Synthesis Of Biotin Derivatives And Preparation Of Their Self Assembled Monolayers

Recently, the ultrathin films materials formed by interfacial self-assembly on solid surfaces have attracted great attention. This stable, ordered and closely packed ultrathin films are fabricated by spontaneously chemical reactions between reactive headgroups of organic molecules and solid surface functional groups, which are known as self assembled monolayers (SAMs). Materials based on SAMs have many applications in the fields such as non-linear optics, molecular biology, science of materials, molecular devices, and biosensors, etc.Biotin has great affinity to streptavidin. Taking use of the formation of self-assembled monolayers with the terminal Biotin, streptavidin can be constructed on the top of various biotin terminated SAMs. Streptavidin is a special protein which posseses four binding sites for biotin molecule. Thus various bitinylated molecules can be further assembled on SAMs with various properties for special applications. Hence, synthesis of biotinylated thiols or disulfides and applications of SAMs of these biotinylaed thiols or disulfides on gold will have great significance.As for the premise work for the further applications of biotin-streptavidin assembled systems, this thesis presents the synthesis of thioctic acid-containing and 11-mercaptoundecanoic acid-containg biotin derivatives with ether linkage, and construction of these biotin derivatives onto gold electrodes to form self-assembled monnolayers. The structures and the properties of these modified elctrodes were studied by electrochemical methods. The main contents are listed as the following:1. Thioctic-(8-biotinoylamido-3,6-dioxaoctyl)amide(TBDA),Thioctic-(13-biotinoy lamido-4,7,10-trioaxatridecaneamine) amide (TBTA) were synthesized. The molecular structures of the intermediates and the target compounds were confirmed by ~1H NMR, GC-MS and FT-IR.2. 11-Mercaptoundecanoic-(8-biotinoylamido-3,6-dioxaoctyl) amide (MBDA), 11-Mercaptoundecanoic-(13-biotinoylamido-4,7,10-trioaxatridecaneamine)amide(MBTA) were synthesized. The molecular structures of the intermediates and the target compounds were confirmed by ~1H NMR, GC-MS and FT-IR.3. The pure SAMs of MBDA/Au, MBTA/Au, TBDA/Au and TBTA/Au were prepared by the self-assembly monolayer technology. Meanwhile, using 11,11'-diundecanolthiol (DT) as the medium molecule, the mixed SAMs of MBDA/DT and TBTA/DT on gold were also fabricated.4. The electrochemical cyclic voltammetry and electrochemical impendence spectra were employed to characterize the structures and the properties of the above mentioned SAMs on gold. The results shows that closely packed and well ordered SAMs have been fabricated and their surface coverages are over 99%. Mixed SAMs have higher coverages than the corresponding pure SAMs, and the coverage increases with the increase of the molar ratio of the medium molecule DT. At the same time, with the lengthening of the ether linkage between thioctic acid or 11-mercaptoundecanoic acid and biotin, the SAMs will have a greater surface coverage.