Biomedical subjects
Publications and source records attributed to Seongpil Hwang.
Asymmetric electrostatic interactions dependent on pH between the redox molecules and the terminal group on the top of the self-assembled monolayer (SAM) afford control of the electron transfer property of the SAM having the imidazole terminal group.
1,3-Dialkylimidazolium salts, known as one of the ionic liquids, are very attractive molecules because their physicochemical properties can easily be tuned by the variation of the alkyl appendages of the imidazolium cations and counteranions. In this paper we report that the self-assembled monolayers (SAMs) terminating in 1,3-dialkylimidazolium salts with various counteranions [except Fe(CN)6(3-)] on a gold substrate exhibited a selective electron-transfer toward redox-probe molecules: the electron transfer occurred in the presence of Fe(CN)6(3-) (anionic redox-probe molecule) but did not occur in the presence of Ru(NH3)6(3+) (cationic redox-probe molecule). The SAM having Fe(CN)6(3-) as an anion showed the electron-transfer toward Ru(NH3)6(3+), and the Ru3+/2+ redox-switchable SAM was generated by reversible anion exchange between Fe(CN)6(3-) and SCN (or OCN-).
We demonstrate the amplified detection of a target DNA based on the enzymatic deposition of silver. In this method, the target DNA and a biotinylated detection DNA probe hybridize to a capture DNA probe tethered onto a gold electrode. Neutravidin-conjugated alkaline phosphatase binds to the biotin of the detection probe on the electrode surface and converts the nonelectroactive substrate of the enzyme, p-aminophenyl phosphate, into the reducing agent, p-aminophenol. The latter, in turn, reduces metal ions in solutions leading to deposition of the metal onto the electrode surface and DNA backbone. This process, which we term biometallization, leads to a great enhancement in signal due to the accumulation of metallic silver by a catalytically generated enzyme product and, thus, the electrochemical amplification of a biochemically amplified signal. The anodic stripping current of enzymatically deposited silver provides a measure of the extent of hybridization of the target oligomers. This biometallization process is highly sensitive, detecting as little as 100 aM (10 zmol) of DNA. We also successfully applied this method to the sequence-selective discrimination between perfectly matched and mismatched target oligonucleotides including a single-base mismatched target.