Visionary NanoBoost: Revolutionizing ocular treatment with positively charged Leciplex for enhanced Fenticonazole nitrate ocular delivery

Abstract

This work outlines the formulation and characterization of Fenticonazoleloaded LeciPlex (FCN-LPX), adopting a simple blending technique for the eradication of oculomycosis. Fenticonazole nitrate (FCN) is a pleiotropic fungistatic and fungicidal agent with sparse aqueous solubility, hampering its transcorneal permeation. Three independent factors were probed using a 2³ factorial design (2 blocks, 2 replicates), namely, X₁: Cationic surfactant type, X₂: Amount of cationic surfactant (mM), and X₃: Amount of soybean phosphatidyl choline (mM). The optimized formulation exhibited remarkable entrapment efficiency (82.74 % ± 0.67 %), as verified by DSC and FT-IR analysis. TEM imaging revealed uniformly nanosized vesicles (189.95 ± 2.90 nm) with a robust positive zeta potential (41.35 ± 2.62 mV), which preserved its stability following gamma sterilization and storage. The optimum FCN-LPX demonstrated a bi-phasic release pattern (48.18 % ± 5.65 % at 4 H and 92.85 % ± 6.77 % at 24 H) and notable mucoadhesive properties, ensuring complete drug release. Safety assessments, including pH, surface tension, and refractive index measurements, along with histopathological evaluation, confirmed the formulation’s safety profile. Furthermore, FCN-LPX achieved superior ex-vivo transcorneal permeation (3.3-fold) and deeper in-vivo corneal uptake (2.4-fold) compared to conventional FCN suspension. Microbiological analysis highlighted the enhanced antifungal activity of FCN-LPX, evidenced by a larger inhibition zone (11 %), significantly lower minimal inhibitory and fungicidal concentrations (8-fold), as well as improved fungal biofilm inhibition and prolonged antifungal effect. In conclusion, FCN-LPX is a propitious nanoformulation for the effective eradication of persistent oculomycosis.

Introduction

Oculomycosis, the second major cause of sight loss, is a severe corneal mycotic infection and a major culprit accused for the ulceration and inflammation of cornea, with a detrimental impact on vision [1]. Twenty years ago, forecasts were made regarding the prevalence of oculomycosis [2]. Such projections are manifested by the recent estimates of annual fresh cases reaching nearly one and a half million cases [3]. The amalgamation of high humidity and high temperature, one of the consequences of global warming, endows a prolific and thriving habitat for such infection to prevail, especially in a tropical-subtropical belt, where over half of the cases are tied to such climatic conditions [4]. Moreover, countries where farming activities are the main livelihood alongside the lack of proper hygienic practices are believed to be at higher risk [5]. Many predisposing factors are believed to increase the likelihood of ocular mycotic infections, including the unsanitary storage of contact lenses, long-term use of steroids, ocular post-operative recovery, superficial ocular diseases, and secondary to immunocompromised conditions [6].

The management of mycotic infections includes the use of antimycotic agents, which are structurally divided into 4 types: allylamines, azoles, echinocandins, and polyenes [7,8]. Fenticonazole nitrate (FCN), is an antimycotic agent classified as imidazole which is a subtype of azoles. It acts as a fungistatic and fungicidal agent at low and high concentrations, respectively. The underlying mechanism for its fungistatic activity takes place by prohibiting ergosterol synthesis [9]. On the other hand, it acts as a fungicidal agent by impairing the fungal cytoplasmic membrane’s permeability [10]. Moreover, FCN thwarts fungal acid protease’s secretion and curbs the synthesis of cytochrome oxidases and peroxidases, thus impeding fungal adhesion to epithelial cells [11]. This antifungal is commonly employed to treat various fungal infections, including oculomycosis, dermatophytosis, and candidiasis. However, its corneal permeation is notably hampered by its lipophilicity (log P = 6.31) and sparse water solubility (<0.1 mg/mL) [40]. However, a review of the literature revealed multiple efforts to explore the potential of ocular FCN delivery, including the formulation of novasomes [12], terpesomes [9], cubosomes [40], and olaminosomes [13].

