Monique Alric

Relevance and challenges in modeling human gastric and small intestinal digestion

Gastric and small intestinal (GSI) models are increasingly used as an alternative to in vivo assays to answer many questions raised by industry and researchers. A broad range of in vitro systems is available, from static monocompartmental to dynamic multicompartmental models. However, these models require a compromise between technological complexity and biological significance. Further efforts and technological innovations are still needed to improve in vitro models and meet growing demands in the areas of nutrition and health. This review describes the models available to date for the human stomach and small intestine and highlights their relevance in nutritional, toxicological, pharmaceutical, and microbiological studies. Limitations and challenges facing artificial digestion technology are also discussed.

A Dynamic Artificial Gastrointestinal System for Studying the Behavior of Orally Administered Drug Dosage Forms Under Various Physiological Conditions

AbstractPurpose. The purpose of this study was to demonstrate the potential of a dynamic, multicompartmental in vitro system simulating the human stomach and small intestine (TIM-1) for studying the behavior of oral drug dosage forms under various physiological gastrointestinal conditions. Methods. Two model drug compounds were studied in TIM-1: a lyophilized Lactobacillus strain and paracetamol (acetaminophen). The Lactobacillus survival rate was determined by bacterial counting in the gastric and ileal effluents while simulating the conditions of the gastrointestinal tract of infants or adults. The availability for absorption of paracetamol from two oral dosage forms was investigated by measuring the drug concentration in jejunal dialysis fluid. The effect of gastrointestinal passage time and food intake on paracetamol absorption was also studied. Results. The Lactobacillus survival rate in both gastric and ileal effluents was higher during simulation of the infant compared to adult conditions. We also showed that (i) paracetamol absorption was faster when it was administered as a free powder than in sustained-release tablet form, (ii) a slow passage time resulted in a delay in the absorption of paracetamol, and (iii) there was a lower rate of absorption when paracetamol was ingested with a standard breakfast as opposed to water. The in vitro results were consistent with in vivo data, showing the predictive value of TIM-1. Conclusions. TIM-1 is a powerful tool for supplying valuable information about the effects of various gastrointestinal conditions on biopharmaceutical behavior and efficacy of drug delivery systems in the development of oral formulations.

Coated whey protein/alginate microparticles as oral controlled delivery systems for probiotic yeast

Viable Saccharomyces boulardii, used as a biotherapeutic agent, was encapsulated in food-grade whey protein isolate (WP) and alginate (ALG) microparticles, in order to protect and vehicle them in gastrointestinal environment. Yeast-loaded microparticles with a WP/ALG ratio of 62/38 were produced with high encapsulation efficiency (95%) using an extrusion/cold gelation method and coated with ALG or WP by a simple immersion method. Swelling, yeast survival, WP loss and yeast release in simulated gastric and intestinal fluids (SGF and SIF, pH 1.2 and 7.5) with and without their respective digestive enzymes (pepsin and pancreatin) were investigated. In SGF, ALG network shrinkage limited enzyme diffusion into the WP/ALG matrix. Coated and uncoated WP/ALG microparticles were resistant in SGF even with pepsin. Survival of yeast cells in microparticles was 40% compared to 10% for free yeast cells and was improved to 60% by coating. In SIF, yeast cell release followed coated microparticle swelling with a desirable delay. Coated WP/ALG microparticles appear to have potential as oral delivery systems for Saccharomyces boulardii or as encapsulation means for probiotic cells in pharmaceutical or food processing applications.

Combining the dynamic TNO-gastrointestinal tract system with a caco-2 cell culture model: application to the assessment of lycopene and α-tocopherol bioavailability from a whole food.

To exert their health effect, phytochemicals such as carotenoids and vitamin E have to be bioavailable. We investigated the digestive stability and intestinal absorption of lycopene and alpha-tocopherol from a whole food containing red tomatoes and sunflower oil using, for the first time, the dynamic gastrointestinal system TNO gastrointestinal tract model (TIM) coupled with Caco-2 cells. Digestive samples were added to Caco-2 cells after appropriate ultracentrifugation, filtration, and dilution. alpha-Tocopherol was stable during digestion in the TIM, whereas a 25% loss was observed for lycopene. The absorption of both compounds was curvilinear, bidirectional, and concentration-dependent. The percentages of alpha-tocopherol absorbed, but not that of lycopene, were lower with digestas compared to those with pure compounds, suggesting competition for absorption with other components of the test meal. According to in vivo data, a lower bioavailability was found for lycopene compared to that for alpha-tocopherol. These results support the usefulness of this in vitro approach for estimating the bioavailability of active compounds from food.

Effect of a New Probiotic Saccharomyces cerevisiae Strain on Survival of Escherichia coli O157:H7 in a Dynamic Gastrointestinal Model

ABSTRACT Survival of Escherichia coli O157:H7 was investigated using a dynamic gastrointestinal model. A high bacterial mortality was observed in the stomach and duodenum. In contrast, bacteria grew in the distal parts of the small intestine. The coadministration of Saccharomyces cerevisiae CNCM I-3856 led to a significant reduction of bacterial resumption, maybe through ethanol production.

