Transdermal Protein Delivery Via a Choline-Based Deep Eutectic Solvent

Transdermal Protein Delivery Via A Choline-based Deep Eutectic Solvent

Presenting Author:  Kelly Ibsen¹

Co-Authors:  Amrita Banerjee¹, Yasunori Iwao², Michael Zakrewsky¹, Samir Mitragotri¹

¹University of California Santa Barbara, USA; ²University of Shizuoka, Japan

The outer layer of the skin is a formidable barrier to drug delivery, and many of currently available methods to increase the permeability of skin, such as chemical penetration enhancers (CPE) ethanol and Transcutol, also cause irritation and damage. This research aims to develop low-irritation compounds that enhance transdermal delivery of proteins. We have shown that CAGE, a benign choline-geranate eutectic, can deliver small proteins.¹ Here, we investigate its ability to enable macromolecule penetration, using three proteins with a range of sizes and hydrophobicity: insulin bovine serum albumin (BSA) and ovalbumin (OVA). Transdermal delivery of macromolecules such as proteins could improve a myriad of treatments that currently require subcutaneous injections such as diabetes, where needle phobia results in poor patient compliance and treatment outcomes.²

To measure skin penetration compared to standard CPEs, fluorescently-labeled proteins in 1) CAGE, 2) ethanol, 3) Transcutol^®, or 4) buffer were applied to porcine skin discs in a diffusion cell. Confocal laser imaging was conducted on skin cross-sections at 24 h.  Insulin and BSA concentrations were quantitatively measured in the separate skin layers and the acceptor compartment after 24 and 48 h via fluorescence or isotope detection. Additionally, in vivo delivery of insulin was examined by measuring blood glucose levels in rats after topical application of insulin-CAGE compared to subcutaneous insulin injection.

Confocal laser imaging showed penetration of insulin, BSA and OVA with CAGE into the skin but not with 50% v/v ethanol, Transcutol or buffer after 24 h. The amount of insulin or BSA delivered through the skin section at 48 h, as measured by concentration in the acceptor chamber, was significantly higher with CAGE than buffer. Topical application of insulin-CAGE on rats resulted in a significant decrease of 40% in blood glucose compared to insulin in buffer after 4 hours that was sustained for the length of the 12-hour study, providing a more sustained effect on blood glucose than subcutaneous injection. These results demonstrate the effectiveness of CAGE as a potential transdermal delivery vehicle for therapeutic proteins.

Acknowledgements:  The presenting author is supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE-1144085.

References

1.     M. Zakrewsky, K. S. Lovejoy, T. L. Kern, T. E. Miller, V. Le, A. Nagy, A. M. Goumas, R. S. Iyer, R. E. Del Sesto, A. T. Koppisch, D. T. Fox, S. Mitragotri. Proc. Natl. Acad. Sci. 2014. 111, 13313.

2.     D. Nathan. Diabetes Care. 2014. 37(1): 9-16.