Synthesis and evaluation of styrene-maleic acid copolymer conjugated amphotericin B

Polymer-Mediated Delivery of Amphotericin B for Fungal Infections

Invasive fungal infections have been an increasingly global issue with high mortality. Amphotericin B (AmB), as the "gold standard" antifungal drug, has broad-spectrum antifungal activity and low clinical resistance. Therefore, AmB is the most commonly used polyene antibiotic for the treatment of invasive fungal infections. However, the serious side effects as well as the low bioavailability of AmB strongly restrict its clinical applications. Polymer, with its diversified molecular design, is widely used in drug delivery in the form of polymeric prodrugs, nanoparticles, hydrogels, etc. Therefore, polymers hold great promise for the delivery of AmB in treating fungal infections. This review summarizes recent advances in polymer-based delivery systems of AmB for the treatment of fungal infections, including polymer-AmB conjugates, nanotechnology-based polymeric delivery systems, hydrogels, and polymeric microneedles. Taking advantage of polymer-based delivery strategies, special attention is paid to reducing the side effects and improving the bioavailability of AmB for safe and effective antifungal therapy. Finally, the limitations and possible future directions of polymer-based AmB delivery systems are discussed.

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.

Nanotherapeutics for the delivery of antifungal drugs

The treatment of fungal infections is challenging with high death rates reported among immunocompromised patients. The currently available antifungals suffer from poor bioavailability and solubility, pharmacokinetics, and drug resistance, with limited cellular uptake. The clinical pipeline of new antifungals is dry. The incorporation of antifungal drugs into polymer-based nanocarriers to form nanotherapeutics is a promising approach to enhance the therapeutic outcomes of the available antifungal drugs. This review summarizes different polymer-based nanotherapeutics strategies that have been explored for the delivery of antifungals, resulting in enhanced therapeutic outcomes, such as improved pharmacokinetics, targeted/sustained delivery, prolonged drug circulation, retention of the drugs at the localized site of action, and overcoming drug resistance when compared with the free antifungal drugs.

Chemical and physical approaches for improved biopharmaceutical activity of amphotericin B: Current and future prospective

Over the last 50 years, the number of patients with mycotic infections has been increasing gradually. Amphotericin-B is a gold standard drug used in serious systemic fungal infections. However, limited solubility and permeability are challenging issues associated with Amphotericin-B. Chemical modification is one of the ways to get its broader applicability along with improved physicochemical properties. The review article provides a comprehensive overview of the chemical modification approach for investigation of the mechanism of action, biological activity, bioavailability, toxicity of Amphotericin B. Further, several drug delivery approaches have also been utilized to provide better therapeutic outcomes. This gives an overview of chemical approaches for the exploration of various factors associated with Amphotericin B and information on its drug delivery approaches for improved biopharmaceutical outcomes.

Amphotericin B nanohydrogel ocular formulation using alkyl glyceryl hyaluronic acid: Formulation, characterization, and in vitro evaluation

The present study focused on the development of an amphotericin B (AmB) nanoformulation for ophthalmic applications. Accordingly, AmB nanohydrogels (AHA/AmB) using alkyl glyceryl hyaluronic acid (Hyalorepair®, AHA), a hydrophobized hyaluronic acid, were prepared by employing the dialysis method, followed by assessments of physical properties, drug efficacy, and toxicity. In the AHA/AmB formulation, AmB existed in a self-aggregated and amorphous state in the hydrophobic environment of the AHA moiety. AHA/AmB was shown in vitro to interact with mucin, which is known to be expressed in the corneal epithelium and was expected to improve its corneal retention. Compared with the conventional AmB formulation, amphotericin B sodium deoxycholate, AHA/AmB had the same in vitro antifungal activity but significantly lower in vitro toxicity. These findings indicate that nanohydrogels prepared with AHA possess high fungal selectivity and serve as a promising system for ophthalmic AmB delivery.

Nanotechnology approaches for delivery and targeting of Amphotericin B in fungal and parasitic diseases

Amphotericin B (AMB), with widespread antifungal and anti-parasitic activities and low cross-resistance with other drugs, has long been identified as a potent antimicrobial drug. However, its clinical toxicities, especially nephrotoxicity, have limited its use in clinical practice. Lately, nano-based systems have been the subject of serious research and becoming an effective strategy to improve toxicity and antimicrobial potency. Commercial AMB lipid formulations have been developed in order to improve the therapeutic index and nephrotoxicity, while limited use is mainly due to their high cost. The review aimed to highlight the updated information on nanotechnology-based approaches to the development of AMB delivery and targeting systems for treatment of fungal diseases and leishmaniasis, regarding therapeutic challenges and achievements of various delivery systems.

