Physico-chemical characterization of meglumine antimoniate

Biomacromolecule chitosan carrying meglumine antimoniate coated on a silver/polyurethane nanocomposite as a wound dressing: Therapeutic efficacy on cutaneous leishmaniasis caused by Leishmania major in BALB/c mice

The high drug-carrying capacity and biocompatibility of chitosan (CS), a versatile biomacromolecule, have received special attention in recent years. This study focused on CS containing meglumine antimoniate (MA) for treating leishmaniasis, which was coated onto a silver/polyurethane (Ag.MA.CS/PUF). The newly synthesized nanocomposite was characterized using Fourier transform infrared spectroscopy (FTIR), inductively coupled plasma (ICP), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area analysis, field emission scanning electron microscope/energy dispersive spectroscopy (FESEM/EDS), and transmission electron microscopy (TEM). To confirm the in vivo results, we administered the Ag.MA.CS/PUF nanocomposite topically to skin lesions caused by L. major (MRHO/IR/75/ER) in 56 inbred BALB/c mice in intervention (n = 42) and control (n = 14) groups, once daily for four weeks. Skin lesion sizes and amastigote counts were measured before treatment and four weeks post-treatment. At these intervals, the average size of skin lesions in the Ag.MA.CS/PUF group decreased by 28 %, from 3.02 ± 0.98 to 2.17 ± 0.33 mm2. In contrast, the average size of lesions in the negative control group significantly increased from 3.58 ± 2.05 to 8.73 ± 5.15 mm2 (p < 0.05). Furthermore, the parasite load in the Ag.MA.CS/PUF nanocomposite group was significantly reduced by 80 % compared to the negative control group (p = 0.001). These findings suggest promising prospects for improving treatment outcomes in the future.

Fabrication of amphotericin B-loaded electrospun core-shell nanofibers as a novel dressing for superficial mycoses and cutaneous leishmaniasis

Amphotericin B (AmB) is an antifungal and antiparasitic agent that is the main drug used for the treatment of mycoses infections and leishmaniasis. However, its high toxicity and side effects are the main difficulties attributed to its application. In this study, to minimize its harmful effects, AmB-loaded core-shell nanofibers were fabricated, using polyvinyl alcohol, chitosan, and AmB as the core, and polyethylene oxide and gelatin as the shell-forming components. The nanofibers were characterized, using scanning electron microscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, tensile test, drug release, and MTT assay. The results showed that the prepared nanofibers were smooth and had a core-shell structure with almost no cytotoxicity against fibroblast cells and the release study suggested that the core-shell structure decreased the burst release. The disk diffusion assay revealed that the nanofibrous mats at different AmB concentrations exhibited significant activity against all the eight evaluated fungal species with the inhibition zones of 1.4-2.6 cm. The flow cytometry assay also showed that the prepared nanofibrous mat significantly killed Leishmania major promastigotes up to 84%. The obtained results indicated that this AmB-loaded nanofibrous system could be a suitable candidate for a topical drug delivery system for the treatment of both superficial mycoses and cutaneous leishmaniasis.

Improved efficacy of meglumine antimoniate incorporated in anionic liposomes against Leishmania infantum infecting canine macrophages

OBJECTIVES

Leishmaniasis is a zoonotic disease and several drugs have been used in the treatment, including meglumine antimoniate (AME). The chemotherapy reaches clinical cure but does not eliminate parasites, contributing to drug resistance. To improve AME efficacy we incorporated it in anionic liposomes. The antiparasitic activity and intracellular localization were investigated in canine macrophages infected with Leishmania infantum.

METHODS

Liposomes (L-AME) is composed of egg phosphatidylcholine, cholesterol, palmitoyl oleoyl phosphatidyl serine and α-tocopherol (4 : 3 : 0.4 : 0.07 mol%) plus AME. L-AME size, polydispersity, zeta potential and morphology were analysed as well as antileishmanial activity and intracellular localization in DH82 macrophages.

KEY FINDINGS

Liposomes (360 nm) zeta potential range from -40 to -65 mV, had 23% encapsulation efficiency and were stable for 180 days at 4°C. Free AME was cytotoxic towards L. infantum infected macrophages (ID50 = 0.012 M) while L-AME did not reduce cell viability. L-AME colocalized with parasites inside macrophages in a time-dependent manner, and reduced the percentage of infected cells and the number of intracellular parasites, decreasing the infection index (75-80%) twice as compared with AME treatment.

