Structural Formula

Product DescriptionPolyethyleneglycols (PEGs) are widely used for material modifications to improve hydrophilicity of the surface. PEG-coated materials are usually more stable under physiological conditions. Since Amino-EG₆-undecanethiol has 6 ethylene glycol units, 11 carbon atoms, and an SH group at the end, it can be used to prepare a highly oriented and hydrophilic SAM on a gold surface. This is suitable for biomaterial labeling on the surface due to the improved hydrophilicity. The hydrophilic surface can prevent proteins or other biomaterials from non-specific binding. Therefore, the SAM prepared by this reagent will provide a better surface to develop biomaterial sensors or DNA/ protein microarrays. To prepare an Amino-EG₆-SAM on a gold surface, hydroxy-EGn-undecanethiols (n=3, 6) are used to dilute the number of amino groups according to the density of the molecules being introduced onto the surface.

How to Prepare SAM1. Soak a gold-coated glass plate in Piranha solutiona) for 10-15 minutes. Wash the plate with purified water.^a)2. Dissolve aminoalkanethiol compound in ethanol to prepare several mM to several ten mM solutions.3. Soak the plate in the aminoalkanethiol solution for a certain time period.^b)4. Wash the SAM-coated plate with ethanol and then water.5. Dry the plate under nitrogen atmosphere, if necessary.

a)Piranha solution: sulfuric acid and 30% hydrogen peroxide, 3:1. Piranha solution is a strong oxidizing agent. Extreme care is necessary when using it. Do not apply Piranha solution to resin-coated plates; it may erode the resin.b)To prepare a SAM-coated plate with the best performance, aminoalkanethiol concentration and soaking time should be individually determined.

Application of SAM-Preparation of DNA Array (Fig. 1)1. Use SF10 glass slides (Schott Glass Technologies) coated with 5 nm chromium and 45 nm gold thin film.2. Soak the glass slide in a 1 mM 1-octadecanethiol (ODT)/ethanol solution overnight to prepare ODT SAM-coated slide.3. Draw 500 μm x 500 μm patterns on the ODT SAM-coated slide by UV irradiation with an Hg-Xe arc lamp.^a)4. Soak the slide in a 1 mM 11-amino-1-undecanethiol (AUT)/ethanol solution for 2 hours to form AUT SAM on the 500 μm x 500 μm photopatterned area.5. Drop 2 mM SPDP solution^b) onto the slide and leave the slide at room temperature.6. Wash the slide and dry under nitrogen atmosphere.7. Apply 1 mM thiol-DNA solution^c) to each 500 μm x 500 μm pattern and incubate at room temperature overnight.8. Incubate the slide with a sample solution for 10 minutes and wash with phosphate buffer, followed by SPR imaging.

a)Irradiation time: 1-1.5 hoursb)SPDP: N-succinimidyl 3-(2-pyridyldithio)propionate. Dissolve SPDP in DMSO to prepare 50 mM solution. Dilute it 25 times with 100 mM triethanolamine buffer, pH 7.0.c)Dissolve thiol-DNA with 100 mM triethanolamine buffer, pH 8.0.

Fig. 1 DNA Array Preparation Scheme

1. C. Pale-Grosdemange, E. S. Simon, K. L. Prime, and G. M. Whitesides, Anal. Chem., 1999, 71, 777-790.