Nanoemulsions loaded with amphotericin B: a new approach for the treatment of leishmaniasis

Nanoemulsions containing amphotericin b and paromomycin for the treatment of cutaneous leishmaniasis

Cutaneous leishmaniasis (CL) is a vector-borne disease characterized by skin lesions that can evolve into high-magnitude ulcerated lesions. Thus, this study aimed to develop an innovative nanoemulsion (NE) with clove oil, Poloxamer® 407, and multiple drugs, such as amphotericin B (AmB) and paromomycin (PM), for use in the topical treatment of CL.

METHODS

Droplet size, morphology, drug content, stability, in vitro release profile, in vitro cytotoxicity on RAW 264.7 macrophages, and antileishmanial activity using axenic amastigotes of Leishmania amazonensis were assessed for NEs.

RESULTS

After optimizing the formulation parameters, such as the concentration of clove oil and drugs, using an experimental design, it was possible to obtain a NE with an average droplet size of 40 nm and a polydispersion index of 0.3, and these parameters were maintained throughout the 365 days. Furthermore, the NE showed stability of AmB and PM content for 180 days under refrigeration (4 °C), presented a pH compatible with the skin, and released modified AmB and PM. NE showed the same toxicity as free AmB and higher toxicity than free PM against RAW 264.7 macrophages. The same activity as free AmB, and higher activity than free PM against amastigotes L. amazonensis.

CONCLUSION

It is possible to develop a NE for the treatment of CL; however, complementary studies regarding the antileishmanial activity of NE should be carried out.

Distearoyl phosphatidylglycerol and dioleoyl phosphatidylglycerol increase the retention and reduce the toxicity of amphotericin B-loaded in nanoemulsions

Aim: To develop nanoemulsions (NEs) loading amphotericin B (AmB) and to evaluate the influence of different excipients on the stability and the supramolecular organization, retention and toxicity of AmB. Materials & methods: The NEs were developed from different oils, surfactants, external media and anionic lipids (disteaoryl phosphatidylglycerol [DSPG] and dioleoyl phosphatidylglycerol [DOPG]). Their impact on the size, pH, zeta potential, AmB encapsulation efficiency, AmB retention and hemolytic potential of the NEs was evaluated. Results & conclusion: The use of soybean oil (lipid matrix), Span 80 (surfactant), phosphate buffer (external phase) and DSPG or DOPG (hydrophobic ion pair) provided better NE stability, higher AmB retention within the NEs and a safer formulation profile in hemolysis tests.

Green SPIONs as a novel highly selective treatment for leishmaniasis: an in vitro study against Leishmania amazonensis intracellular amastigotes

The main goal of this work was to evaluate the therapeutic potential of green superparamagnetic iron oxide nanoparticles (SPIONs) produced with coconut water for treating cutaneous leishmaniasis caused by Leishmania amazonensis. Optical and electron microscopy techniques were used to evaluate the effects on cell proliferation, infectivity percentage, and ultrastructure. SPIONs were internalized by both parasite stages, randomly distributed in the cytosol and located mainly in membrane-bound compartments. The selectivity index for intracellular amastigotes was more than 240 times higher compared to current drugs used to treat the disease. The synthesized SPIONs showed promising activity against Leishmania and can be considered a strong candidate for a new therapeutic approach for treating leishmaniases.

Nanoemulsions for increased penetrability and sustained release of leishmanicidal compounds

In the last decade, the World Health Organization has driven the development of drugs for topical use in patients with cutaneous leishmaniasis (CL), the most prevalent clinical form of leishmaniasis, a neglected tropical disease. The chemicals C₆ I, TC1, and TC2 were reported as promising antileishmanial drugs. We aimed to develop a topical nanoformulation that enhances the advantageous effect of C₆ I, TC1, and TC2, guaranteeing higher stability and bioavailability of the pharmacologically active components through the topical route. Nanoemulsions were prepared by ultrasonication based on oleic acid (0.5 g). A relation of Tween®-80/ethanol (1:3) and water was obtained; physicochemical characterization of all formulations was performed, and the preliminary stability and transdermal penetration of these nanoemulsions were also investigated. Newtonian-type fluids with high load capacity, 147-273 nm globule size, and -15 to -18 mV zeta potential were obtained with differential permeability rates in the first pig ear skin assay, first-order kinetics-release model for C₆ I, and Weibull for TC1 and TC2. The nanoemulsion showed good stability, high encapsulation efficiency, and higher leishmanicidal activity against Leishmania braziliensis with lower cytotoxicity in U937 macrophages. In conclusion, nanoemulsions of ethanol-oleic acid/Tween®-80 increase the activity of compounds with leishmanicidal activity by increasing their penetration and sustained release.

