Development and validation of a porcine artificial colonic mucus model reflecting the properties of native colonic mucus in pigs

Colonic mucus plays a key role in colonic drug absorption. Mucus permeation assays could therefore provide useful insights and support rational formulation development in the early stages of drug development. However, the collection of native colonic mucus from animal sources is labor-intensive, does not yield amounts that allow for routine experimentation, and raises ethical concerns. In the present study, we developed an in vitro porcine artificial colonic mucus model based on the characterization of native colonic mucus. The structural properties of the artificial colonic mucus were validated against the native secretion for their ability to capture key diffusion patterns of macromolecules in native mucus. Moreover, the artificial colonic mucus could be stored under common laboratory conditions, without compromising its barrier properties. In conclusion, the porcine artificial colonic mucus model can be considered a biorelevant way to study the diffusion behavior of drug candidates in colonic mucus. It is a cost-efficient screening tool easily incorporated into the early stages of drug development and it contributes to the implementation of the 3Rs (refinement, reduction, and replacement of animals) in the drug development process

In vitro methods to study colon release : State of the art and an outlook on new strategies for better in-vitro biorelevant release media

The primary focus of this review is a discussion regarding in vitro media for colon release, but we also give a brief overview of colon delivery and the colon microbiota as a baseline for this discussion. The large intestine is colonized by a vast number of bacteria, approximately 10 12 per gram of intestinal content. The microbial community in the colon is complex and there is still much that is unknown about its composition and the activity of the microbiome. However, it is evident that this complex microbiota will affect the release from oral formulations targeting the colon. This includes the release of active drug substances, food supplements, and live microorganisms, such as probiotic bacteria and bacteria used for microbiota transplantations. Currently, there are no standardized colon release media, but researchers employ in vitro models representing the colon ranging from reasonable simple systems with adjusted pH with or without key enzymes to the use of fecal samples. In this review, we present the pros and cons for different existing in vitro models. Furthermore, we summarize the current knowledge of the colonic microbiota composition which is of importance to the fermentation capacity of carbohydrates and suggest a strategy to choose bacteria for a new more standardized in vitro dissolution medium for the colon

Physiological properties, composition and structural profiling of porcine gastrointestinal mucus

The gastrointestinal mucus is a hydrogel that lines the luminal side of the gastrointestinal epithelium, offering barrier protection from pathogens and lubrication of the intraluminal contents. These barrier properties likewise affect nutrients and drugs that need to penetrate the mucus to reach the epithelium prior to absorption. In order to assess the potential impact of the mucus on drug absorption, we need information about the nature of the gastrointestinal mucus. Today, most of the relevant available literature is mainly derived from rodent studies. In this work, we used a larger animal species, the pig model, to characterize the mucus throughout the length of the gastrointestinal tract. This is the first report of the physiological properties (physical appearance, pH and water content), composition (protein, lipid and metabolite content) and structural profiling (rheology and gel network) of the porcine gastrointestinal mucus. These findings allow for direct comparisons between the characteristics of mucus from various segments and can be further utilized to improve our understanding of the role of the mucus on region dependent drug absorption. Additionally, the present work is expected to contribute to the assessment of the porcine model as a preclinical species in the drug development process

Utilising phase diagram to understand barley starch microsphere preparation in an aqueous two-phase system

In this work, a waxy barley starch-PEG aqueous two-phase system (ATPS) phase diagram was constructed, and starch microsphere preparation was explored at different phase diagram positions. The aim was to investigate starch-PEG ATPS phase behaviour and relate this to starch crystallisation and microsphere formation. The hypothesis was that phase diagram position would influence the starch microsphere preparation and the properties of the microspheres. The microsphere formation process was investigated with regard to microsphere development and starch crystallisation kinetics. Microsphere physicochemical properties and their development during different stages of the preparation were studied by examining freshly produced, freeze-dried, and redispersed microspheres. Enzymatic hydrolysis of redispersed microspheres was also investigated. It was possible to produce microspheres from different positions in the phase diagram using 24 h incubation at 25 °C. However, the operational area for the used production conditions was relatively small compared to the biphasic region of the phase diagram. The main findings were that the starch-PEG ATPS phase behaviour can affect the rate of microsphere formation and particle size, but the additional properties of the dried and redispersed microspheres did not differ to a considerable extent. Thus, we have identified a robust production space where production parameters such as time to obtain microspheres can be considerably influenced by the ATPS system phase diagram position