Encapsulation of Lactobacillus casei into Calcium Pectinate-Chitosan Beads for Enteric Delivery.

Gel beads were prepared by extrusion of various types of pectin into 0.15 M calcium chloride. Size, morphology, and textural properties of 3 types of beads were evaluated and it was established that the use of 3 w/v % amidated pectin provides the optimal characteristics suitable for encapsulation of live bacteria. Lactobacillus casei NCIMB 30185 (PXN37) was encapsulated into calcium pectinate gel through the extrusion of a live bacteria dispersion in 3 w/v % pectin into a solution of calcium chloride. The capsules were then additionally coated with chitosan. The viability of bacteria within these capsules was studied under model gastrointestinal conditions in vitro (simulated gastric and intestinal juices). It was established that pectin-chitosan capsules can provide protection to L. casei from the gastric acid and result in high levels of viable bacteria released in the intestine. PRACTICAL APPLICATION: Encapsulation of Lactobacillus casei into calcium pectinate beads coated with chitosan provided capsules capable of delivering live probiotic bacteria into the intestine.

Evaluating and optimizing oral formulations of live bacterial vaccines using a gastro-small intestine model.

Gastrointestinal (GI) models that mimic physiological conditions in vitro are important tools for developing and optimizing biopharmaceutical formulations. Oral administration of live attenuated bacterial vaccines (LBV) can safely and effectively promote mucosal immunity but new formulations are required that provide controlled release of optimal numbers of viable bacterial cells, which must survive gastrointestinal transit overcoming various antimicrobial barriers. Here, we use a gastro-small intestine gut model of human GI conditions to study the survival and release kinetics of two oral LBV formulations: the licensed typhoid fever vaccine Vivotif comprising enteric coated capsules; and an experimental formulation of the model vaccine Salmonella Typhimurium SL3261 dried directly onto cast enteric polymer films and laminated to form a polymer film laminate (PFL). Neither formulation released significant numbers of viable cells when tested in the complete gastro-small intestine model. The poor performance in delivering viable cells could be attributed to a combination of acid and bile toxicity plus incomplete release of cells for Vivotif capsules, and to bile toxicity alone for PFL. To achieve effective protection from intestinal bile in addition to effective acid resistance, bile adsorbent resins were incorporated into the PFL to produce a new formulation, termed BR-PFL. Efficient and complete release of 4.4×10(7) live cells per dose was achieved from BR-PFL at distal intestinal pH, with release kinetics controlled by the composition of the enteric polymer film, and no loss in viability observed in any stage of the GI model. Use of this in vitro GI model thereby allowed rational design of an oral LBV formulation to maximize viable cell release.

Enteric coated spheres produced by extrusion/spheronization provide effective gastric protection and efficient release of live therapeutic bacteria.

We present a novel but simple enteric coated sphere formulation containing probiotic bacteria (Lactobacillus casei). Oral delivery of live bacterial cells (LBC) requires live cells to survive firstly manufacturing processes and secondly GI microbicidal defenses including gastric acid. We incorporated live L. casei directly in the granulation liquid, followed by granulation, extrusion, spheronization, drying and spray coating to produce dried live probiotic spheres. A blend of MCC, calcium-crosslinked alginate, and lactose was developed that gave improved live cell survival during manufacturing, and gave excellent protection from gastric acid plus rapid release in intestinal conditions. No significant loss of viability was observed in all steps except drying, which resulted in approximately 1 log loss of viable cells. Eudragit coating was used to protect dried live cells from acid, and microcrystalline cellulose (MCC) was combined with sodium alginate to achieve efficient sphere disintegration leading to rapid and complete bacterial cell release in intestinal conditions. Viability and release of L. casei was evaluated in vitro in simulated GI conditions. Uncoated spheres gave partial acid protection, but enteric coated spheres effectively protected dried probiotic LBC from acid for 2h, and subsequently released all viable cells within 1h of transfer into simulated intestinal fluid.

A laminated polymer film formulation for enteric delivery of live vaccine and probiotic bacteria.

Live bacterial cells (LBCs) are administered orally as attenuated vaccines to deliver biopharmaceutical agents and as probiotics to improve gastrointestinal (GI) health. However, LBCs present unique formulation challenges and must survive GI antimicrobial defenses including gastric acid after administration. We present a simple new formulation concept, termed polymer film laminate (PFL). LBCs are ambient dried onto cast acid-resistant enteric polymer films that are then laminated together to produce a solid oral dosage form. LBC of a model live bacterial vaccine and a probiotic were dried directly onto a cast film of enteric polymer. The effectiveness at protecting dried cells in a simulated gastric fluid (SGF, pH 2.0) depended on the composition of enteric polymer film used, with a blend of ethylcellulose plus Eudragit L100 55 providing greater protection from acid than Eudragit alone. However, although PFL made from blended polymer films completely released low-molecular-weight dye into intestinal conditions (pH 7.0), they failed to release LBCs. In contrast, PFL made from Eudragit alone successfully protected dried probiotic or vaccine LBC from SGF for 2 h, and subsequently released all viable cells within 60 min of transfer into simulated intestinal fluid. Release kinetics could be controlled by modifying the lamination method.