A Systematic Review of Drug-Carrying Nanosystems Used in the Treatment of Leishmaniasis

Leishmaniasis is an infectious disease responsible for a huge rate of morbidity and mortality in humans. Chemotherapy consists of the use of pentavalent antimonial, amphotericin B, pentamidine, miltefosine, and paromomycin. However, these drugs are associated with some drawbacks such as high toxicity, administration by parenteral route, and most seriously the resistance of some strains of the parasite to them. Several strategies have been used to increase the therapeutic index and reduce the toxic effects of these drugs. Among them, the use of nanosystems that have great potential as a site-specific drug delivery system stands out. This review aims to compile results from studies that were carried out using first- and second-line antileishmanial drug-carrying nanosystems. The articles referred to here were published between 2011 and 2021. This study shows the promise of effective applicability of drug-carrying nanosystems in the field of antileishmanial therapeutics, with the perspective of providing better patient adherence to treatment, increased therapeutic efficacy, reduced toxicity of conventional drugs, as well as the potential to efficiently improve the treatment of leishmaniasis.

Liposomal Amphotericin B for Treatment of Leishmaniasis: From the Identification of Critical Physicochemical Attributes to the Design of Effective Topical and Oral Formulations

The liposomal amphotericin B (AmB) formulation, AmBisome^®, still represents the best therapeutic option for cutaneous and visceral leishmaniasis. However, its clinical efficacy depends on the patient's immunological status, the clinical manifestation and the endemic region. Moreover, the need for parenteral administration, its side effects and high cost significantly limit its use in developing countries. This review reports the progress achieved thus far toward the understanding of the mechanism responsible for the reduced toxicity of liposomal AmB formulations and the factors that influence their efficacy against leishmaniasis. It also presents the recent advances in the development of more effective liposomal AmB formulations, including topical and oral liposome formulations. The critical role of the AmB aggregation state and release rate in the reduction of drug toxicity and in the drug efficacy by non-invasive routes is emphasized. This paper is expected to guide future research and development of innovative liposomal formulations of AmB.

Polyene macrolide antibiotic nanoemulsion: a proposal for the treatment of cutaneous leishmaniasis

Leishmaniasis is a neglected tropical disease that requires timely and inexpensive treatment. For this purpose, a nanoemulsion with a polyene macrolide antibiotic, or amphotericin B (NE-AmB), was developed. This study quantified the amount of drug permeated and retained in intact and lacerated human skin, simulating cutaneous leishmaniasis (CL) processes. Toxicity in macrophage and keratinocyte cell lines, activity against promastigotes and amastigotes of Leishmania tropica, in vivo irritant activity, and histological evidence was evaluated. Results. The amount of drug retained in intact and damaged skin was 750.18 ± 5.43 and 567.97 ± 8.64 µg/g/cm2, respectively. There was no permeation. No apparent toxic effect was observed in HaCaT cell lines. The IC50 of NE-AmB found for promastigotes and amastigotes was 0.26 ± 0.09 and 0.37 ± 0.05 µg/mL, respectively. NE without AmB did show antiparasitic activity. The formulation showed lower IC50 values on both parasite stages than the AmB solution. There was no skin irritation, and histology showed skin improvement with treatment. We suggest that this NE-AmB may be a candidate for in vivo studies in CL patients. Keywords. Leishmaniasis, Amphotericin B, ex vivo permeation studies, in vitro cytotoxicity, in vitro leishmanicidal activity, Draize test, histology.

Effect of Acyl Chain Length on Hydrophobized Cashew Gum Self-Assembling Nanoparticles: Colloidal Properties and Amphotericin B Delivery

Given its many potential applications, cashew gum hydrophobic derivatives have gained increasing attraction in recent years. We report here the effect of acyl chain length on hydrophobized cashew gum derivatives, using acetic, propionic, and butyric anhydrides on self-assembly nanoparticle properties and amphotericin B delivery. Nanoparticles with unimodal particle size distribution, highly negative zeta potential, and low PDI were produced. Butyrate cashew gum nanoparticles presented smaller size (<~100 nm) than acetylated and propionate cashew gum nanoparticles and no cytotoxicity in murine fibroblast cells was observed up to 100 µg/mL for loaded and unloaded nanoparticles. As a proof of concept of the potential use of the developed nanoparticle as a drug carrier formulation, amphotericin B (AmB) was encapsulated and fully characterized in their physicochemical, AmB association and release, stability, and biological aspects. They exhibited average hydrodynamic diameter lower than ~200 nm, high AmB efficiency encapsulations (up to 94.9%), and controlled release. A decrease in AmB release with the increasing of the anhydride chain length was observed, which explains the differences in antifungal activity against Candida albicans strains. An excellent storage colloidal stability was observed for unloaded and loaded AmB without use of surfactant. Considering the AmB delivery, the acyl derivative with low chain length is shown to be the best one, as it has high drug loading and AmB release, as well as low minimum inhibitory concentration against Candida albicans strains.

