Identification of the unknown absorption mechanisms of polysorbate 80 micelles

• Applicant: Professorin Dr. Johanita Malan
• Subject Area: Nutritional Sciences
• Term: since 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 434511263

This research project aims to identify the unknown absorption mechanisms of polysorbate 80 micelles in general, as well as PS80-encapsulated curcumin (PS80/curcumin) micelles and native curcumin in particular. Emulsifiers, such as polysorbate 80 (PS80), are used to create micellar formulations of drugs, micronutrients and phytochemicals with enhanced oral bioavailability. Although PS80 consumption is considered safe by FEEDAP and FDA, there are reports that high dose consumption may cause gut barrier dysfunction and low-grade inflammation. Very little is known about the absorption and metabolism of PS80 micelles. It would be relevant to the safety of PS80 micellar formulations to understand if the micelles dissociate at the intestinal brush border, which could lead to altered gut barrier function, or if they are absorbed intact, for example by endocytosis. Another important gap in our knowledge concerns the effects of gastrointestinal digestion (e.g. pH, presence of bile acids, lipases) on the characteristics (e.g. size and surface charge) and subsequent absorption mechanisms of micelles. This is of particular importance when investigating the absorption mechanisms in vitro. Hitherto, only the original micelles, and not potentially altered micelles generated during intestinal digestion, have been evaluated. In preliminary results, I have found that in vitro digestion of PS80/curcumin micelles significantly changed the micellar surface charge and trans-epithelial transport of curcumin. Because of the low bioavailability of native curcumin, the large improvements in bioavailability achieved by micellar solubilisation with PS80 (up to 185-fold), and reported altered intracellular trafficking of the PS80 micellar curcumin, it is an ideal model compound. This project will systematically investigate the absorption mechanisms of empty PS80 micelles, PS80-encapsulated and native curcumin. The effects of in vitro gastrointestinal digestion on the micellar characteristics and subsequent trans-epithelial transport will be studied. Active absorption and efflux transporters of PS80 micelles and curcumin will be identified by inhibiting specific transporters during Caco-2 trans-epithelial transport studies. The role of identified transporters will be confirmed in Caco-2 cells by knocking the genes out with a lentiviral CRISPR/cas9 system. Endocytosis absorption mechanisms and the intracellular trafficking of the micelles will be investigated in fixed and live cells using fluorescent probes and confocal scanning laser microscopy. The results of this research will provide novel insights into the molecular mechanisms governing the enhanced absorption of PS80 micellar formulations of bioactive compounds in general, and of micellar- and native curcumin in particular. It may aid in the development of novel micellar formulations with further improved bioavailability and in better understanding and addressing potential safety concerns.

• DFG Programme: Research Grants