Pharmacologically Safe Nanomicelles of Amphotericin B With Lipids: Nuclear Magnetic Resonance and Molecular Docking Approach

In vivo evaluation of nephrotoxicity and neurotoxicity of colistin formulated with sodium deoxycholate sulfate in a mice model

Neurotoxicity and nephrotoxicity are the major dose-limiting factors for the clinical use of colistin against multidrug-resistant (MDR) Gram-negative bacteria. This study aimed to investigate the neurotoxic and nephrotoxic effects of colistin formulated with in-house synthesized sodium deoxycholate sulfate (SDCS) in a mouse model. Male mice C57BL/6 were randomly divided into four groups: control (saline solution), colistin (15 mg/kg/day), colistin:SDCS 1:1, and colistin:SDCS 1:2. In the colistin:SDCS treatment groups, the dosage was 15 mg/kg/day colistin equivalent; all mice were treated for 7 successive days. The thermal tolerance, body weight gain and organ weights were measured. The levels of serum blood urea nitrogen (BUN), creatinine (Cr), superoxide dismutase (SOD), and catalase (CAT) were assessed. Histopathological damages were assessed on mice organ. The colistin:SDCS formulations significantly improved thermal pain response of the mice comparable to the control group. The administration did not impair kidney function as evidence from BUN and Cr results; however, the oxidative stress biomarkers decreased in the colistin and colistin-SDCS treated mice. Several abnormalities were observed in the kidney, liver, spleen, and sciatic nerve tissues following colistin treatment, which indicated evidence of toxicity. The colistin-SDCS formulations were associated with less acute toxicity and fewer nephrotoxic and neurotoxic changes compared with the colistin alone group which indicated that SDCS attenuated colistin nephrotoxicity and neurotoxicity. This study highlights the potential application of colistin formulated with SDCS for safer clinical use against MDR Gram-negative bacteria.

Itraconazole Loaded Biosurfactin Micelles with Enhanced Antifungal Activity: Fabrication, Evaluation and Molecular Simulation

Itraconazole (ITZ) is a broad-spectrum antifungal for superficial subcutaneous and systemic fungal infections. This study aimed to enhance the antifungal activity of ITZ using surfactin A (SA), a cyclic lipopeptide produced by the SA-producing Bacillus strain NH-100, possessing strong antifungal activity. SA was extracted, and ITZ-loaded SA micelles formulations were prepared via a single-pot rinsing method and characterized by particle size, zeta potential, and infrared spectroscopy. In vitro dissolution at pH 1.2, as well as hemolysis studies, was also carried out. The fabricated formulations were stable and non-spherical in shape, with an average size of about 179 nm, and FTIR spectra depicted no chemical interaction among formulation components. ITZ-loaded micelles showed decreased hemolysis activity in comparison to pure ITZ. The drug released followed the Korsmeyer-Peppas model, having R2 0.98 with the diffusion release mechanism. In an acidic buffer, drug release of all prepared formulations was in the range of 73-89% in 2 h. The molecular simulation showed the outstanding binding and stability profile of the ITZ-SA complex. The aromatic ring of the ITZ mediates a π-alkyl contact with a side chain in the SA. It can be concluded that ITZ-loaded micelles, owing to significant enhanced antifungal activity up to 6-fold due to the synergistic effect of SA, can be a promising drug delivery platform for delivery of poorly soluble ITZ.

In-silico approach as a tool for selection of excipients for safer amphotericin B nanoformulations

