Pharmaceutical applications of mucoadhesion for the non-oral routes

Collagen/gelatin and polysaccharide complexes enhance gastric retention and mucoadhesive properties

This article has focused on collagen-gelatin, the gelation process, as well as blend interaction between collagen/gelatin with various polysaccharides to boost mucoadhesion and gastric retention. The interaction between mucoadhesive materials and mucin layers is of significant interest in the development of drug delivery systems and biomedical applications for effective targeting and prolonged time in the gastrointestinal tract. This paper reviews the current advancement and mucoadhesive properties of collagen/gelatin and different polysaccharide complexes concerning the mucin layer and interactions are briefly highlighted. Collagen/gelatin and polysaccharide blends biocompatible and biodegradable, the complex biomolecules have shown encouraging mucoadhesive properties due to their cationic nature and ability to form hydrogen bonds with mucin glycoproteins. The mucoadhesion mechanism was attributed to the electrostatic interactions between the positively charged amino (NH2) groups of blend biopolymers and the negatively charged sialic acid residues present in mucin glycoprotein. At the end of this article, the encouraging prospect of collagen/polysaccharide complex and mucin glycoprotein is highlighted.

Chitosan-based films filled with nanoencapsulated essential oil: Physical-chemical characterization and enhanced wound healing activity

The economic burden of chronic wounds, the complexity of the process of tissue repair and the possibility of resistant bacterial infections, have triggered a significant research interest in the application of natural alternative therapies for wound healing. Biomolecules are intrinsically multi-active, as they affect multiple mechanisms involved in tissue repair phenomenon, including immunomodulatory, anti-inflammatory, cell proliferation, extra cellular matrix remodeling and angiogenesis. Chitosan features a unique combination of attributes, including intrinsic hemostatic, antimicrobial, and immunomodulatory properties, that make it an exceptional candidate for wound management, in the development of wound dressings and scaffolds. In this study, we produced nanoemulsions (NE) loaded with SFO, characterized them, and evaluated their tissue repairing properties. Dynamic light scattering (DLS) analysis confirmed the formation of a nanoemulsion with a droplet size of 21.12 ± 2.31 nm and a polydispersity index (PdI) of 0.159, indicating good stability for up to 90 days. To investigate the potential wound healing effects, SFO-loaded NE were applied on male C57BL/6 mice for seven consecutive days, producing a significantly higher wound closure efficiency (p < 0.05) for the group treated with SFO-loaded NE compared to the control group treated with the saline solution. This finding indicates that the SFO-loaded NE exhibits therapeutic properties that effectively promote wound healing in this experimental model. Then, SFO-loaded NE were incorporated into chitosan:polyvinyl alcohol (PVA)-based films. The inclusion of NE into the polymer matrix resulted in increased lipophilicity reflected by the contact angle results, while decreasing moisture absorption, water solubility, and crystallinity. Moreover, FTIR analysis confirmed the formation of new bonds between SFO-NE and the film matrix, which also impacted on porosity properties. Thermal analysis indicated a decrease in the glass transition temperature of the films due to the presence of SFO-NE, suggesting a plasticizing role of NE, confirmed by XRD results, that showed a decrease in the crystallinity of the blend films upon the addition of SFO-NE. AFM images showed no evidence of NE droplet aggregation in the Chitosan:PVA film matrix. Moisture absorption and water content decreased upon incorporation of SFO-loaded NE. Although the inclusion of NE increased hydrophobicity and water contact angle, the values remained within an acceptable range for wound healing applications. Overall, our results emphasize the significant tissue repairing properties of SFO-loaded NE and the potential of Chitosan:PVA films containing nanoencapsulated SFO as effective formulations for wound healing with notable tissue repairing properties.

The Potential of Films as Transmucosal Drug Delivery Systems

Pharmaceutical films are polymeric formulations used as a delivery platform for administration of small and macromolecular drugs for local or systemic action. They can be produced by using synthetic, semi-synthetic, or natural polymers through solvent casting, electrospinning, hot-melt extrusion, and 3D printing methods, and depending on the components and the manufacturing methods used, the films allow the modulation of drug release. Moreover, they have advantages that have drawn interest in the development and evaluation of film application on the buccal, nasal, vaginal, and ocular mucosa. This review aims to provide an overview of and critically discuss the use of films as transmucosal drug delivery systems. For this, aspects such as the composition of these formulations, the theories of mucoadhesion, and the methods of production were deeply considered, and an analysis of the main transmucosal pathways for which there are examples of developed films was conducted. All of this allowed us to point out the most relevant characteristics and opportunities that deserve to be taken into account in the use of films as transmucosal drug delivery systems.

Novel therapeutic approach for the treatment of cystic fibrosis based on freeze-dried tridrug microparticles to treat cystic fibrosis

BACKGROUND

Cystic fibrosis is a severe, autosomal recessive disease that shortens life expectancy. According to studies, approximately 27% of patients with CF aged 2-5 years and 60 to 70% of adult patients are infected with P. aeruginosa. The patients experience bronchospasm leading to a persistent contracted state of the airways.

OBJECTIVES

The current work explores the possibility of combining ivacaftor and ciprofloxacin to combat the bacteria. A third drug L-salbutamol would be coated onto the surface of the drug-entrappped microparticles to instantaneously provide relief from bronchoconstriction.

METHODS

The microparticles were prepared using bovine serum albumin and L-leucine using the freeze-drying approach. The process and formulation parameters were optimized. The prepared microparticles were surface coated by L-salbutamol using the dry-blending method. The microparticles were subjected to rigorous in-vitro characterization for entrapment, inhalability, antimicrobial activity, cytotoxicity study and safety. The performance of the microparticles to be loaded into a inhaler was checked by the Anderson cascade impactor.