Stability Studies and the In Vitro Leishmanicidal Activity of Hyaluronic Acid-Based Nanoemulsion Containing Pterodon pubescens Benth. Oil

The physicochemical and microbiological stability of a hyaluronic acid-based nanostructured topical delivery system containing P. pubescens fruit oil was evaluated, and the in vitro antileishmanial activity of the nanoemulsion against Leishmania amazonensis and the cytotoxicity on macrophages was investigated. The formulation stored at 5 ± 2 °C, compared with the formulation stored at 30 and 40 ± 2 °C, showed a higher chemical and physical stability during the period analyzed and in the accelerated physical stability study. The formulation stored at 40 °C presented a significant change in droplet diameter, polydispersity index, zeta potential, pH, active compound, and consistency index and was considered unstable. The microbiological stability of the formulations was confirmed. The leishmanicidal activity of the selected system against intracellular amastigotes was significantly superior to that observed for the free oil. However, further research is needed to explore the use of the hyaluronic acid-based nanostructured system containing P. pubescens fruit oil for the treatment of cutaneous leishmaniasis.

Current Applications of Plant-Based Drug Delivery Nano Systems for Leishmaniasis Treatment

Leishmania is a trypanosomatid that causes leishmaniasis. It is transmitted to vertebrate hosts during the blood meal of phlebotomine sandflies. The clinical manifestations of the disease are associated with several factors, such as the Leishmania species, virulence and pathogenicity, the host-parasite relationship, and the host's immune system. Although its causative agents have been known and studied for decades, there have been few advances in the chemotherapy of leishmaniasis. The urgency of more selective and less toxic alternatives for the treatment of leishmaniasis leads to research focused on the study of new pharmaceuticals, improvement of existing drugs, and new routes of drug administration. Natural resources of plant origin are promising sources of bioactive substances, and the use of ethnopharmacology and folk medicine leads to interest in studying new medications from phytocomplexes. However, the intrinsic low water solubility of plant derivatives is an obstacle to developing a therapeutic product. Nanotechnology could help overcome these obstacles by improving the availability of common substances in water. To contribute to this scenario, this article provides a review of nanocarriers developed for delivering plant-extracted compounds to treat clinical forms of leishmaniasis and critically analyzing them and pointing out the future perspectives for their application.

Review of Novel Oral Amphotericin B Formulations for the Treatment of Parasitic Infections

Amphotericin B (AmpB) is a polyene macrolide antibiotic used in the treatment of blood-borne parasitic and fungal infections. However, its use, particularly in the developing world, has been limited by dose-dependent kidney toxicity, other systemic-related toxicity issues following injection, the inconvenience of parenteral administration, and accessibility. Oral formulation approaches have focused on the dual problem of solubility and permeability of AmpB, which is poorly water soluble, amphoteric and has extremely low oral bioavailability. Therefore, to enhance oral absorption, researchers have employed micellar formulations, polymeric nanoparticles, cochleates, pro-drugs, and self-emulsifying drug delivery systems (SEDDS). This paper will highlight current uses of AmpB against parasitic infections such as leishmaniasis, preclinical and clinical formulation strategies, applications in veterinary medicine and the importance of developing a cost-effective and safe oral AmpB formulation.

Cholesterol improves stability of amphotericin B nanoemulsion: promising use in the treatment of cutaneous leishmaniasis

Aim: Amphotericin B (AmB) is an antileishmanial drug with high toxicity; however, this drawback might overcome by decreasing the AmB self-aggregation state. This work aimed at evaluating the influence of cholesterol on the aggregation state of AmB loaded in a nanoemulsion (NE-AmB) for the treatment of cutaneous leishmaniasis. NE-AmB (1, 4 and 8 mg/kg/day) was administered intravenously to animals infected by Leishmania major every 2 days for a total of five injections. Results: Ultraviolet-visible spectroscopy and circular dichroism studies demonstrated that cholesterol reduced AmB aggregation state in NE. NE-AmB was stable after 180 days, and its hemolytic toxicity was lower than that observed for the conventional AmB. NE-AmB administered intravenously into animals infected by Leishmania major at 8 mg/kg was capable of stabilizing the lesion size and reducing the parasitic load. Conclusion: These findings support the NE potential as a stable nanocarrier for AmB in the treatment of cutaneous leishmaniasis.

Emerging trends and promises of nanoemulsions in therapeutics of infectious diseases

Infectious diseases are prevalent and have contributed to high morbidity rates by creating havoc like the COVID-19, 1918 influenza and Black Death (the plague) pandemics. Antimicrobial resistance, adverse effects, the emergence of co-infections and the high cost of antimicrobial therapies are major threats to the health of people worldwide while impacting overall healthcare and socioeconomic development. One of the most common ways to address this issue lies in improving existing antimicrobial drug-delivery systems. Nanoemulsions and their modified forms have been successfully employed for the delivery of antimicrobials to treat infectious diseases. In this article, the authors comprehensively reviewed how nanoemulsion-based formulation systems are shifting the paradigm for therapeutics and diagnosis of infectious diseases.

