Amphotericin B-albumin conjugates: Synthesis, toxicity and anti-fungal activity

"Click" amphotericin B in prodrug nanoformulations for enhanced systemic fungemia treatment

Severe nephrotoxicity and infusion-related side effects pose significant obstacles to the clinical application of Amphotericin B (AmB) in life-threatening systemic fungal infections. In pursuit of a cost-effective and safe formulation, we have introduced multiple phenylboronic acid (PBA) moieties onto a linear dendritic telodendrimer (TD) scaffold, enabling effective AmB conjugation via boronate chemistry through a rapid, high yield, catalysis-free and dialysis-free "Click" drug loading process. Optimized AmB-TD prodrugs self-assemble into monodispersed micelles characterized by small particle sizes and neutral surface charges. AmB prodrugs sustain drug release in circulation, which is accelerated in response to the acidic pH and Reactive Oxygen Species (ROS) in the infection and inflammation. Prodrugs mitigate the AmB aggregation status, reduce cytotoxicity and hemolytic activity compared to Fungizone®, and demonstrate superior antifungal activity to AmBisome®. AmB-PEG5kBA4 has a comparable maximum tolerated dose (MTD) to AmBisome®, while over 20-fold increase than Fungizone®. A single dose of AmB-PEG5kBA4 demonstrates superior efficacy to Fungizone® and AmBisome® in treating systemic fungal infections in both immunocompetent and immunocompromised mice.

AmBisome® Formulations for Pediatrics: Stability, Cytotoxicity, and Cost-Effectiveness Studies

Liposomal amphotericin B (Ambisome®) is the gold standard for the treatment and prevention of fungal infections both in the adult and pediatric populations. The lyophilized dosage form has to be reconstituted and diluted by hospital staff, but its management can be challenging due to the spontaneous tendency of amphotericin B to form aggregates with different biological activity. In this study, the colloidal stability of the liposomes and the chemical stability of amphotericin B were investigated over time at storage conditions. Three liposomal formulations of amphotericin B at 4.0 mg/mL, 2.0 mg/mL, and 0.2 mg/mL were prepared and assayed for changes regarding the dimensional distribution, zeta potential, drug aggregation state, and onset of by-products. Our analyses highlighted that the most diluted formulation, kept at room temperature, showed the greatest changes in the aggregation state of the drug and accordingly the highest cytotoxicity. These findings are clinically relevant since the lower dosages are addressed to the more vulnerable patients. Therefore, the centralization of the dilution of AmBisome® at the pharmacy is of fundamental importance for assuring patient safety, and at the same time for reducing medication waste, as we demonstrated using the cost-saving analysis of drug expense per therapy carried out at the G. Gaslini children hospital.

Searching for Conjugates as New Structures for Antifungal Therapies

The progressive increase in fungal infections and the decrease in the effectiveness of current therapy explain research on new drugs. The synthesis of compounds with proven antifungal activity, favorable physicochemical and pharmacokinetic properties affecting their pharmaceutical availability and bioavailability, and limiting or eliminating side effects has become the goal of many studies. The publication describes the directions of searching for new compounds with antifungal activity, focusing on conjugates. The described modifications include, among others, azoles or amphotericin B in combination with fatty acids, polysaccharides, proteins, and synthetic polymers. The benefits of these combinations in terms of activity, mechanism of action, and bioavailability were indicated. The possibilities of creating or using nanoparticles, "umbrella" conjugates, siderophores (iron-chelating compounds), and monoclonal antibodies were also presented. Taking into account the role of vaccinations in prevention, the scope of research related to developing a vaccine protecting against fungal infections was also indicated.

Conjugates of amphotericin B to resolve challenges associated with its delivery

INTRODUCTION

Amphotericin B (AmB), a promising antifungal and antileishmanial drug, acts on the membrane of microorganisms. The clinical use of AmB is limited due to issues associated with its delivery including poor solubility and bioavailability, instability in acidic media, poor intestinal permeability, dose and aggregation state dependent toxicity, parenteral administration, and requirement of cold chain for transport and storage, etc.

AREAS COVERED

Scientists have formulated and explored various covalent conjugates of AmB to reduce its toxicity with increase in solubility, oral bioavailability, and payload or loading of AmB by using various polymers, lipids, carbon-based nanocarriers, metallic nanoparticles, and vesicular carriers, etc. In this article, we have reviewed various conjugates of AmB with polymers and nanomaterials explored for its delivery to give a deep insight regarding further exploration in future.

