| dc.description.abstract | According to WHO, it is expected that about 23 million people will die from MI (known as heart attack) annually by 2030. Cardiac biomarkers are released from myocytes immediately after a heart attack. Among of the biomarkers, cardiac troponin I (cTnI) is highly correlated with myocardial damage. Myocardial infarction is also accompanied by myocardial damage; thus, in the diagnosis of MI, cTnI is also regarded as the gold standard for the detection by European Society of Cardiology. However, it takes time (>1hr) to detect a measurable troponin concentration and a significant concentration rise (troponin blind interval). To solve the problem above, there are many researcher teams committed to the develop a detection method with high sensitivity and good resolution. At the same time, silicon nanowire field effect transistor (SiNW FET) has many advantages, such as, high sensitivity, label-free detection and real-time detection; therefore, it is regarded as a detection platform with great development potential.
Our laboratory previously developed 3-aminopropyltriethoxysilane (APTES) immobilized on the surface of SiNW FET, and then modified glutaraldehyde (GA) and bioprobes for experiments. In the early stage of this research, experiments were carried out by continuing the previous surface modification method. Later, we discussed about the effects of two different surface modification methods on SiNW FET, namely, 1-(3-Aminopropyl)silatrane(APS) and 〖silane-PEG-NH〗_2：silane-PEG-OH =1：10 (mM/mM) mixed self-assembled monolayers (mixed SAMs).
In the thesis, firstly, we use atomic force microscope (AFM) to analyze the surface roughness and morphology of samples. Furthermore, we analyze the surface elements by X-ray photoelectron spectroscopy (XPS). By doing these two experiments, we could claim that the surface modification is successful. Finally, we compare the results of cTnI detection in human serum after immobilizing anti-cTnI aptamers on SiNW FET by using different surface modification methods.
Results reveal that modifying APTES on the surface probably causes the problem of aggregation; it may make the surface rougher and it may also mask the amine group; consequently, reducing the effectiveness of modification. Modified APS could control the silylation process; the amine groups are less likely to be masked; thus, it makes the effect of surface modification better. However, the results of the detection on FET show that APS has worse anti-non-specific adsorption ability. Our final choose is mixed SAM, the reason why is it could provide an enough space for the binding between aptamer and target molecule to make the target capturing more efficiency by regulating the ratio of mixed SAM. What is more, PEG has the ability of anti-fouling, decreasing the detection errors in complex environments. Results of detection on FET shows that LOD obtained is 0.2 pg/mL under the condition that the FET is modified by mixed SAM and cTnI is spiked in undiluted human serum. Besides, the detection time is about 30 minutes.
In brief, our device has a great potential to solve the above problem (troponin blind interval), since not only LOD of our device is lower than clinical use, but the detection time of our device is shorter than clinical detection. | en_US |