Formulation of Amphotericin B in PEGylated Liposomes for Improved Treatment of Cutaneous Leishmaniasis by Parenteral and Oral Routes

Liposomal amphotericin B (AmB) or AmBisome® is the most effective and safe therapeutic agent for visceral leishmaniasis (VL), but its clinical efficacy is limited in cutaneous leishmaniasis (CL) and HIV/VL co-infection. The aim of this work was to develop a formulation of AmB in PEGylated liposomes and compare its efficacy to AmBisome® in a murine model of CL. Formulations of AmB in conventional and PEGylated liposomes were characterized for particle size and morphology, drug encapsulation efficiency and aggregation state. Those were compared to AmBisome® in Leishmania amazonensis-infected BALB/c mice for their effects on the lesion size growth and parasite load. The conventional and PEGylated formulations showed vesicles with 100–130 nm diameter and low polydispersity, incorporating more than 95% of AmB under the non-aggregated form. Following parenteral administration in the murine model of CL, the PEGylated formulation of AmB significantly reduced the lesion size growth and parasite load, in comparison to control groups, in contrast to conventional liposomal AmB. The PEGylated formulation of AmB was also effective when given by oral route on a 2-day regimen. This work reports for the first time that PEGylated liposomal AmB can improve the treatment of experimental cutaneous leishmaniasis by both parenteral and oral routes.

Nanoemulsion-based dissolving microneedle arrays for enhanced intradermal and transdermal delivery

The development of dissolving microneedles (DMN) is one of the advanced technologies in transdermal drug delivery systems, which precisely deliver the drugs through a rapid dissolution of polymers after insertion into the skin. In this study, we fabricated nanoemulsion-loaded dissolving microneedle (DMN) arrays for intradermal and transdermal drug delivery. For this task, model drug (amphotericin B, AmB)-loaded nanoemulsion (NE) were prepared by the probe-sonication method. AmB-loaded-NE was prepared using Capmul MCM C-8 EP/NF, Tween^® 80, poly(vinyl alcohol) (PVA-10 kDa), and poly (vinyl pyrrolidone) (PVP-360 kDa or K29/32) by using SpeedMixer™, followed by probe-sonication and evaluated for particle size and polydispersity index (PDI). Transmission electron microscopy (TEM) was also used to assess the particle size before and after DMN casting. AmB-NE embedded DMN arrays were found to be strong enough, revealed efficient skin insertion, and penetrated down to the fourth layer (depth ≈ 508 μm) of Parafilm M^® (validated skin model). Ex vivo skin deposition experiments in full-thickness neonatal porcine demonstrated that after 24 h, AmB-NE-DMN arrays were able to deposit 111.05 ± 48.4 µg/patch AmB into the skin. At the same time, transdermal porcine skin permeation studies showed significantly higher permeability of AmB (29.60 ± 8.23 μg/patch) from AmB-NE-DMN compared to MN-free AmB-NE patches (5.0 ± 6.15 μg/patch) over 24 h. Antifungal studies of optimized AmB-NE-DMN, AmB-loaded discs and drug-free DMN against Candida albicans, confirmed the synergistic activity of Campul-MCM C-8, used in the nanoemulsion formulation. This study establishes that nanoemulsion based dissolving microneedle may serve as an efficient system for intradermal as well as transdermal drug delivery.

Nanotechnology-aided diagnosis, treatment and prevention of leishmaniasis

Leishmaniasis is a prevalent parasitic infection belonging to neglected tropical diseases. It is caused by Leishmania protozoan parasites transmitted by sandflies and it is responsible for increased morbidity/mortality especially in low- and middle-income countries. The lack of cheap, portable, easy to use diagnostic tools exhibiting high efficiency and specificity impede the early diagnosis of the disease. Furthermore, the typical anti-leishmanial agents are cytotoxic, characterized by low patient compliance and require long-term regimen and usually hospitalization. In addition, due to the intracellular nature of the disease, the existing treatments exhibit low bioavailability resulting in low therapeutic efficacy. The above, combined with the common development of resistance against the anti-leishmanial agents, denote the urgent need for novel therapeutic strategies. Furthermore, the lack of effective prophylactic vaccines hinders the control of the disease. The development of nanoparticle-based biosensors and nanocarrier-aided treatment and vaccination strategies could advance the diagnosis, therapy and prevention of leishmaniasis. The present review intends to highlight the various nanotechnology-based approaches pursued until now to improve the detection of Leishmania species in biological samples, decrease the side effects and increase the efficacy of anti-leishmanial drugs, and induce enhanced immune responses, specifically focusing on the outcome of their preclinical and clinical evaluation.

