AIE Property Of Pvridinium Modified Tetraphenylethene-based Salt And Its Applications In Bio-sensing

High sensitivity, low background noise, low detection limit, good selectivity, less amount of sampling, convenient and quick testing, and wide dynamic ranges make the fluorescence-based techniques the extensively used methods for bioassay. Aggregation-induced emission (AIE), a unique photophysical phenomenon offers a new methodology to solve the aggregation-caused fluorescence quenching problem that the classic fluorescence probes always have. Recently, as a representative AIE-active fluorogen, tetraphenylethene (TPE) and its derivatives have attracted considerable attention for their facile preparation, easy functionlization and promising applications in chemical and biochemical sensing. This work is to design and synthesize pyridinyl-functionalized TPE fluorophores, and explore their possible applications in biochemical sensing.Firstly, a series of TPE derivatives with cationic pyridinyl-functionalities were designed and synthesized. The functionalization bestowed these TPE derivatives positive charge and suitable water solubility, which made them candidates for fluorescent probes of negatively charged biomacromolecules such as DNA and polysaccharides. In DNA detection attempts, it has been found that:The affinity of the probes to DNA are relevant to the following structural factors, (ⅰ) The number of the positive charge on the probe molecules and the size of the salifying groups have strong effects on DNA-probe interaction, which observes Coulomb’s law. (ⅱ) The configuration of the probe molecules has effect on DNA-probe interaction, tarns-isomer showed higher fluorescent response to DNA than cis-isomer. (ⅲ) The fluorescence response of the probes are sensitive to base sequence, they showed higher affinity to AT sequence than to CG one. (ⅳ) The probes can be used as bio-imaging agent to selectively stain mitochondria in living cells.Secondly, it has been found in glycosaminoglycan (GAG, including heparin, chondroitin sulfate or CS, sodium hyaluronate or HA) detection experiments that:(ⅰ) The cationic pyridinyl-functionalized TPE derivatives showed little interaction with GAG without negative charges, indicating the necessary of Columbic interaction between the probe and analyte. (ⅱ) The interaction strength between probe molecules and GAGs is not proportional to the relative content of anions in GAG macromolecules. (iii) The interaction between di-pyridinyl-functionalized TPE and HA showed evidently stronger temperature-dependence than that between the probe and heparin, chondroitin sulfate, and sodium hyaluronate. (iv) The interaction between di-pyridinyl-functionalized TPE and sodium hyaluronate displayed a unique correlation with the trans-/cis-isomers, but this has not been observed in the cases of heparin and chondroitin sulfate. (v) Different buffers have significant effects on the interaction between the probe and heparin and have no effect on that between the probe and HA.