Studies On Manipulation Of Substituent And Aggregation For Detection Of Metal Ions (Al³⁺,Ag⁺) And Protein?HSA?

Fluorescence sensors have been widely used in environmental protection,medical research,life science and other feilds,owing to their simple operation,high sensitivity,good selectivity,wide linear range and real time detection.We chose 3-hydroxyflavone and squaline dyes as the parent fluorophores and conducted the following reaserch for detection of metal ions(Al³⁺,Ag+)and human serum albumin?HSA?.Simple allyl carbonate-substituted?FA?and methylether-substituted flavone probe?FM?have been constructed,respectly,which is based on a new strategy that the enol-keto tautomerism of excited-stated intramolecular proton transfer?ESIPT?can be regulated through the substituent effect of its hydroxyl group.Compared to FM,FA exhibited highly selective and ratiometric fluorescent response to Al³⁺and could detect Al³⁺at a low concentration of 0.8 ?M in aqueous solution.The detection limit of FA is lower than the guidelines for drinking water set by the WHO?7.41 ?M?,which suggests that the good sensor could be used to detect Al³⁺in drinking water.Moreover,FA was successfully explored for detection of Al³⁺ and imaging in living cells.The squaraine dye?SQ?is a kind of special and near-infrared fluorescent dyes,which found in recent years.The background fluorescence intensity of SQ is closely related to its aggregation degree,pyrene-substitutional?SQ-P?and benzene-substitutional squaraine fluorescent probe?SQ-B?have been constructed based on SQ,respectively.Compared to SQ-B,SQ-P could self-assemble into nanoparticles in aqueous solution through multiple interactions?such as ?-?,C-H…? and hydrophobic?.The additional interactions derived from the pyrene segment in SQ-P easily induce to form fluorescence quenching aggregates owing to the aggregation induced fluorescence quenching?ACQ?properties.The present of human serum albumn?HSA?trigger the molecular disassembly through hydrophobic interaction,leading to the fluorescence enhancement of SQ-P.SQ-P could sensitively detect HSA.More importantly,the probe can quantitatively detect serum albumin in human sera?HSA?.A new squaraine dye?PD-SQ?was synthesized based on the unique spectroscopiccharacteristics of SQ.Novel near infrared?NIR?fluorescent hybrid system?PD-SQìBSA?was successfullycongstructed,which is assembled from PD-SQ and bovine serum albumin?BSA?.BSA can cause PD-SQ to partially disaggregate through electrostatic and hydrophobic interactions,but various metal ions including Ag+cannot do.Interestingly,the presence of both BSA and Ag+ can trigger PD-SQ to almost completely disaggregate through synergic binding of multiple S-Ag linkings derived from the biothiol moieties in BSA and PD-SQ with Ag+,resulting in obvious turn-on fluorescence change.PD-SQìBSA could selectively detect Ag+ over other metal ions in absolute PBS.The detection limit of PD-SQìBSA for Ag+ is calculated to be about 8.99×10-8 M,which is lower than the guidelines for drinking water set by the WHO.