Highly sensitive lanthanide complex as a probe for l‐kynurenine: A cancer biomarker

Abstract A lanthanide complex based on europium (Eu) and chelidamic acid was synthesized (Eu–CHE) and characterized. The complex Eu–CHE exhibited intense luminescence at 615 nm under excitation at 300 nm and was further investigated for highly sensitive turn‐off detection of l ‐kynurenine ( l ‐kyn), a cancer biomarker. The probe detected l ‐kyn linearly from 6 nM to 0.2 μM with a limit of detection and limit of quantification of 1.37 and 4.57 nM, respectively. The probe was investigated for selectivity towards l ‐kyn among co‐existing amino acids and further extended for detecting l ‐kyn from human serum and urine samples. A low‐cost paper strip‐based sensing platform was also developed for the visual detection of l ‐kyn.