Porcine buccal mucosa as in vitro model: effect of biological and experimental variables

Tailored Sticky Solutions: 3D-Printed Miconazole Buccal Films for Pediatric Oral Candidiasis

In this research, 3D-printed antifungal buccal films (BFs) were manufactured as a potential alternative to commercially available antifungal oral gels addressing key considerations such as ease of manufacturing, convenience of administration, enhanced drug efficacy and suitability of paediatric patients. The fabrication process involved the use of a semi-solid extrusion method to create BFs from zein-Poly-Vinyl-Pyrrolidone (zein-PVP) polymer blend, which served as a carrier for drug (miconazole) and taste enhancers. After manufacturing, it was determined that the disintegration time for all films was less than 10 min. However, these films are designed to adhere to buccal tissue, ensuring sustained drug release. Approximately 80% of the miconazole was released gradually over 2 h from the zein/PVP matrix of the 3D printed films. Moreover, a detailed physicochemical characterization including spectroscopic and thermal methods was conducted to assess solid state and thermal stability of film constituents. Mucoadhesive properties and mechanical evaluation were also studied, while permeability studies revealed the extent to which film-loaded miconazole permeates through buccal tissue compared to commercially available oral gel formulation. Histological evaluation of the treated tissues was followed. Furthermore, in vitro antifungal activity was assessed for the developed films and the commercial oral gel. Finally, films underwent a two-month drug stability test to ascertain the suitability of the BFs for clinical application. The results demonstrate that 3D-printed films are a promising alternative for local administration of miconazole in the oral cavity.

Preparation, Physicochemical Characterization, and Stability Study of Lippia origanoides Essential Oil-based Nanoemulsion as a Topical Delivery System

INTRODUCTION

Fungal diseases are a priority in research, development, and health care, according to the WHO, mainly due to Candida spp. Essential oils (EOs) of the genus Lippia have demonstrated broad antimicrobial biological activity. Previous studies identified the anti-Candida potential of a thymol/p-cymene chemotype EO from Lippia origanoides H.B.K coded "0018". Nanoemulsions favor the biological activity of EOs and overcome limitations such as low solubility, instability against oxidizing agents, pH, light, and low permeability. To develop, characterize, and adjust a prototype of an O/W nanoemulsion containing the "0018" EO from Lippia origanoides for its evaluation in an in vitro permeability study.

METHODS

Nanoemulsions were obtained using a high energy high shear method. Their particle size distribution, Z potential, viscosity, pH, encapsulation efficiency (EE), thermodynamic stability and the Turbiscan Stability Index (TSI) were evaluated. The nanoemulsion prototype was adjusted to improve performance characteristics and microbiological efficacy. Thymol was used as an analyte in the EO quantification using UHPLC-DAD.

RESULTS

An O/W nanoemulsion with hydrodynamic diameter <200 nm and polydispersity index <0.3, EE >95%, with TSI < 1.5, anti-Candida albicans efficiency >95% was obtained; permeable with a flow of 6.0264 μg/cm2/h and permeability coefficient of 1.3170x10-3 cm/h.

CONCLUSION

A pharmaceutical formulation prototype is obtained that maintains the physical and physicochemical characteristics over time. Permeability is verified in an in-vitro model. It is proposed to evaluate its antifungal activity in preclinical or clinical studies as a contribution to the treatment of topical fungal diseases caused by Candida spp., through the use of biological resources and Colombian biodiversity.

Candesartan exhibits low intrinsic permeation capacity and affects buccal tissue viability and integrity: An ex vivo study in porcine buccal mucosa

Candesartan is a nonpeptide angiotensin II receptor blocker that selectively binds to angiotensin II receptor subtype 1. It is administered orally in its ester form (candesartan cilexetil). However, its poor aqueous solubility results in its low bioavailability; therefore, other routes of administration must be explored. The buccal mucosa has been extensively studied as an alternative route for drug delivery as it improves the bioavailability of drugs administered via the peroral route. Porcine buccal mucosa has been widely used as an ex vivo model to study the permeability of various diffusants; however, studies on candesartan are limited. This study aimed to evaluate the ex vivo permeation profile of candesartan and its effects on the viability and integrity of porcine buccal mucosa. Initially, we evaluated the viability, integrity, and barrier function of the buccal tissue before performing permeability tests using freshly excised tissues or tissues after 12 h of resection. Here, three indicators were used: caffeine, β-estradiol, and FD-20 penetration; mucosal metabolic activity, as determined using MTT reduction assay; and haematoxylin and eosin staining. Our results indicated that the porcine buccal mucosa preserved its viability, integrity, and barrier function before the permeation assay, allowing the passage of molecules with a molecular mass of less than 20 kDa, such as caffeine, but not β-estradiol and FD-20. Furthermore, we analyzed the intrinsic capacity of candesartan to diffuse through the fresh porcine buccal mucosa under two pH conditions. The concentration of candesartan in the receptor chamber of Franz diffusion cell was quantified using ultra-high liquid chromatography. In the permeation assay, candesartan exhibited a low intrinsic permeation capacity that impacted the buccal tissue viability and integrity, suggesting that using the buccal mucosa as an alternative route of administration requires developing a pharmaceutical formulation that reduces the adverse effects on mucosa and increasing the buccal permeability of candesartan.

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.

