given that existing drugs are old and limited, with some having severe side effects. Most resistance mechanisms developed by these parasites are related with a decreased uptake or increased efflux of the drug due to mutations or altered expression of membrane transporters. Different new approaches have been elaborated that can overcome these mechanisms of resistance including the use of inhibitors of efflux pumps and drug carriers for both active and passive targeting. Here we review new formulations that have been successfully applied to circumvent resistance related to drug transporters, opening alternative ways to solve drug resistance in protozoan parasitic diseases.

Improved antitumor efficacy and reduced toxicity of liposomes containing bufadienolides

Long-circulating liposomes are used extensively nowadays for enhancing the therapeutic effect and reducing the toxicity of anticancer drugs. In this paper, a traditional Chinese medicine, toad venom, which has long been used in the clinic for tumor therapy with unpleasant side effects, was incorporated into poloxamer modified liposomes to increase its antitumor effect and reduce its toxicity. Our preparation of bufadienolides liposomes had a particle size of around 70 nm and an entrapment efficiency of about 87.6%. Lyophilized liposomes well retained their appearance, particle size and encapsulation efficiency for 3 months. The in vitro release results verified the sustained release properties of the bufadienolides liposomes. The concentration of bufadienolides in modified liposomes that caused 50% cell killing was much lower than that of free drug for both Lovo cells and NCI-H157 cells. Compared to the bufadienolides solution and the unmodified liposomes, the bufadienolides liposomes significantly prolonged the retention time and increased the area under the curve in vivo. The antitumor efficiency of the bufadienolides liposomes against mice bearing H22 liver cancer cells and Lewis pulmonary cancer cells were 2.15 and 2.96, respectively, times that of a bufadienolides solution at the same toxicity. The safety test results demonstrated that the bufadienolides liposomes had an LD(50) that was 3.5 times the LD(50) of bufadienolides solution and caused no allergen-related or blood vessel irritation effects. All these results proved that poloxamer modified bufadienolides liposomes have improved antitumor efficacy and safety.

Arsonoliposomes: preparation and physicochemical characterization

Arsonoliposomes (ARSL) which are liposomes that contain arsonolipids in their membranes have shown interesting anticancer and antiparasitic activity in vitro. Their lipid composition (the specific arsonolipids and/or phospholipids used for their preparation, and the relative amounts of each lipid type) highly influences their physicochemical properties as well as their in vivo kinetics and antiparasitic activity; however, their cytotoxicity towards cancer cells is minimally--if at all--modified. ARSL are prepared by a modification of the "one step" method followed or not by sonication (for formation of sonicated or non-sonicated ARSL, respectively). Arsonoliposomes may be composed only of arsonolipids (containing or not cholesterol) [plain ARSL], or they may contain mixtures of arsonolipids with phospholipids (with or without Chol) [mixed ARSL]. Herein, we describe in detail the preparation and physicochemical characterization of ARSL.

Preparation and evaluation of lyophilized liposome-encapsulated bufadienolides

OBJECTIVE

The objective of this study was to prepare bufadienolides-loaded liposome (BU-lipo).

METHODS

The BU-lipo was prepared by a thin-film hydration method involving sonication and lyophilization procedures. The lyophilized BU-lipo was characterized with regard to the appearance and particle size by scanning electron microscopy, transmission electron microscopy, and photon correlation spectroscopy. The entrapment efficiency (EE) of BU-lipo was evaluated by the microdialysis technique.

RESULTS

In the optimal formulation, Lipoid E-80 and the mass ratio of cholesterol to lipid were fixed at 1.25% and 0.05. The media diameters of BU-lipo before and after lyophilization were about 100 nm, and the EEs of bufalin (B), cinobufagin (C), and resibufogenin (R) were 86.5%, 90.0%, and 92.1%, respectively. In the EE study, the probe recoveries of B, C, and R were 21.53 +/- 1.14%, 19.49 +/- 1.34%, and 20.19 +/- 1.25%, respectively, at a flow rate of 4 microL/min by the gain method. The EE of BU-lipo evaluated by microdialysis and ultrafiltration were equivalent.

CONCLUSION

The lyophilized BU-lipo contained trehalose (10%) was stable up to 6 months in a desiccator under 2 degrees C-8 degrees C. The microdialysis technique has a wide application perspective in the investigation of the free-drug concentration of microcarrier systems.