Safer and efficacious Amphotericin B (AmB) nanoformulations can be designed by augmenting AmB in the monomeric or super-aggregated state, and restricting the aggregated state, by choosing the appropriate excipient, which can be facilitated by employing in-silico prediction as a tool. Excipients selected for the study included linear fatty acids from caprylic (C₈) to stearic(C₁₈) and the stearate based amphiphilic surfactants polyoxyl-15-hydroxystearate (PS15) and polyoxyl-40-stearate (PS40). Blend module was employed to determine the two miscibility parameters mixing energy (E_mix) and interaction parameter (χ). AmB-excipient interactions were modelled using molecular docking software. The fatty acids revealed a decrease in E_mix and χ values with increase in carbon chain length, suggesting enhanced affinity with increase in fatty acid hydrophobicity. Significantly higher affinity was observed with amphiphilic surfactants, in particular PS40 which exhibited negative values of E_mix and χ proposing very high degree of miscibility. Molecular docking study confirmed extensive interaction of all the excipients with the AmB polyene chain. PS15 and PS40 displayed in addition hydrophilic interactions with the mycosamine and polyol moieties with PS40 exhibiting complete wrapping of the AmB molecule. PS15 demonstrated only partial wrapping, attributed to the shorter ethylene oxide chain. AmB nanosuspensions (NS) were prepared by in situ nanoprecipitation using the excipients and the AmB state identified by UV scanning between 300 and 500 nm. AmB NS with fatty acids and PS15-AmB NS revealed a high intensity peak between 330 nm-350 nm of aggregated AmB and low intensity monomeric peaks between 405 and 415 nm reflecting predominance of the aggregated state. PS40-AmB NS on the other hand revealed complete absence of aggregated state and a high intensity peak between 321 and 325 nm which corresponded to the super-aggregated state. Also, the super-aggregated state slowly released the safe monomeric form without aggregate formation. Furthermore, very low hemolysis seen with PS40-AmB NS confirmed low toxicity attributed to the safer super-aggregated state and while higher hemolysis as anticipated was seen with PS15-AmB NS (aggregated state). The basis for selection of the appropriate excipient for design of safer AmB nanoformulations would be those excipients that exhibit negative values of miscibility parameters E_mix and χ, exhibit interaction with the hydrophobic and hydrophilic regions of AmB and demonstrate complete wrapping of AmB in the molecular docking study. Our study thus demonstrates feasibility of in-silico prediction as a practical tool for excipient selection for safer AmB nanoformulations.

Self-assembling, supramolecular chemistry and pharmacology of amphotericin B: Poly-aggregates, oligomers and monomers

Antifungal drugs such as amphotericin B (AmB) interact with lipids and phospholipids located on fungal cell membranes to disrupt them and create pores, leading to cell apoptosis and therefore efficacy. At the same time, the interaction can also take place with cell components from mammalian cells, leading to toxicity. AmB was selected as a model antifungal drug due to the complexity of its supramolecular chemical structure which can self-assemble in three different aggregation states in aqueous media: monomer, oligomer (also known as dimer) and poly-aggregate. The interplay between AmB self-assembly and its efficacy or toxicity against fungal or mammalian cells is not yet fully understood. To the best of our knowledge, this is the first report that investigates the role of excipients in the supramolecular chemistry of AmB and the impact on its biological activity and toxicity. The monomeric state was obtained by complexation with cyclodextrins resulting in the most toxic state, which was attributed to the greater production of highly reactive oxygen species upon disruption of mammalian cell membranes, a less specific mechanism of action compared to the binding to the ergosterol located in fungal cell membranes. The interaction between AmB and sodium deoxycholate resulted in the oligomeric and poly-aggregated forms which bound more selectively to the ergosterol of fungal cell membranes. NMR combined with XRD studies elucidated the interaction between drug and excipient to achieve the AmB aggregation states, and ultimately, their diffusivity across membranes. A linear correlation between particle size and the efficacy/toxicity ratio was established allowing to modulate the biological effect of the drug and hence, to improve pharmacological regimens. However, particle size is not the only factor modulating the biological response but also the equilibrium of each state which dictates the fraction of free monomeric form available. Tuning the aggregation state of AmB formulations is a promising strategy to trigger a more selective response against fungal cells and to reduce the toxicity in mammalian cells.

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.

Effect of sodium deoxycholate sulfate on outer membrane permeability and neutralization of bacterial lipopolysaccharides by polymyxin B formulations

We demonstrated binding interactions of polymyxin B (PMB), PMB formulations in the mole ratios of 1:2 and 1:3 of PMB:sodium deoxycholate sulfate (SDCS) and a commercial PMB formulation (CPMB) with lipopolysaccharides (LPS). The 1:2 PMB formulation (78.5-135.2 nM) exhibited a lower number of binding sites to the tested LPS compared to CPMB (112.6-140.9 nM) whereas 1:3 PMB formulation exhibited a higher number of binding sites (143.9-340.2 nM). Similarly, in the presence of LPS, the 1:2 PMB formulation (163.8-221.4 nm) exhibited smaller particle sizes compared to PMB, CPMB and 1:3 PMB formulation (248.8-603.5 nm). Molecular docking simulation suggested that the fatty acyl tails of LPS wrap together to produce a pseudo-globular structure of PMB-LPS complex, and among those 1:2 PMB formulation formed a more stable structure. The primary forces behind this complex are hydrogen bonds and salt bridges among the LPS, PMB, and SDCS. This study revealed that the PMB, CPMB, and PMB formulations inserted into the LPS micelles to disrupt the LPS membrane, whereas the SDCS may induce aggregation. The 1:2 PMB formulation also had higher bacterial uptake than other PMB formulations. The 1:2 PMB formulation neutralized the LPS micelles and was effective against Escherichia coli and Pseudomonas aeruginosa.

