Formulation and Evaluation of Prednisolone Sodium Metazoate-Loaded Mucoadhesive Quatsomal Gel for Local Treatment of Recurrent Aphthous Ulcers: Optimization, In Vitro, Ex Vivo, and In Vivo Studies

This study aims to formulate a buccal mucoadhesive gel containing prednisolone sodium metazoate-loaded quatsomes for efficient localized therapy of recurrent aphthous ulcers. Quatsomes were prepared using a varied concentration of quaternary ammonium surfactants (QAS) and cholesterol (CHO). A 2³ factorial design was conducted to address the impact of independent variables QAS type (X₁), QAS to CHO molar ratio (X₂), and sonication time (X₃). The dependent variables were particle size (PS; Y₁), polydispersity index (PDI; Y₂), zeta potential (ZP; Y₃), entrapment efficiency percent (EE%; Y₄) and percent of drug released after 6 h (Q6%: Y₅). Then, the selected quatsomes formula was incorporated into different gel bases to prepare an optimized mucoadhesive gel to be evaluated via in vivo study. The PS of the developed quatsomes ranged from 69.47 ± 0.41 to 113.28 ± 0.79 nm, the PDI from 0.207 ± 0.004 to 0.328 ± 0.004, ZP from 45.15 ± 0.19 to 68.1 ± 0.54 mV, EE% from 79.62 ± 1.44 to 98.60% ± 1.22 and Q6% from 58.39 ± 1.75 to 94.42% ± 2.15. The quatsomal mucoadhesive gel showed rapid recovery of ulcers, which was confirmed by the histological study and the evaluation of inflammatory biomarkers. These results assured the capability of the developed quatsomal mucoadhesive gel to be a promising formulation for treating buccal diseases.

1. Introduction

Recurrent aphthous ulcers (RAUs), also known as recurrent aphthous stomatitis, is a prevalent condition that induces ulcers in the oral mucosa; it also decreases the quality of life as patients experience difficulty in masticating, talking, and swallowing [1]. RAU is an oral mucosal lesion ranging from less than 1 mm to more than 1 cm. It is distinguished by various, more often-occurring oval-shaped ulcers with a yellowish pseudomembrane on the ulcer floor and an erythematous border [2]. With a 50% recurrence rate after three months, these ulcers can affect up to 25% of the general population [3]. The etiopathogenesis of this condition is still unknown; however, it is thought to be multifactorial. Various etiologies of RAU include food allergies, hormonal and gastrointestinal disorders, viral and bacterial infections, mechanical injuries, and stress [4,5,6]. The diagnosis, clinical features, and severity of RAU affect treatment decisions. The goal of therapy includes pain control, suppression of the inflammatory response, reduction of recurrence frequency, reduction of ulcer border, and avoiding harmful effects of systemic treatments. RAU treatment includes topical and systemic drugs such as corticosteroids, antiseptics, and antibacterials, which are used singly or in varied combinations [7,8,9].

Corticosteroids are often recommended as first-line treatment for RAU [10]; however, the efficacy of topical corticosteroids is limited for treating deep and large ulcers; in such cases, systemic corticosteroids are commonly used. However, numerous patients cannot tolerate the side effects of systematic corticosteroids [11].

Prednisolone sodium metazoate (Pred MS) is a synthetic glucocorticoid with anti-inflammatory and immunomodulating properties. It also decreases the number of circulating lymphocytes and induces cell differentiation. Moreover, Pred MS provides topical or local anti-inflammatory effects with reduced systematic corticosteroid concentration compared to prednisolone [12]. Therefore, developing a topical delivery system that maximizes Pred MS localization in the mucosal epithelium tissues is highly beneficial for more efficient treatment of RAU.

Nanoparticles provide numerous advantages for buccal drug delivery as they enhance the solubility of hydrophobic drugs and consequently improve their dissolution rates; also, they may provide controlled drug release. Moreover, the nanoparticles can enhance the stability of active ingredients [13]. Furthermore, the utility of cationic nanoparticles in the buccal route has been studied extensively for improving buccal drug delivery as cationic nanocarriers interact with the negatively charged mucosa; thus, they can prolong the drug residence time and consequently enhance drug penetration into the mucosal tissues [14].

