Original article
Improved yeast delivery of fluconazole with a nanostructured lipid carrier system

https://doi.org/10.1016/j.biopha.2017.02.008Get rights and content

Abstract

Despite the growing trends in the number of patients at risk for invasive fungal infections, management with current antifungal agents results in complications due to changes in the epidemiology and drug susceptibility of invasive fungal infections. In the present research fluconazole-loaded nanostructured lipid carriers were prepared using probe ultrasonication techniques and investigated the efficacy of the optimal formulation on a large number of Candida species. The morphology of the obtained nanostructured lipid carriers was characterized by transmission-electron microscopy. The minimum inhibitory concentrations (MIC) for the new formulations against strains of Candida were investigated using the Clinical and Laboratory Standards Institute document M27-A3 and M27-S4 as a guideline. The fluconazole-loaded nanostructured lipid carriers presented a spherical shape with a mean diameter, zeta potential and entrapment efficiency of 126.4 ± 15.2 nm, −35.1 ± 3.0 mV, and 93.6 ± 3.5%, respectively. The drug release from fluconazole-loaded nanostructured lipid carriers exhibited burst-release behavior at the initial stage followed by sustained release over 24 h. Using a new formulation of fluconazole led to a significant decrease in MICs for all Candida groups (P < 0.05). Furthermore, C. albicans isolates showed more susceptibility to fluconazole-loaded nanostructured lipid carriers than C. glabrata and C. parapsilosis (P < 0.05). The MIC50 drug concentration was obtained as 0.0625, 0.031 and 0.25 μg/ml for fluconazole-resistant strains of C. albicans, C. glabrata, and C. parapsilosis, respectively. In conclusion, a novel delivery system which can be used as part of a strategy to improve the antifungal activity of fluconazole against various Candida strains with different susceptibilities to conventional formulations of fluconazole was evaluated.

Introduction

A variety of novel drug carrier systems have recently been proposed to improve the bioavailability and release of drugs [1]. These systems are aimed at maintaining local effects and enhancing drug accumulation in various strata of skin through liposomes or niosomes [2], gel formulation [3], lecithin-based organogel [4], hydrogel [5] or polymeric mucoadhesive films, [6] poly-lactic co-glycolic acid (PLGA) microspheres [7], solid lipid nanoparticles (SLNs) [8], [9], and nanostructure lipid carriers (NLCs) [10]. In particular, NLCs have emerged as a promising drug delivery system for pharmaceutical and cosmetic molecules, especially for the delivery of lipophilic compounds [11], [12], [13]. Briefly, NLCs are colloidal nanocarriers in the submicron range (40–1000 nm) composed of a solid lipid matrix and a liquid lipid [13]. They have several desirable advantageous such as low toxicity of constituents, and the ability to protect the incorporated drug from degradation by immobilization in the solid/liquid particle matrix [14]. Moreover, NLCs have overcome problems associated with SLNs, including limited drug loading, risk of gelation, and drug leakage during storage caused by lipid polymorphism [14].

Fluconazole (FLZ), a first-generation triazole, is a broad-spectrum anti-fungal agent that inhibits cytochrome P450-dependent 14α-lanosterol demethylation, a vital step in cell membrane ergosterol synthesis [15]. Fluconazole is active against all Candida species except for C. glabrata, which has acquired resistance to fluconazole, and C. krusie, which is resistant to the drug intrinsically [16], [17]. Despite its advantageous pharmacological activity, FLZ can cause several clinically significant side effects, including headache, hives, itching or skin rash, abdominal pain, and hematemesis [3]. While the prevalence and severity of side effects may be decreased by lowering the dose of FLZ, clinical efficacy may be reduced and resistance increased through this approach. This problem is important because FLZ is currently used for both prophylaxis and the treatment of broad spectrum infections of candidiasis, yet, the emergence of drug-resistant isolates continues to increase dramatically [18], [19], [20]. In response to this challenge, the use of new drug formulations and drug delivery systems to reduce resistance while maintaining or increasing clinical efficacy are urgently needed [21], [22]. While there is limited evidence regarding the effectiveness of FLZ loaded NLCs (FLZ-NLC) [1] on Candida albicans, the activity of FLZ-NLCs against a broad range of Candida species, including C. glabrata and C. krusie, has not yet been studied. To this end, the purpose of the present study was to estimate the clinical efficacy of FLZ-NLCs on FLZ-resistant strains of certain Candida species.

Section snippets

Materials

Fluconazole (FLZ, Pharmaceutica grade) was obtained from Arasto Pharmaceuticals Chemicals Inc. (Tehran-Iran). Compritol® 888 ATO (CO), Lipocire and Precirol® ATO 5 were supplied from Gattefossé (Saint-Priest, Cedex, France). Sabouraud dextrose agar (SDA), RPMI medium, stearic acid (SA), Oleic acid, Tween 80 (Tn80), Span 60 (Sn60) and Span 80 (Sn80) were purchased from Merck Co. (Germany). HPLC grade acetonitrile and methanol were supplied by the Merck (Germany). Morpholinepropanesulfonic acid

Screening of lipids

After evaluating the solubility of FLZ in the lipids, four lipids with different physicochemical properties were selected for the formulation of lipid nanoparticles, as listed in Table 1. Since no drug crystals were observed when FLZ and Compritol® 888 ATO or stearic acid were heated together (for all solid lipid:liquid lipid ratios), Compritol® 888 ATO and stearic acid were selected for production of NLCs. In contrast, FLZ was not completely soluble in the other lipids listed in Table 1.

Characterization of SLNs

The

Conclusions

In this study, we evaluated a novel delivery system for combating several Candida strains that exhibit different susceptibility to a conventional formulation of FLZ. An FLZ-loaded NLC consisting of stearic acid was successfully prepared by probe ultrasonication technique. Novel drug formulations may avoid drug recognition by efflux pump proteins, keeping the drug away from transporters. This study was the first to report the effectiveness of FLZ-NLCs as alternative delivery systems for FLZ on

Conflict of interest

There is no conflict of interest.

Acknowledgments

This research was financially supported by a Mazandaran University of Medical Sciences (MazUMS), Iran grant (No. 2013) given to Maryam Moazeni. The funder had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

References (39)

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