Application of Poloxamers for the Development of Drug Delivery System to Treat Leishmaniasis: A Review

Leishmaniasis is a neglected tropical disease affecting more than 1.5 million people annually, with an annual mortality of over 20.000. The drugs used for its treatment are toxic, expensive, require extended treatment times and present variable efficacy. The disease severity and therapy limitations suggest the need for new antileishmanial agents. In this context, in order to identify new options for treatment, a number of studies based on nanotechnological strategies have been carried out. Poloxamers are triblock copolymers very often utilized for nanotherapeutic solutions, resulting in products with better solubility, higher stability, superior therapeutic efficacy and less toxicity. This review will discuss the physicochemical properties of the copolymers, as well as describe the use of poloxamers for the development of therapeutic formulations to treat leishmaniasis.

Biodistribution and histopathology studies of amphotericin B sodium deoxycholate sulfate formulation following intratracheal instillation in rat models

Aerosol inhalation of amphotericin B (AmB) can be a clinically compliant way to administer the drug directly to the pulmonary route for treatment as well as prophylaxis of invasive pulmonary aspergillosis (IPA). We report aerosol formulation of AmB using sodium deoxycholate sulfate (SDCS), a lipid carrier synthesized in-house using natural precursor deoxycholic acid. In vitro toxicity was determined by MTT assay. Biodistribution and histopathology in rats were evaluated in targeted organs including the lungs, kidneys, spleen, and liver. No toxicity was observed when lung and kidney cells treated with AmB-SDCS formulations up to 8 μg/mL and minimal toxicity at higher concentration 16 μg/mL, while the Fungizone®-like formulation induced toxicity to lung and kidney cells with viability decreasing from 86 to 41% and 100 to 49%, respectively, when compared with an equivalent concentration of AmB-SDCS. Renal and hepatic markers were raised for Fungizone®-like formulation-treated rats but not for AmB-SDCS formulations following 7 days of regular dosing by intratracheal instillation. AmB concentrations were highest in the lungs (5.4-8.3 μg/g) which were well above minimum inhibitory concentration (MIC) of all Aspergillus species. Plasma concentration was also above MIC (> 2 μg/mL) for all AmB-SDCS formulations in comparison with Fungizone®-like formulation. No evidence of abnormal histopathology was observed in the lungs, liver, spleen, and kidneys for all AmB-SDCS formulations but was observed for the group treated with Fungizone®-like formulation. It is concluded that AmB-SDCS formulations can be efficiently administered via intratracheal instillation with no evidence of toxicity and may find great value in the treatment as well as prophylaxis of IPA through inhalation route.

Lipid Systems for the Delivery of Amphotericin B in Antifungal Therapy

Amphotericin B (AmB), a broad-spectrum polyene antibiotic in the clinic for more than fifty years, remains the gold standard in the treatment of life-threatening invasive fungal infections and visceral leishmaniasis. Due to its poor water solubility and membrane permeability, AmB is conventionally formulated with deoxycholate as a micellar suspension for intravenous administration, but severe infusion-related side effects and nephrotoxicity hamper its therapeutic potential. Lipid-based formulations, such as liposomal AmB, have been developed which significantly reduce the toxic side effects of the drug. However, their high cost and the need for parenteral administration limit their widespread use. Therefore, delivery systems that can retain or even enhance antimicrobial efficacy while simultaneously reducing AmB adverse events are an active area of research. Among those, lipid systems have been extensively investigated due to the high affinity of AmB for binding lipids. The development of a safe and cost-effective oral formulation able to improve drug accessibility would be a major breakthrough, and several lipid systems for the oral delivery of AmB are currently under development. This review summarizes recent advances in lipid-based systems for targeted delivery of AmB focusing on non-parenteral nanoparticulate formulations mainly investigated over the last five years and highlighting those that are currently in clinical trials.

Development of amphotericin B-loaded propionate Sterculia striata polysaccharide nanocarrier

This work was aimed at the production and characterization of a new nanocarrier based on a Sterculia striata polysaccharide (SSP) modified via acylation reaction with propionic anhydride. Nanocapsules of propionated SSP (PSSP) were produced via spontaneous nanoemulsification process and tested as a potential amphotericin B (AMB) nanocarrier. Stable nanoparticles with a very low polydispersity index (0.08-0.29) and high zeta potential (ζ -42.7 to -53.8 mV) were obtained. Particle size was dependent on the degree of substitution and ranged from 205 to 286 nm. A nanocapsule with a degree of substitution (DS) of 2.53 (NC_P 2.53) was selected for encapsulation, biocompatibility, and antifungal evaluation against Candida albicans strains. A maximum of 98.3% AMB encapsulation was achieved. Encapsulated AMB was in its monomeric form and showed good biocompatibility and antifungal activity against four C. albicans strains. Data indicate that PSSP has potential as a nanocarrier system for AMB.