RESULTS

The freeze-dried microparticles had a particle size of 817.5 ± 5.6 nm with a polydispersity ratio of 0.33. They had a zeta potential of -23.3 ± 1.1 mV. The mass median aerodynamic diameter of the microparticles was 3.75 ± 0.07 μm, and the geometric standard diameter was 1.66 ± 0.033 μm. The microparticles showed good loading efficiency for all three drugs. DSC, SEM, XRD, and FTIR studies confirmed the entrapment of ivacaftor and ciprofloxacin. SEM and TEM scans observed the shape and the smooth surface. Antimicrobial synergism was proven by the agar broth, and dilution technique and the formulation was deemed safe by the results of the MTT assay.

CONCLUSION

Freeze-dried microparticles of ivacaftor, ciprofloxacin, and L-salbutamol could pave way to a hitherto unexplored combination of drugs as a novel approach to treat P. aeruginosa infcetions and bronchoconstriction commonly associated with cystic fibrosis.

Mucoadhesive drug delivery systems: a promising noninvasive approach to bioavailability enhancement. Part II: formulation considerations

INTRODUCTION

Mucoadhesive drug delivery systems (MDDS) are specifically designed to interact and bind to the mucosal layer of the epithelium for localized, prolonged, and/or targeted drug delivery. Over the past 4 decades, several dosage forms have been developed for localized as well as systemic drug delivery at different anatomical sites.

AREAS COVERED

The objective of this review is to provide a detailed understanding of the different aspects of MDDS. Part II describes the origin and evolution of MDDS, followed by a discussion of the properties of mucoadhesive polymers. Finally, a synopsis of the different commercial aspects of MDDS, recent advances in the development of MDDS for biologics and COVID-19 as well as future perspectives are provided.

EXPERT OPINION

A review of the past reports and recent advances reveal MDDS as highly versatile, biocompatible, and noninvasive drug delivery systems. The rise in the number of approved biologics, the introduction of newer highly efficient thiomers, as well as the recent advances in the field of nanotechnology have led to several excellent applications of MDDS, which are predicted to grow significantly in the future.

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].

Thermo and Photoresponsive Emulgel Loaded with Copaifera reticulata Ducke and Chlorophylls: Rheological, Mechanical, Photodynamic and Drug Delivery Properties in Human Skin

Recently, the number of new cases of cutaneous leishmaniasis has been of concern among health agencies. Research that offers new therapeutic alternatives is advantageous, especially those that develop innovative drugs. Therefore, this paper presents the incorporation of Copaifera reticulata Ducke and chlorophyll extract into Pluronic^®® F127 and Carbopol gels, under optimized polymer quantities. The chlorophyll extract (rich in photosensitizing compounds) was obtained by continuous-flow pressurized liquid extraction (PLE), a clean, environmentally friendly method. The system aims to act as as a leishmanicidal, cicatrizant, and antibiotic agent, with reinforcement of the photodynamic therapy (PDT) action. Rheological and mechanical analyses, permeation studies and bioadhesiveness analyses on human skin, and PDT-mediated activation of Staphylococcus aureus were performed. The emulgels showed gelation between 13° and 15 °C, besides pseudoplastic and viscoelastic properties. Furthermore, the systems showed transdermal potential, by releasing chlorophylls and C. reticulata Ducke into the deep layers of human skin, with good bioadhesive performance. The application of PDT reduced three logarithmic colony-forming units of S. aureus bacteria. The results support the potential of the natural drug for future clinical trials in treating wounds and cutaneous leishmania.

Bio-Inspired Muco-Adhesive Polymers for Drug Delivery Applications

Muco-adhesive drug delivery systems continue to be one of the most studied for controlled pharmacokinetics and pharmacodynamics. Briefly, muco-adhesive polymers, can be described as bio-polymers that adhere to the mucosal (mucus) surface layer, for an extended residency period of time at the site of application, by the help of interfacial forces resulting in improved drug delivery. When compared to traditional drug delivery systems, muco-adhesive carriers have the potential to enhance therapeutic performance and efficacy, locally and systematically, in oral, rectal, vaginal, amongst other routes. Yet, the achieving successful muco-adhesion in a novel polymeric drug delivery solution is a complex process involving key physico-chemico-mechanical parameters such as adsorption, wettability, polymer chain length, inter-penetration and cross-linking, to list a few. Hence, and in light of accruing progress, evidence and interest, during the last decade, this review aims to provide the reader with an overview of the theories, principles, properties, and underlying mechanisms of muco-adhesive polymers for pharmaceutics; from basics to design to characterization to optimization to evaluation to market. A special focus is devoted to recent advances incorporating bio-inspired polymers for designing controlled muco-adhesive drug delivery systems.

Advancements in Rectal Drug Delivery Systems: Clinical Trials, and Patents Perspective

The rectal route is an effective route for the local and systemic delivery of active pharmaceutical ingredients. The environment of the rectum is relatively constant with low enzymatic activity and is favorable for drugs having poor oral absorption, extensive first-pass metabolism, gastric irritation, stability issues in the gastric environment, localized activity, and for drugs that cannot be administered by other routes. The present review addresses the rectal physiology, rectal diseases, and pharmaceutical factors influencing rectal delivery of drugs and discusses different rectal drug delivery systems including suppositories, suspensions, microspheres, nanoparticles, liposomes, tablets, and hydrogels. Clinical trials on various rectal drug delivery systems are presented in tabular form. Applications of different novel drug delivery carriers viz. nanoparticles, liposomes, solid lipid nanoparticles, microspheres, transferosomes, nano-niosomes, and nanomicelles have been discussed and demonstrated for their potential use in rectal administration. Various opportunities and challenges for rectal delivery including recent advancements and patented formulations for rectal drug delivery have also been included.

