Permeability of Buccal Mucosa

Nanoemulsion and nanoemulgel-based carriers as advanced delivery tools for the treatment of oral diseases

Oral diseases rank among the most widespread ailments worldwide posing significant global health and economic challenges affecting around 3.5 billion people, impacting the quality of life for affected individuals. Dental caries, periodontal disease, bacterial and fungal infections, tooth loss and oral malignancies are among the most prevalent global clinical disorders contributing to oral health burden. Traditional treatments for oral diseases often face challenges such as poor drug bioavailability, breakdown of medication in saliva, inconsistent antibiotic levels at the site of periodontal infection as well as higher side effects. However, the emergence of nanoemulgel (NEG) as an innovative drug delivery system offers promising solutions where NEG combines the advantages of both nanoemulsions (NEs) and hydrogels providing improved drug solubility, stability, and targeted delivery. Due to their minuscule size and ability to control drug release, NEGs hold promise for improving treatment of oral diseases, where versatility of these delivery systems makes them suitable for various applications, including topical delivery in dentistry. This review concisely outlines the anatomy of the oral environment and investigates the therapeutic potential of NE-based gels in oral disorder treatment. It thoroughly examines the challenges of drug delivery in the oral cavity and proposes strategies to improve therapeutic efficacy, drawing attention to previous research reports for comparison. Through comprehensive analysis, the review highlights the promising role of NEGs as a novel therapeutic approach for oral health management via research advancements and their clinical translation. Additionally, it provides valuable insights into future research directions and development opportunities in this area.

Transmucosal drug delivery: prospects, challenges, advances, and future directions

INTRODUCTION

Traditional administration routes have limitations including first-pass metabolism and gastrointestinal degradation for sensitive drugs (oral) and pain associated with parenteral injections, which also require trained personnel and refrigeration, making them expensive. This has increased interest in alternative routes, with mucosal surfaces being of high priority.

AREAS COVERED

Mucosal routes include ocular, oral (buccal/sublingual), nasal and vaginal mucosae which avoid the limitations of the oral and parenteral routes. Though mucosal routes show great potential, they are still hindered by several barriers, especially for systemic absorption, resulting in the development of more advanced novel drug delivery systems to overcome these limitations and achieve therapeutic actions both locally and systemically, similar to or exceeding the oral route. This paper systematically reviews and compares the different mucosal routes, challenges, and recent advances in advanced novel drug delivery system design for emerging clinical challenges including the advent of large biological macromolecules (proteins, peptides, and RNA) for treatment and prevention of diseases. The review also focuses on current challenges and future perspectives.

EXPERT OPINION

Among the various transmucosal routes discussed, nose-to-brain drug delivery has the greatest translational potential to go beyond the current state of the art and achieve significant clinical impact for neurological diseases.

Exploring the potential of mucoadhesive buccal films in geriatric medicine

As the global demographic shifts toward an aging society, the geriatric patient population is steadily increasing. These patients often suffer from comorbidities and require numerous oral medications, which can be especially challenging for dysphagic geriatric patients. Mucoadhesive buccal films (MBFs) seem promising and could reduce pill burden, simplify administration, and enable individualized drug therapy. This review aims to explore the age-related changes in the oral cavity and their impact on MBF delivery, including potential strategies to overcome these age-related barriers to drug delivery. It was observed that aging impacts the oral mucosa as well the properties of the saliva. There are several studies in the application of buccal films including the use of a wide range of permeation enhancers. The 3D printing of buccal films seems to introduce dosing flexibility to buccal film manufacturing.

Microporous annealed particle hydrogels in cell culture, tissue regeneration, and emerging application in cancer immunotherapy

Microporous annealed particle (MAP) hydrogels consist of densely crosslinked and annealed hydrogel particles. Compared to common hydrogels, the inherent porosity within and among these hydrogel particles offers interconnected channels for substance exchange in addition to sufficient growth space for cells, thereby forming a three-dimensional culture system that highly mimics the in vivo microenvironment. Such characteristics enable MAP hydrogels to adapt to various requirements of biomedical applications, along with their excellent injectability and mechanical properties. This review initially provides a comprehensive summary of the fabrication methods and material types of MAP hydrogels, alongside an assessment of their mechanical properties and porosity. In vitro studies are evaluated based on the impact of MAP hydrogels on cellular behaviors, focusing on cell proliferation, differentiation, migration, activity, and phenotype. In vivo research highlights the promising applications of MAP hydrogels in tissue regeneration, as well as their innovative use in cancer immunotherapy. Current challenges and future research directions are outlined, underscoring the potential of MAP hydrogels to significantly improve clinical outcomes in cancer treatment and regenerative medicine.