Investigation of the Biopharmaceutical Behavior of Theophylline Hydrophilic Matrix Tablets Using USP Methods and an Artificial Digestive System

This work aimed to investigate the biopharmaceutical behavior of hydrophilic matrix tablets of theophylline using different in vitro methods: USP II, USP IV, and a novel in vitro system simulating the gastrointestinal tract in man called the artificial digestive system (ADS). The potentiality of each method was evaluated by establishing in vitro/in vivo correlation. Using USP methods, the drug release was pH-independent and dependent on agitation intensity. Level A IVIVCs could be established using the different in vitro methods but one to one correlation was established only when the ADS method was used. For the prediction of in vivo drug dosage form behavior based on in vitro methods, the ADS showed a high predictability when compared to USP in vitro methods.

Comparison of a static and a dynamic in vitro model to estimate the bioaccessibility of As, Cd, Pb and Hg from food reference materials Fucus sp. (IAEA-140/TM) and Lobster hepatopancreas (TORT-2)

Bioaccessibility, the fraction of an element solubilized during gastrointestinal digestion and available for absorption, is a factor that should be considered when evaluating the health risk of contaminants from food. Static and dynamic models that mimic human physiological conditions have been used to evaluate bioaccessibility. This preliminary study compares the bioaccessibility of arsenic (As), cadmium (Cd), lead (Pb) and mercury (Hg) in two food certified reference materials (CRMs) (seaweed: Fucus sp., IAEA-140/TM; Lobster hepatopancreas: TORT-2), using two in vitro gastrointestinal digestion methods: a static method (SM) and a dynamic multicompartment method (TIM-1). There are significant differences (p<0.05) between the bioaccessible values of As, Cd, Pb and Hg obtained by SM and TIM-1 in the two CRMs. The specific form in which the elements studied are present in the CRM may help to explain the bioaccessibility values obtained.

Recombinant Saccharomyces cerevisiae Expressing P450 in Artificial Digestive Systems: a Model for Biodetoxication in the Human Digestive Environment

ABSTRACT The use of genetically engineered microorganisms such as bacteria or yeasts as live vehicles to carry out bioconversion directly in the digestive environment is an important challenge for the development of innovative biodrugs. A system that mimics the human gastrointestinal tract was combined with a computer simulation to evaluate the survival rate and cinnamate 4-hydroxylase activity of a recombinant model of Saccharomyces cerevisiae expressing the plant P450 73A1. The yeasts showed a high level of resistance to gastric and small intestinal secretions (survival rate after 4 h of digestion, 95.6% ± 10.1% [n = 4]) but were more sensitive to the colonic conditions (survival rate after 4 h of incubation, 35.9% ± 2.7% [n = 3]). For the first time, the ability of recombinant S. cerevisiae to carry out a bioconversion reaction has been demonstrated throughout the gastrointestinal tract. In the gastric-small intestinal system, 41.0% ± 5.8% (n = 3) of the ingested trans-cinnamic acid was converted into p-coumaric acid after 4 h of digestion, as well as 8.9% ± 1.6% (n = 3) in the stomach, 13.8% ± 3.3% (n = 3) in the duodenum, 11.8% ± 3.4% (n = 3) in the jejunum, and 6.5% ± 1.0% (n = 3) in the ileum. In the large intestinal system, cinnamate 4-hydroxylase activity was detected but was too weak to be quantified. These results suggest that S. cerevisiae may afford a useful host for the development of biodrugs and may provide an innovative system for the prevention or treatment of diseases that escape classical drug action. In particular, yeasts may provide a suitable vector for biodetoxication in the digestive environment.

Cross-blot and cross-dot system: A high-performance system for the detection of antigen-antibody complexes on nitrocellulose

We present a reliable, simple, and quick system for screening antibody-antigen complexes on nitrocellulose. The apparatus necessary for this system is inexpensive and easy to use, and it can be adapted to blot or dot analysis without any modification. The number of antibody-antigen combinations that can be tested in one experiment ranges from 25 to 31 for blot analysis and from 345 to 600 for dot analysis. This system also offers numerous experimental advantages: it makes it possible to estimate with only one experiment the contribution of the different reaction stages to background noise and so allows unambiguous interpretation of the antibody-antigen reaction. Furthermore, this system can be used for any hybridization experiment on nitrocellulose.

Investigation of coated whey protein/alginate beads as sustained release dosage form in simulated gastrointestinal environment

Aim: The biopharmaceutical behavior of new formulations based on both food-grade polymers, whey protein (WP) and alginate (ALG) was studied using different in vitro methods. The Biopharmaceutical Classification System (BCS) class I drug Theophylline was chosen as drug model. Method: Drug release was studied (i) at pH 1.2 (2 hours) followed by pH 7.5, and in simulated gastric fluid (SGF; 2 hours) followed by simulated intestinal fluid (SIF) using the paddle method and (ii) in an artificial digestive system. Results: Freeze-dried mixed WP/ALG (62/38) beads were coated with WP or ALG with encapsulation efficiency 34.9% and 18.3%, respectively. At pH 1.2, coated beads exhibited gastroresistant properties (< 10% of drug released after 2 hours) followed at pH 7.5 by a sustained release behavior (< 60% of drug released at 24 hours) controlled by an erosion mechanism. In SGF, despite enzyme hydrolysis, drug release was still controlled due to ALG shrinkage. After transfer in SIF, formulations were completely degraded in less than 2 h with total drug release. In an artificial digestive system, coated beads appeared gastroresistant, intestinal part sustained drug release was controlled by erosion. Conclusion: Combination of in vitro methods allowed prediction of the in vivo potentialities of WP- and ALG- coated WP/ALG beads as oral sustained release systems.