A Novel Sensor for Sequential and Cellular Detection of Copper and Lactic Acid

We report self assembling/aggregation properties of acyl-thiourea derivative, N-((6-methoxy-pyridin-2-yl)carbamothioyl)benzamide(NG1) [i1] and the disaggregation induced emission which leads to its application as fluorescence and colorimetric probe for the sensitive detection of Cu2+. The microscopy analysis of NG1via SEM, and AFM reveal that it self-assembles to give fiber-like morphologies.Interestingly,NG1 also assembles to fluorescent fibers which show tunable emission properties. Addition of Cu2+to these fibers causedisruption/disaggregation of fibers and a golden yellow fluorescence is produced due to disaggregation induced emission enhancement (DIEE). The application of NG1 as selective sensor for copper was further assessed by UV visible and fluorescence spectroscopy. Limit of Detection(LOD) of Cu2+ with colorimetry was 2.5ppm while LOD of Cu2+ with fluorescence was as low as 0.1ppm. This yellow fluorescence is quenched after the addition of lactic acid and hence NG1 could potentially be used for the sequential detection of both Cu and lactate.Further, structural modification of the probe NG1 suggest crucial role of both pyridine and acyl-thiourea moiety in the binding of Cu2+. The experimental results of interaction of NG1 with Cu2+ and lactate were also validated theoretically by quantum chemical calculations based on density functional theory (DFT). Finally, we explore the ability of NG1for the sequential detection of Cu2+ and lactate in cells, which suggestsNG1 can be used effectively for the cellular imaging applications and to selectively sense Cu2+. To, the best of our knowledge,this is the first report wherein a dual sensor for Cu2+and lactate ion is synthesized and it may in allpossibilities pave the way for the diagnosis of Cu2+associated disorders like Wilson’s disease and in the detection of elevated lactate levels which are associated with the wide range of pathologies likemitochondrial diseases, cerebral ischemia and cancer.