Evaluation of Drug Permeation Enhancement by Using In Vitro and Ex Vivo Models

Drugs administered by means of extravascular routes of drug administration must be absorbed into the systemic circulation, which involves the movement of the drug molecules across biological barriers such as epithelial cells that cover mucosal surfaces or the stratum corneum that covers the skin. Some drugs exhibit poor permeation across biological membranes or may experience excessive degradation during first-pass metabolism, which tends to limit their bioavailability. Various strategies have been used to improve drug bioavailability. Absorption enhancement strategies include the co-administration of chemical permeation enhancers, enzymes, and/or efflux transporter inhibitors, chemical changes, and specialized dosage form designs. Models with physiological relevance are needed to evaluate the efficacy of drug absorption enhancement techniques. Various in vitro cell culture models and ex vivo tissue models have been explored to evaluate and quantify the effectiveness of drug permeation enhancement strategies. This review deliberates on the use of in vitro and ex vivo models for the evaluation of drug permeation enhancement strategies for selected extravascular drug administration routes including the nasal, oromucosal, pulmonary, oral, rectal, and transdermal routes of drug administration.

Analysis of Key Factors for Evaluating Mucosal Adhesion Using Swine Buccal Tissue

The assessment of the mucoadhesive properties peak mucoadhesive force (Fmax) and work of mucoadhesion (Wmuc) with texture analyzers is a common in vitro method for analyzing formulation capabilities. Challenges arise in selecting and standardizing experimental conditions due to various variables influencing mucoadhesion. This complexity hampers direct product performance comparisons. In our study, we explored factors (contact force and time, probe speed and mucin in artificial saliva) impacting a model formulation's mucoadhesive capacity. Using Omcilon-A®Orabase on porcine buccal mucosa, we systematically varied experimental conditions, employing a statistical approach (Central Composite Design - CCD). Three variables (contact force, contact time, probe speed) and their interactions were assessed for their impact on Fmax and Wmuc. Results showed that contact time and force positively affected Fmax, while only contact time influenced Wmuc. In the mucin artificial saliva test, a force of 0.5 N, time of 600 s, and speed of 1 mm/s yielded optimal Fmax (0.587 N) and Wmuc (0.468 N.s). These conditions serve as a reference for comparing mucoadhesive properties of formulations for topical oral use.

Advances in Modeling Approaches for Oral Drug Delivery: Artificial Intelligence, Physiologically-Based Pharmacokinetics, and First-Principles Models

Oral drug absorption is the primary route for drug administration. However, this process hinges on multiple factors, including the drug's physicochemical properties, formulation characteristics, and gastrointestinal physiology. Given its intricacy and the exorbitant costs associated with experimentation, the trial-and-error method proves prohibitively expensive. Theoretical models have emerged as a cost-effective alternative by assimilating data from diverse experiments and theoretical considerations. These models fall into three categories: (i) data-driven models, encompassing classical pharmacokinetics, quantitative-structure models (QSAR), and machine/deep learning; (ii) mechanism-based models, which include quasi-equilibrium, steady-state, and physiologically-based pharmacokinetics models; and (iii) first principles models, including molecular dynamics and continuum models. This review provides an overview of recent modeling endeavors across these categories while evaluating their respective advantages and limitations. Additionally, a primer on partial differential equations and their numerical solutions is included in the appendix, recognizing their utility in modeling physiological systems despite their mathematical complexity limiting widespread application in this field.

Biopolymer Drug Delivery Systems for Oromucosal Application: Recent Trends in Pharmaceutical R&D

Oromucosal drug delivery, both local and transmucosal (buccal), is an effective alternative to traditional oral and parenteral dosage forms because it increases drug bioavailability and reduces systemic drug toxicity. The oral mucosa has a good blood supply, which ensures that drug molecules enter the systemic circulation directly, avoiding drug metabolism during the first passage through the liver. At the same time, the mucosa has a number of barriers, including mucus, epithelium, enzymes, and immunocompetent cells, that are designed to prevent the entry of foreign substances into the body, which also complicates the absorption of drugs. The development of oromucosal drug delivery systems based on mucoadhesive biopolymers and their derivatives (especially thiolated and catecholated derivatives) is a promising strategy for the pharmaceutical development of safe and effective dosage forms. Solid, semi-solid and liquid pharmaceutical formulations based on biopolymers have several advantageous properties, such as prolonged residence time on the mucosa due to high mucoadhesion, unidirectional and modified drug release capabilities, and enhanced drug permeability. Biopolymers are non-toxic, biocompatible, biodegradable and may possess intrinsic bioactivity. A rational approach to the design of oromucosal delivery systems requires an understanding of both the anatomy/physiology of the oral mucosa and the physicochemical and biopharmaceutical properties of the drug molecule/biopolymer, as presented in this review. This review summarizes the advances in the pharmaceutical development of mucoadhesive oromucosal dosage forms (e.g., patches, buccal tablets, and hydrogel systems), including nanotechnology-based biopolymer nanoparticle delivery systems (e.g., solid lipid particles, liposomes, biopolymer polyelectrolyte particles, hybrid nanoparticles, etc.).