Mucoadhesive drug delivery systems: a promising non-invasive approach to bioavailability enhancement. Part I: biophysical considerations

INTRODUCTION

Mucoadhesive drug delivery systems (MDDS) are specifically designed to interact and bind to the mucosal layer for localized, prolonged, and/or targeted drug delivery. Over the past 4 decades, different sites have been explored for mucoadhesion including the nasal, oral, and vaginal cavities, the gastrointestinal tract and ocular tissues.

AREAS COVERED

The present review aims to provide a comprehensive understanding of different aspects of MDDS development. Part I focuses on the anatomical and biological aspects of mucoadhesion, which include a detailed elucidation of the structure and anatomy of the mucosa, the properties of mucin, the different theories of mucoadhesion and evaluation techniques.

EXPERT OPINION

The mucosal layer presents a unique opportunity for effective localization as well as systemic drug delivery via MDDS. Formulation of MDDS requires a thorough understanding of the anatomy of mucus tissue, the rate of mucus secretion and turnover, and the physicochemical properties of mucus. Further, the moisture content and the hydration of polymers are crucial for interaction with mucus. A confluence of different theories used to explain the mechanism of mucoadhesion is useful for understanding the mucoadhesion of different MDDS and their evaluation is subject to factors, such as the site of administration, type of dosage form, and duration of action. [Figure: see text].

A method for evaluating drug penetration and absorption through isolated buccal mucosa with highly accuracy and reproducibility

The purpose of the project is to establish a standardized operation method of the in vitro permeability model to maximize mucosal integrity and viability. The model drug lidocaine permeability, 20 kDa fluorescein isothiocyanate-dextran, H&E staining, and mucosal viability were used as evaluation indicators. Firstly, the buccal mucosae of rats, rabbits, dogs, porcine, and humans were analyzed by H&E staining and morphometric analysis to compare the differences. Then, we studied a series of operation methods of isolated mucosa. The buccal mucosae were found to retain their integrity in Kreb's bicarbonate ringer solution at 4 °C for 36 h. Under the long-term storage method with program cooling, freezing at -80 °C, thawing at 37 °C, and using cryoprotectants of 20% glycerol and 20% trehalose, mucosal integrity and biological viability can be maintained for 21 days. The heat separation method was used to prepare a permeability model with a mucosal thickness of 500 μm, which was considered to be the optimal operation. In summary, this study provided an experimental basis for the selection and operation of in vitro penetration models, standardized the research process of isolated mucosa, and improved the accuracy of permeability studies.

Oral transmucosal delivery of eletriptan for neurological diseases

Migraine is a highly prevalent neurological disease affecting circa 1 billion patients worldwide with severe incapacitating symptoms, which significantly diminishes the quality of life. As self-medication practice, oral administration of triptans is the most common option, despite its relatively slow therapeutic onset and low drug bioavailability. To overcome these issues, here we present, to the best of our knowledge, the first study on the possibility of oral transmucosal delivery of one of the safest triptans, namely eletriptan hydrobromide (EB). Based on a comprehensive set of in vitro and ex vivo experiments, we highlight the conditions required for oral transmucosal delivery, potentially giving rise to similar, or even higher, drug plasma concentrations expected from conventional oral administration. With histology and tissue integrity studies, we conclude that EB neither induces morphological changes nor impairs the integrity of the mucosal barrier following 4 h of exposure. On a cellular level, EB is internalized in human oral keratinocytes within the first 5 min without inducing toxicity at the relevant concentrations for transmucosal delivery. Considering that the pK_a of EB falls within the physiologically range, we systematically investigated the effect of pH on both solubility and transmucosal permeation. When the pH is increased from 6.8 to 10.4, the drug solubility decreases drastically from 14.7 to 0.07 mg/mL. At pH 6.8, EB gave rise to the highest drug flux and total permeated amount across mucosa, while at pH 10.4 EB shows greater permeability coefficient and thus higher ratio of permeated drug versus applied drug. Permeation experiments with model membranes confirmed the pH dependent permeation profile of EB. The distribution of EB in different cellular compartments of keratinocytes is pH dependent. In brief, high drug ionization leads to higher association with the cell membrane, suggesting ionic interactions between EB and the phospholipid head groups. Moreover, we show that the chemical permeation enhancer DMSO can be used to enhance the drug permeation significantly (i.e., 12 to 36-fold increase). Taken together, this study presents important findings on transmucosal delivery of eletriptan via the oral cavity and paves the way for clinical investigations for a fast and safe migraine treatment.

Development of buccal film formulations and their mucoadhesive performance in biomimetic models

When developing buccal films for oromucosal drug administration, adhesion is essential to ensure sufficient time for permeation of the active ingredient(s) through the oral mucosa and avoid the detachment and subsequent swallowing of the film. In this study, biomimetic materials were evaluated as a replacement for buccal mucosa in mucoadhesion testing and potential adhesives were compared regarding their suitability to increase the adhesion of hypromellose-based oromucosal films. Gelatin gels, as possible biomimetics, failed to mimic the buccal mucosa. Furthermore, esophageal tissue lead to a wider variance of adhesion data despite showing a good correlation with buccal tissue. A synthetic copolymer hydrogel based on hydroxyethylmethacrylate (HEMA) and N-acryloyl glucosamine (AGA) was able to mimic the buccal mucosa in these tests and reduced the variation in the data compared to animal tissue. Adding polyacrylic acid and polyvinylpyrrolidone to the film formulations at a concentration of 5% w/w approximately doubled the maximum detachment force and work of adhesion. Sodium alginate enhanced the adhesive properties moderately but adding chitosan did not significantly increase mucoadhesion. Polyvinylpyrrolidone and polyacrylic acid are rated as strong adhesion enhancers for buccal films and the HEMA/AGA hydrogel is considered as a suitable alternative for animal mucosa in mucoadhesion testing.