Binding interactions of bacterial lipopolysaccharides to polymyxin B in an amphiphilic carrier 'sodium deoxycholate sulfate'

This work presents the outcomes of a comparative study of molecular interactions of polymyxin B (PMB) and F12 and F13 formulations in the mole ratios of 1:2 and 1:3 of PMB:sodium deoxycholate sulfate (SDCS), respectively, and a commercial PMB formulation (CPMB) with lipopolysaccharides (LPS). Several spectroscopic and interfacial studies were performed to obtain LPS-peptide interactions at a molecular level. The fluorescence titrimetry method revealed that the F12 formulation (325 nM) exhibited a lower number of binding sites to the LPS compared to CPMB and F13 as well as PMB alone (537 nM). Similarly, in the presence of LPS, the F12 formulation (88 nm) exhibited smaller particle sizes in the dynamic light scattering study compared to PMB (116 nm), CPMB, and the F13 formulation. An interfacial study and circular dichroism spectroscopy revealed PMB and CPMB insertion into the LPS micelles to destabilize and disrupt the LPS membrane, whereas the F12 and F13 formulations may induce pseudo-aggregation. The NMR and IR studies showed that the presence of SDCS, the hydrophobicity of PMB increased by hydrogen bonding and electrostatic interactions and formed stabilized PMB-SDCS micelles. The PMB-SDCS formulation is likely to release PMB for easy penetration into the lipid membrane and cause disruption of the complex LPS micelles. Furthermore, the PMB-SDCS formulations neutralized and detoxified the LPS micelles with minimal toxicity to normal kidney tubular cells as well as an immortalised kidney cell line. The antimicrobial properties of PMBloaded SDCS nanomicelles were effective against a resistant strain of Pseudomonas aeruginosa.

Biomolecular interactions of amphotericin B nanomicelles with serum albumins: A combined biophysical and molecular docking approach

In this work, we investigated the interaction of amphotericin B (AmB) nanomicelles on the binding affinity and conformational change of human serum albumin (HSA) in comparison with bovine serum albumin (BSA) under physiological conditions by conducting several spectroscopic techniques further confirmed through molecular docking approaches. The experimental results showed that AmB nanomicelles could bind to both HSA and BSA to form protein/drug complexes with one binding site, and the binding process was spontaneous under physiological conditions. Fluorescence studies revealed that the quenching mechanism of these complexes was static quenching rather than dynamic quenching and exhibited strong binding between serum albumin and AmB nanomicelles. The results from UV-Visible spectra, FT-IR spectra, and CD spectra revealed that the AmB formulations affected the structure of both HSA and BSA proteins by changing the microenvironment around the tryptophan residues of protein and caused a secondary structure change of the protein with the loss of helical stability. The molecular docking experiments also supported the above results and effectively proved the binding and changes in the conformation of serum albumins by AmB micelles. This finding provides information of in vitro drug-plasma protein interactions for further study on the AmB binding mechanism and the pharmacodynamics and pharmacokinetics.

Bioactivity, Safety, and Efficacy of Amphotericin B Nanomicellar Aerosols Using Sodium Deoxycholate Sulfate as the Lipid Carrier

We report nanomicelles of amphotericin B (AmB) using various molar ratios of AmB and sodium deoxycholate sulfate (SDCS) for inhalation with improved stability, solubility, bioactivity, and safety. The particle sizes of all aerosolized formulations are expressed as mass median aerodynamic diameter (0.9-1.6 μm), fine particle fraction (70.3-86.5%), and geometric standard deviation (1.4-2.1) which indicated their sizes are appropriate for use as an inhaler. In vitro cytotoxicity studies conducted using respiratory and kidney cell lines demonstrated that the marketed Fungizone^® was toxic to macrophage and embryonic kidney cells and cell viability decreased from 96 to 48% and from 97 to 67%, respectively when the AmB equivalent concentration was increased from 1 to 16 μg/mL. However, AmB-SDCS formulations showed no evidence of toxicity even up to 8 μg/mL compared to Fungizone^®. Minimum inhibitory and fungicidal concentrations were significantly reduced against Cryptococcus neoformans, and Candida albicans. Also, antileishmanial activity significantly improved for AmB-SDCS formulations. There was an evidence of phagocytosis of the AmB-SDCS formulation by alveolar macrophages NR 8383. Molecular modeling studies suggested the role of hydrogen bonding in stabilization of the AmB-SDCS complex. This study indicated that AmB-SDCS nanomicelles can be used to design a safe and cost-effective AmB for inhalation. Graphical abstract ᅟ.