SAM surface

Experiments witli chemically grafted SAMs displayed much larger wear resistance tlian films produced by tire LB technique [188]. Also it was found tliat wear properties of SAMs can be furtlier improved by chemically grafting CgQ molecules onto SAM surfaces [189]. 

Fig. 10. Formation of noncentrosymmetric multilayer film by combining self-assembly and a surface S 2 reaction, where R = (CH2)30H procedure I = spin-coating followed by annealing at 110°C and procedure II = reaction of Cl2Si0SiCl20SiCl2, ie, a dilute solution of 4-[A/,A/,-bis-(3-hydroxyprop5l)-aminophenylazo]-4 -pyridine on a benzyl chloride SAM surface was used, resulting in facile formation of SAMs having high...

TIRFM was used for time-lapse observations of initial cell adhesion to SAMs with different surface functionalities (Fig. 2). After 10 min of plating a suspension of human umbilical vein endothelial cells (HUVECs), a few bright spots were observed on SAMs with COOH and NH2 functionalities this indicated cell adherence. The number of bright spots increased and the spot areas enlarged with incubation time, indicating that HUVECs adhered and spread well on COOH-SAM and NH2-SAM surfaces. Quantitative analysis of the number of adherent cells and cell adhesion areas... 

Figure 4c shows that the amount of adsorbed proteins is rapidly saturated within several minutes of exposing serum-containing medium to a surface. Albumin, the most abundant serum protein, was expected to preferentially adsorb onto the surfaces during early time points. Then, adsorbed albumin was expected to be displaced by cell adhesion proteins. To investigate the effect of preadsorbed albumin displacement on cell adhesion, SAMs were first exposed to albumin then, HUVECs suspended in a serum-supplemented medium were added [21, 42]. Very few cells adhered to hydrophobic SAMs that had been pretreated with albumin, due to the large interfacial tension between water and the hydrophobic surfactant-like surface. Albumin was infrequently displaced by the cell adhesive proteins Fn and Vn. One the other hand, HUVECs adhered well to hydrophilic SAM surfaces that had been preadsorbed with albumin. In that case, the preadsorbed albumin was readily displaced by cell adhesive proteins. 

Fig. 9 Surface modification of cells with ssDNA-PEG-lipid. (a) Real-time monitoring of PEG-lipid incorporation into a supported lipid membrane by SPR. (r) A suspension of small unilamellar vesicles (SUV) of egg yolk lecithin (70 pg/mL) was applied to a CH3-SAM surface. A PEG-lipid solution (100 pg/mL) was then applied, (ii) Three types of PEG-lipids were compared PEG-DMPE (C14), PEG-DPPE (C16), and PEG-DSPE (C18) with acyl chains of 14, 16, and 18 carbons, respectively, (b) Confocal laser scanning microscopic image of an CCRF-CEM cell displays immobilized FITC-oligo(dA)2o hybridized to membrane-incorporated oligo(dT)20-PEG-lipid. (c) SPR sensorigrams of interaction between oligo(dA)2o-urokinase and the oligo (dT)2o-PEG-lipid incorporated into the cell surface, (i) BSA solution was applied to block nonspecific sites on the oligo(dT)20-incorporated substrate, (ii) Oligo(dA)20-urokinase (solid line) or oligo(dT)20-urokinase (dotted line) was applied...

Figure 2.3 SAM surface modification has been done using monothiol and dithiol compounds containing PEG linkers. Useful coatings typically contain mainly PEG-hydroxyl or PEG-monomethyl ether linkers that provide a biocompatible lawn, which prevents nonspecific binding of proteins to the metallic surface. About 10 percent of the surface modifications are done using a longer carboxylate-containing thiol-PEG linker that provides sites for attachment of affinity ligands.

Coupling of affinity molecules to surfaces also can be enhanced by the use of discrete PEG linkers. Nishimura et al. (2005) modified an amino surface with a NHS-PEG -maleimide crosslinker to create a hydrophilic self-assembled monolayer (SAM) surface that was thiol reactive for the conjugation of sulfhydryl-modified RNAs. This array then was used to investigate the binding specificity of synthetic kanamycins with selected RNA sequences to prove the specific interaction of ribosomal RNA with this molecule. The PEG linkers on surfaces provide lower nonspecific binding character than alkyl linkers, when preparing SAM surfaces for affinity interactions. 

Figure 1.23 Scheme of long aliphatic molecules to project redox molecules above the environment (left) and the utilization of rigid molecules to probe into proteins and project redox molecules above the SAM surface (right). 

For microarray work, PLL-PEG-biotin-sAV monolayers adsorbed onto underlying titanium dioxide surfaces (pillars) replaced the b-SAM gold-coated glass surface. While oriented capture agents out-performed their random counterparts, distinct differences in Fab and antibody performance between this new surface and the b-SAM surface were apparent. 

SAM surface will not participate in H-bonding with the bulk liquid crystal (EG) and therefore the bulk material will not exhibit polar order thus, the SHG signal should be very low. 

A perfect top contact would have a highly uniform layer of metal with complete, conformal contact at the SAM surface to form a sharp interface in which there is good overlap of the electronic states of the metal surface and the molecule terminal groups. This ideal situation is not to be expected in real device processing as a number of physical and chemical defects can easily arise, as summarized in the schematic in Fig. 6. 

Another well-represented category was that of self-assembled monolayers (SAMS) and other supramolecular systems. The experiments on the SAMS included studies of the surface pKa of one system (110), the kinetics and thermodynamics of the self-assembly process (111), and the characterization of the SAM surface by study of solution contact angles (112). The experiments on supramolecular systems included studies on chemical equilibria in such systems (113, 114, 115), the kinetics of inclusion phenomena (116), and the use of solvatochromic probes in studying inclusion phenomena (117). 

Fig. 52. Scanning with a platinum coated SFM tip over a SAM surface containing terminal azide groups in the presence of H2 leads to the reduction of azide groups to primary amino groups. Derivatization of the resulting amine surface with aldehyde-modified latex beads results in specific labelling of the reduced areas. Reproduced from [469]...

This approach has been shown to work with a number of different fluorescent probes such as the short-wavelength fluorophores dansyl sul-fonyl chloride and coumarin chloride and the long-wavelength fluorophores tetramethylrhodamine-5-(and-6)-isothiocyanate [5(6)-TRITC], 5-(and-6)-carboxytetramethylrhodamine, succinimidyl ester [5(6)-TAMRA, succin-imidyl ester] and lissamine rhodamine B sulfonyl chloride (each in conjunction with different binding functionalities on the SAM surface. 

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