| Genotoxic carcinogens can react covalently with DNA to form DNA adducts, which can lead to mutations in critical genes and subsequently to the development of diseases such as cancer. Consequently, the role of DNA damage and their subsequent biomarkers are considered important in studies involving cancer and other aging-related diseases. Analytical methods with high resolving power and sensitive detection are needed to detect neurotransmitters (e.g. dopamine (DA) and DA-derived DNA adduct), catechol estrogen-derived DNA adducts, and 8-hydroxy-deoxyguanosine DNA adduct in human fluids, as their presence is difficult to determine by standard chromatography with UV absorbance detection. Furthermore, these DNA adducts are weakly fluorescent at room temperature. Thus, native fluorescence detection methods are ineffective with this class of biomarkers. Interestingly, capillary electrophoresis (CE) combined with electrochemical detection (ED) has been found to be a sensitive, selective technique for analyzing a large number of compounds including these analytes. Therefore, a CE-based PDMS/glass hybrid microfluidic device for free solution electrophoresis with totally integrated gold electrodes and simplified gated sample injection were fabricated to separate and detect various DNA adducts and other related biomarkers. Various arrangements of the ED system were tested and evaluated including in-channel and end-channel detection. The best electrode configuration was optimized based on in-channel detection with an in situ fabricated palladium decoupler serving as the electrophoretic ground located inside the microchannel. With these microdevices, excellent separation of the above analytes can be accomplished in relatively short times (< 2 minutes); with a limit of detection (LOD) in the sub-femto mole range. Different buffer systems were used including 2-[N-morpholino] ethanesulfonic acid (MES), phosphate, and borate buffers. Interestingly, significant improvement in the resolution was achieved by using borate buffer, where injecting a mixture of five analytes yield only two peaks with MES buffer, whereas five well-resolved peaks were obtained with borate buffer. These results show that these microdevices have promising separation resolving power and sensitivity for future medical diagnostics. |
