Solvents effect on dansyl cysteamine depletion and reactivity classification of skin sensitizers: Tackling the challenges using binary solvent systems.

Abstract The high throughput method using dansyl cysteamine (HTS-DCYA™) is a sensitive and rapid in chemico approach to characterize skin sensitizers' thio-reactivity. The direct quantification of fluorescent hapten-DCYA adducts facilitates the rapid testing of pure chemicals as well as mixtures. Poor solubility in acetonitrile was occasionally observed and can represent a limitation. To enable the range of solvent options compatible with the testing, the effect of binary solvent systems on thio-reactivity and the HTS-DCYA classification was explored. The method's robustness was validated using five different solvent modifiers: water, DMSO, methanol, ethanol, and tetrahydrofuran. Some modifiers, viz., water and methanol, resulted in unexpected DCYA depletion, negatively affecting the thio-reactivity and classification of potential sensitizers. This undesirable, non-specific depletion was circumvented by optimizing the original HTS-DCYA™ method's workflow, resulting in a more robust and reliable thio-reactivity and hence classification with a binary solvent system. The results were validated for both pure compounds and plant extracts as examples of complex test samples. Based on the obtained results, the modified HTS-DCYA optimal conditions in the various solvent systems were established. Concentrations of modifiers up to 10% DMSO, 40% water, 40% EtOH, 60% MeOH, or 60% THF in acetonitrile were found acceptable for the modified protocol, with results comparable to the original method. The improved workflow with binary solvent systems provides significant advantages by expanding the applicability of the HTS-DCYA to a wider array of chemicals poorly soluble in acetonitrile.