Innovative Solutions for the Control of Leishmaniases: Nanoscale Drug Delivery Systems

Background:

Leishmania are sandfly-transmitted protozoan parasites that harbour within the macrophages of a mammalian host and cause leishmaniasis, a serious zoonotic disease that threatens the lives of millions worldwide. Its numerous forms (cutaneous, mucocutaneous, and visceral) are currently treated with a sparse arsenal of drugs, specifically antimonials, amphotericin B, miltefosine, and paromomycin, for which drug resistance and clinical failure are rampant. Medicine is presently trending towards nanotechnology to aid in the successful delivery of drugs. Vehicles such as lipid-based nanocarriers, polymer-based nanoparticles, and metal ions and oxides have been previously demonstrated to improve bioavailability of drugs and decrease toxicity for the patient. These cutting-edge solutions can be combined with existing active molecules, as well as novel drugs or plant extracts with promising antileishmanial activity.

Conclusion:

This review explores the current evidence for the treatment of leishmaniases using nanoscale drug delivery systems (specifically lipid-, polymer- and metal-based systems) and encourages further development of the aforementioned nanotechnologies for treatment of Leishmania.

Exploiting knowledge on pharmacodynamics-pharmacokinetics for accelerated anti-leishmanial drug discovery/development

Introduction: Being on the top list of neglected tropical diseases, leishmaniasis has been marked for elimination by 2020. In the light of small armamentarium of drugs and their associated drawbacks, the understanding of pharmacodynamics and/or pharmacokinetics becomes a priority to achieve and sustain disease elimination. Areas covered: The authors have looked into pharmacological aspects of existing and emerging drugs for treatment of leishmaniasis. An in-depth understanding of pharmacodynamics and pharmacokinetics (PKPD) provides a rationale for drug designing and optimizing the treatment strategies. It forms a key to prevent drug resistance and avoid drug-associated adverse effects. The authors have compiled the researches on the PKPD of different anti-leishmanial formulations that have the potential for improved and/or effective disease intervention. Expert opinion: Understanding the pharmacological aspects of drugs forms the basis for the clinical application of novel drugs. Tailoring drug dosage and individualized treatment can avoid the adverse events and bridge gap between the in vitro models and their clinical application. An integrated approach, with pragmatic use of technological advances can improve phenotypic screening and physiochemical properties of novel drugs. Concomitantly, this can serve to improve clinical efficacies, reduce the incidence of relapse and accelerate the drug discovery/development process for leishmaniasis elimination.

Recent insights on nanomedicine for augmented infection control

Antimicrobial agents have been widely investigated for protecting against microbial infections in modern health. Drug-related limitations, poor bioavailability, toxicity to mammalian cells, and frequent bacteria drug resistance are major challenges faced when exploited in nanomedicine forms. Specific attention has been paid to control nanomaterial-based infection against numerous challenging pathogens in addition to improved drug delivery, targeting, and pharmacokinetic (PK) profiles, and thus, efficient antimicrobials have been fabricated using diverse components (metals, metal oxides, synthetic and semisynthetic polymers, natural or biodegradable polymers, etc). The present review covers several nanocarriers delivered through various routes of administration, highlighting major findings to control microbial infection as compared to using the free drug. Results over the past decade support the consistent development of various nanomedicines capable of improving biological significance and therapeutic benefits against an array of microbial strains. Depending on the intended application of nanomedicine, infection control will be challenged by various factors such as weighing the risk-benefits in healthcare settings, nanomaterial-induced (eco)toxicological hazards, frequent development of antibiotic resistance, scarcity of in vivo toxicity data, and a poor understanding of microbial interactions with nanomedicine at the molecular level. This review summarizes well-established informative data for nanomaterials used for infection control and safety concerns of nanomedicines to healthcare sectors followed by the significance of a unique "safe-by-design" approach.

Antifungal and Mucoadhesive Properties of an Orally Administered Chitosan-Coated Amphotericin B Nanostructured Lipid Carrier (NLC)

Surface-modified nanostructured lipid carriers (NLC) represent a promising mode of drug delivery used to enhance retention of drugs at absorption site. Formulated chitosan-coated amphotericin-B-loaded NLC (ChiAmp NLC) had a size of 394.4 ± 6.4 nm, encapsulation and loading efficiencies of 86.0 ± 3% and 11.0 ± 0.1% respectively. Amphotericin-B release from NLCs was biphasic with no changes in physical properties upon exposure to simulated gastrointestinal conditions. Antifungal properties of Amphotericin-B and ChiAmpB NLC were comparable but ChiAmpB NLC was twice less toxic to red blood cells and ten times safer on HT-29 cell lines. In vitro mucoadhesion data were observed ex vivo, where ChiAmpB NLC resulted in higher retention within the small intestine compared to the uncoated formulation. The data strongly offers the possibility of orally administering a non-toxic, yet effective Amphotericin-B nanoformulation for the treatment of systemic fungal infections.

