Ultrasensitive detection of cholecystokinin (CCK) by laser-induced time-resolved fluorescence diagnostics

摘要

An ultrasensitive detection method of CCK in aqueous solution was developed. This method utilizes intrinsic native fluorescence properties of CCK-molecules. A new delay-line multichannel plate photomultiplier (MCP PMT) was used to measure both time and wavelength resolved fluorescence properties simultaneously. Both CCK4 and CCK8 showed biexponential fluorescence decay. While the short lived fluorescence decay time components were rather similar, the long-lived components differed by about 1 ns. In the case of CCK8 the long-lived component was red-shifted by 30 nm. Based on these photophysical data an experimental setup for an ultrasensitive detection was developed. The lowest detection limit was achieved by investigating the fluorescence intensity within a time gate (gate duration 2 ns) in the fluorescence maximum. In combination with a confocal setup, using a Cassegrainean configuration, CCK could be detected up to 10$+$MIN@12$/ M.