Fluorescence-based histamine sensing with inorganic-organic hybrid nanoparticles

Four novel inorganic-organic hybrid nanoparticles (IOH-NPs) are presented that allow a fluorescence detection of biogenic amines such as histamine. Namely, the IOH-NPs are Cu 2+ [Calc] 2− , Ag 2 + [Calc] 2− (Calc: calcein, C 30 H 24 N 2 O 13 ), Cu 2 2+ [PTC] 4− and Ag 4 + [PTC] 4− (PTC: perylenetetracarboxylate, C 24 H 8 O 8 ) that contain extremely high dye loads of calcein (90 wt% in Cu 2+ [Calc] 2− , 70 wt% in Ag 2 + [Calc] 2− ) and of the perylene derivative (77 wt% in Cu 2 2+ [PTC] 4− , 50 wt% in Ag 4 + [PTC] 4− ). The saline compounds are prepared by water-based synthesis, which instantaneously results in highly stable nanoparticle suspensions. Whereas the calcein- and perylenetetracarboxylate-related fluorescence is essentially quenched in the solid nanoparticles, the respective dye is released into solution in the presence of histamine and, thereafter, shows bright emission with an intensity depending on the concentration of histamine. Specifically, Ag 4 + [PTC] 4− shows promising performance with high colloidal and chemical stability as well as a remarkable concentration-depending fluorescence increase upon addition of histamine ( e.g. 180-times higher emission upon addition of 100 μM of histamine). In fact, only Ag 4 + [PTC] 4− IOH-NPs show off/on-like emission in the absence/presence of histamine, which is preferable for reliable fluorescence detection. Ag 4 + [PTC] 4− (PTC: perylenetetracarboxylate) inorganic-organic hybrid nanoparticles indicate the presence of histamine with off/on-like switching of fluorescence.