Commercial hydrogel product for drug delivery based on route of administration

Hydrogels are hydrophilic, three-dimensional, cross-linked polymers that absorb significant amounts of biological fluids or water. Hydrogels possess several favorable properties, including flexibility, stimulus-responsiveness, versatility, and structural composition. They can be categorized according to their sources, synthesis route, response to stimulus, and application. Controlling the cross-link density matrix and the hydrogels' attraction to water while they're swelling makes it easy to change their porous structure, which makes them ideal for drug delivery. Hydrogel in drug delivery can be achieved by various routes involving injectable, oral, buccal, vaginal, ocular, and transdermal administration routes. The hydrogel market is expected to grow from its 2019 valuation of USD 22.1 billion to USD 31.4 billion by 2027. Commercial hydrogels are helpful for various drug delivery applications, such as transdermal patches with controlled release characteristics, stimuli-responsive hydrogels for oral administration, and localized delivery via parenteral means. Here, we are mainly focused on the commercial hydrogel products used for drug delivery based on the described route of administration.

Development and Characterization of New Miconazole-Based Microemulsions for Buccal Delivery by Implementing a Full Factorial Design Modeling

This research aimed to develop miconazole-based microemulsions using oleic acid as a natural lipophilic phase and a stabilizer mixture comprising Tween 20 and PEG 400 to solubilize miconazole as an antifungal agent known for its activity in oral candidiasis and to improve its bioavailability. The formulation and preparation process was combined with a mathematical approach using a 23-full factorial plan. Fluid and gel-like microemulsions were obtained and analyzed considering pH, conductivity, and refractive index, followed by extensive analyses focused on droplet size, zeta potential, rheological behavior, and goniometry. In vitro release tests were performed to assess their biopharmaceutical characteristics. Independent variables coded X1-Oleic acid (%, w/w), X2-Tween 20 (%, w/w), and X3-PEG 400 (%, w/w) were analyzed in relationship with three main outputs like mean droplet size, work of adhesion, and diffusion coefficient by combining statistical tools with response surface methodology. The microemulsion containing miconazole base-2%, oleic acid-5%, Tween 20-40%, PEG 400-20%, and water-33% exhibited a mean droplet size of 119.6 nm, a work of adhesion of 71.98 mN/m, a diffusion coefficient of 2.11·10-5 cm2/s, and together with remarked attributes of two gel-like systems formulated with higher oil concentrations, modeled the final optimization step of microemulsions as potential systems for buccal delivery.

A Synthetic Model of the Mucosa for Oral Penetration Studies

The main objective of this study is the evaluation of the use of a synthetic membrane, Nuclepore, as a model for permeation studies through sublingual mucosa. The permeability of two types of membranes, porcine sublingual oral mucosa and a synthetic Nuclepore membrane, to water was compared. Moreover, the water permeability of membranes modified with waterproofing formulations was measured to study their ability to protect against the penetration of viruses, toxins, etc. A relatively high correlation (R2 0.88) was obtained between the transmucosal water loss (TMWL) values of the artificial membrane and the mucosa. These results support the possible use of this synthetic membrane in the screening of the water permeability of formulations. In addition, studies of the permeation of different actives, drugs, and biocides through the two membranes were carried out, and these results were compared with their skin permeation data. The synthetic membrane does not seem to discern between compounds in terms of permeability. However, the permeation of caffeine through intact or modified membranes incorporating waterproofing formulations presents similar permeation profiles through the synthetic membrane and mucosa. The results from these assays should lend support to the use of this synthetic membrane when screening formulations to be applied in oral penetration studies.

Development of a buccal in vitro permeation method - exploring aQbD implementation

The buccal mucosa is arising within the pharmaceutical landscape as an attractive option for local and systemic drug delivery, mostly due to its high vascularization, inherent permeability and robustness. Still, one of the major challenges in bringing oromucosal preparations to market remains the accurate evaluation of permeability. During pre-clinical drug development, in vitro permeation assessment is essential, and methodologies, based on the selection of a proper membrane in a diffusion cell, have become appealing alternatives to the conventional cell-based models. The development of such methods is being constrained by the number of variables - related to study conditions, setup and formulation - that need to be optimized to accurately estimate buccal permeation. The gap of knowledge over the mentioned variables may lead to long costly developments and poorly accurate methods, especially if the empirical analytical approach is used. In this paper, a systematic risk-based analytical quality by design approach was applied to the development of a buccal in vitro permeation method, ensuring that all sources of variability affecting permeation process were identified, explained and managed by appropriate measures. Researchers are guided through a step by step model, successfully demonstrating with experimental data the impact of critical variables on method's performance.