Exploring the transmucosal permeability of cyclobenzaprine: A comparative preformulation by standardized and controlled ex vivo and in vitro permeation studies

As part of early drug development, preformulation studies are used to comprehensively explore the properties of new drugs. In particular, this includes the biopharmaceutical characterization and evaluation of impacting factors (e.g. excipients, microenvironmental conditions etc.) by permeation studies. To overcome the limitations of current studies, a novel standardized ex vivo procedure using esophageal mucosa as surrogate has been established successfully and applied to preformulation studies for oromucosal delivery of cyclobenzaprine hydrochloride, a tricyclic muscle relaxant with potential for psychopharmacotherapeutic use. By using the standardized ex vivo permeation process, a twofold enhancement of permeability (0.98 ± 0.16 to 1.96 ± 0.10 * 10^-5 cm/s) was observed by adjustment and controlling of microenvironmental pH, empowering a targeted and effective development of sublingual formulations. Predictivity and suitability were superior compared to in vitro experiments using artificial biomimetic membranes, revealing a determination coefficient (R²) of 0.995 vs. 0.322 concerning pH-dependent permeability of cyclobenzaprine. In addition, diffusion properties were extensively examined (e.g. influence of mucosal thicknesses, tissue freezing etc.). The alignment of the study design regarding physiologically/clinically relevant conditions resulted in ex vivo data that allowed for the estimation of plasma AUC levels in the extend of reported in vivo ranges.

Resistivity Technique for the Evaluation of the Integrity of Buccal and Esophageal Epithelium Mucosa for In Vitro Permeation Studies: Swine Buccal and Esophageal Mucosa Barrier Models

Permeation assays are important for the development of topical formulations applied on buccal mucosa. Swine buccal and esophageal epithelia are usually used as barriers for these assays, while frozen epithelia have been used to optimize the experimental setup. However, there is no consensus on these methods. In transdermal studies, barrier integrity has been evaluated by measuring electrical resistance (ER) across the skin, which has been demonstrated to be a simple, fast, safe, and cost-effective method. Therefore, the aims here were to investigate whether ER might also be an effective method to evaluate buccal and esophageal epithelium mucosa integrity for in vitro permeation studies, and to establish a cut-off ER value for each epithelium mucosa model. We further investigated whether buccal epithelium could be substituted by esophageal epithelium in transbuccal permeation studies, and whether their permeability and integrity were affected by freezing at -20 °C for 3 weeks. Fresh and frozen swine buccal and esophageal epithelia were mounted in Franz diffusion cells and were then submitted to ER measurement. Permeation assays were performed using lidocaine hydrochloride as a hydrophilic drug model. ER was shown to be a reliable method for evaluating esophageal and buccal epithelia. The esophageal epithelium presented higher permeability compared to the buccal epithelium. For both epithelia, freezing and storage led to decreased electrical resistivity and increased permeability. We conclude that ER may be safely used to confirm tissue integrity when it is equal to or above 3 kΩ for fresh esophageal mucosa, but not for buccal epithelium mucosa. However, the use of esophageal epithelium in in vitro transmucosal studies could overestimate the absorption of hydrophilic drugs. In addition, fresh samples are recommended for these experiments, especially when hydrophilic drugs are involved.

Development and characterization of thermopressed polyvinyl alcohol films for buccal delivery of benznidazole

Given that oral preparations of benznidazole (BZN) have demonstrated limited efficacy in the treatment of Chagas' disease due to pharmacokinetic or toxicological problems, the development of buccal polymeric films was purposed in this study. These systems ensure high patient acceptability and direct access to the systemic circulation, improving drug bioavailability and toxicological profile. Polymer films were prepared through a thermopressing method by mixing BZN and polyvinyl alcohol (PVAL). In some preparations, propylene glycol (PG) and thymol (TM) were also included as plasticizer and chemical absorption enhancer, respectively. Morphology, X-ray diffraction, spectroscopic, thermal, mechanical, and water uptake properties, as well as ex vivo permeability studies, were performed to characterize the film formulations. BZN remained stable and in an amorphous form over 90 days. The addition of PG and TM improved the mechanical properties of the films, making them soft, flexible and tear-resistant. Also, these additives increased the water sorption rate of the films at 50 and 75% relative humidity and the TM increased the film erosion properties and drug permeability (close to 6×) compared to control. It was hypothesized that the permeability improvement of thymol-based films that follow a drug release profile through erosion is also associated with the inhibition of the crystallization of BNZ when the film is in contact with the buccal mucosa. Once the thymol has previously demonstrated a significant in vivo and in vitro trypanocidal action and even improved film characteristics, these systems may be considered promising for Chagas' disease treatment.