Bioadhesive Nanoparticles for Local Drug Delivery

Local drug delivery is an effective strategy for achieving direct and instant therapeutic effects. Current clinical treatments have fallen short and are limited by traditional technologies. Bioadhesive nanoparticles (NPs), however, may be a promising carrier for optimized local drug delivery, offering prolonged drug retention time and steadily maintained therapeutic concentrations. In addition, the possibility of clinical applications of this platform are abundant, as most polymers used for bioadhesion are both biodegradable and biocompatible. This review highlights the major advances in the investigations of polymer-based bioadhesive nanoparticles and their innumerable applications in local drug delivery.

Composition of Piperine with Enteric-Coated Chitosan Microspheres Enhances the Transepithelial Permeation of Curcumin in Sheep Intestinal Mucosa and Caco-2 Cells

Objectives The purpose of this study was to investigate the efficacy of enteric-coated chitosan microspheres with herbal bioenhancer, piperine, as a suitable composition for improving the permeation of curcumin through biological membranes using suitable ex vivo models.

Material and Methods Chitosan microspheres of curcumin and piperine were prepared by an emulsion cross-linking method using glutaraldehydes the cross-linking agent and characterized for size, shape, entrapment efficiency, mucoadhesion, and in vitro release. The effect of piperine on the permeation of curcumin through excised sheep intestinal mucosa and Caco-2-cell monolayer was investigated.

Statistical Analysis The data from permeation studies were analyzed by Student's t-test using Statistical Package for the Social Sciences (SPSS) software (SPSS, Chicago, IL, United States) with p-values <0.05 indicating statistical significance.

Results The formulations showed mucoadhesion for a period of more than 6 hours which was influenced by the chitosan content. The rate of drug release of uncoated formulation followed first-order kinetics, and the mechanism of release was non-Fickian transport. Optimized formulation was coated with a pH-sensitive polymer, Eudragit S-100, by a solvent evaporation technique in different concentrations and evaluated for ex vivo permeation through sheep intestinal mucosa and Caco-2-cell monolayer. Scanning electron microscopy images of the optimized coated formulation showed spherical particles with smooth surfaces. The calculated permeation flux and permeability coefficient of curcumin from microspheres were at least 20% greater in the presence of piperine through the intestinal mucosa and 30% through the Caco-2-cell monolayer model. The permeability coefficient of curcumin from microspheres with piperine was 1.93 × 10 to 5 cm/sec and significantly greater (p < 0.05) than that of microspheres devoid of piperine and from aqueous dispersion (p < 0.005).

Conclusion The study confirmed the contribution of piperine and mucoadhesive microspheres toward improved permeation of curcumin through biological membranes, thereby providing an approach that has the potential of increasing transport through intestinal epithelial cells and possibly enhancing the oral bioavailability of this drug.

A review: Gelatine as a bioadhesive material for medical and pharmaceutical applications

Bioadhesive polymers offer versatility to medical and pharmaceutical inventions. The incorporation of such materials to conventional dosage forms or medical devices may confer or improve the adhesivity of the bioadhesive systems, subsequently prolonging their residence time at the site of absorption or action and providing sustained release of actives with improved bioavailability and therapeutic outcomes. For decades, much focus has been put on scientific works to replace synthetic polymers with biopolymers with desirable functional properties. Gelatine has been considered one of the most promising biopolymers. Despite its biodegradability, biocompatibility and unique biological properties, gelatine exhibits poor mechanical and adhesive properties, limiting its end-use applications. The chemical modification and blending of gelatine with other biomaterials are strategies proposed to improve its bioadhesivity. Here we discuss the classical approaches involving a variety of polymer blends and composite systems containing gelatine, and gelatine modifications via thiolation, methacrylation, catechol conjugation, amination and other newly devised strategies. We highlight several of the latest studies on these strategies and their relevant findings.

Recent advances in electrospun nanofiber vaginal formulations for women's sexual and reproductive health

Electrospinning is an innovative technique that allows production of nanofibers and microfibers by applying a high voltage to polymer solutions of melts. The properties of these fibers - which include high surface area, high drug loading capacity, and ability to be manufactured from mucoadhesive polymers - may be particularly useful in a myriad of drug delivery and tissue engineering applications. The last decade has witnessed a surge of interest in the application of electrospinning technology for the fabrication of vaginal drug delivery systems for the treatment and prevention of diseases associated with women's sexual and reproductive health, including sexually transmitted infections (e.g. infection with human immunodeficiency virus and herpes simplex virus) vaginitis, preterm birth, contraception, multipurpose prevention technology strategies, cervicovaginal cancer, and general maintenance of vaginal health. Due to their excellent mechanical properties, electrospun scaffolds are also being investigated as next-generation materials in the surgical treatment of pelvic organ prolapse. In this article, we review the latest advances in the field.

Naturally Occurring Polyelectrolytes and Their Use for the Development of Complex-Based Mucoadhesive Drug Delivery Systems: An Overview

Biopolymers have several advantages for the development of drug delivery systems, since they are biocompatible, biodegradable and easy to obtain from renewable resources. However, their most notable advantage may be their ability to adhere to biological tissues. Many of these biopolymers have ionized forms, known as polyelectrolytes. When combined, polyelectrolytes with opposite charges spontaneously form polyelectrolyte complexes or multilayers, which have great functional versatility. Although only one natural polycation-chitosan has been widely explored until now, it has been combined with many natural polyanions such as pectin, alginate and xanthan gum, among others. These polyelectrolyte complexes have been used to develop multiple mucoadhesive dosage forms such as hydrogels, tablets, microparticles, and films, which have demonstrated extraordinary potential to administer drugs by the ocular, nasal, buccal, oral, and vaginal routes, improving both local and systemic treatments. The advantages observed for these formulations include the increased bioavailability or residence time of the formulation in the administration zone, and the avoidance of invasive administration routes, leading to greater therapeutic compliance.

