Quantitative determination of protamine using a fluorescent protein chromophore-based AIE probe

An aggregation induced emission (AIE) fluorescent protein chromophore derivative CIC-FP for detecting protamine and heparin under physiological environment was designed and synthesized. CIC-FP exhibited good biocompatibility and a large stoke shift (91 nm), thus well attenuating the background interference, which could be used for quantitative detection of heparin and protamine . Since protamine has strong positively groups, it can interact with CIC-FP where bearing carboxyl through electrostatic interactions to form a tightly bound CIC-FP/protamine complex, thus showing superior fluorescence intensity response with a detection limit of 65.28 ng/mL. Because heparin has a stronger affinity with protamine, it would compete with CIC-FP on protamine, resulting in the release of CIC-FP and making CIC-FP change into free state with decreased fluorescence intensity . Besides, CIC-FP was successfully applied to detect spiked protamine in human serum samples. In summary, CIC-FP can be used to sensitive detection of protamine with good accuracy, which provides a new idea for designing protamine probes.