Clinical evaluation of bioadhesive hydrogels for topical delivery of hexylaminolevulinate to Barrett's esophagus

Evaluation of Oromucosal Natural Gum-Based Emulgels as Novel Strategy for Photodynamic Therapy of Oral Premalignant Lesions

Photodynamic therapy (PDT) recently has been shown as a promising option in the treatment of premalignant lesions of the soft oral tissues. Effective delivery of photosensitizer is challenging due to poor drug adherence to the oromucosal epithelium. In the present work, emulgels composed of natural polysaccharide gums (tragacanth, xanthan and gellan) were evaluated as novel oromucosal platforms of delta-aminolevulinic acid (ALA) for PDT. Apart from mucoadhesive and textural analysis, the specific steps involved studies on drug penetration behavior and safety profile using a three-dimensional human oral epithelium model (HOE). All designed emulgels presented greater mucoadhesiveness when compared to commercial oromucosal gel. Incorporation of ALA affected textural properties of emulgels, and tragacanth/xanthan formulation with greater hardness and cohesiveness exhibited a protective function against the mechanical tongue stress. Permeability studies revealed that ALA is capable of penetrating across oromucosal epithelium by passive transport and all formulations promoted its absorption rate when compared to a commercial topical product with ALA. Importantly, the combination of tragacanth and xanthan profoundly enhanced photosensitizer retention in the buccal epithelium. Tested samples performed negligible reduction in cell viability and moderately low IL-1β release, confirming their non-irritancy and compatibility with HOE. Overall, the presented findings indicate that tragacanth/xanthan emulgel holds promise as an oromucosal ALA-carrier for PDT strategy.

Evaluation of bioadhesive gels for local action in the esophagus

Direct drug administration to the esophagus faces several obstacles, including continuous salivary dilution and removal of the dosage form from the tissue surface due to esophageal peristalsis. These actions often result in short exposure times and reduced concentrations of drug at the esophageal surface, providing limited opportunities for drug absorption into or across the esophageal mucosa. A variety of bioadhesive polymers were investigated for their ability to resist removal by salivary washings using an ex vivo porcine esophageal tissue model. Hydroxypropylmethylcellulose and carboxymethylcellulose both have reported bioadhesive properties, but neither was able to withstand repeated exposure to saliva, and the gels formulated with these polymers were quickly removed from the esophageal surface. Two polyacrylic polymers, carbomer and polycarbophil, also showed limited esophageal surface retention when exposed to salivary washing, likely due to the ionic composition of saliva affecting the inter-polymer interactions necessary for these polymers to maintain their increased viscosities. In situ gel forming polysaccharide gels (ion-triggered), including xanthan gum, gellan gum, and sodium alginate, showed superior tissue surface retention, and formulations containing these bioadhesive polymers along with ciclesonide, an anti-inflammatory soft prodrug, were investigated as potential, locally-acting esophageal delivery systems. Exposure of a segment of esophagus to the ciclesonide-containing gels resulted in therapeutic concentrations of des-ciclesonide, the active drug metabolite, in the tissues within 30 min. Increasing des-CIC concentrations were also observed over a 3-hour exposure interval suggesting continued release and absorption of ciclesonide into the esophageal tissues. These results demonstrate the ability to achieve therapeutic drug concentrations in the esophageal tissues using in situ gel-forming bioadhesive polymer delivery systems, and these systems provide promising opportunities for the local treatment of esophageal disease.

Poly(lactic acid)-hyperbranched polyglycerol nanoparticles enhance bioadhesive treatment of esophageal disease and reduce systemic drug exposure

The effective treatment of esophageal disease represents a significant unmet clinical need, as existing treatments often lead to unnecessary systemic drug exposure and suboptimal concentrations at the disease site. Here, surface-modified bioadhesive poly(lactic acid)-hyperbranched polyglycerol nanoparticles (BNPs), with an average 100-200 nm diameter, were developed for local and sustained esophageal drug delivery. BNPs showed significantly higher adhesion and permeation into ex vivo human and rat esophageal tissue than non-adhesive nanoparticles (NNPs) and had longer residence times within the rat esophagus in vivo. Incubation with human esophagus (Het-1A) cells confirmed BNPs' biocompatibility at clinically relevant concentrations. In a rat model of achalasia, nifedipine-loaded BNPs significantly enhanced esophageal drug exposure, increased therapeutic efficacy, and reduced systemic drug exposure compared to NNPs and free drug. The safety of BNPs was demonstrated by an absence of intestinal, hepatic, and splenic toxicity following administration. This study is the first to demonstrate the efficacy of BNPs for esophageal drug delivery and highlight their potential for improving the lives of patients suffering with esophageal conditions.

