Modifying Fluorescent Protein Chromophore to Detect Protamine and Application in Real Serum Samples

Graphical In this research, a new TICT probe (IDL-FP) was designed for sensitive detection of protamine. The introduction of indole-3-carboxaldehyde and 4-dimethylaminobenzaldehyde gave IDL-FP both an electron-donor and electron-acceptor, which urged the complete intramolecular charge transfer and a large stokes shift, allowing IDL-FP to process minimal background noise and excellent biocompatibility. Additionally, protamine can directly induce the aggregation of IDL-FP caused by electrostatic attraction. In this way, the turn-on detection of protamine was achieved and the detection limit was as low as 8.87 ng mL −1 , which showed a better sensitivity and higher stability. As IDL-FP exhibited good stability in physiological pH environment, we successfully applied IDL-FP to detect spiked-in protamine in human serum. In summary, probe IDL-FP is a promising tool for the quantitative determination of protamine for potential clinical usage. As effective methods to accurately and rapidly detect protamine remains a major challenge, here we present a fluorescent protein chromophore-based probe (IDL-FP) utilizing twisted-intramolecular charge transfer (TICT) to detect protamine. The introduction of an electron-donor group 4-dimethylaminobenzaldehyde extends the emission wavelength of IDL-FP to the red region. The deprotection of t-butyloxy carbonyl groups can then generate an electronegative carboxyl group, which promotes the binding to protamine via electrostatic attraction. Thus, IDL-FP is sensitive and specific towards protamine and can serve as a highly selective detector for protamine with a detection limit as low as 8.87 ng/mL. As IDL-FP exhibited good stability in physiological pH environment, we successfully apply IDL-FP to detect spiked-in protamine in human serum. In summary, probe IDL-FP is a promising tool for the quantitative determination of protamine.