Reduced renal toxicity of nanoparticular amphotericin B micelles prepared with partially benzylated poly-L-aspartic acid

Phospholipid-Conjugated PEG-b-PCL Copolymers as Precursors of Micellar Vehicles for Amphotericin B

Amphotericin B (AmB) is a widely used antifungal that presents a broad action spectrum and few reports on the development of resistance. However, AmB is highly toxic, causing renal failure in a considerable number of treated patients. Although when AmB is transported via polymer micelles (PMs) as delivery vehicles its nephrotoxicity has been successfully attenuated, this type of nanoparticle has limitations, such as low encapsulation capacity and poor stability in aqueous media. In this research, the effect of modifying polyethyleglicol-block-poly(ε-caprolactone) (PEG-b-PCL) with 1,2-distearoyl-sn-glycero-3-phosphorylethanolamine (DSPE) on the performance of PMs as vehicles for AmB was studied. PEG-b-PCL with two different lengths of a PCL segment was prepared via ring opening polymerisation and modified with DSPE at a post-synthesis stage through amidation. Upon modification with DSPE, a copolymer was self-assembled, thereby producing particles with hydrodynamic diameters below 100 nm and a lower critical micelle concentration than that of the raw copolymers. Likewise, in the presence of DSPE, the loading capacity of AmB increased because of the formed intermolecular interactions, such as hydrogen bonds, which also caused a lower aggregation of this drug. The assessment of in vitro toxicity against red blood cells indicated that the toxicity of AmB decreased upon encapsulation; however, its antifungal action against clinical yeasts was maintained and enhanced, as indicated by a decrease in its minimum inhibitory concentration.

Development of Amphotericin B Micellar Formulations Based on Copolymers of Poly(ethylene glycol) and Poly(ε-caprolactone) Conjugated with Retinol

Amphotericin B (AmB) is a broad spectrum of antifungal drug used to treat antifungal diseases. However, due to the high toxicity of AmB, treated patients may suffer the risk of side effects, such as renal failure. Nanoencapsulation strategies have been reported to elicit low toxicity, albeit most of them possess low encapsulation efficiency. The aim of this research is to develop micellar delivery systems for AmB with reduced toxicity while maintaining its affectivity by employing retinol (RET)-conjugated amphiphilic block copolymers (ABCs) as precursors. Copolymers composed of poly(ε-caprolactone) (A) and polyethylenglycol (B) of types AB and ABA were synthesized by ring opening polymerization and subsequently conjugated with RET by Steglich esterification. 1H-NMR spectroscopy was used to corroborate the structure of copolymers and their conjugates and determine their molecular weights. Analysis by gel permeation chromatography also found that the materials have narrow distributions. The resulting copolymers were used as precursors for delivery systems of AmB, thus reducing its aggregation and consequently causing a low haemolytic effect. Upon conjugation with RET, the encapsulation capacity was enhanced from approximately 2 wt % for AB and ABA copolymers to 10 wt %. AmB encapsulated in polymer micelles presented improved antifungal efficiency against Candida albicans and Candida auris strains compared with Fungizone®, as deduced from the low minimum inhibitory concentration.

Getting the Jump on the Development of Bullfrog Oil Microemulsions: a Nanocarrier for Amphotericin B Intended for Antifungal Treatment