Covalently Crosslinked Hydrogels via Step-Growth Reactions: Crosslinking Chemistries, Polymers, and Clinical Impact

Hydrogels are an important class of biomaterials with the unique property of high-water content in a crosslinked polymer network. In particular, chemically crosslinked hydrogels have made a great clinical impact in past years because of their desirable mechanical properties and tunability of structural and chemical properties. Various polymers and step-growth crosslinking chemistries are harnessed for fabricating such covalently crosslinked hydrogels for translational research. However, selecting appropriate crosslinking chemistries and polymers for the intended clinical application is time-consuming and challenging. It requires the integration of polymer chemistry knowledge with thoughtful crosslinking reaction design. This task becomes even more challenging when other factors such as the biological mechanisms of the pathology, practical administration routes, and regulatory requirements add additional constraints. In this review, key features of crosslinking chemistries and polymers commonly used for preparing translatable hydrogels are outlined and their performance in biological systems is summarized. The examples of effective polymer/crosslinking chemistry combinations that have yielded clinically approved hydrogel products are specifically highlighted. These hydrogel design parameters in the context of the regulatory process and clinical translation barriers, providing a guideline for the rational selection of polymer/crosslinking chemistry combinations to construct hydrogels with high translational potential are further considered.

Thermoreversible mucoadhesive polymer-drug dispersion for sustained local delivery of budesonide to treat inflammatory disorders of the GI tract

Mucoadhesive drug formulations have been studied and used as alternatives to conventional formulations in order to achieve prolonged retention at the intended site. In addition to providing a controlled drug release, several drugs and disease conditions might benefit from mucoadhesive formulations, contributing to better therapeutic outcomes. Here, we describe the development and the in vitro/in vivo characterization of a mucoadhesive in situ gellifying formulation using PF127, a thermo reversible polymer, entrapping budesonide (BUD), a potent corticosteroid used for the treatment of a wide range of inflammatory diseases, including those affecting mucosas, such as in the GI tract. PF127 formulations (15-17%) were successfully prepared by a cold method as a thermo reversible in situ gelling dispersion for mucosal drug delivery, as confirmed by DSC. Sol-gel temperatures of PF127 formulations (25-39 °C) were observed by dynamic gelation and determined by microrheology and oscillatory rheometry. X-ray diffractograms and TEM images showed that BUD was completely solubilized within the polymeric micelles. In vitro, the gels showed 5-14 g force of mucoadhesion, and the ex vivo studies confirmed that the formulation efficiently adhered to the mucosa. Histopathological analysis combined with fluorescence images and ex vivo intestinal permeation confirmed that the formulation remained on the TGI mucosa for at least 4 h after administration. In vivo studies conducted in a murine model of intestinal mucositis demonstrated that the 16% PF127 BUD formulation was able to resolve the inflammatory injury in the intestinal mucosa. Results demonstrate that fine-tuning of PF127 formulations along with adequate selection of the drug agent, thorough characterization of the dispersions and their interactions with biological interfaces leads to the development of effective controlled drug delivery systems targeted to GI inflammatory diseases.

Emerging Implications for Extracellular Matrix-Based Technologies in Vascularized Composite Allotransplantation

Despite recent progress in vascularized composite allotransplantation (VCA), limitations including complex, high dose immunosuppression regimens, lifelong risk of toxicity from immunosuppressants, acute and most critically chronic graft rejection, and suboptimal nerve regeneration remain particularly challenging obstacles restricting clinical progress. When properly configured, customized, and implemented, biomaterials derived from the extracellular matrix (ECM) retain bioactive molecules and immunomodulatory properties that can promote stem cell migration, proliferation and differentiation, and constructive functional tissue remodeling. The present paper reviews the emerging implications of ECM-based technologies in VCA, including local immunomodulation, tissue repair, nerve regeneration, minimally invasive graft targeted drug delivery, stem cell transplantation, and other donor graft manipulation.