Leishmania infantum 5'-Methylthioadenosine Phosphorylase presents relevant structural divergence to constitute a potential drug target

BACKGROUND

The 5'-methylthioadenosine phosphorylase (MTAP), an enzyme involved in purine and polyamine metabolism and in the methionine salvage pathway, is considered as a potential drug target against cancer and trypanosomiasis. In fact, Trypanosoma and Leishmania parasites lack de novo purine pathways and rely on purine salvage pathways to meet their requirements. Herein, we propose the first comprehensive bioinformatic and structural characterization of the putative Leishmania infantum MTAP (LiMTAP), using a comparative computational approach.

RESULTS

Sequence analysis showed that LiMTAP shared higher identity rates with the Trypanosoma brucei (TbMTAP) and the human (huMTAP) homologs as compared to the human purine nucleoside phosphorylase (huPNP). Motifs search using MEME identified more common patterns and higher relatedness of the parasite proteins to the huMTAP than to the huPNP. The 3D structures of LiMTAP and TbMTAP were predicted by homology modeling and compared to the crystal structure of the huMTAP. These models presented conserved secondary structures compared to the huMTAP, with a similar topology corresponding to the Rossmann fold. This confirmed that both LiMTAP and TbMTAP are members of the NP-I family. In comparison to the huMTAP, the 3D model of LiMTAP showed an additional α-helix, at the C terminal extremity. One peptide located in this specific region was used to generate a specific antibody to LiMTAP. In comparison with the active site (AS) of huMTAP, the parasite ASs presented significant differences in the shape and the electrostatic potentials (EPs). Molecular docking of 5'-methylthioadenosine (MTA) and 5'-hydroxyethylthio-adenosine (HETA) on the ASs on the three proteins predicted differential binding modes and interactions when comparing the parasite proteins to the human orthologue.

CONCLUSIONS

This study highlighted significant structural peculiarities, corresponding to functionally relevant sequence divergence in LiMTAP, making of it a potential drug target against Leishmania.

Nanopharmaceuticals as a solution to neglected diseases: Is it possible?

The study of neglected diseases has not received much attention, especially from public and private institutions over the last years, in terms of strong support for developing treatment for these diseases. Support in the form of substantial amounts of private and public investment is greatly needed in this area. Due to the lack of novel drugs for these diseases, nanobiotechnology has appeared as an important new breakthrough for the treatment of neglected diseases. Recently, very few reviews focusing on filiarasis, leishmaniasis, leprosy, malaria, onchocerciasis, schistosomiasis, trypanosomiasis, and tuberculosis, and dengue virus have been published. New developments in nanocarriers have made promising advances in the treatment of several kinds of diseases with less toxicity, high efficacy and improved bioavailability of drugs with extended release and fewer applications. This review deals with the current status of nanobiotechnology in the treatment of neglected diseases and highlights how it provides key tools for exploring new perspectives in the treatment of a wide range of diseases.

Recent updates and perspectives on approaches for the development of vaccines against visceral leishmaniasis

Visceral leishmaniasis (VL) is one of the most important tropical diseases worldwide. Although chemotherapy has been widely used to treat this disease, problems related to the development of parasite resistance and side effects associated with the compounds used have been noted. Hence, alternative approaches for VL control are desirable. Some methods, such as vector control and culling of infected dogs, are insufficiently effective, with the latter not ethically recommended. The development of vaccines to prevent VL is a feasible and desirable measure for disease control; for example, some vaccines designed to protect dogs against VL have recently been brought to market. These vaccines are based on the combination of parasite fractions or recombinant proteins with adjuvants that are able to induce cellular immune responses; however, their partial efficacy and the absence of a vaccine to protect against human leishmaniasis underline the need for characterization of new vaccine candidates. This review presents recent advances in control measures for VL based on vaccine development, describing extensively studied antigens, as well as new antigenic proteins recently identified using immuno-proteomic techniques.

Metabolomics as a tool to evaluate the toxicity of formulations containing amphotericin B, an antileishmanial drug

Amphotericin B (AmB) is a drug of choice against life-threatening systemic fungal infections and an alternative therapy for the treatment of all forms of leishmaniasis. It is known that AmB and its conventional formulation cause renal damage; however, the lipid formulations can reduce these effects. The aim of the present study was to identify metabolic changes in mice treated with two different AmB formulations, a nanoemulsion (NE) (lipid system carrier) loaded with AmB and the conventional formulation (C-AmB). For this purpose, metabolic fingerprinting represents a valuable strategy to monitor, in a non-targeted manner, the changes that are at the base of the toxicity mechanism of AmB. Plasma samples of BALB-c mice were collected after treatment with 3 alternate doses of AmB at 1 mg kg-1 administered intravenously and analysed with CE, LC and GC coupled to MS. Blood urea nitrogen (BUN) and plasma creatinine levels were also analysed. Kidney tissue specimens were collected and evaluated. It was not observed that there were any alterations in BUN and creatinine levels as well as in histopathological analysis. Approximately 30 metabolites were identified as potentially related to early C-AmB-induced nephrotoxicity. Disturbances in the arachidonic acid, glycerophospholipid, acylcarnitine and polyunsaturated fatty acid (PUFA) pathways were observed in C-AmB-treated mice. In the AmB-loaded NE group, it was observed that there were fewer metabolic changes, including changes in the plasma levels of cortisol and pyranose. The candidate biomarkers revealed in this study could be useful in the detection of the onset and severity of kidney injury induced by AmB formulations.