Amphotericin B (AmB), a potent antifungal drug, presents physicochemical characteristics that impair the development of suitable dosage forms. In order to overcome the AmB insolubility, several lipid carriers such as microemulsions have been developed. In this context, the bullfrog oil stands out as an eligible oily phase component, since its cholesterol composition may favor the AmB incorporation. Thus, the aim of this study was to develop a microemulsion based on bullfrog oil containing AmB. Moreover, its thermal stability, antifungal activity, and cytotoxicity in vitro were evaluated. The microemulsion formulation was produced using the pseudo-ternary phase diagram (PTPD) approach and the AmB was incorporated based on the pH variation technique. The antifungal activity was evaluated by determination of minimal inhibitory concentration (MIC) against different species of Candida spp. and Trichosporon asahii. The bullfrog oil microemulsion, stabilized with 16.8% of a surfactant blend, presented an average droplet size of 26.50 ± 0.14 nm and a polydispersity index of 0.167 ± 0.006. This system was able to entrap AmB up to 2 mg mL^-1. The use of bullfrog oil as oily phase allowed an improvement of the thermal stability of the system. The MIC assay results revealed a growth inhibition for different strains of Candida spp. and were able to enhance the activity of AmB against T. asahii. The microemulsion was also able to reduce the AmB toxicity. Finally, the developed microemulsion showed to be a suitable system to incorporate AmB, improving the system's thermal stability, increasing the antifungal activity, and reducing the toxicity of this drug.

ESTRATÉGIAS TECNOLÓGICAS PARA FORMULAÇÕES DE ANFOTERICINA B EM SISTEMAS LIPÍDICOS DISPONÍVEIS NO MERCADO FARMACÊUTICO E OUTROS PROMISSORES SISTEMAS DE ADMINISTRAÇÃO

A anfotericina B (AmB) é um fármaco antifúngico utilizado no tratamento de micoses sistêmicas desde sua descoberta nos anos de 1950. O objetivo deste trabalho foi estabelecer o estado da arte das estratégias tecnológicas envolvidas nas formas de administração da AmB, nas intervenções diretas nos aspectos de melhoria de solubilidade do fármaco, que possibilitem sua administração por via intravenosa (iv) e minimizem sua toxicidade. Devido à limitada utilidade clínica do sal de desoxicolato (Fungizon®) em razão de sua alta toxicidade, sistemas de liberação mais eficientes foram desenvolvidos. Neste trabalho, são apresentadas as principais formulações disponíveis no mercado farmacêutico e outras formulações lipídicas promissoras, as quais se mostraram mais eficazes como veículos de solubilização e menos tóxicas quando comparadas com a AmB esoxicolato, mas ainda não fazem parte da rotina hospitalar para o tratamento de micoses profundas.

Self-assembled amphotericin B-loaded polyglutamic acid nanoparticles: preparation, characterization and in vitro potential against Candida albicans

In the present study, we developed a self-assembled biodegradable polyglutamic acid (PGA)-based formulation of amphotericin B (AmB) and evaluated its in vitro antifungal potential against Candida albicans. The AmB-loaded PGA nanoparticles were prepared in-house and had a mean size dimension of around 98±2 nm with a zeta potential of -35.2±7.3 mV. Spectroscopic studies revealed that the drug predominantly acquires an aggregated form inside the formulation with an aggregation ratio above 2. The PGA-based AmB formulation was shown to be highly stable in phosphate-buffered saline as well as in serum (only 10%-20% of the drug was released after 10 days). The AmB-PGA nanoparticles were less toxic to red blood cells (<15% lysis at an AmB concentration of 100 μg/mL after 24 hours) when compared with Fungizone(®), a commercial antifungal product. An MTT assay showed that the viability of mammalian cells (KB and RAW 264.7) was negligibly affected at AmB concentrations as high as 200 μg/mL. Histopathological examination of mouse kidney revealed no signs of tissue necrosis. The AmB-PGA formulation showed potent antimicrobial activity similar to that of Fungizone against C. albicans. Interestingly, AmB-bearing PGA nanoparticles were found to inhibit biofilm formation to a considerable extent. In summary, AmB-PGA nanoparticles showed highly attenuated toxicity when compared with Fungizone, while retaining equivalent active antifungal properties. This study indicates that the AmB-PGA preparation could be a promising treatment for various fungal infections.

Recent advances in development of amphotericin B formulations for the treatment of visceral leishmaniasis

PURPOSE OF REVIEW

Amphotericin B (AmpB) is considered the first-line treatment for visceral leishmaniasis in areas in which resistance to antimony is prevalent. This review describes recent advances in clinically available and novel drug delivery systems of AmpB to treat visceral leishmaniasis.

