(559c) Strawberry Polyphenols As Intestinal Permeation Enhancers for Oral Drug Delivery

Introduction: Oral delivery of biologic drugs, especially therapeutic proteins and nucleic acids, is highly desired due to its ease of use and improved patient compliance when compared with injection¹. However, successful oral formulations must overcome poor transport of large therapeutic molecules from the intestines to the bloodstream. Many studies have examined the use of chemical permeation enhancers to improve the absorption of biologics through the intestinal epithelium². However, effective species tend to induce cytotoxicity or damage the intestinal mucosa. Given the lingering need for efficacious permeation enhancers that are well-tolerated by the intestines, this work presents the results of screening an extensive, food-base library for natural chemicals that improve intestinal absorption of large molecules. Of these, refined strawberry extracts are identified as the most promising, achieving successful oral macromolecule delivery in treated mice.

Methods: A library of crude extracts prepared from over 100 fruits, vegetables, herbs, and fungi was screened for cytotoxicity and absorption enhancing effects on Caco-2 intestinal barrier models. The most effective and well-tolerated permeation enhancing extract (strawberry) was chosen for separation via sequential adsorption/desorption on an acrylic ester resin, yielding active polyphenol fractions. To test in vivo efficacy of the materials, mice received oral gavages of strawberry polyphenols, then gavages of 4 kDa FITC-labelled dextran (FITC-DX4) or 40 kDa FITC-dextran (FITC-DX40). Blood samples were collected and screened for FITC fluorescence. For mechanistic studies, Caco-2 monolayers were used in conjunction with fluorescent confocal microscopy to investigate tight junction rearrangement.

Results: Of the crude food extracts examined, the vast majority did not induce cytotoxicity in intestinal cells. Those that did significantly reduce cell viability mostly contained portions of the foods not typically consumed in large quantities (e.g. citrus rinds). Among the non-toxic extracts, most did not significantly change the barrier properties of Caco-2 monolayers, though some did significantly increase permeability. Of these, strawberry was the most effective and was chosen for further separation and investigation. Isolation of the polyphenol contents from the strawberry extract via Amberlite resin yielded fractions that were highly potent permeabilizers of Caco-2 barriers. When combined and orally administered to mice, these fractions boosted the intestines-to-bloodstream transport of both FITC-DX4 and FITC-DX40 by over 100%. Further, in vitro mechanistic studies revealed that the nanoparticle treatment does cause a rearrangement of the cytoskeletal protein actin, as well as the tight junction protein ZO-1, an integral component to the barrier function of the intestinal epithelium.

Conclusions and Implications: This is the first study demonstrating the use of nontoxic, food-derived chemicals for improving adsorption of orally administered protein drugs. The extensive library of crude extracts examined demonstrated that most foods do not appreciably change intestinal permeability. Of the few that do, strawberry was the most potent permeation enhancer, and demonstrated increased potency as extracts were refined and screened for oral drug delivery capabilities in mice. These conclusive in vivo results demonstrate the ability of strawberry polyphenols to effectively increase epithelial permeability, enabling the oral delivery of macromolecular drugs. Future investigations will include delivery of active protein drugs and comprehensive safety studies in mice and higher animal models.

Acknowledgements: N. Lamson would like to acknowledge financial support from the NSF Graduate Research Fellowship Program under Grant No. DGE1252522.

References:

1. Caffarel-Salvador, E., Abramson, A., Langer, R., & Traverso, T. Curr Opin Pharmacol. 2017 (36) 8-13.
2. Moroz, E., Matoori, S., & Leroux, J. Adv Drug Deliv Rev. 2016 (101) 108-121.