Optical Detection of E. coli Bacteria by Mesoporous Silicon Biosensors |
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Authors: | Naama Massad-Ivanir Giorgi Shtenberg Ester Segal |
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Institution: | 1.Department of Biotechnology and Food Engineering, Technion - Israel Institute of Technology;2.The Inter-Departmental Program of Biotechnology, Technion - Israel Institute of Technology;3.The Russell Berrie Nanotechnology Institute, Technion - Israel Institute of Technology |
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Abstract: | A label-free optical biosensor based on a nanostructured porous Si is designed for rapid capture and detection of Escherichia coli K12 bacteria, as a model microorganism. The biosensor relies on direct binding of the target bacteria cells onto its surface, while no pretreatment (e.g. by cell lysis) of the studied sample is required. A mesoporous Si thin film is used as the optical transducer element of the biosensor. Under white light illumination, the porous layer displays well-resolved Fabry-Pérot fringe patterns in its reflectivity spectrum. Applying a fast Fourier transform (FFT) to reflectivity data results in a single peak. Changes in the intensity of the FFT peak are monitored. Thus, target bacteria capture onto the biosensor surface, through antibody-antigen interactions, induces measurable changes in the intensity of the FFT peaks, allowing for a ''real time'' observation of bacteria attachment.The mesoporous Si film, fabricated by an electrochemical anodization process, is conjugated with monoclonal antibodies, specific to the target bacteria. The immobilization, immunoactivity and specificity of the antibodies are confirmed by fluorescent labeling experiments. Once the biosensor is exposed to the target bacteria, the cells are directly captured onto the antibody-modified porous Si surface. These specific capturing events result in intensity changes in the thin-film optical interference spectrum of the biosensor. We demonstrate that these biosensors can detect relatively low bacteria concentrations (detection limit of 104 cells/ml) in less than an hour. |
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Keywords: | Bioengineering Issue 81 analytical chemistry silicon materials microbiology optical materials Porous Si optical biosensor bacteria detection label-free biosensor nanostructure E coli bacteria |
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