Electrical bio-sensing based on non-antibody recognition elements

This study focuses on monitoring of sports fatigue related biomarkers using electrical assays (i.e., field-effect transistor sensing and tunable resistive pulse sensing) that are based on non-antibody recognition elements. The main hypothesis is that assays based on synthetic receptors can deliver sensing performances comparable to that of conventional antibody based ones, while providing advantages such as excellent stability in harsh environments, facile synthesis process, and small molecular sizes. Three specific hypotheses have been proposed. First, it is proposed that sports fatigue related biomarkers can be measured quantitatively in real time using carbon nanomaterial based FET sensors. Second, it is proposed that synthetic receptors such as liposomes and polypeptides can be used in combination with carbon nanomaterial based FET sensors for the monitoring of sports fatigue related biomarkers. Third, it is proposed that aptamers can be used in combination with tunable resistive pulse sensing for bio-sensing applications. In the first part, detection of interleukin-6, which is a typical sports fatigue related biomarker, using a portable field-effect transistor biosensor is demonstrated. This sensing assay exhibits superior sensitivity (LOD = 1.37 pg/mL) in virtue of the reduced tube-to-tube contact resistance, good selectivity as a result of the highly specific interaction between interleukin-6 and its receptor, and excellent stability in virtue of the strong adhesion of CNT to the quartz substrate and good horizontal alignment of these tubes. This section suggests that sports fatigue related biomarkers can be measured quantitatively in real time using carbon nanomaterial based FET sensors. In the second part, detections of two different analytes (phospholipase A2 and matrilysin) using field-effect transistor biosensors based on non-antibody recognition elements are demonstrated, indicating that it is viable to combine the field-effect transistor sensing platform with non-antibody recognition elements. Protein detection using rGO-based FET sensor with liposomes or polypeptides as recognition element is demonstrated to be viable and the sensing performance is comparable (in terms of sensitivity and specificity) with assays using antibodies as recognition element. In the third part, an aptamer sensor using a Dipstick and Tunable Resistive Pulse Sensing for rapid and label free detection of human cardiac troponin I is proposed. The cTnI aptamers were immobilized on a slide (used as a dipstick), which enabled the immobilization of nanoparticles modified with partially complementary sequences. The presence of the target protein caused a conformational change to the aptamer and the release of immobilized nanoparticles into solution. The concentration of nanoparticles released was proportional to the concentration of the target protein. Optimization of the partially complementary sequence produces an assay that was reliable and easy to setup with a LOD of 6.7 ng/mL in buffer. The outcome of this part verifies the hypothesis that aptamers can be used in combination with tunable resistive pulse sensing for bio-sensing applications. The results obtained demonstrated all three hypotheses proposed in the beginning. Hence, monitoring of sports fatigue related biomarkers using electrical assays (i.e., field-effect transistor sensing and tunable resistive pulse sensing) that are based on non-antibody recognition elements is demonstrated.Doctor of Philosophy (MSE