Sublingual insulin administration: application of hydroxypropyl beta-cyclodextrin and poloxamer188 as permeation enhancers

The objective of this investigation is to investigate the feasibility of sublingual insulin administration. Insulin solutions formulated with permeation enhancers (HPβCD/poloxamer 188) and their in-vitro and in-vivo performances were evaluated. Thereafter, insulin fast-dissolving film was further developed to have similar properties, upon dissolving the film, of the optimized insulin solution. In-vitro performance was evaluated via effect of HPβCD and/or poloxamer 188 concentration across cellulose acetate membrane and porcine esophagus. In-vivo performance was evaluated via pharmacodynamic and pharmacokinetic profiles of insulin solution administered. Cumulative amounts of insulin permeated at 60 min formulated with HPβCD (5%), poloxamer 188 (0.5%), and their combination were 1.31, 3.23, and 4.99 IU/cm², respectively, indicating an additive effect of combination of HPβCD and poloxamer 188. Insulin-induced hypoglycemic effect was observed for insulin solutions with combination of HPβCD and poloxamer 188 after sublingual administration to Sprague-Dawley rats. Microscopic evaluation of porcine oesophageal tissue indicates that HPβCD and poloxamer 188 are safe. Furthermore, the cumulative amount permeated across cellulose acetate membrane at 30 min was 1.13 and 1.00 IU/cm² for insulin solution and fast-dissolving film, respectively, demonstrating to be similar. In conclusion, the use of HPβCD/poloxamer 188 is feasible for the development of sublingual insulin solutions/films.

Development, validation and standardization of oromucosal ex-vivo permeation studies for implementation in quality-controlled environments

Tissue-based ex-vivo studies on the oromucosal permeability of drugs are often insufficiently adapted to physiological and clinical conditions, which limits their predictivity. Moreover, the scientific community demands for the standardization of ex-vivo studies, since conceptual limitations (e.g. low sensitivity of analytical methods, insufficient monitoring, different designs) restrict the wide implementation in preclinical drug development. Therefore, an innovative ex-vivo permeation process consisting of novel Kerski diffusion cell coupled to fully automated sampling and sample preparation with LC-MS/MS quantification was developed and standardized. Novel assays for routine examination of tissue integrity and viability were developed and embedded in a comprehensive analytical control system. The high level of standardization and automation reduced the differences of between-run to within-run precision to ≤ 0.27 % CV. Successful validation proved a broad calibration range of 0.93-952.38 ng/mL of the model drug cyclobenzaprine with guideline-compliant relative errors from -7.9-12.6 % (between-run accuracy). Consequently, the method allowed the physiological-clinical alignment of the study conditions to therapeutic doses and the short residence time of intraoral drugs (sampling times 1-60 min). Applicability was demonstrated by assessing the oromucosal permeability for different sublingual cyclobenzaprine hydrochloride formulations representing the excipient selection as a common aspect during galenic development. Thereby, expressive evaluation of the dosage forms was achieved resulting in an improved permeation by replacing croscarmellose into polyvinylpyrrolidone (cumulative amount of 42.6 vs. 112.6 μg/cm²). Thus, the automated permeation process ensured lean, standardized and reproducible assessment of oromucosal permeability within quality-controlled academic and regulatory environments. Simultaneously, the improved ex-vivo predictivity through physiological-clinical adjustments facilitates the reduction of costly in-vivo studies.

Bilayer mucoadhesive buccal films with prolonged release of ciclopirox olamine for the treatment of oral candidiasis: In vitro development, ex vivo permeation testing, pharmacokinetic and efficacy study in rabbits

The incidence of fungal infections has increased in recent decades not only in patients with predisposing and risk factors, but it has also spread up due to the widespread use of broad-spectrum antibiotics, immunosuppressants and corticosteroids. A limited number of drugs are currently used to treat oral candidiasis (OC). There is an emerging need to look for new antifungals, to rework or to explore the already known molecules. Ciclopirox olamine (CPX), a broad-spectrum antifungal agent, is currently used for topical dermatologic treatment. In this study, bilayer mucoadhesive buccal films (MBFs) containing poly(ethylene oxide) (PEO) and Eudragit® NM 30D (EU) with the prolonged release of ciclopirox olamine, were developed for the treatment of oral candidiasis. During ex vivo testing it was found that CPX does not pass through the porcine buccal tissue but it accumulates in it, which may be beneficial for the treatment of candidiasis in the oral cavity. In a pharmacokinetic study, the drug release from mucoadhesive films was prolonged with the maximum plasma concentration at 3.4 (1.4; 5.5) h. All rabbits with stomatitis showed progressive healing after the treatment with CPX bilayer mucoadhesive buccal films without organ pathologies.

Transbuccal Delivery of Isoniazid: Ex Vivo Permeability and Drug-Surfactant Interaction Studies

The oral administration of isoniazid (INH) may lead to discontinuation of tuberculosis treatment due to drug-related hepatotoxicity events, and thus, the transbuccal delivery of this drug was investigated, for the first time, as an alternative administration route. Ex vivo permeability assays were performed in Franz-type diffusion chambers, applying INH alone and in combination with sodium dodecyl sulfate (SDS) and sodium taurocholate (ST). After confirming the formation of micelle structures by dynamic light scattering analysis, UV-visible spectroscopy and zeta potential analyses were used to investigate drug-micelle interactions. In zeta potential analyses, no electrostatical interactions were identified for both surfactants in saliva buffer pH 6.8. Spectrophotometric analyses, in turn, indicated chemical interactions between INH and SDS in both pH values (2.0 and 6.8) whereas no interaction between the drug and ST was observed. Despite the interaction between SDS and drug, this surfactant increased the buccal transport rate of INH by approximately 11 times when compared with the control. In contrast, ST did not increase the drug permeability. The INH retention in SDS-treated mucosa was significantly higher when compared with the control and an effect on intercellular lipids was suggested. In vivo studies are needed to confirm the high INH absorption found here. Grapical abstract.