RECENT FINDINGS

Over the past two decades, lipid-based AmpB formulations developed to tackle the toxicity of AmpB have been used clinically for the treatment of visceral leishmaniasis. Liposomal AmpB (AmBisome) has been the most successful lipid formulation, and recent clinical studies on visceral leishmaniasis have shown the potential of single-dose AmBisome treatment as well as its use in short course combinations with other antileishmanial drugs. Current research is focussed on the development of more stable and affordable nonlipid formulations of AmpB. Although a diverse range of nonlipid-based AmpB formulations have been evaluated, none have yet reached the clinic.

SUMMARY

Liposomal AmpB (AmBisome) has become a standard treatment, by intravenous infusion, for visceral leishmaniasis and the basis for new short course treatments. There have been extensive efforts to develop new AmpB formulations on the basis of polymers, lipids or physical aggregates of AmpB to replace the costly lipid-based formulations. However, no nonlipid-based AmpB delivery systems have yet reached the clinic.

Noncovalent complexation of amphotericin-B with Poly(α-glutamic acid)

A noncovalent complex of amphotericin B (AmB) and poly(α-glutamic acid) (PGA) was prepared to develop a safe and stable formulation for the treatment of leishmaniasis. The loading of AmB in the complex was in the range of ∼20-50%. AmB was in a highly aggregated state with an aggregation ratio often above 2.0. This complex (AmB-PGA) was shown to be stable and to have reduced toxicity to human red blood cells and KB cells compared to the parent compound; cell viability was not affected at an AmB concentration as high as 50 and 200 μg/mL respectively. This AmB-PGA complex retained AmB activity against intracellular Leishmania major amastigotes in the differentiated THP-1 cells with an EC50 of 0.07 ± 0.03-0.08 ± 0.01 μg/mL, which is similar to Fungizone (EC50 of 0.06 ± 0.01 μg/mL). The in vitro antileishmanial activity of the complex against Leishmania donovani was retained after storage at 37 °C for 7 days in the form of a solution (EC50 of 0.27 ± 0.03 to 0.35 ± 0.04 μg/mL) and for 30 days as a solid (EC50 of 0.41 ± 0.07 to 0.63 ± 0.25 μg/mL). These encouraging results indicate that the AmB-PGA complex has the potential for further development.

Optimization of the hydrophobic domain in poly(ethylene oxide)-poly(varepsilon-caprolactone) based nano-carriers for the solubilization and delivery of Amphotericin B

The aim of the study was to develop a polymeric nano-carrier based on methoxy poly(ethylene oxide)-b-poly(epsilon-caprolactone) (MePEO-b-PCL) for the optimum solubilization and delivery of Amphotericin B (AmB). For this purpose, MePEO-b-PCL block co-polymers containing palmitoyl substituent on PCL (at a 100% substitution level) were synthesized through preparation of substituted monomer, that is, alpha-palmitoyl-epsilon-caprolactone, and further ring opening polymerization of this monomer by methoxy PEO (5000 g mol(-1)) using stannous octoate as catalyst. Prepared block co-polymers were characterized for their molecular weight by (1)H NMR and gel permeation chromatography, and assembled to polymeric nano-carriers. The self-assembly of synthesized MePEO-b-PPaCL to spherical particles of nanometer size range was shown by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The efficacy of nano-carriers formed from this structure (abbreviated as MePEO-b-PPaCL) in comparison to unmodified MePEO-b-PCL and those with benzyl and cholesteryl substituent on PCL (abbreviated as MePEO-b-PBCL and MePEO-b-PChCL, respectively) on the solubilization and hemolytic activity of AmB against rat red blood cells was assessed. Under identical conditions, the maximum solubilization of AmB was achieved by nano-carriers prepared from MePEO-b-PPaCL (436 microg/mL), followed by MePEO-b-PChCL (355 microg/mL), MePEO-b-PBCL (296 microg/mL) and MePEO-b-PCL (222 microg/mL). The hemolytic activity of AmB was reduced the most by its encapsulation in MePEO-b-PChCL nano-particles which showed only 7% hemolysis at 30 microg/mL AmB concentration. This was followed by MePEO-b-PCL nano-particles which illustrated 15% hemolysis, MePEO-b-PPaCL with 40% hemolysis and MePEO-b-PBCL with 60% hemolysis at 30 microg/mL AmB concentrations, respectively. In contrast Fungizone showed 90% hemolysis at 30 microg/mL AmB concentration. Based on the improved solubility and reduced hemolytic activity, the MePEO-b-PChCL nano-carriers are considered as optimum structures for AmB delivery.

