荧光增强型共轭聚电解质的合成及对肝素的双通道检测

通过Suzuki偶联反应制备了含有四苯基乙烯和苯并噻二唑2种结构单元的阳离子型共轭聚电解质P1,并通过核磁共振氢谱确定了2种结构单元的比例为0.803:0.197,与投料比基本一致.当在P1的水溶液中加入不良溶剂THF时,在紫外光照下可以观察到其溶液颜色由土黄色(无聚集态)转变为橙黄色(聚集态).利用P1在不同聚集态下的荧光强度和发光颜色变化,可以实现对肝素的双通道检测.当肝素逐渐滴加到P1的水溶液中,P1的荧光发射强度随着肝素浓度的增加而线性增加,且其最大发射峰峰位发生线性红移,正负电荷饱和时强度达到最大且波长不再移动,该性质可作为双通道检测信号来标定肝素的浓度,从而提高肝素浓度检测的准确性.动态激光光散射的测试以及肝素滴定紫外图谱的变化结果表明,肝素与P1作用时聚集诱导发光和荧光共振能量转移两种作用共存,从而导致了荧光强度的增强,且伴随最大发射波长的红移.

A WATER-SOLUBLE DUAL-CHANNEL FLUORESCENCE-ENHANCED BIOSENSOR FOR HEPARIN BASED ON A CATIONIC CONJUGATED POLYELECTROLYTE CONTAINING TETRAPHENYLETHENE AND 2,1,3-BENZOTHIADIAZOLE

A conjugated polymer(P0) containing tetraphenylethene(TPE) group and benzothiadiazole(BT) group has been designed and synthesized by Suzuki coupling reaction of 1,2-di4-(6-bromohexyloxy)phenyl]-1,2-di(4-bromophenyl)ethene(M1),1,2-di4-(6-bromohexyloxy) phenyl]-1,2-di(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)ethylene(M2) and 4,7-dibromo-2,1,3-benzothiadiazole(M3).The ratio of TPE unit to BT unit at 0.803∶0.197 was determined by 1H-NMR spectrum.A water-soluble cationic conjugated polyelectrolyte(P1) is obtained by quaternization P0 with trimethylamine,which is completely soluble in water and insoluble in common organic solvents such as THF and acetone.When P1 is aggregated by adding a poor solvent such as THF into P1 aqueous solution,the fluorescence intensity and color of P1 change drastically.The intensity increases up to seven times and the maximum emission peak is red-shifted up to 30 nm.The color is changing from khaki(no aggregation)to orange(aggregation)under ultraviolet irradiation.Therefore,dual-channel fluorescence response as the unique properties of P1 was applied to detect heparin,a highly sulfated glycosaminoglycan with the highest negative charge density among the known biological molecules.The fluorescence intensity gradually increased upon addition of heparin into P1 aqueous solution with a linear response to concentration of heparin,and the correlation coefficient was up to 0.9999.In addition,a linear red shift of the maximum emission peak was observed as the concentration of heparin increased with a correlation coefficient up to 0.9998.These results indicate that P1 is a potential material for developing dual-channel fluorescence probe for heparin quantification.The UV spectra of P1/heparin complexing titration don't show any change.This indicates that there is no inter-chains or intra-chains π-π stacking of P1.DLS result indicates some aggregates can be formed through electrostatic interaction between P1 and heparin,which can reduce the radiative decay when the intramolecular rotation of phenyl group on the side chains is restricted and the fluorescent emission can correspondingly be enhanced.Moreover,due to existence of BT,a typical fluorescence acceptor in fluorescence resonance energy transfer,the fluorescence of TPE segments can effectively be transferred to BT segments when the aggregates are formed by electrostatic interaction between P1 and heparin,which leads to red-shifts of the maximum emission wavelength.Based on these different responses to electrostatic interaction between P1 and heparin,dual-channel signals can be obtained as the above discussion.This study thus provides a new concept for designing dual-channel fluorescence sensing material.