CONCLUSIONS

Liposomal AME is a promising delivery system for treating visceral leishmaniasis, improving meglumine efficacy against L. infantum and minimizing its cytotoxicity towards canine macrophages.

Glucantime-loaded electrospun core-shell nanofibers composed of poly(ethylene oxide)/gelatin-poly(vinyl alcohol)/chitosan as dressing for cutaneous leishmaniasis

Leishmaniasis, one of the main concerns of the World Health Organization, is a parasitic disease caused by Leishmania species. The main objective of this study was to prepare a topical drug delivery system that can deliver glucantime to the site of cutaneous Leishmania wounds. Using the electrospinning method, a core-shell nanofibrous mat composed of macromolecules including polyethylene oxide, gelatin, poly (vinyl alcohol) and chitosan was prepared. The prepared nanofibers were characterized by scanning electron microscopy (SEM), transmission electron microscopy, Fourier transform infrared spectroscopy (FT-IR), tensile test and in vitro drug release test. The anti-Leishmania activities of drug-loaded nanofibers against Leishmania promastigotes and its cytotoxicity on fibroblasts were determined respectively by flow-cytometry and indirect MTT methods. Results of morphological studies showed that uniform nanofibers were prepared without any bead with average diameter of 404 nm. The TEM investigation confirmed the core-shell structure of the fibers. The in-vitro drug release assay was executed using Franz diffusion cell, which indicted 84% of glucantime was released during the first 9 h. The results indicated that 4 and 6 cm² of nanofibers mat were significantly killed promatigotes up to 78%. Moreover, the MTT assay also showed that the fabricated nanofibers do not possess any cytotoxicity towards fibroblast cells.

Mixed antimony(V) complexes with different sugars to modulate the oral bioavailability of pentavalent antimonial drugs

Previous studies have shown that the association of the drug meglumine antimoniate (MA) with β-cyclodextrin can improve its bioavailability by the oral route. In this work, ribose and maltose were investigated for their ability to form mixed or association complexes with MA, release MA and modulate the serum levels of Sb after oral administration in mice. Analysis of the MA/ribose composition by high performance liquid chromatography coupled to mass spectrometry (LCMS-IT-TOF) revealed the presence of mixed meglumine-Sb-ribose and Sb-ribose complexes. Analysis of the MA/maltose composition suggested the formation of MA-maltose association compounds. Circular dichroism characterization of these compositions following dilution in water at 37 °C suggested a partial and slow dissociation of the association compounds. When the MA/ribose composition was administered orally and compared to MA, the serum concentration of Sb was significantly lower after 1 h and greater after 3 h. On the other hand, the MA/maltose composition showed similar serum Sb concentration after 1 h and higher level of Sb after 3 h, when compared to MA. In conclusion, the present study has demonstrated the formation of mixed or association complexes of MA with sugars, such as maltose and ribose, which promoted sustained serum level of Sb after oral administration.

Synthesis and photodynamic activities of novel water soluble purpurin-18-N-methyl-D-glucamine photosensitizer and its gold nanoparticles conjugate

A new type of water soluble ionic photosensitizer (PS), purpurin-18-N-methyl-D-glucamine (Pu-18-NMGA) has been synthesized and it was conjugated into gold nanoparticles (GNPs) stabilized by the PS without adding any particular reducing agents and surfactants. In vitro anticancer efficacy of the PS and its PS–GNPs conjugate against A549 lung cancer cell lines was evaluated. The PS–GNPs conjugate based on water-soluble Pu-18-NMGA afforded good PDT efficacy which was three times greater than that of the water-soluble PS.