Branched amphotericin functional poly(N-isopropyl acrylamide): an antifungal polymer

Branched poly(N-isopropylacrylamide) was functionalized with Amphotericin B (AmB) at the chain ends to produce an antifungal material. The polymer showed antifungal properties against AmB-sensitive strains of Candida albicans, Fusarium keratoplasticum and Aspergillus flavus (minimal inhibitory concentration ranged from 5 to 500 µg ml^-1) but was not effective against an AmB resistant strain of C. albicans nor against Candida tropicalis. The polymer end groups bound to the AmB target, ergosterol, and the fluorescence spectrum of a dye used as a solvatochromic probe, Nile red, was blue shifted indicating that segments of the polymer became desolvated on binding. The polymer was less toxic to corneal and renal epithelial cells and explanted corneal tissue than the free drug. Also, the polymer did not induce reactive oxygen species release from peripheral blood mononuclear cells, nor did it cause a substantial release of the proinflammatory cytokines, tumour necrosis factor-α and interleukin-1β (at 0.5 mg ml^-1).

Development of an amphotericin B micellar formulation using cholesterol-conjugated styrene-maleic acid copolymer for enhancement of blood circulation and antifungal selectivity

Amphotericin B (AmB) is an effective antifungal agent for life-threatening systemic fungal infections. However, its poor solubility in water and organic solvents makes it difficult to formulate. We previously reported AmB-encapsulated micellar formations using styrene-maleic acid copolymer (SMA) and butylated SMA. These micelles make AmB water-soluble; however, the blood circulation of AmB by these intravenous administrations was as low as that of Fungizone®, a conventional micellar formulation of AmB. The destabilization of SMA micelles by salt in the blood has been suggested to be a cause of low blood circulation. Therefore, in this study, to reduce salt-induced instability and increase blood circulation of the micelles, we covalently attached cholesterol molecules to the SMA backbone because AmB interacts with sterols. This AmB nanoparticle micellar formulation (Cho-SMA/AmB micelles) was water-soluble, stable in the presence of salts, and formed a complex with albumin. Compared with Fungizone®, this formulation had equal antifungal activity and markedly improved blood circulation and lower toxicity. Its toxicity was further reduced in the presence of albumin. Taken together, our results indicate that Cho-SMA/AmB micelles could be an intravenous formulation with high antifungal selectivity, and drug interactants-conjugated SMA system could be applied to a variety of drug-loaded nanomicellar systems.

[Nanoparticle Formation and Delivery of Poorly Water-soluble Drugs by Hydrophobized Polymers]

When a hydrophobic group is introduced into a water-soluble polymer, self-assembly with the hydrophobic group as nucleus occurs in water. In the 1990s, many researchers focused on this phenomenon and various self-aggregates were prepared. Among them, a block copolymer consisting of a hydrophilic chain and a hydrophobic chain is associated in water, producing polymer micelles with the hydrophilic chain oriented in the outer shell and the hydrophobic chain as core. Meanwhile, many studies were conducted to create polymer self-associates by introducing hydrophobic groups into water-soluble polymers. In this review, the author describes hydrophobized polymers with polysaccharides and synthetic polymers that are frequently used as pharmaceutical raw materials. In addition are outlined the usefulness of hydrophobized polymers as carriers with the function of encapsulating and solubilizing poorly water-soluble drugs, along with the results of our research.

Coenzyme Q10-Polyethylene Glycol Monostearate Nanoparticles: An Injectable Water-Soluble Formulation

Therapeutic applications of coenzyme Q10 (CoQ10) are greatly limited by its lack of solubility in aqueous media. In this study, polyethylene glycol monostearate (stPEG) was used to construct micelles containing CoQ10 as a new formulation. The micellar formulations (stPEG/CoQ10) were prepared using five types of stPEG with 10, 25, 40, 55, and 140 PEG repeat units, respectively. The micellar preparation was simple, consisting of only stPEG and CoQ10. Next, we compared the physical properties and blood circulation of these micelles. The CoQ10 load of this formulation was approximately 15 w/w%. Based on the dynamic light scattering method, the average molecular size of the stPEG/CoQ10 micelles was approximately 15 to 60 nm. The zeta potentials of these micelles were approximately −10 to −25 mV. The micelles using stPEG25, 40, and 55 demonstrated high solubility in water. Furthermore, these micelles had in vitro antioxidant activity. On comparing the blood circulation of micelles using stPEG25, 40, 55, and 140, micelles using stPEG55 had a significantly higher circulation in blood. The stPEG55/CoQ10 micelle demonstrated a protective effect against acetaminophen-induced liver injury in mice. In conclusion, these data indicate that the intravenous administration of the stPEG/CoQ10 micellar aqueous formulation is of great value against oxidant stress.