Study Of Poly(Indole-6-Carboxylic Acid)(Pica)/CNTs Modified Electrochemical Biosensor And Application

Conducting polymers(CP), which is not only used as an immobilization carrierbutalsoplaysanactiveroleintransductionforbiosensor,haveshowngreatpromiseasamaterialforbiosensingapplicationduetotheirunusualproperties,likerapid electrontransfer, specificity, high sensitivity and biocompatibility. CP/CNTs composites havelower charge transfer resistance and mass transfer impedance than CNTs alone, thusyielding a nanomaterial with improved and synergic properties. A novelnanocomposite consisting of PICA and CNTs has been successfully obtained byElectrochemical polymerization and designed to construct biosensors. The majorcontentsofthethesisareasfollows:1. A novel"multinanostructured"composite material obtained from PICA/CNTswas electrodeposited directly and used to construct a simple label-free gene sensor.Cyclic voltammetry (CV) was used with this sensor as a readout method to obtainelectrical readout from these DNA sensors. The performance of the DNA biosensorsystem was studied in respect to sensitivity, selectivity, reproducibility andregeneration.Thesensitivityofsensorswasimprovedduetotheincreaseinthesurfaceareaoftheelectrode, whichcanbindmoreODNprobe.Thedetectionlimit is 2.0fmolL-1. In addition to constituting a novel label-free DNA sensor, we anticipate that thisnovel"multinanostructured"composite material will provide a unique platform inelectrochemical DNA sensors for highly sensitive and sequence-specific detection oftargetDNA.2. A specific immunosensor for detecting cancer biomarkersalpha-fetoprotein(AFP) was successfully constructed and the signal amplification procedure was also demonstrated. The detection limit is 4.06×10-4 ng mL-1. Thegreatly enhanced sensitivity relies upon a dual signal amplification scheme: (1) themore porous structure, larger surface area and better conductivity of the PICA/CNTscomposite film facilitated the ECL reaction in the presence of CdSe QD, and then (2)the gold nanoparticle plays an important role similar to a conducting wire making iteasierfortheelectrontransferinECLreaction.Theproposedimmunosensorpossesseshigh sensitivity, good reproducibility, fine biocompatibility, and excellentfilm-forming ability, which made it a promising candidate fordetecting other relevantbiomarkers and has the potential for reliable point-of-care diagnostics of cancer andotherdiseases.3. A novel nanocomposite consisting of PICA and CNTs has been designed toconstruct an ECL-cell sensor, which could detect Ramos cells with a low detectionlimit of 390 cell mL-1. The cell-based ECL sensor shows a wide linear range forsensitive quantification of cells. High sensitivity was achieved due to the PICA/CNTsnanocomposite and the amplification of nanoparticles. These assays have the potentialto provide a simple, rapid, sensitive, and cost-effective approach for the early andaccuratedetectionofcancerbytheutilizationofnanotechnologyandaptamers.