Reduced Tissue Parasitic Load and Infectivity to Sand Flies in Dogs Naturally Infected by Leishmania ( Leishmania ) chagasi following Treatment with a Liposome Formulation of Meglumine Antimoniate

The toxicity and antileishmanial effectiveness of a novel liposome formulation of meglumine antimoniate in mongrel dogs with visceral leishmaniasis (VL) obtained from a region where VL is endemic in Brazil have been investigated. Groups of 12 animals received by the intravenous route four doses (with 4-day intervals) of either liposomal meglumine antimoniate (group I [GI], 6.5 mg Sb/kg of body weight/dose), empty liposomes (GII), or isotonic saline (GIII). Evaluation of markers of hematopoietic, hepatic, and renal functions before and just after treatment showed no significant change. On the other hand, transitory adverse reactions, including prostration, defecation, tachypnea, and sialorrhea, were observed during the first 15 min after injections in GI and GII. Parasitological evaluation of sternal bone marrow 4 days after the last dose showed a significant reduction of parasite burden in GI, compared to the other groups. Immunocytochemical evaluations of the skin, bone marrow, cervical lymph nodes, livers, and spleens of dogs for parasites, 150 days after treatment, indicated significant parasite suppression (higher than 95.7%) in the lymph nodes, livers, and spleens of GI, compared to control groups. Feeding of Lutzomyia longipalpis phlebotomines on dogs from GI, 150 days after treatment, resulted in a significant reduction of sand fly infection efficiency, compared to feeding on animals from GII and GIII. This is the first report of both long-term parasite suppression and reduction of infectivity to sand flies in naturally infected dogs following treatment with a liposome-encapsulated drug. Importantly, this was achieved using a 20-fold-lower cumulative dose of Sb than is used for conventional antimonial treatment.

Characterization of reactions of antimoniate and meglumine antimoniate with a guanine ribonucleoside at different pH

It has been shown previously that Sb(V) forms mono- and bis-adducts with adenine and guanine ribonucleosides, suggesting that ribonucleosides may be a target for pentavalent antimonial drugs in the treatment of leishmaniasis. In the present work, the reactions of antimoniate (KSb(OH)(6)) and meglumine antimoniate (MA) with guanosine 5'-monophosphate (GMP) have been characterized at 37 degrees C in aqueous solution and two different pH (5 and 6.5), using ESI(-)-MS and (1)H NMR. Acid and base species for both 1:1 and 1:2 Sb(V)-GMP complexes were identified by ESI(-)-MS. The (1)H NMR anomeric region was explored for determining the concentrations of mono- and bis-adducts. This allows for the determination of stability constants for these complexes (5,900 L mol(-1) for 1:1 complex and 370 L mol(-1) for 1:2 complex, at pD 5 and 37 degrees C). Kinetic studies at different pH indicated that formation and dissociation of both 1:1 and 1:2 Sb-GMP complexes are slow processes and favored at acidic pH (2,150 L mol(-1) h(-1) for the rate constant of 1:1 complex formation and 0.25 h(-1) for the rate constant of 1:1 complex dissociation, at pD 5 and 37 degrees C). When MA was used, instead of antimoniate, formation of 1:1 Sb-GMP complex occurred, but with a slower rate constant. Assuming that MA consists essentially of a 1:1 Sb-meglumine complex, a stability constant for MA could also be estimated (8,600 L mol(-1) at pD 5 and 37 degrees C). Thermodynamic and kinetic data are consistent with the formation of 1:1 Sb-ribonucleoside complexes in vertebrate hosts, following treatment with pentavalent antimonial drugs.

Mode of action of beta-cyclodextrin as an absorption enhancer of the water-soluble drug meglumine antimoniate

It has been previously reported that beta-cyclodextrin (beta-CD) enhances the oral absorption of the pentavalent antimony (Sb) drug, meglumine antimoniate (MA). Contrary to the drugs commonly used in association with beta-CD, MA is highly soluble in water (solubility >300 mg/mL) and, therefore, the mode of action of beta-CD in this system requires clarification. ESI(-)-MS analysis of MA and of the MA/beta-CD composition indicated the formation of a 1:1 association compound between 1:1 Sb-meglumine complex and beta-CD. A stability constant on the order of 100 Lmol(-1) was determined for this association compound. When MA solution was heated for 48 h at 55 degrees C to mimic the conditions used to prepare MA/beta-CD, MA was found to suffer dissociation, from high molecular weight Sb complexes into species of lower molecular weight. Strikingly, heated MA was found to be more extensively absorbed in mice by the oral route than MA freshly prepared at room temperature. In vitro skin permeation experiments using MA and MA/beta-CD indicated a two-fold increase in the Sb flux for MA/beta-CD. These findings support the hypothesis that the improved oral absorption of Sb arises from the increased permeation of MA across lipid bilayers, as a result of the enhanced availability of 1:1 Sb-meglumine complex.

