Colon targeting in rats, dogs and IBD patients with species-independent film coatings

Polysaccharides were identified, which allow for colon targeting in human Inflammatory Bowel Disease (IBD) patients, as well as in rats and dogs (which are frequently used as animals in preclinical studies). The polysaccharides are degraded by colonic enzymes (secreted by bacteria), triggering the onset of drug release at the target site. It has to be pointed out that the microbiota in rats, dogs and humans substantially differ. Thus, the performance of this type of colon targeting system observed in animals might not be predictive for patients. The aim of this study was to limit this risk. Different polysaccharides were exposed to culture medium inoculated with fecal samples from IBD patients, healthy dogs and “IBD rats” (in which colonic inflammation was induced).

Dynamic changes in the pH of the culture medium were used as an indicator for the proliferation of the bacteria and, thus, the potential of the polysaccharides to serve as their substrate. Fundamental differences were observed with respect to the extent of the pH variations as well as their species-dependency. The most promising polysaccharides were used to prepare polymeric film coatings surrounding 5-aminosaliciylic acid (5-ASA)-loaded starter cores. To limit premature polysaccharide dissolution/swelling in the upper gastro intestinal tract, ethylcellulose was also included in the film coatings.

Drug release was monitored upon exposure to culture medium inoculated with fecal samples from IBD patients, healthy dogs and “IBD rats”. For reasons of comparison, also 5-ASA release in pure culture medium was measured. Most film coatings showed highly species-dependent drug release kinetics or limited colon targeting capacity. Interestingly, extracts from aloe vera and reishi (a mushroom) showed a promising potential for colon targeting in all species.

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Materials

5-aminosalicylic acid (5-ASA, Alfa Aesar, Kendel, Germany); BactoTM Tryptone, BactoTM desiccated Beef extract (Becton, Dickinson and Co., Le Pont de Claix, France); sodium chloride and dibutyl sebacate (DBS) (Acros organics, Geel, Belgium); yeast extract (Oxoid, Dardilly, France); L-cysteine hydrochloride, pectin from citrus, pectin from apple and 2,4,6-trinitrobenzene sulfonic acid (TNBS) (Sigma-Aldrich, Steinheim, Germany); aqueous ethylcellulose dispersion (Aquacoat ECD, FMC Corporation, Philadelphia, USA); sucrose starter cores (Suglets, mesh 30/35, 500–600 μm; Colorcon, Dartford, UK); partially pregelatinized maize starch (Starch 1500) and hydroxypropyl methylcellulose (HPMC, Methocel K3 premium LV) (Colorcon, Kent, UK); aloe vera extract powder (aqueous extract from the leaves of Aloe barbadensis Mill., Aloaceae), reishi extract powder (ReiSHIELD, aqueous extract from the fruiting body of Ganoderma lucidum, Ganodermataceae), goji berry extract powder, coix lacryma esculentus extract powder, and abelmoscus esculentus extract powder (Specialty Natural Products Co. Ltd., Chon Buri, Thailand); inulin (Orafti Synergy 1: oligofructose-enriched inulin; Orafti HIS: “standard inulin”; and Orafti HP: “long chain inulin”), isomaltulose (Palatinose PST-N) and rice protein (Remypro N80+) (Beneo-Orafti, Oreye, Belgium); low acyl gellan gum (Special Ingredients, Chesterfield, UK); spray-dried acacia gum and karaya gum powders (Alland & Robert, Saint-Aubin sur Gaillon, France); xylan from corn core (Tokyo Chemical industry, Zwijndrecht, Belgium); starch (Novelose 240; Ingredion, Hamburg, Germany) and carrageenan (Satia) (Ceca, Velizy-villacoublay, France); chitosan (Chitoclear; Primex, Siglufjourdur, Iceland); corn maltodextrin (Glucidex 17), cook-up maize starch (Clearam), maltitol (SweetPearl P300 DC) and sodium starch glycolate (Glycolys) (Roquette Freres, Lestrem, France); raffinose [D-(+)-raffinose pentahydrate, Alfa Aesar, Kendel, Germany]; rice starch (Cooper, Melun cedex, France); hydrochloric acid (HCl), sodium hydroxide (NaOH, white pellets) and glacial acetic acid (Fisher Scientific, Loughborough, UK); methanol (Carlo Erba Reagents, Val de Reuil, France).

F. Ferraro, L.M. Sonnleitner, C. Neut, S. Mahieux, J. Verin, J. Siepmann, F. Siepmann, Colon targeting in rats, dogs and IBD patients with species-independent film coatings, International Journal of Pharmaceutics: X, Volume 7, 2024, 100233, ISSN 2590-1567, https://doi.org/10.1016/j.ijpx.2024.100233.