A high yield procedure for the preparation of arsonolipids (2,3-diacyloxypropylarsonic acids)

The crucial step in the preparation of the title arsonolipids starting from the dichloromethane-soluble dithioarsonite CH(2)(OH)CH(OH)CH(2)-As(SPh)(2) is to avoid an internal cyclization during the acylation which protects the primary -OH group from being acylated. This was to a large extent accomplished by using fatty acyl chloride in the presence of the weak base pyridine and controlling the temperature and rate of the acyl chloride addition, giving approximately 70% yields of arsonolipids. The presence of catalytic amounts of 4-dimethylaminopyridine boosted the yields to 82-85%. This yield is a great improvement over the yields (20-55%) previously achieved. The acylating systems (RCO)(2)O or RCOCl and BF(3).Et(2)O gave only moderate yields (25-60%) of arsonolipids.

Effect of free versus liposomal-complexed pentamidine isethionate on biological characteristics of Acanthamoeba castellanii in vitro

Acanthamoeba is an opportunistic protozoan pathogen that can cause blinding keratitis and a rare but fatal encephalitis involving the central nervous system with a very poor prognosis. This is due to limited availability of effective anti-acanthamoebic drugs. Here, we tested whether the use of liposomes can improve the potency of pentamidine isethionate, an anti-amoebic compound. The liposomes consisted of l-alpha-phosphatidylcholine and cholesterol or ergosterol in a molar ratio of 1 : 5. Pentamidine isethionate was incorporated to achieve a final drug to lipid ratio of 1 : 5. At a drug concentration of 10 microg ml(-1), the liposomal drug was >12 times more effective than the free drug at preventing Acanthamoeba binding to human cells and significantly more effective in reducing parasite-mediated human cell cytopathogenicity, compared with the drug alone. Both the free and liposomal drug blocked Acanthamoeba encystation.

In vivo distribution of arsonoliposomes: Effect of vesicle lipid composition

Sonicated arsonoliposomes were prepared using arsonolipid with palmitic acid acyl chain (C16), mixed with 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC-based), and cholesterol (Chol) with a molar ratio C16/DSPC/Chol 8:12:10. PEG-lipid (1,2-distearoyl-sn-glycero-3-phosphoethanolamine conjugated to polyethylenoglycol 2000) containing vesicles (Pegylated-arsonoliposomes) were also prepared. DSPC-based and Pegylated-arsonoliposomes, were administered by intraperitoneal injection in balb/c mice (15 mg arsenic/kg) and the distribution of As in the organs was measured by atomic absorption spectroscopy. Results demonstrate that a high portion of the dose administered is rapidly excreted since 1 h post-injection only about 30-40% of the dose was detected cumulatively in animal tissues. After this, the whole body elimination of arsenic was a slow process with a half-life of 27.6 h for Pegylated-arsonoliposomes, and 83 h, for the DSPC-based ones. For both arsonoliposomes, arsenic distribution was greater in intestines, followed by liver, carcass+skin stomach, spleen, kidney, lung and heart. Different arsenic kinetics in blood between the two liposome types were observed. Compared to the results obtained previously with PC-based arsonoliposomes, both the DSPC-based and Pegylated-arsonoliposomes have better bioavailability. This proves that arsonoliposome lipid composition (and consequently their integrity) influences their pharmacokinetic profile. Thus, the proper arsonoliposome composition should be used according to the intended application.

Trypanocidal activity of arsonoliposomes: Effect of vesicle lipid composition

Sonicated arsonoliposomes were prepared using an arsonolipid with palmitic acid acyl chain (C16), mixed with phosphatidylcholine (PC-based) or 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC-based), and cholesterol (Chol) with a molar ratio C16 /PC or DSPC/ Chol 8:12:10. PEG-lipid (1,2-distearoyl-sn-glycero-3-phosphoethanolamine conjugated to polyethylenoglycol 2000) containing vesicles (pegylated-arsonoliposomes) were also prepared. The in vitro and in vivo trypanocidal activity of the various types of arsonoliposomes was evaluated. Although PC-based arsonoliposomes exhibited in vivo activity on an acute trypanosomiasis animal model, no evidence of activity was demonstrated for DSPC-based or pegylated-arsonoliposomes on a chronic model. Despite the fact that DSPC-based and pegylated-arsonoliposomes have better bioavailability compared to PC-based ones, their in vitro activity is lower than that of PC-based arsonoliposomes, indicating the importance of arsonoliposome lipid composition on their trypanocidal activity and suggesting that further arsonoliposome structure design is required to overcome these disadvantages.