EXPERT OPINION

Covalent conjugates of AmB have been investigated by scientists, and preliminary in vitro and animal investigations have given successful results, which are required to be validated further with systematic investigation on safety and therapeutic efficacy in animals followed by clinical trials.

Evaluation of proline-rich antimicrobial peptides as potential lead structures for novel antimycotics against Cryptococcus neoformans

Background

Cryptococcosis and cryptococcal meningitis, caused by Cryptococcus neoformans infections, lead to approximately 180,000 deaths per year, primarily in developing countries. Individuals with compromised immune systems, e.g., due to HIV infection (AIDS) or chemotherapy, are particularly vulnerable. Conventional treatment options are often limited and can cause severe side effects. Therefore, this study aimed to investigate the antifungal effect of insect-derived proline-rich antimicrobial peptides (PrAMPs) against C. neoformans. These peptides are known for their low toxicity and their high efficacy in murine infection models, making them a promising alternative for treatment.

Results

A preliminary screening of the minimal inhibitory concentrations (MICs) of 20 AMPs, including the well-known PrAMPs Onc112, Api137, and Chex1Arg20 as well as the cathelicidin CRAMP against the C. neoformans strains 1841, H99, and KN99α revealed promising results, with MICs as low as 1.6 μmol/L. Subsequent investigations of selected peptides, determining their influence on fungal colony-forming units, confirmed their strong activity. The antifungal activity was affected by factors such as peptide net charge and sequence, with stronger effects at higher net charges probably due to better intracellular uptake confirmed by confocal laser scanning microscopy. Inactive scrambled peptides suggest a specific intracellular target, although scanning electron microscopy showed that PrAMPs also damaged the cell exterior for a low proportion of the cells. Possible pore formation could facilitate entry into the cytosol.

Development of a yeast cell based method for efficient screening of high yield tacrolimus production strain

Tacrolimus (FK506) is a widely used and clinically important immunosuppressant drug that can be produced by fermentation of Streptomyces tsukubaensis. The industrial strains are typically obtained through multiple rounds of mutagenesis and screening, a labor-intensive process. We have established an efficient yeast cell based screening method for the evolutionary process of high-FK506-yielding strain. The S. tsukubaensis strains of different FK506 yields were tested for zone of growth inhibition of the wild type and calcineurin mutant (cnb1∆) yeast strains. We found that different FK506 yields correspond well to altered yeast growth inhibitions. Based on the combinational inhibition effects of FK506 with different antifungals that have been frequently reported, we also tested the zone of inhibition by addition of fluconazole, amphotericin B and caspofungin to the medium. In the end, for the best screening performance, we systemically evaluated the strategy when different yeast strains and different antifungals were used according to the clarity, size, and divergence of the inhibition circles. Using different yeast strains and antifungals, we successfully broadened the screening spectrum. An efficient high-FK506-yield S. tsukubaensis screening method has been established and optimized.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03870-y.

Role of Polyanions and Surfactant Head Group in the Formation of Polymer-Colloid Nanocontainers

OBJECTIVES

This study was aimed at the investigation of the supramolecular systems based on cationic surfactants bearing cyclic head groups (imidazolium and pyrrolidinium) and polyanions (polyacrylic acid (PAA) and human serum albumin (HSA)), and factors governing their structural behavior to create functional nanosystems with controlled properties. Research hypothesis. Mixed PE-surfactant complexes based on oppositely charged species are characterized by multifactor behavior strongly affected by the nature of both components. It was expected that the transition from a single surfactant solution to an admixture with PE might provide synergetic effects on structural characteristics and functional activity. To test this assumption, the concentration thresholds of aggregation, dimensional and charge characteristics, and solubilization capacity of amphiphiles in the presence of PEs have been determined by tensiometry, fluorescence and UV-visible spectroscopy, and dynamic and electrophoretic light scattering.

RESULTS

The formation of mixed surfactant-PAA aggregates with a hydrodynamic diameter of 100-180 nm has been shown. Polyanion additives led to a decrease in the critical micelle concentration of surfactants by two orders of magnitude (from 1 mM to 0.01 mM). A gradual increase in the zeta potential of HAS-surfactant systems from negative to positive value indicates that the electrostatic mechanism contributes to the binding of components. Additionally, 3D and conventional fluorescence spectroscopy showed that imidazolium surfactant had little effect on HSA conformation, and component binding occurs due to hydrogen bonding and Van der Waals interactions through the tryptophan amino acid residue of the protein. Surfactant-polyanion nanostructures improve the solubility of lipophilic medicines such as Warfarin, Amphotericin B, and Meloxicam.