Development of a Multifunctional Bioerodible Nanocomposite Containing Metronidazole and Curcumin to Apply on L-PRF Clot to Promote Tissue Regeneration in Dentistry

Teeth extractions are often followed by alveolar bone reabsorption, although an adequate level of bone is required for reliable rehabilitations by dental implants. Leukocyte and platelet-rich fibrin (L-PRF) has been widely applied in regenerative procedures and with antibiotic and antioxidant agents could play an essential role in hard and soft tissue healing. In this work, a nanocomposite (Sponge-C-MTR) consisting of a hyaluronate-based sponge loaded with metronidazole (MTR) and nanostructured lipid carriers containing curcumin (CUR-NLC) was designed to be wrapped in the L-PRF™ membrane in the post-extraction sockets and characterized. CUR-NLCs, obtained by homogenization followed by high-frequency sonication of the lipid mixture, showed loading capacity (5% w/w), drug recovery (95% w/w), spherical shape with an average particle size of 112.0 nm, and Zeta potential of -24 mV. Sponge-C-MTR was obtained by entrapping CUR-NLC in a hydrophilic matrix by a freeze-drying process, and physico-chemical and cytocompatibility properties were evaluated. Moreover, the aptitude of CUR and MTR to the penetrate and/or permeate both L-PRF™ and porcine buccal tissue was assessed, highlighting MTR penetration and CUR accumulation promoted by the system. The results positively support the action of nanocomposite in dental tissues regeneration when applied together with the L-PRF™.

Transbuccal delivery of benznidazole associated with monoterpenes: permeation studies and mechanistic insights

Benznidazole (BZN) represents the only drug currently available for the treatment of Chagas disease in most endemic countries. When administered orally, high doses are required due to its extensive hepatic metabolism and its toxicity represents the main reason for treatment withdrawals. Because of these complications, transbuccal administration of BZN was investigated. This route avoids the first-pass hepatic metabolism and presents high permeability, with direct access to the systemic circulation. BZN was applied on porcine buccal mucosa after pretreatment with pure eugenol, carvacrol or limonene. Thermal (DSC) and spectroscopic (FT-IR) analyzes were performed to investigate the mechanisms of drug absorption enhancement. The permeability coefficient values of BZN increased 2.6, 2.9 and 4.9-fold after pretreatment with eugenol, carvacrol and limonene, respectively. The lag time, in turn, was shortened in the pretreated samples. The DSC and FT-IR analyzes suggested that transport of BZN through the buccal mucosa is associated with log P and size of monoterpenes. Limonene, the most effective absorption enhancer, contributed to greater interaction with non-polar domains of the buccal epithelium. Overall, BZN showed to be efficiently transported through the buccal route, but in vivo pharmacokinetic studies should be performed to confirm these findings.

In vivo, ex vivo and in vitro assessment of buccal permeation of drugs from delivery systems

Introduction: Buccal mucosa has been described as an attractive site for local and systemic drug delivery, owing its accessibility, safety, and excellent blood supply. The absorption of drugs through buccal mucosa has been assessed by in vivo, ex vivo and in vitro permeability studies, using animal and cell-based models with close resemblance to the human buccal mucosa.Areas covered: This paper focuses on the current in vivo, ex vivo and in vitro permeability studies to analyze the absorption of compounds of interest through buccal mucosa, as well as their advantages and limitations in the preclinical studies of the drugs absorption profiles. The techniques for preparation and preservation of the animal buccal tissue are also discussed to evaluate their interference in the integrity and permeability of the tissues.Expert opinion: Overall, the permeability studies have been useful to evaluate the drugs absorption and to clarify the mechanism of transport of drugs across human buccal mucosa, as well as to explain the enhancement of permeability provided by certain dosage forms. Currently, several researchers have demonstrated particular interest in ex vivo permeability studies, due to their effectiveness in the evaluation of drug absorption and low costs in the acquisition of buccal mucosa samples.

In vitro testing of flash-frozen sublingual membranes for storage and reproducible permeability studies of macromolecular drugs from solution or nanofiber mats

Sublingual drug delivery allows systemic delivery of drug without difficulties connected with the gastrointestinal pathway. We developed a new simple protocol for easy-to-use processing and storage of porcine sublingual mucosal membrane for in vitro studies using "flash freezing" in liquid nitrogen. All the dextrans used as mucosal membrane integrity and permeability markers permeated only slowly through sublingual mucosa illustrating usability both the "fresh" and "flash frozen" sublingual membranes whereas conventional cold storage "frozen" membranes have shown significantly higher permeabilities for macromolecules due to the sustained damage. The permeability values were too low to expect dextrans to be potential carriers at this context. To test albumin as a drug carrier we compared FITC-albumin permeation from solutions vs. nanofiber mats donors. To increase the amounts and prolong the transport, we manufactured nanofiber mats loaded with fluorescently marked albumin using well-scalable electrospinning technology. Nanofiber mats have allowed albumin passage through the sublingual membrane in similar amounts as from the pure artificial saliva solution. Since salivary washout strictly limits the duration of liquid dosages, nanofiber mats may thus permit prolonged sublingual administration.