An evaluation of the adhesion of solid oral dosage form coatings to the oesophagus

There is a requirement for the development of oral dosage forms that are adhesive and allow extended oesophageal residence time for localised therapies, or are non-adhesive for ease of swallowing. This study provides an initial assessment of the in vitro oesophageal retention characteristics of several widely utilised pharmaceutical coating materials. To this end, a previously described apparatus has been used to measure the force required to pull a coated disc-shaped model tablet across a section of excised oesophageal tissue. Of the materials tested, the well-studied mucoadhesive polymer sodium alginate was found to be associated with significant oesophageal adhesion properties that was capable of 'self-repairing'. Hydroxypropylmethylcellulose exhibited less pronounced bioadhesive behaviour and blending this with plasticiser or with low molecular weight polymers and surfactants did not significantly affect this. Low molecular weight water soluble polymers, were found to behave similarly to the uncoated glass control disc. Polysorbates exhibited bioadhesion behaviour that was majorly influenced by the nature of the surfactant. The insoluble polymer ethylcellulose, and the relatively lipophilic surfactant sorbitan monooleate were seen to move more readily than the uncoated disc, suggesting that these may have a role as 'easy-to-swallow' coatings.

Chitosan-based mucoadhesive films containing 5-aminolevulinic acid for buccal cancer's treatment

Photodynamic therapy (PDT) is a relatively new method to treat various kinds of tumors, including those of the oral cavity. The topical 5-ALA-PDT treatment for tumors of the oral mucosa is preferred, since when administered systemically, there is a general photosensitization drawback in the patient. However, 5-ALA is a hydrophilic molecule and its penetration and retention is limited by topical route, including oral mucosa. We propose a topical delivery system of chitosan-based mucoadhesive film, aiming to promote greater retention of 5-ALA in tissue. The chitosan (CHT) films (4% w/w) were prepared using the solvent evaporation/casting technique. They were tested without 5-ALA resulting in permeability to water vapor (W.V.P=2.15-8.54 g mm/(h cm(2)Pa) swelling ∼300.0% (±10.5) at 4 h or 24 h and in vitro residence time >24 h for all tests. CHT films containing 10.0% (w/w) 5-ALA have resulted in average weight of 0.22 g and thickness of 0.608 mm as suitable characteristics for oral application. In the presence of CHT films both in vitro permeation and retention of 5-ALA (1.0% or 10.0%) were increased. However, 10.0% 5-ALA presented highest values of permeation and retention (∼4 and 17 times respectively, compared to propylene glycol vehicle). On the other hand, in vitro mucoadhesion of CHT films was decreased (18.2-fold and 3.1-fold) by 5-ALA addition (1.0% or 10.0% respectively). However, CHT film containing 10.0% of 5-ALA can be a potential delivery system for topical use in the treatment of tumors of the oral cavity using PDT because it favored the retention of 5-ALA in this tissue and has shown convenient mucoadhesion.

An in vitro model for the evaluation of the adhesion of solid oral dosage forms to the oesophagus

Adhesion of solid oral dosage forms to the oesophagus can be a disadvantage when delivering drugs that may cause oesophageal damage, or can be an advantage when developing localised therapies for this region. In this study, apparatus to investigate coatings that may influence oesophageal retention was developed and evaluated. The apparatus incorporated a section of porcine oesophageal mucosa held flat by the application of a gentle vacuum and kept moist by the application of a simulated saliva solution. The resistance to the application of more physiologically relevant shear stresses was evaluated. Using a range of materials it was found that differences in oesophageal adhesion could be identified. Materials like sodium alginate were highly adhesive and had a tendency to re-adhere while paraffin waxes showed no adhesion. The rapid loss of the polymer coat from the surface for water swellable materials was identified as an issue.

