Pre-treatment strategies based on aqueous two-phase systems comprising ionic liquids to improve the adrenal cancer diagnosis

Cancer remains the cause of millions of deaths every year worldwide, and reliable early-stage diagnosis methods are essential to prevent them. Cancer biomarkers quantification in human fluids has gained relevance in detecting cancer in an early-stage. Among these, the levels of the biomarkers epinephrine, norepinephrine and vanillylmandelic acid in urine have been used for the diagnosis of adrenal cancer. However, due to their low levels in human fluids, expensive and multistep pretreatment methods are necessary to increase their concentration to meet the detection limits of the analytical equipments. In this work, we propose the use of aqueous two-phase systems (ATPS) composed of ionic liquids (ILs), K3PO4 and synthetic/natural urine as an alternative pretreatment strategy to improve the concentration of adrenal cancer biomarkers from human fluids. The ATPS ternary phase diagrams, as well as the respective tie-lines and tie-line lengths, were determined at 25 °C. The performance of these IL-based ATPS for the extraction and concentration of epinephrine, norepinephrine and vanillylmandelic acid from human urine was then evaluated. The obtained results show that in the studied systems, with the exception of IL-based ATPS constituted by ILs with longer alkyl side chains at the cation, all the studied cancer biomarkers preferably migrate to the IL-rich phase. The best ATPS investigated is constituted by 1-ethyl-3-methylimidazolium methylsulfate ([C2mim][CH3SO4]) that allows the complete extraction of all cancer biomarkers to the IL-rich phase in a single-step and a concentration factor up to 500-fold. All biomarkers were accurately quantified in the IL-rich phase after the extraction from urine and the concentration step by UHPLC. According to the obtained results, IL-based ATPS could be used as a novel and effective method for the pretreatment and concentration of cancer biomarkers from human fluids to improve cancer diagnosis.