الفهرس 
AbstractOnly 14 pages are availabe for public view
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Abstract
Fast and efficient identification of bacterial pathogens in water and biological fluids is an important issue in medical, food safety, and public health concerns that requires low cost and efficient sensing strategies. Progress in the field of pathogen detection relies on at least one of the following three qualities: selectivity, speed, and cost-effectiveness. Development of nanobiosensors is currently an attractive solution for fast and efficient diagnosis of bacterial pathogen due to their simplicity and sensitive real time analysis. Conjugated polymer nanoparticles are one of interesting nanomaterials used in biomedical applications including, fluorescence and photoacoustic imaging, biosensor, optoelectronic device materials and photothermal therapy for microbial infections. The great interest in using Conjugated polymer nanoparticles is motivated by their outstanding photophysical properties, excellent photo stability, high quantum efficiency, super sensitivity, and amplified fluorescent quenching effect with less toxicity, high biocompatibility and biodegradability.
Chapter one gives a comprehensive review of bacterial infections and current detection techniques including Biosensors. Biosensor components and types of biosensors based on transduction mechanism (electrochemical, mechanical and optical) are described. The chapter further highlights the fundamental aspects of conjugated polymers and their interesting optoelectronic properties in biosensor devices and their therapeutic application in microbial infections. The objective and aim of thesis have been illustrated.
Chapter two reports a study on new biointerface-based amphiphilic poly(3-hexylthiophene)-b-poly(3- triethylene-glycol-thiophene), P3HT-b-P3TEGT, for label-free impedimetric detection of Escherichia coli (E. coli). The developed Biointerface is fabricated by the self-assembly of P3HT-b-P3TEGT into core−shell nanoparticles, which was further decorated with mannose, leading to an easy-to-use solution-processable nanoparticle material for biosensing. The hydrophilic block P3TEGT promotes antifouling and prevents nonspecific interactions, while improving the ionic and electronic transport properties, thus enhancing the electrochemical-sensing capability in aqueous solution. Self-assembly and micelle formation of P3HT-b-P3TEGT were analyzed by 2D-NMR, Fourier transform infrared, dynamic light scattering, contact angle, and microscopy characterizations. Detection of E. coli was characterized and evaluated using electrochemical impedance spectroscopy and optical and scanning electron microscopy techniques. The sensing layer based on the mannose-functionalized P3HT-b-P3TEGT nanoparticles demonstrates targeting ability toward E. coli pili protein with a detection range from 103 to 107 cfu/mL, and its selectivity was studied with Gram (+) bacteria. Application to real samples was performed by detection of bacteria in tap and the Nile water. The approach developed here shows that water/alcohol-processable-functionalized conjugated polymer nanoparticles are suitable for use as electrode materials, which have potential application in fabrication of a low cost, label-free impedimetric biosensor for the detection of bacteria in water.
Chapter three describes designing therapeutic and sensors material to diagnose and eliminate bacterial infections remains a significant challenge for active theragnostic nanoprobes. In the present work, fluorescent/electroactive poly(3-hexylthiophene) P3HT nanoparticles (NPs) stabilized with quaternary ammonium salts using cetyltrimethylammonium bromide (CTAB), (CTAB-P3HT NPs) were prepared using a simple mini-emulsion method. The morphologies, spectroscopic properties and electronic properties of CTAB-P3HT NPs were characterized by DLS, zeta potential, SEM, TEM, UV-vis spectrophotometry, fluorescence spectroscopy and electrochemical impedance spectroscopy (EIS). In an aqueous solution, CTAB-P3HT NPs were revealed to be uniformly sized, highly fluorescent and present a highly positively charged NP surface with a good electroactivity. Dual detection was demonstrated as the binding of the bacteria to NPs could be observed by fluorescence quenching as well as by the changes in EIS. Binding of E. coli to CTAB-P3HT NPs was demonstrated and LODs of 5 CFU/mL and 250 CFU/mL were obtained by relying on the fluorescence spectroscopy and EIS, respectively. The antimicrobial activity of CTAB-P3HT NPs on bacteria and fungi was also studied under dark and nutritive conditions. An MIC and an MBC of 2.5 µg/mL were obtained with E. coli and with S. aureus, and of 0.312 µg/mL with C. albicans. Additionally a good biocompatibility toward normal human cells (WI38) was observed which opens the way to their possible use as therapeutic agent. Chapter four provides a brief summary and general conclusion from the results obtained from this thesis work.