Investigation Of Biosensors Based On Fluorescent Conjugated Polymers

As novel fluorescent sensing materials, fluorescent conjugated polymers have a number ofadvantages such as high absorption coefficients and high fluorescence quantum yields. At the sametime, conjugated polymers are provided with molecular wire effect, and can amplify fluorescencesignal. Conjugated polymer-based chemical and biological sensors research has made tremendousdevelopment in recent years, they have great potential applications in medical diagnostics,environmental monitoring and other fields, but there are still many critical issues need to beaddressed. In this dissertation, througth choosing excellent conjugated polymer sensing materials,design different biological sensors to achieve high sensitivity detection of biological molecules, theresults are summarized as follows:(1) A fluorescent turn-on detection for ascorbic acid has been developed based on hyperbranchedconjugated polyelectrolyte. The fluorescence probe benefits from the high signal amplification fromhyperbranched molecular structure of the conjugated polymer and produce fluorescencesuperquenching by Cu2+ions with a detection limit down to the micromolar range. Upon addition ofascorbic acid, the paramagnetic Cu2+ions can be transformed into adiamagnetic Cu1+ions, whichinhibits the quenching and thus lead to fluorescence enhancement of the hyperbranched conjugatepolymer. Other biologically relevant species, such as glucose, uricacid, L-arginine andacetaminophen do not lead to significant fluorescence change of the conjugated polymer-Cu2+complex, indicating that the hyperbranched conjugated polymer-Cu2+complex can thus serve as aneffective chemosensor to detect ascorbic acid.(2) A smart and versatile approach to controllably prepare multi-color conjugated polymers andpolymer nanoparticles has been developed. In operation to obtain different colors PPV solution(PPVseg) by heating the solution of MEH-PPV, by UV spectroscopy, fluorescence spectroscopy andinfrared spectra, PPVsegof different colors were characterized. Conjugated polymer nanoparticleswere prepared by re-precipitation method and the effect of various such as concentration,ultrasonictime on morphology and size of nanoparticles were studied. PPVsegCPNs with average diameters assmall as2.8nm can be observed. The small particle size and high brightness also make these PPVsegnanoparticles promising probes for biological imaging and bioanalytical applications.