Comparison of solvate ionic liquids and DMSO as an in vivo delivery and storage media for small molecular therapeutics

Abstract

Background: Solvate ionic liquids (SILs) are a new class of ionic liquids that are equimolar solutions of lithium bistrifluoromethanesulfonimide in either triglyme or tetraglyme, referred to as G3LiTFSA and G4LiTFSA, respectively. SILs play a role in energy storage lithium batteries, and have been proposed as potential alternatives to traditional organic solvents such as DMSO. G3TFSA and G4TFSA have been shown to exhibit no toxicity in vivo up to 0.5% (v/v), and solubilize small compounds (N,N-diethylaminobenzaldehyde) with full penetrance, similar to DMSO delivered DEAB. Herein, we compare the effects of storage (either at room temperature or - 20 °C) on DEAB solubilized in either DMSO, G3TFSA or G4TFSA to investigate compound degradation and efficacy.

Results: The findings show that DEAB stored at room temperature (RT) for 4 months solubilized in either G3TFSA, G4TFSA or DMSO displayed no loss of penetrance. The same was observed with stock solutions stored at - 20 °C for 4 months; however G4TFSA remained in a liquid state compared to both G3TFSA and DMSO. Moreover, we examined the ability of G3TFSA and G4TFSA to solubilize another small molecular therapeutic, the FGFR antagonist SU5402. G4TFSA, unlike G3TFSA solubilized SU5402 and displayed similar phenotypic characteristics and reduced dlx2a expression as reported and shown with SU5402 in DMSO; albeit more penetrative.

Conclusion: This study validates the use of these ionic liquids as a potential replacement for DMSO in vivo as organic solubilizing agents.

Keywords: Aldh1a2; DEAB; Embryogenesis; FGFR; Ionic liquids; Retinoic acid; SU5402; Zebrafish.

Fig. 1

Solvate ionic liquids and DMSO which are the focus of this study

Fig. 2

Room temperature DEAB exposure in developing zebrafish embryos. Embryos exposed to DEAB at 5 μM in solution at room temperature for 4 months in either DMSO (b), G3TFSA (c), or G4TFSA (d) displayed the reported characteristic of loss of RA (compared to control (DMSO exposed only (a): lack of pectoral fin induction (arrowhead), shortening of the posterior head (asterisk), malformation of the otic vesical (arrow) and pericardial edema

Fig. 3

Frozen DEAB exposure in developing zebrafish embryos. Embryos exposed to DEAB at 5 μM that have been stored for 4 months at -20 °C in either DMSO (b), G3TFSA (c), or G4TFSA (d) display the reported characteristics of loss of RA (compared to control (DMSO exposed only (a): lack of pectoral fin induction (arrowhead), shortening of the posterior head (asterisk), malformation of the otic vesical (arrow) and pericardial edema

Fig. 4

SU5402 exposure in developing zebrafish embryos. Embryos are exposed to SU5402 (d) at 2.5 μM (b & c) or 5 μM (e & f) in either DMSO or G4TFSA display the reported characteristics of FGF signaling inhibition compared to control (untreated (a) or DMSO exposed only (b & e)): lack of pectoral fin induction (marked by an asterisk), malformation of the otic vesicle (arrow). Lloss of MHB (open arrow head) was observed in embryos treated with 5 μM DEAB. 100× magnification

Fig. 5

Expression of dlx2a visualized using whole mount in situ hybridization. Embryos exposed to SU5402 at 2.5 μM in either DMSO (b & e) or G4TFSA (c & f) display reduced localization and expression of dlx2a compared to control (DMSO exposed only (a & d) in the hindbrain (arrow) and in the pharyngeal arches (arrow head, * lack of pharyngeal arches). The first row depicts the embryos in a later orientation, the second row depicts the embryos in a ventral orientation