Tailoring Lipid and Polymeric Nanoparticles as siRNA Carriers towards the Blood-Brain Barrier - from Targeting to Safe Administration

Blood-brain barrier is a tightly packed layer of endothelial cells surrounding the brain that acts as the main obstacle for drugs enter the central nervous system (CNS), due to its unique features, as tight junctions and drug efflux systems. Therefore, since the incidence of CNS disorders is increasing worldwide, medical therapeutics need to be improved. Consequently, aiming to surpass blood-brain barrier and overcome CNS disabilities, silencing P-glycoprotein as a drug efflux transporter at brain endothelial cells through siRNA is considered a promising approach. For siRNA enzymatic protection and efficient delivery to its target, two different nanoparticles platforms, solid lipid (SLN) and poly-lactic-co-glycolic (PLGA) nanoparticles were used in this study. Polymeric PLGA nanoparticles were around 115 nm in size and had 50 % of siRNA association efficiency, while SLN presented 150 nm and association efficiency close to 52 %. Their surface was functionalized with a peptide-binding transferrin receptor, in a site-oriented manner confirmed by NMR, and their targeting ability against human brain endothelial cells was successfully demonstrated by fluorescence microscopy and flow cytometry. The interaction of modified nanoparticles with brain endothelial cells increased 3-fold compared to non-modified lipid nanoparticles, and 4-fold compared to non-modified PLGA nanoparticles, respectively. These nanosystems, which were also demonstrated to be safe for human brain endothelial cells, without significant cytotoxicity, bring a new hopeful breath to the future of brain diseases therapies.

New Trends on Antineoplastic Therapy Research: Bullfrog (Rana catesbeiana Shaw) Oil Nanostructured Systems

Bullfrog oil is a natural product extracted from the Rana catesbeiana Shaw adipose tissue and used in folk medicine for the treatment of several diseases. The aim of this study was to evaluate the extraction process of bullfrog oil, to develop a suitable topical nanoemulsion and to evaluate its efficacy against melanoma cells. The oil samples were obtained by hot and organic solvent extraction processes and were characterized by titration techniques and gas chromatography mass spectrometry (GC-MS). The required hydrophile-lipophile balance and the pseudo-ternary phase diagram (PTPD) were assessed to determine the emulsification ability of the bullfrog oil. The anti-tumoral activity of the samples was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay for normal fibroblast (3T3) and melanoma (B16F10) cell lines. Both extraction methods produced yielded around 60% and the oil was mainly composed of unsaturated compounds (around 60%). The bullfrog oil nanoemulsion obtained from PTPD presented a droplet size of about 390 nm and polydispersity = 0.05 and a zeta potential of about -25 mV. Both the bullfrog oil itself and its topical nanoemulsion did not show cytotoxicity in 3T3 linage. However, these systems showed growth inhibition in B16F10 cells. Finally, the bullfrog oil presented itself as a candidate for the development of pharmaceutical products free from cytotoxicity and effective for antineoplastic therapy.

Evaluation of the in vivo leishmanicidal activity of amphotericin B emulgel: An alternative for the treatment of skin leishmaniasis

The American Cutaneous Leishmaniasis (ACL) is an infectious disease that can be fatal. The first line of treatment is pentavalent antimonies. However, due to its potential to develop resistance, Amphotericin B (AmB) started to be used as an alternative medicine. Current treatments are limited, a fact that has led to a growing interesting in developing new therapies. This study aims to evaluate the therapeutic potential in vivo of an amphotericin B + oleic acid (OA) emulgel in the treatment of cutaneous leishmaniasis in an experimental model. Strains of Leishmania major MHOM/IL/80/Friendlin of Leishmania major were used. The animals were inoculated subcutaneously. After the development of leishmanial, nodular or ulcerative lesions, the animals were divided into three groups (control, Group A and Group B) and treated twice a day for twelve days. The weight of the animals was measured and the size of the lesions was observed. A histopathological analysis was performed with skin fragments of lesions and with the spleen of animals treated with different treatments (emulgel, AmB 3% emulgel and AmB 3% plus OA 5% emulgel). It was observed that when subjected to treatment with AmB 3% emulgel during the study period using both formulations, with enhancer and without enhancer, ulcerative lesions regress gradually or even complete cure. The quantification of the average number of parasites recovered from the inoculation site was made after the treatment in each group and the differences were considered significant. The treatment with AmB 3% and OA 5% emulgel had the best in vivo therapeutic response, showing good prospects for cutaneous leishmaniasis therapy as an alternative therapy.