Non-invasive ‘turn-on’ optical monitoring of homocysteine in urine, live cells and sweat

Hydroxyquinoline based ‘turn-on’ sensor (HQN) for the detection of Hcy over Cys, H2S and GSH is reported. The probe can detect homocysteine with LOD 0.94 µM (fluorescence) 0.3 µM (uv), over cysteine with LOD 2.45 µM (fluorescence) 0.5 µM (uv) and H2S with LOD 16.6 µM (fluorescence) 1 µM (uv). The applications of HQN in solution and after immobilization on silica for the visual detection of Hcy in water with LOD 15.3 pg and urine with LOD 18.4 ng has been demonstrated. The data has been supported by optical techniques such as NMR, UV, Fluorescence, AFM and DLS. We also developed latent fingerprinting as a non-invasive method for the detection of Hcy in sweat. HQN has low cytotoxicity (IC50 = >100 µM) and can be used for bioimaging of Hcy in MCF-7 cells.