Distribution of liposome-encapsulated antimony in dogs

The achievement of complete cure in dogs with visceral leishmaniasis is currently a great challenge, since dogs are the main reservoir for the transmission of visceral leishmaniasis to humans and they respond poorly to conventional treatment with pentavalent antimonials. In order to improve the efficacy of treatment, we developed a novel formulation for meglumine antimoniate based on the encapsulation of this drug in freeze-dried liposomes (LMA). The aim of the present study was to evaluate the biodistribution of antimony (Sb) in dogs following a single intravenous bolus injection of LMA. Four healthy male mongrel dogs received LMA at 3.8 mg Sb/kg body weight and were sacrificed 3, 48 and 96 h and 7 days later. Antimony was determined in the blood, liver, spleen and bone marrow. In the bone marrow, the highest Sb concentration was observed at 3 h (2.8 microg/g wet weight) whereas in the liver and spleen it was demonstrated at 48 h (43.6 and 102.4 microg/g, respectively). In these organs, Sb concentrations decreased gradually and reached levels of 19.1 microg/g (liver), 28.1 microg/g (spleen) and 0.2 microg/g (bone marrow) after 7 days. Our data suggest that the critical organ for the treatment with LMA could be the bone marrow, since it has low Sb levels and, presumably, high rates of Sb elimination. A multiple dose treatment with LMA seems to be necessary for complete elimination of parasites from bone marrow in dogs with visceral leishmaniasis.

Antimony(V) complex formation with adenine nucleosides in aqueous solution

Despite the clinical use of pentavalent antimonial drugs for over half a century, their mode of action against leishmaniasis remains poorly understood. In this paper, we investigated the ability of Sb(V) to form in aqueous solution complexes with adenine nucleosides and deoxynucleosides, using circular dichroism (CD) and (1)H and (13)C NMR spectroscopies. We report that the ribonucleosides, adenosine (A) and adenosine monophosphate (AMP), form in water complexes with Sb(V), as evidenced by the changes induced in their CD spectra. On the other hand, 2'-deoxyadenosine (dA) did not show such a change. CD titration of the ribonucleosides with Sb(V) suggests the formation of 1:2 Sb(V)-nucleoside complexes. NMR analysis indicates that Sb(V) binds to the sugar moiety at the 2' position. Furthermore, the incubation of the antimonial drug, meglumine antimonate, with adenosine at 37 degrees C led to the transfer of Sb(V) from its original ligand to the nucleoside molecule, at acidic pH (pH 5), but not at neutral pH (7.2). Our data therefore suggests that the formation of such complexes may take place in vivo within the acidic cell compartments, including the phagolysosome of macrophage in which Leishmania resides.

Glutathione-induced conversion of pentavalent antimony to trivalent antimony in meglumine antimoniate

The standard treatment of human leishmaniases involves the use of pentavalent antimony [Sb(V)] compounds, including meglumine antimoniate. The mode of action of these compounds has not been fully elucidated. The possibility that Sb(III) is involved has been suggested; however, the biomolecule that may induce the conversion of Sb(V) to Sb(III) has not yet been identified. In the present study, we investigated both the ability of reduced glutathione (GSH) to promote the reduction of Sb(V) into Sb(III) in meglumine antimoniate and the effects of pH and temperature on this transformation. GSH did promote the reduction of Sb(V) into Sb(III) in a dose-dependent manner. When GSH and meglumine antimoniate were incubated together at a GSH/Sb molar ratio superior or equal to 5:1, all antimony was encountered in the reduced form, indicating a stoichiometry of 5:1 between GSH and Sb(V) in the reaction. The reaction between Sb(V) and GSH was favored at an acidic pH (pH 5) and an elevated temperature (37 degrees C), conditions found within the phagolysosome, in which Leishmania resides. For instance, about 30% of the Sb(V) (concentration, 2mM) was converted to Sb(III) following incubation for 3 days with 10 mM GSH at pH 5 and 37 degrees C. Our data support the hypothesis that Sb(V) would be converted by GSH, or a related thiol compound, to more toxic Sb(III) in the phagolysosome of macrophages.