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6 March 2014 Real-time multi-analyte label-free detection of proteins by white light reflectance spectroscopy
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Label-free optical sensors are considered ideal for biomedical analysis since they provide the advantages of multiplex and real-time detection. They still suffer; however, from lower sensitivity and/or more sophisticated equipment as compared to indirect detection methods. Here, we propose a label-free sensor based on White Light Reflectance Spectroscopy that overcomes the limitation of high cost and low detection sensitivity. The optical setup consists of a VIS-NIR light source, a spectrometer and a reflection probe. The sensor is Si with 1-μm thick thermal SiO2 and functionalized with antibodies. The incident light is directed vertically to sensor surface and the reflected interference spectrum is recorded through the spectrometer. The evolution of the biomolecular reactions are monitored in real-time by monitoring the shifts in the interference spectrum. Up to seven different reactions sites have been created onto the same sensing surface allowing for multi-analyte determinations. The analytical capabilities of the proposed sensor were demonstrated through the development of a sensitive immunoassay for the detection of C-Reactive Protein (CRP) in human serum samples. CRP, a biomarker related to acute inflammatory incidents, it has attracted particular interest as a marker of inflammation associated with cardiovascular diseases. The lowest CRP concentration detected was 10 ng/mL, and the dynamic range of the assay was extended up to 500 ng/mL. Regeneration of antibody coated sensing areas for up to 20 times without loss of immobilized antibody reactivity is also presented. In conclusion, the proposed sensing system is characterized by low cost, high assay sensitivity and, reliability.
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Panagiota Petrou, Georgios Koukouvinos, Dimitrios Drygiannakis, Dimitris Goustouridis, Ioannis Raptis, Konstantinos Misiakos, and Sotirios E. Kakabakos "Real-time multi-analyte label-free detection of proteins by white light reflectance spectroscopy", Proc. SPIE 8976, Microfluidics, BioMEMS, and Medical Microsystems XII, 897616 (6 March 2014);

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