PERSPECTIVES

Surfactant-PE composition demonstrated beneficial solubilization activity and can be recommended for the construction of nanocontainers for hydrophobic drugs, with their efficacy tuned by the variation in surfactant head group and the nature of polyanions.

Amphiphilic hyperbranched polyglycerol nanoarchitectures for Amphotericin B delivery in Candida infections

Although Amphotericin B (AMB) is considered the most effective anti-mycotic agent for treating Candida infections, its clinical use is limited due to its high toxicity. To address this issue, we developed cholesterol-based dendritic micelles of hyperbranched polyglycerol (HPG), including cholesterol-cored HPG (Chol-HPG) and cholesterol end-capped HPG (HPG@Chol), for AMB delivery. The findings suggested that the presence of cholesterol moieties could control AMB loading and release properties. Dendritic micelles inhibited AMB hemolysis and cytotoxicity in HEK 293 and RAW 264.7 cell lines while increasing antifungal activity against C. albicans biofilm formation. Furthermore, significantly lower levels of renal and liver toxicity biomarkers compared to Fungizone® ensured AMB-incorporated dendritic micelle biosafety, which was confirmed by histopathological evaluations. Overall, the Chol-HPG and HPG@Chol dendritic micelles may be a viable alternative to commercially available AMB formulations as well as an effective delivery system for other poorly soluble antifungal agents.

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.

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.

Hyaluronic acid-Amphotericin B Nanocomplexes: a Promising Anti-Leishmanial Drug Delivery System

The development of an effective amphotericin B (AmB) formulation to replace actual treatments available for leishmaniasis, which present serious drawbacks, is a challenge. Here we report the development of hyaluronic...

Alginate-amphotericin B nanocomplexes covered by nanocrystals from bacterial cellulose: physico-chemical characterization and in vitro toxicity

Nanocomplexes systems made up natural poylymers have pharmacotechnical advantages such as increase of water solubility and a decrease of drugs toxicity. Amphotericin B (AmB) is a drug apply as anti-leishmanial and anti-fungal, however it has low water solubility and high toxicity, limiting its therapeutic application. With this in mind, the present study aimed to produce nanocomplexes composed by alginate (Alg), a natural polymer, with AmB covered by nanocrystals from bacterial cellulose (CNC). For this reason, the nanocomplexes were produced utilizing sodium alginate, amphotericin B in a borate buffer (pH 11.0). The CNC was obtained by enzymatic hydrolysis of the bacterial cellulose. To CNC cover the nanocomplexes 1 ml of the nanocomplexes was added into 1 ml of 0.01% CNC suspension. The results showed an ionic adsorption of the CNC into the Alg-AmB nanocomplexes surface. This phenomena was confirmed by an increase in the particle size and PDI decrease. Besides, nanocomplexes samples covered by CNC showed uniformity. The amorphous inclusion of AmB complex into the polysaccharide chain network in both formulations. AmB in the nanocomplexes was in supper-aggregated form and showed good biocompatibility, being significantly less cytotoxic in vitro against kidney cells and significantly less hemolytic compared to the free-drug. The in vitro toxicity results indicated the Alg-AmB nanocomplexes can be considered a non-toxic alternative to improve the AmB therapeutic effect. All process to obtain nanocomplexes and it coat was conduce without organic solvents, can be considered a green process, and allowed to obtain water soluble particles. Furthermore, CNC covering the nanocomplexes brought additional protection to the system can contribut advancement in the pharmaceutical.

Recent Advancements in Serum Albumin-Based Nanovehicles Toward Potential Cancer Diagnosis and Therapy

Recently, drug delivery vehicles based on nanotechnology have significantly attracted the attention of researchers in the field of nanomedicine since they can achieve ideal drug release and biodistribution. Among the various organic or inorganic materials that used to prepare drug delivery vehicles for effective cancer treatment, serum albumin-based nanovehicles have been widely developed and investigated due to their prominent superiorities, including good biocompatibility, high stability, nontoxicity, non-immunogenicity, easy preparation, and functionalization, allowing them to be promising candidates for cancer diagnosis and therapy. This article reviews the recent advances on the applications of serum albumin-based nanovehicles in cancer diagnosis and therapy. We first introduce the essential information of bovine serum albumin (BSA) and human serum albumin (HSA), and discuss their drug loading strategies. We then discuss the different types of serum albumin-based nanovehicles including albumin nanoparticles, surface-functionalized albumin nanoparticles, and albumin nanocomplexes. Moreover, after briefly discussing the application of serum albumin-based nanovehicles used as the nanoprobes in cancer diagnosis, we also describe the serum albumin-based nanovehicle-assisted cancer theranostics, involving gas therapy, chemodynamic therapy (CDT), phototherapy (PTT/PDT), sonodynamic therapy (SDT), and other therapies as well as cancer imaging. Numerous studies cited in our review show that serum albumin-based nanovehicles possess a great potential in cancer diagnostic and therapeutic applications.