Several studies have suggested that buccally applied liposomes provide appropriate drug concentration in the oral mucosal tissues while minimizing systematic drug effects [15,16]. In addition, liposomes can release the encapsulated drug in a more controlled pattern. Moreover, liposomes enhance drug localization in ulcerated areas and enhance anti-inflammatory drugs’ efficacy by targeting mononuclear phagocytic systems [17]. However, encapsulation inefficiencies, aggregation, fusion, partially controlled particle size and poor aqueous stability are the major limitation of liposomes [18,19].

Therefore, several studies have been conducted to prepare novel lipid vesicles with inherent stability. Quatsomes are unilamellar nanovesicles made mainly of cholesterol and quaternary ammonium surfactants (QAS). Quatsomes have excellent stability, homogeneity, and high drug-loading capacity [20]. In addition, quatsomes enhance the bioactivity and stability of proteins. Furthermore, quatsomes can be labeled with fluorescent dyes for bioimaging and biodistribution assays [21]. Therefore, quatsomes are considered promising alternatives to conventional liposomes. Moreover, the presence of QAS that possess antimicrobial activity in the components of quatsomes is considered beneficial in treating wounds [22]. However, the cationic nanoparticles formulated with QAS, especially with dimethyldidodecylammonium bromide (DDAB) or cetyltrimethylammonium bromide (CTAB), bear a greater risk of toxicity, despite several studies that pointed out that the toxicity of QAS has been greatly diminished after association with lipidic molecules as soy lecithin [23,24], further studies are needed to assess the toxicity of quatsomes.

The nanoparticles should be dispersed in a gel base to increase the residence time of the drug on the buccal mucosa. Mucoadhesive gels have a more potent effect, have a longer duration, target specific ulceration sites, and reduce the dosing frequency. Chitosan and polyacrylic acid-based polymers are commonly used gelling agents. Chitosan is a cationic polysaccharide with bioadhesive and antimicrobial properties, and it can extend the contact time of the drug with buccal mucosa [25]. Noveon is a polyacrylic acid-based polymer with good bioadhesive properties due to a high percentage of carboxylic groups that enable hydrogen bonding with mucosal mucin [26].

The initial analyses of the quatsomes found that several independent factors, such as quaternary ammonium surfactants (QAS) and cholesterol (CHO) molar ratio, QAS type, and sonication time, impacted the quatsomes characteristics. Therefore, a 2³ factorial design was performed using Design Expert^® software version 13 (Stat Ease, Inc., Minneapolis, MN, USA) where the QAS type (X₁), quaternary ammonium surfactants (QAS) and cholesterol (CHO) molar ratio (X₂), and sonication time (X₃) were chosen as independent factors, whereas particle size (PS; Y₁), polydispersity index (PDI; Y₂), zeta potential (ZP; Y₃), entrapment efficiency percent (EE%; Y₄) and the percentage of drug released after 6 h (Q6%; Y₅) were set as dependent factors. The optimized quatsomal formula was selected and incorporated into different gel bases to prepare mucoadhesive gel. The mucoadhesive gel was evaluated by determining drug content, rheology properties, spreadability, ex vivo mucoadhesive force, and in vitro drug release. Furthermore, the in vivo performance of the mucoadhesive gel loaded with Pred MS quatsomes in treating RAUs was evaluated via an in vivo pharmacodynamic study, including histological testing and the evaluation of inflammatory biomarkers.

2. Materials and Methods

2.1. Materials

Prednisolone sodium metazoate (CAS number 630-67-1) was a gift from AL-Andalous Medical Company Ltd. (6th October City, Giza, Egypt). Cholesterol, dimethyldidodecylammonium bromide (DDAB), and cetyltrimethylammonium bromide (CTAB) were obtained from Sigma-Aldrich Chemical Co. (St. Louis, MO, USA). Noveon AA-1^® was purchased from Lubrizol Advanced Materials Europe BVBA (Chaussee de Wavre, Brussels, Belgium). Chitosan was purchased from El-Nasr Pharmaceutical Chemicals Co. (Cairo, Egypt). Wistar albino rats were obtained from Misr University for Science and Technology animal center (6th October City, Giza, Egypt).

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Kassem, A.; Refai, H.; El-Nabarawi, M.A.; Abdellatif, M.M. Formulation and Evaluation of Prednisolone Sodium Metazoate-Loaded Mucoadhesive Quatsomal Gel for Local Treatment of Recurrent Aphthous Ulcers: Optimization, In Vitro, Ex Vivo, and In Vivo Studies. Pharmaceutics 2023, 15, 1947.
https://doi.org/10.3390/pharmaceutics15071947

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