Oral Mucosa Models to Evaluate Drug Permeability

Due to its numerous advantages, such as excellent drug accessibility, rapid absorption, and bypass of first-pass metabolism, the route of drug administration that involves crossing the oral mucosa is highly favored. As a result, there is significant interest in investigating the permeability of drugs through this region. The purpose of this review is to describe the various ex vivo and in vitro models used to study the permeability of conveyed and non-conveyed drugs through the oral mucosa, with a focus on the most effective models. Currently, there is a growing need for standardized models of this mucosa that can be used for developing new drug delivery systems. Oral Mucosa Equivalents (OMEs) may provide a promising future perspective as they are capable of overcoming limitations present in many existing models.

Characterization of Porcine Gingiva for Drug Absorption

Gingiva or gum is a part of the periodontium that surrounds the tooth. Its main function is to provide an effective barrier to both mechanical trauma and bacterial invasion. Gingiva is the target site for some topical drugs. The most common disease in gingiva is periodontal diseases (gum infections). Understanding the gingiva barrier properties could provide insights into approaches to effective drug delivery for the gingiva. Porcine gingiva was chosen as the model in the present membrane transport study. The permeability coefficients of gingiva were determined using a modified Franz diffusion cell with small diffusional area (0.03 cm2) and 12 model permeants with different physicochemical properties. The influences of edge effect and aqueous boundary layers were not observed in the modified diffusion cell setup for the small pieces of gingiva tissue samples. Lipophilic permeants exhibit higher permeability coefficients than hydrophilic permeants. A correlation was observed between the Log permeability coefficient (Log P) and Log octanol-water distribution coefficient (Log Dow) in the analysis. The permeant molecular weight (MW) was also a factor in the Log P vs. Log Dow relationship. The coefficient of Log Dow in this three-factor relationship (0.42) suggested that the gingiva barrier was less lipophilic than octanol.

Buccal Permeation of Polysaccharide High Molecular Weight Compounds: Effect of Chemical Permeation Enhancers

The greatest achievement in the advanced drug delivery field should be the optimization of non-invasive formulations for the delivery of high molecular weight compounds. Peptides, proteins, and other macromolecules can have poor membrane permeation, principally due to their large molecular weight. The aim of this work was to explore the possibility of administering fluorescently labeled dextrans (molecular weight 4-150 kDa) across the buccal mucosa. Permeation experiments across pig esophageal mucosa were carried out using fatty acids and bile salts as penetration enhancers. The data obtained show that it is possible to increase or promote the mucosa permeation of high molecular weight dextrans by using caprylic acid or sodium taurocholate as the chemical enhancers. With these enhancers, dextrans with molecular weight of 70 and 150 kDa, that in passive conditions did not permeate, could cross the mucosa in detectable amounts. FD-70 and FD-150 showed comparable permeability values, despite the molecular weight difference. The results obtained in the present work suggest that the buccal administration of high molecular weight compounds is feasible.

Buccal Thin Films as Potent Permeation Enhancers for Cytisine Transbuccal Delivery

Cytisine (CYT) is a powerful anti-smoking compound which could greatly benefit from transbuccal delivery because of both its unfavorable pharmacokinetics after oral administration and its intrinsic ability to permeate the buccal mucosa. This work aims to design CYT-loaded buccal thin films suitable for transbuccal drug delivery due to its capability of promoting the interaction between CYT and the buccal membrane. The solvent casting method was employed to prepare several thin films combining various excipients such as matrixing polymers, mucoadhesion agents, plasticizers and other compounds as humectants and sweeteners, component ratios and solvents. A total of 36 compositions was prepared and four of them emerged as the most promising in terms of aspect and flexibility. They all demonstrated homogeneity, thinness, low swelling degree, and controlled drug release according to the Power Law and Peppas-Sahlin mathematical models. Mainly, they proved able to interact with the ex vivo porcine buccal mucosa producing mucoadhesive effects, and act as potent permeation enhancers. In particular, Film B emerged as suitable as it produced a 10.6-fold Kp enhancement and a great Js value (52.33 μg/cm²·h^-1), even when compared to highly concentrated CYT solutions.