Synergic activity of oligostyrylbenzenes with amphotericin B against Candida tropicalis biofilms

Antimicrobial drug resistance is a serious challenge in clinical settings worldwide, with biofilm formation having been associated with this problem. In the present study, the synergism of oligostyrylbenzene (OSB) compounds in combination with amphotericin B (AmB) against Candida tropicalis biofilms was investigated. In addition, the toxicity in human blood cells was determined. Synergistic combinations of OSBs and AmB were evaluated to consider future effects of OSBs in vivo. The checkerboard microdilution method was used to study the interactions of one anionic (1) and two cationic (2 and 3) OSBs with AmB. We investigated the effects of OSBs on reactive oxygen species (ROS) and the levels of the reactive nitrogen intermediates (RNIs). The cellular stress affected biofilm growth through an accumulation of ROS and RNI, at synergistic concentrations of OSBs and AmB. Furthermore, significant surface topography differences were noted upon treatment with the OSB 2/AmB combination, using confocal laser scanning microscopy in conjunction with the image analysis software COMSTAT. The results revealed a low toxicity to leukocytes and red blood cells at synergistic combinations of cationic OSBs with AmB. These findings demonstrated the antibiofilm effects of OSBs and the synergism of AmB with cationic OSBs against biofilms of C. tropicalis for the first time.

Delivery strategies of amphotericin B for invasive fungal infections

Invasive fungal infections (IFIs) represent a growing public concern for clinicians to manage in many medical settings, with substantial associated morbidities and mortalities. Among many current therapeutic options for the treatment of IFIs, amphotericin B (AmB) is the most frequently used drug. AmB is considered as a first-line drug in the clinic that has strong antifungal activity and less resistance. In this review, we summarized the most promising research efforts on nanocarriers for AmB delivery and highlighted their efficacy and safety for treating IFIs. We have also discussed the mechanism of actions of AmB, rationale for treating IFIs, and recent advances in formulating AmB for clinical use. Finally, this review discusses some practical considerations and provides recommendations for future studies in applying AmB for combating IFIs.

Antibiotics armed neutrophils as a potential therapy for brain fungal infection caused by chemotherapy-induced neutropenia

Chemotherapy-induced neutropenia, a symptom of neutrophil depletion, makes cancer patients highly susceptible to invasive fungal infection with substantial morbidity and mortality. To address the cryptococcal brain infection in this condition, this study attempts to arm neutrophils (NEs) with antibiotics to potentiate the antifungal capability of NEs. To allow effective integration, amphotericin B, a potent antibiotic, is assembled with albumin nanoparticles through hydrophobic and hydrogen-bond interactions to form AmB@BSA nanoparticles (A-NPs). The nutrient composition (albumin) and virus-like size (~40 nm) facilitate efficient uptake of A-NPs by NEs to construct the antibiotics-armed NEs. It is demonstrated that the armed NEs can maintain the intrinsic biological functions of NEs, such as cell viability and capacity of migration to an inflammatory site. In a neutropenic mouse model of brain fungal infection, the treatment with the armed NEs allows for preventing fungal invasion more effectively than that with the native NEs, without the apparent systemic toxicity. Such a synergistic anti-infection system maximizes the antifungal effects by taking advantage of NEs and antibiotics. It provides a potential NEs-mediated therapeutic approach for treating fungal infection caused by chemotherapy-induced neutropenia.