Full-Thickness Intraoral Mucosa Barrier Models for In Vitro Drug-Permeation Studies Using Microneedles

The use of permeation enhancers such as microneedles (MNs) to increase drug penetration across intraoral mucosa has increased in recent years. Permeation studies, commonly performed using vertical diffusion cells, are a well-established way to preview formulations and enhance their performance during the development stage. However, to our knowledge, the existing intraoral mucosa barrier models do not permit permeation using MN-pretreated mucosa due to their insufficient thickness. Therefore, the objective of this study was to develop a barrier model using thick palate tissues to perform in vitro permeation studies, with physical enhancement of the permeability of intraoral mucosa by pretreatment with MNs. The adapted Franz-type cells used in the permeation experiments were validated (cell dimensions and volume, sealing effectiveness, stirring and dissolution efficiency, temperature control, and establishment of uniaxial flux). Commercially available MNs were used in the palatal mucosa. Optical images of the mucosa were acquired to analyze the microperforations created. In vitro permeation studies were conducted with the MN-pretreated mucosa. This work presents a new in vitro method for the evaluation of MNs as permeation enhancers, with the aim of improving the absorption of drug formulations topically applied within the oral cavity.

Use of buccal morphine in the management of pain in children with life-limiting conditions: Results of a laboratory study

BACKGROUND

Children and infants with impaired swallow or compromised enteral absorption require alternative routes for administration of analgesia. Recent clinical guidance and practice for paediatric palliative care teams, who often treat such children, supports buccal morphine sulphate as a fast acting, effective and easily administered agent for pain relief. However, a consideration of the physicochemical properties and potency of morphine would suggest that it is not a suitable candidate for delivery via the transmucosal route, raising questions about its use in children and infants.

AIM

To explore the permeability of buccal morphine sulphate in an established ex vivo porcine buccal mucosa as a necessary step in examining efficacy for use in children with life-limiting conditions and life-threatening illnesses.

DESIGN

A permeation study conducted with morphine sulphate in an ex vivo porcine buccal tissue model. Flux values and pharmacokinetic data were used to calculate the plasma values of morphine that would result following buccal administration in a 20kg child.

RESULTS

Results show that the estimated steady state plasma values of morphine sulphate following buccal administration in this model do not achieve minimum therapeutic concentration.

CONCLUSION

These data strongly suggest that morphine sulphate is not suitable for buccal administration and that further research is needed to establish its efficacy in relief of pain in children with life-limiting conditions and life-threatening illnesses.

Development and Evaluation of a Novel Mucoadhesive Film Containing Acmella oleracea Extract for Oral Mucosa Topical Anesthesia

Purpose

To develop an anesthetic mucoadhesive film containing Acmella oleracea (jambu) extract for topical use on oral mucosa.

Methods

Ethanolic extracts from aerial parts of jambu were prepared by maceration. Pigment removal was obtained by adsorption with activated carbon. Three mucoadhesive films were developed using a film casting method: 10 or 20% of crude jambu extract (10% JB and 20% JB), and 10% of crude jambu extract treated with activated carbon (10% JBC). The mucoadhesive films were characterized regarding their uniformity, thickness, pH, and spilanthol content, and their stability was evaluated during 120 days. Gas chromatography was used to quantify the amount of spilanthol. In vitro tests determined the permeation of spilanthol across pig esophageal epithelium mucosa in Franz diffusion cells. Topical anesthetic efficacy was assessed in vivo using a tail flick test in mice.

Results

The three mucoadhesive films showed physical stability and visual appearances suitable for use on oral mucosa. The permeation study revealed that the spilanthol from 10% JBC presented higher flux and permeability coefficient values, compared to 10% or 20% JB (p < 0.001). Moreover, 10% JBC showed better topical anesthetic efficacy than the other films (p < 0.01).

Conclusion

Mucoadhesive film containing crude extract of jambu treated with activated carbon is a potential alternative for oral, topical use, encouraging future clinical studies.

Synergistic Antibacterial Effects of Nanoparticles Encapsulated with Scutellaria baicalensis and Pure Chlorhexidine on Oral Bacterial Biofilms

Scutellariabaicalensis (SB) is a traditional Chinese medicine for treating infectious and inflammatory diseases. Our recent study shows potent antibacterial effects of nanoparticle-encapsulated chlorhexidine (Nano-CHX). Herein, we explored the synergistic effects of the nanoparticle-encapsulated SB (Nano-SB) and Nano-CHX on oral bacterial biofilms. Loading efficiency of Nano-SB was determined by thermogravimetric analysis, and its releasing profile was assessed by high-performance liquid chromatographyusing baicalin (a flavonoid compound of SB) as the marker. The mucosal diffusion assay on Nano-SB was undertaken in a porcine model. The antibacterial effects of the mixed nanoparticles (Nano-MIX) of Nano-SB and Nano-CHX at 9:1 (w/w) ratio were analyzed in both planktonic and biofilm modes of representative oral bacteria. The Nano-MIX was effective on the mono-species biofilms of Streptococcus (S.) mutans, S. sobrinus, Fusobacterium (F.) nucleatum, and Aggregatibacter (A.) actinomycetemcomitans (MIC 50 μg/mL) at 24 h, and exhibited an enhanced effect against the multi-species biofilms such as S. mutans, F. nucleatum, A. actinomycetemcomitans, and Porphyromonas (P.) gingivalis (MIC 12.5 μg/mL) at 24 h that was supported by the findings of both scanning electron microscopy (SEM) and confocal scanning laser microscopy (CLSM). This study shows enhanced synergistic antibacterial effects of the Nano-MIX on common oral bacterial biofilms, which could be potentially developed as a novel antimicrobial agent for clinical oral/periodontal care.

