Cytokines are a general class of proteins involved in inflammatory response, and abnormal concentrations of cytokines in humans have been linked to a number of diseases. Aptamers are single-stranded DNA or RNA oligonucleotide sequences developed using in vitro selection that can selectivity bind with specific cytokines. These aptamers can be covalently linked to a number of surfaces in order to measure cytokine concentrations. Aptamer-based biosensors have been shown to be a legitimate alternative to the current antibody-based sensors, showing more sensitivity while being easier to produce and more important, reusable. This thesis demonstrates an aptamer based sensor using a quartz crystal microbalance system for the purpose of detection the cytokine Interleukin-6 (IL-6). The aptamer, attached to a silicon wafer with gold electrodes, binds with the cytokine exposed to it, changing the crystals resonant frequency which is measured by the system, from which the mass of cytokine can be determined. This thesis explains the surface functionalization and aptamer attachment process as well as a number of experiments testing the sensitivity, selectivity, and reusability of the sensor.
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