The Integration Of Aggregation Induced Emission Effect Into Electrospun Fibers As Biosensor Carriers

Biosensor has wide applications in multitudinous fields including biomedical research,environmental monitoring, food safety and fermentation industrial production, due to their incomparable advantages compared with traditional detection methods. With the development of materials science and the progress of processing technology, these biosensors offer high selectivity and sensitivity and need further advancement in terms of miniaturization,simplification and convenience in a real sample testing. Electrospun fibers provide a large surface area, leading to a high availability of graft sites and an increase in the reaction rate for developing high-performance biosensor applications. In addition, their high porosity allows more efficient transport of the analytes through the nanofibrous membrane, thus originating more rapid responses and increased sensitivity. Aggregation-induced emission (AIE)fluorogens exhibit high fluorescence quantum yields in the solid state or in colloidal aggregates, overcoming the quenching problem caused by the high concentration in most conventional chromophores. Thus, a series of functionalized AIE chromophores were synthesized and conjugated onto electrospun fibers for sensing different targets in this thesis.Based on the mechanism of AIE, the fluorogenic fibrous mats was established for bacterial detection. To solve the problems that signal intensity changes may be susceptible to external factors in "turn on" or "turn off' detection, the electrospun fibrous strips were developed for ratiometric detection of biomarkers. In order to decrease the detection limit and time, self-amplified electrospun fibrous strips and self-propelled Janus fibers rods were prepared for hydrogen peroxide (H2O2) and bacteria detection.Tetraphenylethylene (TPE) derivative with conjugated cyanuric chloride was prepared, and its photoluminescence properties indicated the maintenance of AIE activities. This derivative and mannose were conjugated onto polystyrene-co-maleic anhydride (PSMA) fibers and the resulting PSMA-PEG-TPEC-Man fibers showed turn on fluorescence detection of E.coli induced by the specific binding between mannose and bacterial filmbria. It is concluded that bacteria capture reached the saturated level when PSMA content increased over 90%. An equation was drafted of the fluorescence intensities of fibrous mats against E. coli concentrations ranging from 102 to 105 CFU/ml. The test strip format allows rapid visualization of bacteria concentrations with detection limit as low as 102 CFU/ml in a matter of minutes.The cephalosporin-containing TPE probe was synthesized using TPE-OH and cephalosporin analogues as raw materials. It was confirmed that the probe can produce specific fluorescence response to ?-lactamase. The aptamer-grafted fibers (PSMA/PS-A) enabled the selective analysis of E. coli strains (E. coli JM109/pUC19 and E. coli JM109), and their E.coli capture efficiency was affected by the aptamer grafting density. This assay system allowed visual sensing of resistant bacteria (E. coli JM109/pUC19) based on the p-lactamase catalyzed reaction and the limit of detection (LOD) was determined to be 102 CFU/ml. Furthermore, the results of ultraviolet irradiation showed that the TPE probe could effectively kill the resistant bacteria.A ratiometric assay of ALP activity has been realized by covalent immobilization of fluorescein onto polyethylene terephthalate (PET) fibers, followed by electrostatic adsorption of bisquaternary ammonium salt of TPE. Fibers with surface amine densities of 30 nmol/mg showed the almost linear increases in I514/I471 ratios with increasing ALP concentrations from 0 to 100 mU/ml. The LOD was around 1.5 mU/ml based on signal to noise of 3. The color changes were suitable for an eyeball detection of ALP levels ranging from 0 to 80 mU/ml.Thus, this color strip of fibrous mats has the potential for a rapid determination of ALP levels in biological fluids through naked eye without complicated equipments.PSMA fibers were conjugated with TPE derivative and phloxine B (PhB), followed by protamine adsorption to provide straightforward observation of ratiometric color changes with naked eyes in the presence of heparin or trypsin. The grafting densities of PhB and the TPE derivative were essential to achieve the optimal fluorescence-intensity ratio of I574/I472 for the ratiometric detection. The LOD was calculated to be 0.02 U/ml for heparin. The fluorescent color strip of PSMA-PhB+TPE/Pro fibers enabled a visual test of 0-0.8U/ml heparin and 0-8?g/ml trypsin. The practical utility of PSMA-PhB+TPE/Pro fibers in clinical diagnosis was demonstrated by the detection of heparin and trypsin in serum and urine samples.In order to improve the sensitivity of detection of H2O2, a new electrospun fibrous strips were prepared by immobilization of self-amplifying choline molecule and adsorption of TPE derivative onto PET fiber surface. The signal-amplification was realized based on catalytic reaction of choline oxidase immobilized on the surface of PSMA fiber. It was found that the adsorption quantity of TPE could affect testing result, and the mechanism of H2O2 sensing was confirmed by fluorescence response experiments. Compared with traditional detection, the signal amplification detection showed great advantage in decreasing detection limit and detection time. The activity of enzyme remained no significant change after repeated testing for 8 cycles, which indicated that multipoint immobilization of the multimeric enzyme was essential to improve the enzyme stability. The two-component fiber also showed excellent performance in the amplification detection of choline.A new self-propelled Janus fibers rods, functionalized with catalase (CAT) and TPE derivatives, were exploited for selective and "active" detection of E. coli. The active motion of Janus fibers rods with different aspect ratios is characterized by a mean-square displacement(MSD) analysis. We found that the optimum H2O2 concentration and fiber length were 3.5%and 10?m, respectively. The successful demonstration of enzyme-powered active Janus fibers rods provided a great potential for bacterial detection of 65-105 CFU/ml in lmin.In this thesis, a series of biosensors based on electrospinning ultrafine fibers and AIE effect were constructed for rapid detection of bacteria and biomolecules with high sensitivity and simplicity in operation. The fluorescent color strip of fibers enabled a visual test of analyte in real time, without the need of complex experimental procedures compared to the traditional electrochemical detection systems. Furthermore, the biosensors could improve the detection sensitivity and response speed through a variety of ways such as AIE effect, ratiometric fluorescence response, self-signal amplification, as well as catalytically self-propelled motion,which provided new ideas for designing efficient, sensitive and portable sensors in clinical testing.