Importance of the fatty acid chain length on in vitro and in vivo anticancer activity of fattigation-platform albumin nanoparticles in human colorectal cancer xenograft mice model

The aims of this study were to design different chain length fatty acid-conjugated albumin nanoparticles (ANPs) and evaluate their anticancer activity in the HCT116 human colorectal cancer xenograft mouse model. Doxorubicin hydrochloride (DOX·HCl) was chosen as a model drug. The different chain lengths of fatty acids (butyric acid; C4, and stearic acid; C18) in albumin conjugates exhibited different physicochemical properties and anticancer activity. Fatty acid-conjugated albumin aided the formation of self-assembled structures with an average size of approximately 200 nm and a negative charge when incubated with excess DOX in an aqueous solution. DOX-loaded long-chain C18-conjugated ANPs allowed efficient encapsulation of hydrophobic DOX into the core of the self-assembled structure, enabling higher drug loading, enhanced colloidal stability and controlled release behavior in PBS pH 7.4 medium as compared with free DOX·HCl or non-fatty acid conjugated ANPs. Furthermore, DOX-loaded fatty acid-conjugated ANPs showed an increased cellular uptake intensity and cytotoxic effects in vitro. In vivo, HCT116 xenograft model experiments confirmed that DOX-loaded C18-conjugated ANPs showed improved anticancer activity and reduced side effects compared with the DOX-treated groups. The long-chain fatty acid-conjugated ANPs synergistically activated the interaction with the free-fatty acid receptor (FFAR) on HCT116 colorectal cancer cells as compared with short-chain C4 or other non-conjugated ANPs. Specifically, DOX-loaded C18-conjugated NPs exhibited significant performance to overexpressed FFAR4 on HCT116 colorectal cancer cells. The fatty acid chain length in the fattigation-platform system could be a promising molecular moiety to improve targeting efficiency and drug accumulation in various cancer therapy.

Turning weakness into strength: Albumin nanoparticle-redirected amphotericin B biodistribution for reducing nephrotoxicity and enhancing antifungal activity

As the gold standard treatment for invasive fungal infection, amphotericin B (AmB) is limited by its severe nephrotoxicity. It has been shown that AmB complex with albumin in vivo forms a sub-10 nm nanocomplex within kidney excretion size range and eventually induces the nephrotoxicity. This study presents an approach to take advantage of the "weakness" of such unique interaction between AmB and albumin to form AmB nanocomplex beyond the size range of kidney excretion. Herein, a novel strategy was developed by directly assembling molecular BSA into larger-sized nanostructures with the reconstructed intermolecular disulfide bond and hydrophobic interaction. The rich binding sites of AmB within BSA nanostructures enabled the efficient AmB loading and forming nanoparticle (AmB-NP) which exceeds the size range of kidney excretion (~ 60 nm). We found nanoassembly with BSA redirected biodistribution of AmB with a 2.8-fold reduction of drug accumulation in the kidney and significantly improved its renal impairment in mice. Furthermore, we found that nanoassembly with BSA significantly increased the biodistribution of AmB in brain and endowed it 100-folds increase in pharmacological effect against meningoencephalitis caused by common fungal pathogen Cryptococcus neoformans. Together, this study not merely overcomes the nephrotoxicity of AmB using its "weakness" by a nanoassembly method, and provides a new strategy for reducing toxicity of drugs with high albumin binding rate in vivo.

Development of dextrin-amphotericin B formulations for the treatment of Leishmaniasis

The most effective medicines available for the treatment of leishmaniasis, a life-threatening disease, exhibit serious toxicological issues. To achieve better therapeutic efficiency while decreasing toxicity associated with amphotericin B (AmB), water-soluble dextrin-AmB (Dex-AmB) formulations were developed. Self-assembled nanocomplexes were formed by dissolving Dex and AmB in alkaline borate buffer, followed by dialysis and either freeze-drying (FD) or nano spray-drying (SD), yielding water dispersible particles with a diameter of 214 nm and 347 nm, respectively. The very simple production process allowed the formation of amorphous inclusion complexes containing 14% of AmB in the form of monomers and water-soluble aggregates. Nanocomplexes were effective against parasites in axenic culture (IC₅₀ of 0.056 and 0.096 μM for L. amazonensis and 0.030 and 0.044 μM for L. infantum, respectively for Dex-AmB FD and Dex-AmB SD) and in decreasing the intramacrophagic infection with L. infantum (IC₅₀ of 0.017 and 0.023 μM, respectively for Dex-AmB FD and Dex-AmB SD). Also, the formulations were able to significantly reduce the cytotoxicity of AmB. Overall, this study demonstrates the suitability of dextrin as an AmB carrier and the facile and inexpensive development of a delivery system for the treatment of leishmaniasis.

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.

