Polyenes in Medium Chain Length Polyhydroxyalkanoate (mcl-PHA) Biopolymer Microspheres with Reduced Toxicity and Improved Therapeutic Effect against Candida Infection in Zebrafish Model

Abstract

Immobilizing antifungal polyenes such as nystatin (Nys) and amphotericin B (AmB) into biodegradable formulations is advantageous compared to free drug administration providing sustained release, reduced dosing due to localized targeting and overall reduced systemic drug toxicity. In this study, we encapsulated Nys and AmB in medium chain length polyhydroxyalkanoates (mcl-PHA) microspheres (7–8 µm in diameter). The obtained formulations have been validated for antifungal activity in vitro against a panel of pathogenic fungi including species of Candida, Aspergillus, Microsporum and Trichophyton genera and toxicity and efficacy in vivo using the zebrafish model of disseminated candidiasis. While free polyenes, especially AmB, were highly toxic to zebrafish embryos at the effective (MIC) doses, after their loading into mcl-PHA microspheres, inner organ toxicity and teratogenicity associated with both drugs were not observed, even at 100 × MIC doses. The obtained mcl-PHA/polyene formulations have successfully eradicated C. albicans infection and showed an improved therapeutic profile in zebrafish by enhancing infected embryos survival. This approach is contributing to the antifungal arsenal as polyenes, although the first broad-spectrum antifungals on the market are still the gold standard for treatment of fungal infections.

A Review of Current Achievements and Recent Challenges in Bacterial Medium-Chain-Length Polyhydroxyalkanoates: Production and Potential Applications

“…While free polyenes, notably, amphotericin B, exhibited high toxicity to zebrafish embryos at effective minimum inhibitory concentration doses, this toxicity was not observed when the drugs were loaded into mcl-PHA microspheres. The mcl-PHA/polyene formulations obtained from this study significantly improved the therapeutic profile in zebrafish by increasing the survival rate of infected embryos . Another potential use for PHAs is in creating antimicrobial wound dressings .…”

“…The mcl-PHA/polyene formulations obtained from this study significantly improved the therapeutic profile in zebrafish by increasing the survival rate of infected embryos. 110 Another potential use for PHAs is in creating antimicrobial wound dressings. 109 In a study by Balcucho et al, 109 it was found that incorporating poly(3-hydroxyoctanoate)-co-(3hydroxyhexanoate) with silver nanoparticles into wound dressings yielded promising results for treating skin and soft tissue infections associated with chronic skin conditions.…”

“…The prominence of PHAs stems from their inherent characteristics, including thermoplasticity, biodegradability, nontoxicity, and biocompatibility . In recent years, the investigation of mcl-PHA toxicity has garnered attention for various biomedical applications, such as drug delivery, antimicrobial agents, and wound dressing. , For example, due to the pronounced toxicity of polyenes, which limits their systemic application despite their general effectiveness as antifungal drugs, and considering the scarcity of new antifungal agents, Pavic et al’s study suggested that immobilizing antifungal polyenes like nystatin and amphotericin B into mcl-PHA microspheres offers several advantages over free drug administration. These advantages include sustained release, reduced dosing requirements due to localized targeting, and an overall decrease in systemic drug toxicity.…”

“…Among PHA family members, mcl-PHAs can be used in medical device fabrication and tissue engineering fields such as cardiovascular application sutures, matrices for controlled drug delivery, bone marrow scaffolds, etc. , They can be used in delivery systems by improving the polymeric nanoparticles for controlled drug delivery in the human body. ,, For example, Pavic et al used a biodegradable and biocompatible matrix of mcl-PHA microspheres to encapsulate polyenes, including nystatin and amphotericin B, for the effective treatment of fungal infections. In the market for more than 60 years, polyenes are the oldest class of antifungal drugs.…”

“…111,159 They can be used in delivery systems by improving the polymeric nanoparticles for controlled drug delivery in the human body. 151,160,161 For example, Pavic et al 110 used a biodegradable and biocompatible matrix of mcl-PHA microspheres to encapsulate polyenes, including nystatin and amphotericin B, for the effective treatment of fungal infections. In the market for more than 60 years, polyenes are the oldest class of antifungal drugs.…”