Design and formulation of mebeverine HCl semisolid formulations for intraorally administration

Gel formulations of mebeverine hydrochloride (MbHCl) containing hydroxypropylmethylcellulose (HPMC), metolose (MTL), and poloxamer 407 (PLX) were prepared to be used in the treatment of different oral painful conditions. HPMC was used as a mucoadhesive gel base while MTL and PLX were used to prepare sol-gel thermosensitive gels. MTL and PLX formulations showed proper sol-gel transition temperature for intraoral application. Formulations were evaluated in terms of their viscosity, mechanical properties, mucoadhesivity, stability, and in vitro drug release. The formulation prepared with 2% of HPMC K100M provided the highest viscosity at room temperature. However, the viscosity of HPMC-PLX mixture showed a significant increase at body temperature. The greatest mucoadhesion was also noted in HPMC-PLX combinations. Texture profile analysis exhibited the differences of the adhesion, hardness, elasticity, cohesiveness, and compressibility of the formulations. The release profiles of MbHCl were obtained, and non-Fickian release was observed from all the formulations. The formulations were stored at different temperature and relative humidity. No significant changes were observed at the end of the 3 months. HPMC-PLX formulation of MbHCl was chosen for in vivo studies, and it remained longer than dye solution on the rabbit's intraoral mucosal tissue. It was found worthy of further clinical evaluation.

Preparation and in vitro evaluation of a new fentanyl patch based on functional and non-functional pressure sensitive adhesives

In this study, some single-layer and double-layer transdermal drug delivery systems (TDDSs) with different functional and non-functional acrylic pressure-sensitive adhesives (PSAs) were prepared. For this purpose, fentanyl as a drug was used. The effects of PSAs type, single-layer and double-layer TDDSs on skin permeation and in vitro drug release from devices were evaluated using a hydrodynamically well-characterized Chien permeation system fitted with excised rat abdominal skin. The adhesion properties of devices such as peel strength and tack values were obtained as well. It was found that TDDS with -COOH functional PSA showed the lowest steady-state flux. Double-layer TDDS displayed a constant flux up to 72 h. In double- and single-layer devices after 1 and 3 h, respectively, drug release followed Higuchi's kinetic model. Formulations with the highest percentage of -COOH functional PSA have displayed the lowest flux. The double-layer TDDSs with non-functional PSA demonstrated the suitable skin permeation rate close to Duragesic(R) TDDS and suitable adhesion properties.

Formulation of thermoresponsive and bioadhesive gel for treatment of oesophageal pain and inflammation

The aim of this study was the formulation and examination of a novel thermoresponsive and bioadhesive, in situ gelling drug delivery system, which can be used in the treatment of oesophageal pain and inflammation. A bioadhesive cellulose derivative (Metolose) 60SH) was used as a thermoresponsive material, because Metolose has thermal gelation properties at certain temperature. The thermal gelation temperature (T(2)) of Metolose 60SH 2 w/w% solution is above body temperature (65-66 degrees C), but by using different methods (Metolose 60SH concentration, auxiliary materials), it can be shifted near to body temperature. The pH alteration between pH=2-10 and the application of different alcohols did not influence the gelation temperature, but using water-soluble salts and changing the concentration of Metolose 60SH solution between 2 and 3 w/w% the thermal gelation point could be decreased. Different NSAIDs were used as model drugs and which had not influence on thermal gelation temperature, but difference in in vitro liberation and penetration can be observed. In vitro adhesion test pointed out that the condition of investigated membrane can change the adhesion. Morphological test of oesophageal tissue showed that investigated materials had no irritative or tissue-damaging effect on the oesophageal mucosa even after 12h.

Photodynamic therapy using 5-aminolaevulinic acid for the treatment of dysplasia in Barrett's oesophagus

BACKGROUND

5-Aminolaevulinic acid (ALA) is the naturally occurring metabolic precursor of an endogenously formed photosensitiser, protoporphyrin IX. It is used topically to treat benign and malignant skin disorders by a process called photodynamic therapy (PDT). Recently, data are emerging on its systemic use in the treatment of dysplasia in Barrett's oesophagus.

OBJECTIVE

To investigate the use of ALA-PDT for the treatment of dysplasia and early cancer in Barrett's oesophagus.

METHODS

A systematic literature review and synopsis is given.

CONCLUSION

ALA is an attractive alternative to the currently approved photosensitiser (porfimer sodium) due to its oral route of administration, shorter generalised skin photosensitivity period and lower rate of stricture formation. The studies presented demonstrate that ALA-PDT is both safe and effective for the treatment of dysplasia and early cancer in Barrett's oesophagus.