| Summary: | 碩士 === 國立中興大學 === 生物產業機電工程學系所 === 98 === In Taiwan, Salmonella is one of common sitotoxism-inducing microbes, causing diseases such as septicemia and gastroenteritis. Therefore, it is a very important issue to quickly detect the existence of Salmonella. This study attempts to develop a chip-type nucleic acid sensor for the detection of Salmonella by using electrochemical impedence spectroscopy (EIS) and cyclic voltammetry (CV) to measure the variation of impedence and current when performing the DNA hybridization.
However, the initial cleanness states of chip-type electrodes would affect results such as the sensing reproducibility and the probe-DNA modification. Therefore, three kinds of cleaning procedures including (1) acetone, (2) oxygen plasma, and (3) piranha and aqua regia are compared for the electrode cleanness. The results show that the treatment of soaking in piranha for 2 min and in aqua regia for 1 min gives the best cleanness for the electrodes which obtains the smallest electron-transfer resistance and the best reproducibility. In addition, the effect of structures and charges of different buffering molecules on the sensing characteristics was compared. The results reveal that use of TES buffer can obtain the largest response of electron-transfer resistance to the MUA-modified or dsDNA- hybridized electrode-solution interfaces. The linear range and the detection limit for Target-DNA measured in TES buffer was 10-10~10-15 M and 10-15 M, respectively, which is better than the linear range (10-10~10-13 M) and the detection limit (10-13 M) measured in PBS buffer. Moreover, this nucleic acid sensor using EIS measurements can identity the signal difference between the single basepair mismatch and the 40-mer target-DNA and the complete complementary hybridization. The miniaturzied nucleic acid chip is beneficial for the integration of micro-fluidic system and has the advantages of portability and mass production.
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