Emulsion-Based Multicompartment Vaginal Drug Carriers: From Nanoemulsions to Nanoemulgels

In order to overcome the limitations associated with vaginal administration of drugs, e.g., the short contact time of the drug form with the mucosa or continuous carrier wash-out, the development of new carriers for gynecological use is necessary. Furthermore, high individual anatomical and physiological variability resulting in unsatisfactory therapeutic efficacy of lipophilic active substances requires application of multicompartment drug delivery systems. This manuscript provides an up-to-date comprehensive review of the literature on emulsion-based vaginal dosage forms (EVDF) including macroemulsions, microemulsions, nanoemulsions, multiple emulsions and self-emulsifying drug delivery systems. The first part of the paper discusses (i) the influence of anatomical-physiological conditions on therapeutic efficacy of drug forms after local and systemic administration, (ii) characterization of EVDF components and the manufacturing techniques of these dosage forms and (iii) methods used to evaluate the physicochemical and pharmaceutical properties of emulsion-based vaginal dosage forms. The second part of the paper presents (iv) the results of biological and in vivo studies as well as (v) clinical evaluation of EVDF safety and therapeutic efficacy across different indications.

Ocular drug delivery to the anterior segment using nanocarriers: A mucoadhesive/mucopenetrative perspective

There is a growing demand for effective treatments for ocular conditions that improve patient compliance and reduce side-effects. While methods such as implants and injections have proven effective, topical administration remains the method of choice for the delivery of therapeutics to the anterior segment of the eye. However, topical administration suffers from multiple drawbacks including low bioavailability of the target therapeutic, systemic toxicity, and the requirement for high therapeutic doses due to the effective clearance mechanisms that exist in the eye. Nanoparticles that have tunable mucoadhesion and/or mucopenetration offer outstanding potential to overcome the anatomical and physiological barriers present to improve ocular bioavailability, reduce toxicity, and increase ocular retention, among other benefits. The current review highlights recent advances in the field of developing nanocarriers with tunable mucoadhesion and mucopenetration for drug delivery to the eye.

Amorphous Ropinirole-Loaded Mucoadhesive Buccal Film: A Potential Patient-Friendly Tool to Improve Drug Pharmacokinetic Profile and Effectiveness

Nowadays the therapeutic strategies to manage Parkinson’s Disease are merely symptomatic and consist of administering L-DOPA and/or dopamine receptor agonists. Among these, Ropinirole (ROP) is a widely orally-administered molecule, although it is extensively susceptible to hepatic metabolism. Since literature reports the buccal mucosa as a potentially useful route to ROP administration, the development of novel, effective, and comfortable oromucosal formulations should prove desirable in order to both enhance the therapeutic efficacy of the drug and allow a personalized therapeutic strategy able to meet the patient’s needs. The results of the proposed ROP film as a new dosage form show that it is flexible; uniform; and characterized by suitable surface pH; good mucoadhesiveness; low swelling degree; and fast, complete drug release. Moreover, after ex vivo evaluation on a film having an area of 0.282 cm² and dose of 2.29 mg, the results of drug flux through the buccal mucosa are closely comparable to the amount of ROP that reaches the bloodstream at the steady-state condition after ROP-PR 4 mg oral administration, calculated according to the literature (0.237 mg/cm²·h⁻¹ vs. 0.243 mg/h, respectively). Moreover, drug flux and ROP dose could be accurately modulated time-by-time depending on the patient’s need, by varying the administered disk area. In addition, the proposed ROP film displays no lag time, producing an immediate drug input in the bloodstream, which could result in a prompt therapeutic response. These findings make ROP film a potentially comfortable and patient-friendly formulation, and a promising candidate for further clinical trials.

Visualizing pectin polymer-polymer entanglement produced by interfacial water movement

In this report, we investigated the physical conditions for creating pectin polymer-polymer (homopolymer) entanglement. The potential role of water movement in creating pectin entanglement was investigated by placing water droplets-equivalent to the water content of two gel phase films-between two glass phase films and compressing the films at variable probe velocities. Slow probe velocity (0.5 mm/sec) demonstrated no significant debonding. Corresponding videomicroscopy demonstrated an occasional water bridge, but no evidence of stranding or polymer entanglement. In contrast, fast probe velocity (5 mm/sec) resulted in 1) an increase in peak adhesion strength, 2) a progressive debonding curve, and 3) increased work of cohesion (p < .001). Corresponding videomicroscopy demonstrated pectin stranding and delamination between pectin films. Scanning electron microscopy images obtained during pectin debonding provided additional evidence of both stranding and delamination. We conclude that water movement can supply the motive force for the rapid chain entanglement between pectin films.

Chitosan Derivatives with Mucoadhesive and Antimicrobial Properties for Simultaneous Nanoencapsulation and Extended Ocular Release Formulations of Dexamethasone and Chloramphenicol Drugs

The aim of this work was to evaluate the effectiveness of neat chitosan (CS) and its derivatives with 2-acrylamido-2-methyl-1-propanesulfonic acid (AAMPS) and [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (MEDSP) as appropriate nanocarriers for the simultaneous ocular administration of dexamethasone sodium phosphate (DxP) and chloramphenicol (CHL). The derivatives CS-AAMPS and CS-MEDSP have been synthesized by free-radical polymerization and their structure has been proved by Fourier-Transformed Infrared Spectroscopy (FT-IR) spectroscopy. Both derivatives exhibited low cytotoxicity, enhanced mucoadhesive properties and antimicrobial activity against Staphylococcus aureus (S.aureus) and Escherichia coli (E. coli). Encapsulation was performed via ionic crosslinking gelation using sodium tripolyphosphate (TPP) as the crosslinking agent. Dynamic light scattering measurements (DLS) showed that the prepared nanoparticles had bimodal distribution and sizes ranging from 50–200 nm and 300–800 nm. Drugs were encapsulated in their crystalline (CHL) or amorphous (DexSP) form inside nanoparticles and their release rate was dependent on the used polymer. The CHL dissolution rate was substantially enhanced compared to the neat drug and the release time was extended up to 7 days. The release rate of DexSP was much faster than that of CHL and was prolonged up to 3 days. Drug release modeling unveiled that diffusion is the main release mechanism for both drugs. Both prepared derivatives and their drug-loaded nanoparticles could be used for extended and simultaneous ocular release formulations of DexSP and CHL drugs.