Drug coated microneedles for minimally-invasive treatment of oral carcinomas: development and in vitro evaluation

Treatment of recurring oral cancers is challenging as common surgical approaches are not feasible for these patients. In addition, these patients do not respond well to systemic chemotherapy. Localized intratumoral injection of anti-cancer drugs is considered to be an attractive alternative treatment approach for these patients. However, conventional hypodermic injections result in poor distribution of the drug in the tumor and leakage of the drug from the injection site to systemic circulation, in addition to causing pain to the patient. The objective of this study was to develop coated microneedles as a novel device for direct and minimally invasive intratumoral delivery of anti-cancer drugs. Poly(lactic-co-glycolic) acid (PLGA) nanoparticles encapsulating doxorubicin (DOX) were prepared and coated on inplane (1D) microneedles. Microscopic evaluation of 3D tissue phantoms and porcine cadaver buccal tissues that were treated with 1D microneedle arrays coated with DOX-PLGA nanoparticles demonstrated that DOX could diffuse both laterally and vertically in to the tissues and produced cellular cytotoxicity. Out of plane (2D) microneedle arrays measuring 1 cm x 1 cm with 57 microneedles coated with free DOX could produce uniform distribution of DOX in a porcine cadaver buccal tissue up to a depth greater than 3 mm. Hypodermic injection of different volumes in to a porcine buccal tissue confirmed significant leakage of the injected volume (about 25% of the injected 80 μl). In summary, this study demonstrates that drug coated microneedles is an attractive microscale device that can uniformly and effectively deliver drugs to localized oral cancers. This microscale device has potential to impact the treatment of oral cancer patients.

Evaluation of different pig oral mucosa sites as permeability barrier models for drug permeation studies

The objective of the present study was to investigate the influence of preparation and storage conditions on the histology and permeability of different parts of porcine oral mucosa used for in vitro studies of transbuccal formulations. Fresh and frozen (-20°C and -80°C, with or without cryoprotectant) epithelia of porcine palatal, gingival, dorsum of the tongue, and buccal mucosa were submitted for histological analyses to determine the effects of storage conditions on barrier integrity. Permeation of lidocaine hydrochloride (used as a hydrophilic model drug) across fresh and previously frozen oral epithelium was measured in order to evaluate the barrier function. Histological evaluation demonstrated that the oral epithelium was successfully separated from the connective tissue, except for gingival mucosa. After storage under different conditions, all tissues presented desquamation of superficial layers and spherical spaces induced by the freezing process. The permeability of lidocaine hydrochloride varied among the fresh oral mucosa and generally increased after freezing. In conclusion, fresh epithelium from the buccal and dorsum of the tongue mucosa should be used for in vitro studies investigating hydrophilic drug transport when these are the desired clinical application sites. However, when the palate is the target site, both fresh and frozen (for up to 4weeks, without addition of cryoprotectant) samples could be used. The addition of glycerol as a cryoprotectant should be avoided due to increased lidocaine hydrochloride permeability.

Poloxamer bioadhesive hydrogel for buccal drug delivery: Cytotoxicity and trans-epithelial permeability evaluations using TR146 human buccal epithelial cell line

A salbutamol sulfate (SS)-Poloxamer bioadhesive hydrogel specially developed for buccal administration was investigated by studying interactions with TR146 human buccal epithelium cells (i.e. cellular toxicity (i) and trans-epithelial SS diffusion (ii)). The assessment of cell viability (MTT, Alamar Blue), membrane integrity (Neutral Red), and apoptosis assay (Hoechst 33342), were performed and associated to Digital Holographic Microscopy analysis. After the treatment of 2h, SS solution induced drastic cellular alterations that were prevented by hydrogels in relation with the concentrations of poloxamer and xanthan gum. The formulation containing P407 19%/P188 1%/Satiaxane 0.1% showed the best tolerance after single and multiple administrations and significantly reduced the trans-epithelial permeability from 5.00±0.29 (×10(3)) (SS solution) to 1.83±0.22 cm/h. Digital Holographic Microscopy images in good agreement with the viability data confirmed the great interest of this direct technique. In conclusion, the proposed hydrogels represent a safe and efficient buccal drug delivery platform.

Gingiva laser welding: preliminary study on an ex vivo porcine model

OBJECTIVE

The use of lasers to fuse different tissues has been studied for 50 years. As none of these experiments concerned the oral soft tissues, our objective was to assess the feasibility of laser gingiva welding.

MATERIALS AND METHODS

Porcine full-thickness gingival flaps served to prepare calibrated samples in the middle of which a 2 cm long incision was closed, either by conventional suture or by laser tissue welding (LTW). To determine the irradiation conditions yielding the best tensile strength, 13 output power values, from 0.5 to 5 W, delivered either at 10 Hz or in continuous wave mode, were tested on six indocyanine green (ICG) concentrations, from 8% to 13% (588 samples). Then, some samples served to compare the tensile strength between the laser welded and the sutured gingiva; the other samples were histologically processed in order to evaluate the thermal damage extent. The temperature rise during the LTW was measured by thermocouples. Another group of 12 samples was used to measure the temperature elevation by thermal camera.

