TY - JOUR N2 - The transdermal delivery of sparingly soluble drugs is challenging due to of the need for a drug carrier. In the past few decades, ionic liquid (IL)-in-oil microemulsions (IL/O MEs) have been developed as potential carriers. By focusing on biocompatibility, we report on an IL/O ME that is designed to enhance the solubility and transdermal delivery of the sparingly soluble drug, acyclovir. The prepared MEs were composed of a hydrophilic IL (choline formate, choline lactate, or choline propionate) as the non-aqueous polar phase and a surface-active IL (choline oleate) as the surfactant in combination with sorbitan laurate in a continuous oil phase. The selected ILs were all biologically active ions. Optimized pseudo ternary phase diagrams indicated the MEs formed thermodynamically stable, spherically shaped, and nano-sized (<100 nm) droplets. An in vitro drug permeation study, using pig skin, showed the significantly enhanced permeation of acyclovir using the ME. A Fourier transform infrared spectroscopy study showed a reduction of the skin barrier function with the ME. Finally, a skin irritation study showed a high cell survival rate (>90) with the ME compared with Dulbeccoâ??s phosphate-buffered saline, indicates the biocompatibility of the ME. Therefore, we conclude that IL/O ME may be a promising nano-carrier for the transdermal delivery of sparingly soluble drugs. © 2020 by the authors. Licensee MDPI, Basel, Switzerland. IS - 4 N1 - cited By 48 KW - aciclovir; carboxylic acid derivative; choline derivative; ionic liquid; oil; sorbitan laurate KW - animal tissue; Article; cell survival; controlled study; drug delivery system; Fourier transform infrared spectroscopy; human; human tissue; hydrophilicity; in vitro study; microemulsion; nonhuman; particle size; physical phase; pig; process optimization; survival rate; thermodynamics TI - Ionic liquid-in-oil microemulsions prepared with biocompatible choline carboxylic acids for improving the transdermal delivery of a sparingly soluble drug ID - scholars13279 AV - none UR - https://www.scopus.com/inward/record.uri?eid=2-s2.0-85083987634&doi=10.3390%2fpharmaceutics12040392&partnerID=40&md5=e2bc3b6e8b2de06b2ddb1eca70d4c676 A1 - Islam, M.R. A1 - Chowdhury, M.R. A1 - Wakabayashi, R. A1 - Kamiya, N. A1 - Moniruzzaman, M. A1 - Goto, M. JF - Pharmaceutics VL - 12 Y1 - 2020/// SN - 19994923 PB - MDPI AG ER -