Improving the sensitivity of protein fluorescent probes by molecular structural fine-tuning based on aggregation-induced emission mechanism

Three 1,3-butadiene derivatives were synthesized to investigate the effect of small structural changes on the detection sensitivity with bovine serum albumin (BSA). The compound 2-MFDNa with methyl group added to the 5-furan ring showed a 132-fold fluorescent enhancement response to BSA, while 3-FDNa with no methyl group on the 5-furan ring showed a 52-fold fluorescent enhancement response to BSA. Compared with the detection limits of 3-FDNa 0.19 μg/mL and 2-FDNa 0.17 μg/mL, that of 2-MFDNa was reduced to 0.01 μg/mL. 2-MFDNa achieved a higher selective and sensitive detection to BSA. Molecular docking analysis revealed that the improved detection sensitivity was due to the enhanced restriction of intramolecular motion, with more C–H···π interactions limiting the rotation of the rotor of the probe molecule, leading to enhanced fluorescence. These results provide a simple and effective strategy for the molecular design of aggregation-induced emission probes for the detection of proteins with higher sensitivity.