Recent Advances in the Design of Topical Ophthalmic Delivery Systems in the Treatment of Ocular Surface Inflammation and Their Biopharmaceutical Evaluation

Ocular inflammation is one of the most common symptom of eye disorders and diseases. The therapeutic management of this inflammation must be rapid and effective in order to avoid deleterious effects for the eye and the vision. Steroidal (SAID) and non-steroidal (NSAID) anti-inflammatory drugs and immunosuppressive agents have been shown to be effective in treating inflammation of the ocular surface of the eye by topical administration. However, it is well established that the anatomical and physiological ocular barriers are limiting factors for drug penetration. In addition, such drugs are generally characterized by a very low aqueous solubility, resulting in low bioavailability as only 1% to 5% of the applied drug permeates the cornea. The present review gives an updated insight on the conventional formulations used in the treatment of ocular inflammation, i.e., ointments, eye drops, solutions, suspensions, gels, and emulsions, based on the commercial products available on the US, European, and French markets. Additionally, sophisticated formulations and innovative ocular drug delivery systems will be discussed. Promising results are presented with micro- and nanoparticulated systems, or combined strategies with polymers and colloidal systems, which offer a synergy in bioavailability and sustained release. Finally, different tools allowing the physical characterization of all these delivery systems, as well as in vitro, ex vivo, and in vivo evaluations, will be considered with regards to the safety, the tolerance, and the efficiency of the drug products.

Mucoadhesive hydrogels for buccal drug delivery: In vitro-in vivo correlation study

AIM

It was the aim of this study to assess in vitro methods for the characterization of mucoadhesive hydrogels for their potential to predict the residence time on human buccal mucosa.

METHODS

Mixtures of hydrogels comprising hydroxyethyl cellulose (HEC), sodium carboxymethyl cellulose (CMC), xanthan gum (XTGM), hyaluronic acid sodium salt (HA), sodium alginate (ALG), carbopol (CP) as well as polycarbophil (PCP) and porcine mucus were analysed for relative rheological synergism. Furthermore, hydrogels were characterized for their texture and mechanical properties. For the assessment of mucoadhesive strength of formulations tensile studies were performed on porcine buccal mucosa. To facilitate a direct comparability of data the residence time of stained hydrogels was determined ex vivo on porcine buccal mucosa and in the oral cavity of volunteers.

RESULTS

The extent of relative rheological synergism was in good agreement with data from in vivo residence time studies. Results of tensile studies were further effected by textural properties of hydrogels leading to a restricted correlation with data from the in vivo experiment. The resistance towards removal by artificial saliva flow ex vivo revealed the highest correlation to the in vivo experiment with increasing mucosal residence time in the rank order CP < HEC, HA, ALG, PCP < CMC < XTGM.

CONCLUSIONS

This overview of measurement principles to predict the residence time of hydrogels for buccal application in humans may be a potent tool for the development of semisolid intraoral formulations.

Investigation of Combined Cyclodextrin and Hydrogel Formulation for Ocular Delivery of Dexamethasone Acetate by Means of Experimental Designs

Dexamethasone acetate (DXMa) has proven its efficiency to treat corneal inflammation, without a great propensity to increase intraocular pressure. Unfortunately, its poor aqueous solubility, associated with a rapid precorneal elimination, results in a low drug bioavailability and a low penetration after topical ocular administration. The main objective of this study was to improve the apparent aqueous solubility of DXMa using cyclodextrins. First, hydroxypropyl-β-CD (HPβCD) and hydroxypropyl-γ-CD (HPγCD) were used to enhance DXMa concentration in aqueous solution. The β and γ HPCD derivatives allowed the increase of the DXMa amount in solution at 25 °C by a factor of 500 and 1500, respectively. Second, with the aim of improving the persistence of the complex solution after instillation in the eye, the formulations of DXMa-based CD solutions with marketed ophthalmic gels (CELLUVISC^®, GEL-LARMES^®, and VISMED^®) were investigated and optimized by means of special cubic mixture designs, allowing the defining of mixed gels loaded with 0.7% (HPβCD) and 2% (HPγCD) DXMa with osmolality within acceptable physiological range. Finally, in vitro drug release assays from the mixed gels were performed and compared with reference eye drops. Similarly to MAXIDEX^® and DEXAFREE^®, in the case of mixed gel containing HPβCD, more than 90% of the drug was released within 2 h, while in mixed gel containing HPγCD, the release of DXMa was partial, reaching ≈60% in 2 h. This difference will have to be further addressed with ex vivo and in vivo ocular delivery experiments.

