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Self-assembled monolayer tuning in electrochemical DNA sensor fabricated by "click" chemistry
The stability, uniform surface structure and relative ease of varying effective thickness are attractive attributes of SAMs for the development of biosensors. The exposed surfaces of SAMs can be modified by using chemical conjugation techniques such as "click" chemistry. This dissertation is meant to explore the use of "click" chemistry as a SAM-modification approach in the fabrication of electrochemical DNA (E-DNA) sensors while taking advantage of the inherent tunability of SAM systems in tailoring the performance of electrochemical sensors fabricated by "click" chemistry. Reported in this document is a folding-based electrochemical DNA (E-DNA) sensor fabricated by Sharpless "click" chemistry which compares favorably to a sensor fabricated via the conventional "two-step approach. Also reported here is the fabrication of a 3-pixel electrochemical DNA sensor array via potential-assisted "click'' chemistry. It is found that the sensors in the fabricated array exhibit close to identical sensor performance when compared to sensors constructed via conventional "click'' chemistry. To explore further the phenomena surrounding the "click" chemistry approach in biosensor fabrication, it is reported here, the application of synchrotron FTIR microspectroscopy to determine the spatial distribution of methylene blue conjugated onto a self-assembled monolayer surface via Sharpless "click'' chemistry. When different SAM systems are employed, sensor performance in terms of hybridization efficiency and hybridization kinetics were significantly affected where there is increasing efficiency with increasing thickness of the SAM and decreasing hybridization kinetics with decreasing electron transfer rates. The differences in terms of the fundamental characteristics of the underlying SAM system in terms of electron transfer rates (ks) and the electrode interfacial capacitance is discussed. Also demonstrated here is the control of probe density by using different ratios of azide- to hydroxy-thiol ratio (&phis;azide). It is popularly known that probe density affects the rate of hybridization. Taken together, it is argued that the "click" chemistry approach in sensor fabrication is a robust and versatile way in tailoring the performance of the resulting sensors by tuning the precursor SAM. When two aromatic twin-chain dithiol amphiphiles were incorporated into a folding-based electrochemical DNA (E-DNA) sensor as passivating thiols, interesting differences in key parameters commonly used to characterize E-DNA sensors (e.g., hybridization kinetics, signal suppression, electron transfer kinetics and electrode capacitance) were observed. Electrochemical characterization of individual SAM systems comprising of only the passivating thiols were discussed in light of their contribution to the observed sensor performance.
Canete, Socrates Jose P, "Self-assembled monolayer tuning in electrochemical DNA sensor fabricated by "click" chemistry" (2013). ETD collection for University of Nebraska - Lincoln. AAI3559670.