RESULTS

In the laser welding groups, the best tensile strength (p<0.05) was yielded by the 9% ICG saline solution (117 mM) at 4.5 W, 10 Hz, and a fluence of 31.3 kJ/cm(2). The apposition strength revealed no statistically significant difference (p<0.05) between the sutured and the laser welded gingiva at 4.5 W, 10 Hz, and 9% ICG solution. The mean temperature was 74±5.4°C at the upper surface and 42±8.9°C at the lower surface. The damaged zone averaged 333 μm at the upper surface.

CONCLUSIONS

The 808 nm diode laser associated with ICG can achieve oral mucosa LTW, which is conceivable as a promising technique of gingival repair.

Oral transmucosal drug delivery--current status and future prospects

Oral transmucosal drug delivery (OTDD) dosage forms have been available since the 1980s. In contrast to the number of actives currently delivered locally to the oral cavity, the number delivered as buccal or sublingual formulations remains relatively low. This is surprising in view of the advantages associated with OTDD, compared with conventional oral drug delivery. This review examines a number of aspects related to OTDD including the anatomy of the oral cavity, models currently used to study OTDD, as well as commercially available formulations and emerging technologies. The limitations of current methodologies to study OTDD are considered as well as recent publications and new approaches which have advanced our understanding of this route of drug delivery.

Promoting effects of chemical permeation enhancers on insulin permeation across TR146 cell model of buccal epithelium in vitro

To find potential enhancers for facilitating the buccal delivery of insulin, a TR146 cell-culture model of buccal epithelium, cultured on commercially available insert plates, was used to evaluate the permeability-enhancing effects of several traditional and new types of chemical enhancers, including N-acetyl-L-cysteine (NAC), sodium deoxycholate (SDC), sodium nitroprusside (SNP), reduced glutathione (GSH), glutamine (Gln), chitosan (CS), L-arginine (Arg), 1-dodecylazacycloheptan-2-one (Azone), and soybean lecithin (SPC) (50 and 10 μg/mL respectively). Permeability studies were performed to determine the enhancing effects of these compounds on insulin permeation across the cell-culture model. The enhancing effects of the enhancers were assessed by calculating the apparent permeability coefficients and enhancement ratio. Cytotoxicity of the permeation enhancers at different concentrations was investigated by using the methylthiazolydiphenyl-tetrazolium bromide (MTT) assay. Results showed that 50 μg/mL of NAC, SDC, GSH, CS, Arg, Azone, SPC, SNP, and 10 μg/mL of SNP had a significant enhancing effect on promoting the transport of insulin across the TR146 cell model. MTT assays showed that 50 μg/mL of Gln, Azone, SDC, SNP, Arg, 10 μg/mL SDC, and Arg had obvious toxic effects on TR146 cells. Therefore, NAC, GSH, CS, SPC, and SNP appear to be safe, effective permeability enhancers that promote the transport of insulin across the TR146 cell-culture model of buccal epithelium and may be potential enhancers for buccal delivery of insulin with both low toxicity and high efficiency.

Effect of experimental temperature on the permeation of model diffusants across porcine buccal mucosa

The influence of experimental temperature on the permeability of model diffusants across porcine buccal mucosa was investigated in vitro. The permeability increased significantly as the experimental temperature was increased in increments of approximately 7°C. It was observed that the apparent permeability and temperature were related by an exponential relationship that conformed to the Arrhenius equation. Diffusants with higher lipophilicities--buspirone and bupivacaine--had lower activation energies for diffusion when compared to hydrophilic diffusants--antipyrine and caffeine. The activation energy for diffusion of the model diffusants decreased linearly with increasing distribution coefficients across porcine buccal mucosa. The results suggested that the buccal mucosa acts as a stronger barrier to the diffusion of hydrophilic diffusants than the lipophilic ones. The log-linear relationship between permeability and temperature indicates that temperature should be carefully controlled in diffusion experiments. These results also point to the possibility of developing heat-generating buccal delivery devices, especially for hydrophobic diffusants.

Vaginal microbicide gel for delivery of IQP-0528, a pyrimidinedione analog with a dual mechanism of action against HIV-1

Pyrimidinediones, a novel class of compounds, have previously been shown to possess antiviral activity at nanomolar concentrations. One member of this class of compounds, IQP-0528, was selected as the lead molecule for formulation development owing to its stability at physiologically relevant conditions, wide therapeutic window, and antiviral activity in the nanomolar range. Here, we report the development of two vaginal gels--3.0% hydroxyethyl cellulose (HEC) formulation and a 0.65% Carbopol formulation--for the sustained delivery of IQP-0528. Stability studies under accelerated conditions confirmed the chemical stability of IQP-0528 and mechanical stability of the gel formulation for 3 months. In vitro release studies revealed that diffusion-controlled release of IQP-0528 occurred over 6 h, with an initial lag time of approximately 1 h. Based on the drug release profile, the 3.0% HEC gel was selected as the lead formulation for safety and activity evaluations. The in vitro and ex vivo safety evaluations showed no significant loss in cell viability or significant inflammatory response after treatment with a 3.0% HEC gel containing 0.25% IQP-0528. In an in vitro HIV-1 entry inhibition assay, the lead formulation showed an 50% effective concentration of 0.14 μg/ml for gel in culture media, which corresponds to ∼0.001 μM IQP-0528. The antiviral activity was further confirmed by using polarized cervical explants, in which the formulation showed complete protection against HIV infection. In summary, these results are encouraging and warrant further evaluation of IQP-0528 gel formulations in in vivo models, as well as the development of alternative formulations for the delivery of IQP-0528 as a microbicide.