Structural Heteropolysaccharide Adhesion to the Glycocalyx of Visceral Mesothelium

Bioadhesives are biopolymers with potential applications in wound healing, drug delivery, and tissue engineering. Pectin, a plant-based heteropolysaccharide, has recently demonstrated potential as a mucoadhesive in the gut. Since mucoadhesion is a process likely involving the interpenetration of the pectin polymer with mucin chains, we hypothesized that pectin may also be effective at targeting the glycocalyx of the visceral mesothelium. To explore the potential role of pectin as a mesothelial bioadhesive, we studied the interaction of various pectin formulations with the mesothelium of the lung, liver, bowel, and heart. Tensile strength, peel strength, and shear resistance of the bioadhesive-mesothelial interaction were measured by load/displacement measurements. In both high-methoxyl pectins (HMP) and low-methoxyl pectins, bioadhesion was greatest with an equal weight % formulation with carboxymethylcellulose (CMC). The tensile strength of the high-methoxyl pectin was consistently greater than low-methoxyl or amidated low-methoxyl formulations (p < 0.05). Consistent with a mechanism of polymer-glycocalyx interpenetration, the HMP adhesion to tissue mesothelium was reversed with hydration and limited by enzyme treatment (hyaluronidase, pronase, and neuraminidase). Peel and shear forces applied to the lung/pectin adhesion resulted in a near-interface structural failure and the efficient isolation of intact en face pleural mesothelium. These data indicate that HMP, in an equal weight % mixture with CMC, is a promising mesothelial bioadhesive for use in experimental and therapeutic applications.

Transmucosal Nanoparticles: Toxicological Overview

Nanoparticles have specific physicochemical properties different to bulk materials of the same composition and such properties make them very attractive for commercial and medical applications. Mucoadhesive nanoparticulate dosage forms are designed to enable prolonged retention of these nanoparticles at the site of application, providing a controlled drug release for improved therapeutic outcome. Moreover, drug delivery across the mucosa bypasses the first-pass hepatic metabolism and avoids the degradation by gastrointestinal enzymes. However, like most new technologies, there is a rising debate concerning the possible transmucosal side effects resulting from the use of particles at the nano level. In fact, these nanoparticles on entering the body, deposit in several organs and may cause adverse biological reactions by modifying the physiochemical properties of living matter. Several investigators have found nanoparticles responsible for toxicity in different organs. In addition, the toxicity of nanoparticles also depends on whether they are persistent or cleared from the different organs of entry and whether the host can raise an effective response to sequester or dispose of the particles. In contrast to many efforts aimed at exploiting desirable properties of nanoparticles for medicine, there are limited attempts to evaluate potentially undesirable effects of these particles when administered intentionally for medical purposes. This chapter focuses on the overview of the mucosal systems, fate of nanoparticles, mechanism of nanoparticle's toxicity and the various toxicity issues associated with nanoparticles through mucosal routes.

Development of Nanoemulsion Based Gel Loaded with Phytoconstituents for the Treatment of Urinary Tract Infection and in Vivo Biodistribution Studies

Purpose: A nanoemulsion based gel containing Polyphenon 60 (P60) and cranberry (CRB) has been developed to deliver via intravaginal route for the treatment of urinary tract infection.

Methods: Polyphenon 60 and cranberry were loaded in a single nanoemulsion gel (NBG) by ultra-sonication method and characterized for particle size, rheological properties, in vitro release and growth curve analysis. P60+CRB NBG were radiolabelled using technetium pertechnetate (^99mTc) to perform in vivo pharmacokinetic studies in animals.

Results: The finalized NE had a droplet size of 58±1 nm. In vitro release of 90.92 ± 0.6% in 8 hr for P60 and 99.39 ± 0.5% in 6 hr for CRB was observed in simulated vaginal fluid. Growth curve of E. coli indicated the inhibitory action of nanoemulsion based gel at the fifth hour of inoculation. Gamma scintigraphy studies on female Sprague-Dawley rats showed transport of nanoemulsion based gel from the vaginal cavity into the systemic circulation. Further, biodistribution studies with radiolabelled P60+CRB NBG showed significant higher uptake of radiolabelled actives by kidney (3.20±0.16) and urinary bladder (3.64±0.29), when administered intravaginally.

Conclusion: The findings suggested ^99mTc-P60+CRB NBG can potentially be transported through vaginal cavity and reach the target organs and showed effective distribution in organs affected in urinary tract infection

Chrysophyllum cainito (apple-star): a fruit with gastroprotective activity in experimental ulcer models

The gastroprotective potential of the methanolic extracts from peels (MEPe), seeds (MESe) and pulp (MEPu) of Chrysophyllum cainito L. (Sapotaceae) fruits was evaluated in mice using ethanol/HCl- and indomethacin-induced ulcer, as well as the antiulcer effect of the juice and flour from this fruit. The lowest oral gastroprotective dose of MEPe, MESe and MEPu against ethanol/HCl was 3, 3 and 10 mg/kg, respectively. Moreover, all extracts increased mucin secretion at 176, 198 and 193%. Intraperitoneal administration of MEPe (0.3 mg/kg), MESe (0.3 mg/kg) and MEPu (1 mg/kg) also promoted gastroprotection against ethanol/HCl. In addition, MEPe (3 mg/kg, p.o), MESe (3 mg/kg, p.o) and MEPu (10 mg/kg, p.o) reduced indomethacin-induced gastric ulcer in mice by 78, 70 and 50%, respectively. Regarding the mode of action, the gastroprotective effect of MEPe was decreased by the pre-administration of N-ethylmaleimide (NEM, a sulfhydryl group chelator, 10 mg/kg, i.p), glibenclamide (a potassium channel blocker, 10 mg/kg, i.p), yohimbine (10 mg/kg, i.p, an alpha-adrenergic receptor antagonist, 10 mg/kg, i.p) and indomethacin (a cyclooxygenase inhibitor, 10 mg/kg, i.p). The gastroprotective effect of MESe was reduced by the pre-administration of NEM, glibenclamide, N-Nitro-L-arginine methyl ester (L-NAME, a nitric oxide synthase inhibitor, 70 mg/kg, i.p) and yohimbine, while MEPu had the gastroprotective effect decreased in animals pretreated with NEM and L-NAME. However, the extracts did not reduce gastric acid secretion. The supplementation with the flour from C. cainito fruit at 10% by 7 days, but not the juice intake, displayed gastroprotective potential, evidencing the fruit as a promising functional food. Together, the antiulcer effect of extracts of the C. cainito fruit in different experimental models was confirmed by the favoring of mucosal protective mechanisms among different, but complementary, modes of action. In parallel, the gastroprotective effects of the flour from C. cainito fruit were also described.

