Gastrointestinal diseases and their impact on drug solubility: Ulcerative Colitis

An overview on recent approaches for colonic drug delivery systems

Colon-targeted drug delivery systems have garnered significant interest as potential solutions for delivering various medications susceptible to acidic and catalytic degradation in the gastrointestinal (GI) tract or as a means of treating colonic diseases naturally with fewer overall side effects. The increasing demand for patient-friendly drug administration underscores the importance of colonic drug delivery, particularly through noninvasive methods like nanoparticulate drug delivery technologies. Such systems offer improved patient compliance, cost reduction, and therapeutic advantages. This study places particular emphasis on formulations and discusses recent advancements in various methods for designing colon-targeted drug delivery systems and their medicinal applications.

Ilex rotunda Thunb Protects Against Dextran Sulfate Sodium-Induced Ulcerative Colitis in Mice by Restoring the Intestinal Mucosal Barrier and Modulating the Oncostatin M/Oncostatin M Receptor Pathway

Ilex rotunda Thunb (IR) is a traditional Chinese medicine used for the clinical treatment of gastric ulcers and duodenal ulcers; however, the effect of IR on ulcerative colitis (UC) and its underlying mechanism remains unclear. This study investigated the therapeutic effect of IR on UC mice induced by dextran sulfate sodium (DSS) as well as the potential underlying mechanism. The main components of IR were analyzed by ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry. Then we established a model of UC mice by administering 2.0% DSS for 7 days followed by 2 weeks of tap water for three cycles and administered IR. On day 56, the disease activity index (DAI), colon length, pathological changes, and inflammatory response of the colon tissue of mice were assessed. The oxidative stress and apoptosis of colon tissue were detected, and the integrity of the intestinal mucosal barrier was evaluated to assess the effect of IR. Furthermore, the relationship between oncostatin M (OSM) and its receptor (OSMR) in addition to the IR treatment of UC were evaluated using a mouse model and Caco2 cell model. The results showed that IR significantly alleviated the symptoms of UC including rescuing the shortened colon length; reducing DAI scores, serum myeloperoxidase and lipopolysaccharide levels, pathological damage, inflammatory cell infiltration and mRNA levels of interleukin one beta, tumor necrosis factor alpha, and interleukin six in colon tissue; alleviating oxidative stress and apoptosis by decreasing kelch-like ECH-associated protein 1 expression and increasing nuclear factor-erythroid factor 2-related factor 2 and heme oxygenase-1 protein expression; and promoting the regeneration of epithelial cells. IR also promoted the restoration of the intestinal mucosal barrier and modulated the OSM/OSMR pathway to alleviate UC. It was found that IR exerted therapeutic effects on UC by restoring the intestinal mucosal barrier and regulating the OSM/OSMR pathway.

Clinical translation of advanced colonic drug delivery technologies

Targeted drug delivery to the colon offers a myriad of benefits, including treatment of local diseases, direct access to unique therapeutic targets and the potential for increasing systemic drug bioavailability and efficacy. Although a range of traditional colonic delivery technologies are available, these systems exhibit inconsistent drug release due to physiological variability between and within individuals, which may be further exacerbated by underlying disease states. In recent years, significant translational and commercial advances have been made with the introduction of new technologies that incorporate independent multi-stimuli release mechanisms (pH and/or microbiota-dependent release). Harnessing these advanced technologies offers new possibilities for drug delivery via the colon, including the delivery of biopharmaceuticals, vaccines, nutrients, and microbiome therapeutics for the treatment of both local and systemic diseases. This review details the latest advances in colonic drug delivery, with an emphasis on emerging therapeutic opportunities and clinical technology translation.

Modelling and Simulation of the Drug Release from a Solid Dosage Form in the Human Ascending Colon: The Influence of Different Motility Patterns and Fluid Viscosities

For colonic drug delivery, the ascending part of the colon is the most favourable site as it offers the most suitable environmental conditions for drug dissolution. Commonly, the performance of a drug formulation is assessed using standardised dissolution apparatus, which does not replicate the hydrodynamics and shear stress evoked by wall motion in the colon. In this work, computer simulations are used to analyse and understand the influence of different biorelevant motility patterns on the disintegration/drug release of a solid dosage form (tablet) under different fluid conditions (viscosities) to mimic the ascending colonic environment. Furthermore, the ability of the motility pattern to distribute the drug in the ascending colon luminal environment is analysed to provide data for a spatiotemporal concentration profile. The motility patterns used are derived from in vivo data representing different motility patterns in the human ascending colon. The applied motility patterns show considerable differences in the drug release rate from the tablet, as well as in the ability to distribute the drug along the colon. The drug dissolution/disintegration process from a solid dosage form is primarily influenced by the hydrodynamic and shear stress it experiences, i.e., a combination of motility pattern and fluid viscosity. Reduced fluid motion leads to a more pronounced influence of diffusion in the tablet dissolution process. The motility pattern that provoked frequent single shear stress peaks seemed to be more effective in achieving a higher drug release rate. The ability to simulate drug release profiles under biorelevant colonic environmental conditions provides valuable feedback to better understand the drug formulation and how this can be optimised to ensure that the drug is present in the desired concentration within the ascending colon.

Dual-Degradable Biohybrid Microgels by Direct Cross-Linking of Chitosan and Dextran Using Azide-Alkyne Cycloaddition

In this work, biocompatible and degradable biohybrid microgels based on chitosan and dextran were synthesized for drug delivery applications. Two kinds of bio-based building blocks, alkyne-modified chitosan and azide-modified dextran, were used to fabricate microgels via single-step cross-linking in water-in-oil emulsions. The cross-linking was initiated in the presence of copper(II) without the use of any extra cross-linkers. A series of pH-responsive and degradable microgels were successfully synthesized by varying the degree of cross-links. The microgels were characterized using ¹H NMR and FTIR spectroscopy which proved the successful cross-linking of alkyne-modified chitosan and azide-modified dextran by copper(II)-mediated click reaction. The obtained microgels exhibit polyampholyte character and can carry positive or negative charges in aqueous solutions at different pH values. Biodegradability of microgels was shown at pH 9 or in the presence of Dextranase due to the hydrolysis of carbonate esters in the microgels or 1,6-α-glucosidic linkages in dextran structure, respectively. Furthermore, the microgels could encapsulate vancomycin hydrochloride (VM), an antibiotic, with a high loading of approximately 93.67% via electrostatic interactions. The payload could be released in the presence of Dextranase or under an alkaline environment, making the microgels potential candidates for drug delivery, such as colon-specific drug release.