Oil-in-water lecithin-based microemulsions as a potential delivery system for amphotericin B

In this work the structural features of microemulsions (MEs) containing the pharmaceutical biocompatible Soya phosphatidylcholine/Tween 20 (1:1) as surfactant (S), Captex 200 as oil phase (O), and phosphate buffer 10mM, pH 7.2 as aqueous phase (W) were studied. Systems obtained with different proportions of the components were described by pseudo-ternary phase diagrams in order to characterize the microemulsions studied here. MEs were prepared with and without the polyene antifungal drug amphotericin B (AmB). The maximum AmB incorporation into the ME system was dependent on both the oil phase and surfactant proportions with 6.80 and 5.7 mg/mL in high contents, respectively. The incorporation of AmB into the ME systems significantly increased the profile of the droplet size of the ME for all ranges of surfactant proportions used in the formulations. The microstructures of the system were characterized by dynamic light scattering (DLS) and rheological behavior. The DLS results showed that the size of the oil droplets increases 4.6-fold when AmB is incorporated into the ME system. In all cases the increase in the proportion of the oil phase of the ME leads to a slight increase in the diameter of the oil droplets of the system. Furthermore, for both the AmB-loaded and AmB-unloaded MEs, the size of the oil droplets decrease significantly with the increase of the S proportion in the formulations, demonstrating the efficiency of the surfactant in stabilizing the ME. Depending on the ME composition, an anti-thixotropic behavior was found. The maximum increases of the consistency index caused by the increase of the oil phase of the ME were of 17- and 25-times for the drug-loaded and drug-unloaded MEs, respectively. However, the observed effect for the drug-loaded ME was about 4.6 times higher than that for the drug-unloaded one, demonstrating the strong effect of the drug on the rheological characteristics of the ME system. Therefore, it is possible to conclude that the investigated ME can be used as a very promising vehicle for AmB.

Mixed micellar nanoparticle of amphotericin B and poly styrene-block-poly ethylene oxide reduces nephrotoxicity but retains antifungal activity

Mixed micellar nanoparticle consisting of amphotericin B (AmB) and poly styrene-block-poly ethylene oxide (PS-block-PEO) was prepared by high pressure homogenizer. Nephrotoxicity of the nanoparticle was investigated along with antifungal activity and self-aggregation status of the drug in the nanoparticle. Nephrotoxicity was markedly reduced when AmB was intravenously administered to rats as mixed micellar nanoparticle with PS-block-PEO in terms of transmission electron microscopy of tubular cells and creatinine clearance. Antifungal activity of AmB was not altered when the drug was in the form of mixed micellar nanoparticle compared to both conventional formulation and AmB micelle treated by same procedure without PS-block-PEO. Self-aggregation status of AmB molecules revealed monomeric in the mixed micellar nanoparticle with PS-block-PEO up to the therapeutic level of the drug (1-3 mM). The reduced nephrotoxicity of AmB in mixed micellar nanoparticle may be associated with the existence of the drug as monomeric form in the nanoparticle. Based on our result, formulation of AmB as mixed micellar nanoparticle with PS-block-PEO may be a promising alternative for the treatment of fungal diseases in patients who are at risk of renal dysfunction.