Mechanical properties, structure, bioadhesion, and biocompatibility of pectin hydrogels

The surface structure, biocompatibility, textural, and adhesive properties of calcium hydrogels derived from 1, 2, and 4% solutions of apple pectin were examined in this study. An increase in the pectin concentration in hydrogels was shown to improve their stability toward elastic and plastic deformation. The elasticity of pectin hydrogels, measured as Young's modulus, ranged from 6 to 100 kPa. The mechanical properties of the pectin hydrogels were shown to correspond to those of soft tissues. The characterization of surface roughness in terms of the roughness profile (Ra) and the root-mean-square deviation of the roughness profile (Rq) indicated an increased roughness profile for hydrogels depending on their pectin concentration. The adhesion of AU2% and AU4% hydrogels to the serosa abdominal wall, liver, and colon was higher than that of the AU1% hydrogel. The adhesion of macrophages and the non-specific adsorption of blood plasma proteins were found to increase as the pectin concentration in the hydrogels increased. The rate of degradation of all hydrogels was higher in phosphate buffered saline (PBS) than that in DMEM and a fibroblast cell monolayer. The pectin hydrogel was also found to have a low cytotoxicity. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2572-2581, 2017.

Polymer coated liposomes for use in the oral cavity - a study of the in vitro toxicity, effect on cell permeability and interaction with mucin

In this study we investigated the in vitro toxicity, impact on cell permeability and mucoadhesive potential of polymer-coated liposomes intended for use in the oral cavity. A TR146 cell line was used as a model. The overall aim was to end up with a selection of safe polymer coated liposomes with promising mucoadhesive properties for drug delivery to the oral cavity. The following polymers were tested: chitosan, low-methoxylated pectin (LM-pectin), high-methoxylated pectin (HM-pectin), amidated pectin (AM-pectin), Eudragit, poly(N-isopropylacrylamide-co-methacrylic acid) (p(NIPAAM-co-MAA)), hydrophobically modified hydroxyethyl cellulose (HM-HEC), and hydrophobically modified ethyl hydroxyethyl cellulose (HM-EHEC). With chitosan as an exception, all the systems exhibited no significant effect on cell viability and permeability at the considered concentrations. Additionally, all the formulations showed to a varying degree an interaction with mucin (BSM type I-S); the positively charged formulations exhibited the strongest interaction, while the negatively and neutrally charged formulations displayed a moderate or low interaction. The ability to interact with mucin makes all the liposomal formulations promising for oromucosal administration. Although the chitosan-coated liposomes affected the cell viability, this formulation also influenced the cell permeability, which makes it an interesting candidate for systemic drug delivery from the oral cavity.

Biopolymeric Mucin and Synthetic Polymer Analogs: Their Structure, Function and Role in Biomedical Applications

Mucin networks are viscoelastic fibrillar aggregates formed through the complex self-association of biopolymeric glycoprotein chains. The networks form a lubricious, hydrated protective shield along epithelial regions within the human body. The critical role played by mucin networks in impacting the transport properties of biofunctional molecules (e.g., biogenic molecules, probes, nanoparticles), and its effect on bioavailability are well described in the literature. An alternate perspective is provided in this paper, presenting mucin’s complex network structure, and its interdependent functional characteristics in human physiology. We highlight the recent advances that were achieved through the use of mucin in diverse areas of bioengineering applications (e.g., drug delivery, biomedical devices and tissue engineering). Mucin network formation is a highly complex process, driven by wide variety of molecular interactions, and the network possess structural and chemical variations, posing a great challenge to understand mucin’s bulk behavior. Through this review, the prospective potential of polymer based analogs to serve as mucin mimic is suggested. These analog systems, apart from functioning as an artificial model, reducing the current dependency on animal models, can aid in furthering our fundamental understanding of such complex structures.

Mucoadhesive and thermogelling systems for vaginal drug delivery

This review focuses on two formulation approaches, mucoadhesion and thermogelling, intended for prolonging residence time on vaginal mucosa of medical devices or drug delivery systems, thus improving their efficacy. The review, after a brief description of the vaginal environment and, in particular, of the vaginal secretions that strongly affect in vivo performance of vaginal formulations, deals with the above delivery systems. As for mucoadhesive systems, conventional formulations (gels, tablets, suppositories and emulsions) and novel drug delivery systems (micro-, nano-particles) intended for vaginal administration to achieve either local or systemic effect are reviewed. As for thermogelling systems, poly(ethylene oxide-propylene oxide-ethylene oxide) copolymer-based and chitosan-based formulations are discussed as thermogelling systems. The methods employed for functional characterization of both mucoadhesive and thermogelling drug delivery systems are also briefly described.

Local treatment of the inner ear: a study of three different polymers aimed for middle ear administration

CONCLUSION

A formulation based on sodium hyaluronate (NaHYA) was the most promising candidate vehicle for intra-tympanic drug administration regarding conductive hearing loss, inflammatory reactions, and elimination.

OBJECTIVES

Recent advances in inner ear research support the idea of using the middle ear cavity for drug administration to target the inner ear. This paper presents rheological and safety assessments of three candidate polymer formulations for intra-tympanic drug administration.