Preparation of dl-2,3,4-trihydroxybutylarsonic acid and dl-2,3-dihydroxybutane-1,4-bis(arsonic acid): starting compounds for novel arsonolipids

The reaction of DL-1,3-butadiene diepoxide and of DL-1,4-dibromo-2,3-butanediol with aqueous alkaline sodium arsenite, "Na(3)AsO(3)", gave mixtures of the title arsonic acids which can be separated by anion exchange resin. Characterization of by-products leads to a better understanding of these reactions. These compounds are valuable intermediates for the preparation of novel arsonic acids and bis(arsonic acids).

Thermal behavior of novel non-sonicated arsonolipid-containing liposomes

The thermal properties of novel arsonolipid-containing liposomes in PBS pH 7.4 and in water in absence and presence of Ca(2+) ions are reported. Liposomes composed of arsonolipids with different acyl chains (C(12), C(16) and C(18)) were prepared by the one step method. Microcalorimetry results showed that (i) the thermotropic transitions of arsonoliposomes (in PBS, pH 7.4, and in water) increase as a function of arsonolipid fatty acyl chain length, (ii) arsonoliposomes of long fatty acyl chain arsonolipids (C(16) and C(18)) showed higher enthalpy and transition temperature in the buffer compared to those observed in water (for arsonoliposomes of C(12)-fatty acyl chain arsonolipid, the order was reversed which might be attributed to their different structure), and (iii) the presence of 2 mM CaCl(2) has more pronounced effects on the thermal properties of arsonoliposomes in distilled water than in buffer, which suggests that the ionic strength of the dispersion medium plays an important role in determining the thermal properties of arsonoliposomes.

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

We investigated the effect of pegylation on the physical stability, morphology and membrane integrity of arsonoliposomes. Arsonoliposomes composed of distearoylglycerophosphocholine (DSPC), cholesterol (Chol) and the palmitoyl side chain arsonolipid (with concentrations ranging from 0 mol% [DSPC/Chol vesicles] to 53 mol% of total lipid) containing either 4 or 8 mol% DPPE-PEG2000 or DSPE-PEG2000, were prepared by sonication. Arsonoliposome membrane integrity was evaluated by measuring the retention of encapsulated calcein in vesicles (during incubation in buffer or fetal calf serum [FCS]) while physical stability was evaluated by measuring vesicle dispersion turbidity (during incubation in water or CaCl(2)). Vesicle morphology was studied by cryo-electron microscopy. Experimental results show that: (i) PEG-lipids are incorporated in arsonoliposomes (as confirmed by the vesicle zeta potential modulation), (ii) pegylation of arsonoliposomes prevents their aggregation and fusion in the presence of calcium ions and (iii) when 8 mol% of PEG-DSPE is incorporated in arsonoliposomes based on their arsonolipid content, two groups of pegylated vesicles are formed: low content arsonoliposomes (<20 mol% arsonolipid) which are highly leaky and high content arsonoliposomes (>27 mol% arsonolipid) which are highly stable (70% calcein retention after 24h incubation in fetal calf serum [FCS]). In addition to high membrane integrity, the high content pegylated arsonoliposomes are morphologically perfect round-shaped vesicles without the sharp edges typically observed with non-pegylated DSPC-containing arsonoliposomes.

Physical Stability of Sonicated Arsonoliposomes: Effect of Calcium Ions

The physical stability of sonicated arsonoliposomes in the absence and presence of Ca(2+) ions is evaluated. Cholesterol-containing arsonoliposomes composed of arsonolipids [having different acyl chains (C(12)-C(18))], or mixtures of arsonolipids with phospholipids (phosphatidylcholine or distearoyl-phosphatidylcholine) were prepared, and physical stability was evaluated in the absence and presence of CaCl(2), by vesicle dispersions turbidity measurements and cryo-electron microscopy morphological assessment. In some cases, vesicle zeta-potential was measured, under identical conditions. Results demonstrate that self-aggregation of the vesicles studied is low and influenced by the acyl chain length of the arsonolipid used, whereas calcium-induced aggregation is higher, correlating well with the decreased values of vesicle zeta-potential in the presence of Ca(2+) ions (weaker electrostatic repulsion). Acyl chain length of arsonolipids used has a significant quantitative effect on Ca(2+)-induced vesicle aggregation mainly for arsonoliposomes that contain phospholipids (mixed), compared with the vesicles that consist of plain arsonolipids (significant effect only for initial aggregation at time 0). Another difference between plain and mixed arsonoliposomes is that for mixed arsonoliposomes Ca(2+)-induced increases in turbidity are irreversible by ethylenediaminotetraacetic acid, suggesting that vesicle fusion is taking place. This was confirmed by cryo-electron microscopy observations. Finally, when phosphatidylcholine is replaced by distearoyl-phosphatidylcholine, arsonoliposomes are more stable in terms of self-aggregation, but in the presence of calcium, the turbidity and morphology results are similar.

