Self-assembled monolayers hydroxyl terminated

These nanometer-thick layers are easily fabricated from commercially available substances, or can at least be synthesized with relative ease [4]. The first applications of self-assembled monolayers (SAM) for biosensor use were described in the late 1980s and originally developed for Biacore instruments [5,6]. Hydroxyl-terminated long chain thiol alkanes were designed for the formation of the SAM on gold. Such layers can be activated for direct Hnkage of various molecules or further derivatized with different chemistries... 

Fig. 20 Multilayer deposition on a hydrophilically/hydrophobically patterned gold substrate. Upper AFM images height (left) and friction force (right) images of patterned methyl- and hydroxyl- alkanethiol self-assembled monolayers. Adsorption of poly(ferrocenylsilane) polyions (5/7, 12 bUayers) occms selectively on the broad methyl-terminated stripes (lower AFM images). Reprinted with permission from [94]. Copyright 2002, American Chemical Society...

Figure 9.1 Relationship between contact angle and cell adhesion. Human umbilical vein endothelial cells open circles) and HeLa cells closed circles) were allowed to attach to self-assembled monolayers (SAMs) carrying methyl (CH3), hydroxyl (OH), carboxylic acid (COOH), or amino (NH2) terminal functional groups mixed with two kinds of alkane thiols (CH3/OH, CH3/COOH and CH3/NH2) for 1 h. A clear trend showing increasing cell adhesion with decreasing contact angle was observed for aU SAMs.

Tegoulia and Cooper studied S. aureus adhesion on self-assembled monolayers terminated with methyl, hydroxyl, carboxylic acid, and tri(ethylene oxide) groups. Results showed how bacterial adhesion was lower on the hydrophilic ethylene oxide-bearing and hydroxyl-bearing surfaces. However, preincubation of surfaces with fibrinogen increased microbial adhesion on all surfaces and minimized the effect of the surface properties of the substrate. The authors concluded that even if surfaces rich in ethylene oxide groups can be used to prevent bacterial adhesion under physiological conditions, most of the substrate properties are masked and their effect on adhesion becomes minimal. 

AFM with tips chemically modified by means of methyl and hydroxyl terminated self-assembled monolayers (SAMs) of alkanethiols has been used... 

Wiencek KM, Fletcher M (1995) Bacterial adhesion to hydroxyl-and methyl-terminated alkanethiol self-assembled monolayer. J Bacteriol... 

A surface-initiated enzymatic ROP has also been reported, whereby CL and DXO were grafted from hydroxyl-terminated self-assembled monolayers (SAMs) on gold, using Novozym 435 [117], while polycaprolactone-modified hydroxyethylcel-lulose films were prepared by the enzymatic ROP of CL [118]. 

Stabilization of a lipid membrane onto a solid support by covalent attachment also provides the physical stability necessary for the development of practical sensors. An oriented membrane can be prepared by allowing self-assembly of individual amphiphilic molecules onto a solid surface through either the reaction of terminal silane moieties with a hydroxylated surface to form a silyl ether [33,34], or by the reaction of sulfur-terminated compounds (alkylthiols or disulfides) with gold surfaces [35,36]. A variety of species, both with and without polar head groups, have been deposited onto surfaces such as glass, quartz, silicon, and gold [37-39]. These include phospholipids, fatty acids, and fatty amines which were synthetically altered so as to contain either a silyl chloride or a thiol moiety at the terminus of the acyl chain [40]. Both monolayers... 

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