Ophthalmic drops are one of the commonly used delivery systems for antimycotic agents for the management of oculomycosis [14]. The popularity of such a system is attributed to its low invasiveness, rapid effectiveness, simplicity of use, minimal side effects, cost efficiency, and increased patient adherence. [15]. Unfortunately, such benefits are constrained by the intricacies hindering transcorneal permeation, such as reflex-blinking, tight epithelium junctions, and metabolic processes [[16], [17], [18]]. Tears, a natural hydration mechanism, lead to the dilution (10x) of the instilled drugs in the tear film alongside nasolacrimal drainage and rapid elimination due to reflex-blinking; thus, limited bioavailability (<5 %) is expected [19].

LeciPlex are emerging nanocarriers bearing positive surface charge which were first introduced by Date et al. [20]. LeciPlex are simply composed of cationic surfactants such as DDAB and CTAB alongside lecithin and cosolvent such as Transcutol® or ethanol. Such discerning composition is aligned with the intricate architecture of corneal tissue, which features a hydrophilic stroma and a hydrophobic epithelium [21]. LeciPlex provides a modulated paragon of conventional cationic nanocarriers offering many advantages such as ease of preparation by simple mixing with minimal energy input and convenient scale-up. Also, it doesn’t require solvent evaporation, commonly needed in traditional nano-systems preparation techniques [22]. Their eminent surface positive charge is particularly useful for transcorneal delivery, fostering electrostatic attraction with the anionic sialic acid component of the corneal membrane, imparting mucoadhesive nature, hence prolonged ocular retention and improved permeability [23]. LeciPlex has been exploited for ophthalmic delivery of many therapeutic agents for the management of glaucoma, bacterial and mycotic infections, including Acetazolamide [22], Brinzolamide [24], Itraconazole [25], Carvedilol [23] and Moxifloxacin [26]. Heretofore, through literature review, we did not find Fenticonazole loaded LeciPlex system for the management of oculomycosis.

Herein, we aimed to prepare FCN-loaded LeciPlex (FCN-LPX) as a potential new cationic nanocarrier for the eradication of deeply seated oculomycosis by adopting a 23 factorial design (2 blocks, 2 replicates) to scrutinize the effect of cationic SAA type, amount of cationic SAA, and amount of SPC. The selected target responses include the measurement of percentage entrapment, particles’ size and surface charge as well as the polydispersity index. Following numerical optimization, the optimum formula was further investigated through differential scanning calorimetry (DSC), mucoadhesion measurement, infra-red (IR) spectroscopy, and in-vitro drug release. Stability was assessed following short-term storage and gamma sterilization studies. The safety was meticulously evaluated through pH, refractive index, surface tension measurements alongside corneal histopathological examination to confirm risk-free instillation. Moreover, ex-vivo transcorneal permeation study versus FCN suspension was performed to elucidate the permeation performance while corneal permeation was captured using Confocal microscopy in addition to multiple microbiological evaluations to assess the extent of antimycotic activity.

Materials

Fenticonazole nitrate (FCN) was generously gifted as a free sample from Al Andalous Pharmaceutical Co. (Cairo, Egypt). Transcutol® HP (Diethylene glycol monoethyl ether) was procured from Gattefossé Co. (St-Priest, France). DDAB (didodecyldimethylammonium bromide), CTAB (cetyltrimethylammonium bromide), SPC (Soybean phosphatidylcholine), mucin from porcine stomach (type II) and Spectra Por® dialysis membrane (cutoff 12–14 KDa) were purchased from Sigma-Aldrich® (St. Louis, MO, USA).

Asmaa Ashraf Nemr, Michael M. Farag, Doaa Hegazy, Heba Attia, Eman Abdelhakeem, Visionary NanoBoost: Revolutionizing ocular treatment with positively charged Leciplex for enhanced Fenticonazole nitrate ocular delivery, Journal of Drug Delivery Science and Technology, Volume 114, Part A, 2025, 107477, ISSN 1773-2247, https://doi.org/10.1016/j.jddst.2025.107477.