METHOD

The formulations were based on sodium carboxymethyl cellulose (NaCMC), sodium hyaluronate (NaHYA), and poloxamer 407 (POL). Rheological studies were performed with a controlled rate instrument of the couette type. Safety studies were performed in guinea pigs subjected to an intra-tympanic injection of the formulations. Hearing function was explored with ABR before and 1, 2, and 3 weeks after the injection. Elimination of the formulations marked with coal was explored with an endoscopic digital camera 1, 2, and 3 weeks after injection. Middle and inner ear morphology was examined with light microscopy 6 days after injection.

RESULTS

The results speak in favor of NaHYA, since it did not cause prolonged hearing threshold elevations. The results of the elimination and morphological investigations support the conclusion of NaHYA being the most promising candidate for intra-tympanic administration.

Polymeric films as a promising carrier for bioadhesive drug delivery: Development, characterization and optimization

Bioadhesive films using tamarind seed polysaccharide were prepared for the treatment of candida vaginitis using nystatin as the model drug. Films were prepared by solvent casting method. A 3² factorial design was employed to study the effect of independent variables (polymer and plasticizer concentration) on a range of dependent variables namely mechanical, swelling, interfacial, and bioadhesive properties through response surface methodological approach, using Design Expert® software. Formulation composition that provided the most desired and optimized results was selected using desirability approach. Nystatin was solubilized using Tween 60 and was incorporated into the selected film. Drug solubilization and dispersion were confirmed by scanning electron microscopy and differential scanning calorimetry. The optimized film released 73.92 ± 2.54% of nystatin at the end of 8 h in simulated vaginal fluid and the release data showed best fit to Korsmeyer–Peppas model with R² of 0.9990 and the release mechanism to be super case-II. The optimized film also showed appropriate anti candida activity through appearance of zone of inhibition during antifungal activity testing study.

Magnetic resonance imaging of the middle and inner ear after intratympanic injection of a gadolinium-containing gel

OBJECTIVE

To investigate the distribution and elimination of a gadolinium containing high viscosity formulation of sodium hyaluronan (HYA gel) after injection to the middle ear.

MATERIALS AND METHODS

The T1 contrast agent gadolinium-diethylenetriamine pentaacetic acid-bis methylamine (Gd-DTPA-BMA) was added to HYA gel and delivered to the middle ear of 13 albino guinea pigs by 3 different ways of injection. Magnetic resonance imaging was performed with a 4.7 T MRI system using a T1-weighted 3-dimentional rapid acquisition with relaxation enhancement sequence.

RESULTS

An injection technique where the Gd-DTPA-BMA-containing HYA gel was delivered to the middle ear through a percutaneous injection through the auditory bulla after a small incision had been made in the tympanic membrane gave the best filling of the middle ear, covering the cochlea and the region of the round window niche for 24 hours in a majority of the ears studied. Ears injected without an incision in the tympanic membrane showed an immediate uptake of Gd-DTPA-BMA in the inner ear as a sign of rupture of the round window membrane.

CONCLUSION

A percutaneous injection of a HYA gel into the tympanic bulla is distributed in a predictable way and gives a good filling of the middle ear cavity. The HYA gel remains in close vicinity to the RWM for more than 24 hours. Injection should be performed after an incision of the tympanic membrane has been made to prevent rupture of the round window membrane.

Enhancing the buccal mucosal delivery of peptide and protein therapeutics

With continuing advances in biotechnology and genetic engineering, there has been a dramatic increase in the availability of new biomacromolecules, such as peptides and proteins that have the potential to ameliorate the symptoms of many poorly-treated diseases. Although most of these macromolecular therapeutics exhibit high potency, their large molecular mass, susceptibility to enzymatic degradation, immunogenicity and tendency to undergo aggregation, adsorption, and denaturation have limited their ability to be administered via the traditional oral route. As a result, alternative noninvasive routes have been investigated for the systemic delivery of these macromolecules, one of which is the buccal mucosa. The buccal mucosa offers a number of advantages over the oral route, making it attractive for the delivery of peptides and proteins. However, the buccal mucosa still exhibits some permeability-limiting properties, and therefore various methods have been explored to enhance the delivery of macromolecules via this route, including the use of chemical penetration enhancers, physical methods, particulate systems and mucoadhesive formulations. The incorporation of anti-aggregating agents in buccal formulations also appears to show promise in other mucosal delivery systems, but has not yet been considered for buccal mucosal drug delivery. This review provides an update on recent approaches that have shown promise in enhancing the buccal mucosal transport of macromolecules, with a major focus on proteins and peptides.

Effect of novel mucoadhesive buccal patches of carvedilol on isoprenaline-induced tachycardia

The main aim of the study was designed to develop bioadhesive buccal patches of carvedilol (CR) and evaluate for isoprenaline-induced tachycardia. Buccal patches of carvedilol were prepared by using chitosan (CH), sodium salt of carboxy methyl cellulose (NaCMC), and polyvinyl alcohol (PVA) as mucoadhesive polymers. The solvent evaporation method was used for the preparation of buccal patches. The patches were evaluated for their physical characteristics like patch thickness, weight variation, content uniformity, folding endurance, surface pH, residence time, in vitro drug release, and in vivo pharmacodynamic study. The swelling index of the patches was found to be proportional to the polymer concentration, whereas surface pH of all the formulated bioadhesive patches was found to lie between neutral ranges. In-vitro release study shows that 94.75% drug was release in 8 hours from the patch, which containing 2% w/v chitosan. The folding endurance result shows good elasticity in all the patches. Application of buccal patches on buccal mucosa of rabbit shows a significant result in % inhibition of isoprenaline-induced tachycardia. Prepared buccal patches of chitosan, NaCMC, and PVA containing Carvedilol meet the ideal requirement for the delivery of cardiovascular drugs and inhibit the isoprenaline tachycardia.