2010

Paracellular Drug Delivery Through Baker’s Yeast Microcapsules

The yeast has the ability to open up the junctions between cells to aid drug delivery.

Oral mucosal drug delivery is an alternative method of systemic drug delivery that offers several advantages over both injectable and enteral methods. Since the oral mucosa is highly vascularised, drugs that are absorbed through the oral mucosa directly enter the systemic circulation, bypassing the gastrointestinal tract and first-pass metabolism in the liver. This avoids some of the problems typically experienced with traditional oral medication like analgesics that have to be absorbed by the lining of the stomach or the intestine, either of which they can irritate.

For some drugs, this results in rapid onset of action via a more comfortable and convenient delivery route than the intravenous route. Not all drugs, however, can be administered through the oral mucosa because of the characteristics of the oral mucosa and the physicochemical properties of the drug. Nitroglycerin is one of the most common drugs delivered through the oral mucosa.

There is a need for drugs to be delivered non-invasively, and in some cases, also bypassing the stomach as a drug absorption target. The preferential route of absorption of poorly soluble active ingredients is via transcellular transport as opposed to more water-soluble drugs, or other therapeutic agents resistant to transcellular transport, which are typically delivered by the paracellular route.

As an alternative to traditional microencapsulation processes, the use of preformed natural microorganisms as microcapsules was first considered in the 1970s when it was observed that yeast cells (Saccharomyces cerevisiae), when treated with a plasmolyser, could be used to encapsulate water-soluble substances. When grown in fermenters, yeast microbial capsules reach a uniform size distribution and their physical makeup can be modified simply by altering the nutrient balance within the fermentation medium. In microencapsulation processes, the encapsulation takes place in dead as well as live cells, indicating that encapsulation takes place by simple diffusion.

Initial focus was on using yeast-based microencapsulation technology as a novel means of turning a volatile liquid into a powder for ease of handling. When it was observed that the yeast capsules released their flavor payload on contact with the mucosal surfaces of the mouth more readily than in saliva alone, the possibility of targeted drug delivery using yeast cell capsules was first proposed.

The yeast microencapsulation system is designed for the encapsulation of high concentrations of lipophilic active pharmaceutical ingredients and is able to deposit a localized, concentrated active on the mucosal surface of choice.

Coating the yeast particles with conventional materials (e.g. enteric coating systems) allows targeted delivery of the yeast and subsequent delivery of a lipophilic active anywhere from the mouth to the lower bowel. Once released, the yeast cells disperse within the GI tract fluids and at the mucosal surface, deliver their contents for absorption into the systemic circulation system.

The yeast microcapsules can be incorporated into a variety of conventional cream bases and can be modified to form an aqueous-based cream without addition of other excipients.

The encapsulation of essential oils together with antibiotic and/or biocidal compounds within fungal cells (or fungal cell fragments) can open new opportunities for novel wound dressings. When applied to the epithelium of exposed wounds, it has been shown to inhibit microbial development in the wound.

With the permeation enhancement and mucoadhesive properties offered by yeast cells, this technology offers clear benefits to pharmaceutical producers seeking safe delivery mechanisms by means of nasal powders and sprays. Application could be by means of powder, tablet, capsule, chewable tablet, chewing gum, melting film strip, spray, cream, or gel.

The focus of this technology is the ability of yeast reversibly to open up the junctions between cells to aid drug delivery. By microencapsulating active ingredients inside the yeast cells, this technology enhances paracellular movement of active ingredients in mucus-rich areas.

This technology is offered by Licensing Technology Network. For more information, view the yet2.com TechPak at http://info.hotims.com/28049-142.

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