The effect of pH on the electrophoretic behaviour of a new class of liposomes: arsonoliposomes

Herein we report the effect of pH on the surface charge of a new class of liposomes: arsonoliposomes. Plain or mixed arsonoliposomes with cholesterol (Chol) and distearoyl-phosphatidylcholine (DSPC) in 1:1 molar ratio were prepared with lauryl-(C12), myristoyl-(C14) and palmitoyl-(C16) acyl side chain arsonolipids. The one step hydration method was used for vesicle preparation and zeta potential measurements were performed in the pH range from 3 to 9. The results revealed that these lipids hold a negative surface charge at all pH values investigated. The presence of cholesterol in 1:1 molar ratio results in higher zeta potential compared with plain arsonoliposomes with the exception of palmitoyl-(C16) acyl chain arsonolipids in neutral and slightly basic pH values. Oppositely, the DSPC (1:1 molar ratio) containing arsonoliposomes had lower values of zeta potential compared with plain arsonoliposomes. Concluding, the experimental results reveal that zeta potential of arsonoliposomes is indeed modified when the vesicles are incubated in environments with different acidity. In most cases these changes are in accordance with the ionization pattern of the arsonolipid headgroup, while some peculiar deviations may be connected with the known difference in the structure between some of the vesicle types studied.

In vivo distribution of arsenic after i.p. injection of arsonoliposomes in balb-c mice

We recently showed that arsonoliposomes (novel arsenic containg liposomes) demonstrate differential toxicity towards various types of cancer and normal cells, in cell culture studies, as well as anti-parasitic activity. In this study, the in-vivo distribution of the active moiety of these vesicles, As, is evaluated. Sonicated arsonoliposomes were prepared using the arsonolipid with palmitic acid acyl chain (C16) mixed with egg-phosphatidyl choline (PC) and cholesterol (Chol) [C16/PC/Chol at 8:12:10 mol/mol/mol]. A dose of arsonoliposomes, corresponding to 5 mg arsenate/kg was administered by intraperitoneal injection in balb-c mice. At various time points post-injection the mice were sacrificed and the distribution of As in the organs was measured, by atomic absorption spectroscopy. Results demonstrate that a high portion of the dose administered is rapidly excreted; since 1-h post-injection only about 30% of the dose administered was detected cumulatively in the animal tissues. After this the elimination of arsenic was a slow process with a total body elimination rate constant of 0.023 h(-1), corresponding to a half-life of 30 h. Tissues with the highest arsenic concentration during the study period are: spleen-kidneys-stomach, followed by lung, liver, intestines-heart, carcass+skin and finally blood. No acute toxicity, or effect on the body or organ weight of the mice was observed.

Arsenolipids

Natural arsenolipids are analogues of neutral lipids, like monoglycerides, glycolipids, phospho- and also phosphonolipids. They have been found in microorganisms, fungi, plants, lichens, in marine mollusks, sponges, other invertebrates, and in fish tissues. This review presented structures of natural arsenolipids (and derivatives), their distribution, biogenesis in algae and invertebrates, synthesis, and also biological activity. Arsenolipids are thought to be end products of arsenate detoxification processes, involving reduction and oxidative methylation and adenosylation. The proposed biogenesis of arsenolipids is based on the natural occurrence of arsenic metabolites, and all the intermediates in the proposed pathway have been identified as natural products of algal origin. Different arseno species are shown to be inhibitors of glycerol kinase, bovine carbonic anhydrase, and also is an effective therapy for acute promyelocytic leukemia, and there has been promising activity noted in other hematologic and solid tumors. Arsonoliposomes demonstrated high anti-trypanosomal activity against Trypanosoma brucei and inhibit growth of some types of cancer cells (HL-60,C6 and GH3).