Linolenic acid-modified MPEG-PEI micelles for encapsulation of amphotericin B

Aim: To encapsulate amphotericin B (AmB) with reduced toxicity and comparable activity. Results & methodology: The α-linolenic acid (ALA)-modified monomethoxy polyethylene glycol-g-PEI-g-ALA conjugate was employed to prepare AmB-loaded micelles (AmB-M). In vitro activity and release behavior of AmB-M were investigated. AmB-M enhanced AmB's water-solubility to 1.2 mg/ml, showing good storage stability. AmB-M could achieve a sustained and slow release of AmB, low hemolysis activity and negligible kidney toxicity when compared with commercial AmB injection. Antifungal activity and biofilm inhibition experiments confirmed that the antifungal activity of AmB-M against Candida albicans was similar to that of AmB injection. Conclusion: Monomethoxy polyethylene glycol-g-PEI-g-ALA micelles could be a preferable choice to treat systemic fungal infections as an efficient drug delivery system.

Polymer–Drug Conjugates for Treating Local and Systemic Fungal Infections

In immunocompromised patients, fungal infections are the major cause of morbidity and mortality. Currently, three major classes of drugs—polyenes, azoles, and echinocandins—with different mechanisms of action are used as antifungals for systemic infections. However, these conventional drugs were reported to induce toxic effects due to their low specificity, narrow spectrum of activity and drug–drug interactions. Some of these limitations could be overcome by altering the properties of existing drugs through physical and chemical modifications. For example, modification of amphotericin B (AmB), a polyene antibiotic includes the micellar suspension of AmB in deoxycholic acid (Fungizone®), non-covalent AmB lipid complexes (ABLC™), liposomal AmB (AmBisome®), and AmB colloidal dispersion (Amphocil™). All these formulations ensure the smoother release of AmB accompanied by its restricted distribution in the kidney, thereby lowering its nephrotoxicity. Although various methods such as polymeric micelles, nanoparticles and dendrimers were explored for enhancing the efficacy of the antifungal drugs, polymer–drug conjugates of antifungal drugs have received more attention in recent years. Polymer–drug conjugates improve the aqueous solubility of water-insoluble drugs, are stable in storage and reduce the toxicity of highly toxic drugs and are capable of releasing the drug at the site of action. This chapter discusses the polymer conjugates of antifungal drugs, their merits, and demerits. Studies reported so far show that the polymer–drug conjugates have significant advantages compared to conventional dosage forms for antifungal therapy.

Conjugating doxorubicin to polymannose: a new strategy for target specific delivery to lung cancer cells

As mannose receptors are known to be over-expressed in cancer cells, we synthesized polymannose-doxorubicin (PM-DOX) conjugates with the objective of targeting the drug to cancer cells. DOX was conjugated to oxidized PM through Schiff's linkages to obtain PM-DOX conjugates. In order to examine the superior targeting efficacy of PM-DOX conjugate, sodium alginate (SA) was conjugated to DOX by similar chemistry and compared with PM-DOX conjugate. The cytotoxicity of the conjugates was investigated in A549 cell lines using MTT Assay and the cell uptake and retention studies, were performed using flow cytometry and cell imaging. In vitro drug release studies with both PM-DOX and SA-DOX conjugates showed an initial burst release of DOX up to 37-39% at 1 h, followed by a steady release up to 58-62% at 24 h in human plasma while negligible release was observed in phosphate buffered saline. The conjugates exhibited negligible hemolytic potential to human erythrocytes compared to free DOX. The PM-DOX conjugate showed better cytotoxic potential against A549 cells at lower concentration (equivalent to 0.27 μg/mL of DOX) at 72 h compared to free DOX and SA-DOX conjugate. Further, PM-DOX conjugate showed enhanced uptake by the cells in comparison with SA-DOX conjugate thereby confirming the target specificity of PM to the cancer cells.

Synthesis and characterization of NH2-(AEEA)n-amphotericin B derivatives

To find novel amphotericin B (AmB) derivatives with high therapeutic potential, low toxicity, and water solubility, a series of nine N-substituted AmB derivatives were evaluated for their antifungal activity using the broth dilution method and for their hemolytic toxicity with sterile defibrinated sheep blood. Qualitative screening of the effect of the derivatives on two reference Candida albicans strains and of their solubility was performed based on the value of n (n is a positive integer), resulting in the identification of an optimal compound, NH₂-(AEEA)₅-AmB (DMR005; AEEA is 8-amino-3,6- dioxaoctanoic acid). Preliminary safety assessments of DMR005 were carried out via the MTT cell viability assay in vitro and acute toxicity assay in vivo. In general, DMR005 not only has higher water solubility and less toxicity than the parent polyene but also retains antifungal potency.