11 amino 1 undecanethiol hydrochloride

To prepare a molecularly smooth gold surface, which has a low root-mean-square roughness of <0.2 nm, gold (∼45 nm) was deposited onto freshly cleaved muscovite mica (grade #1, S&J Trading, Floral Park, NY, USA) with a uniform surface via electron beam evaporation. 22 The gold-coated mica was adhered to cylindrical disks (radius of curvature, R = 2 cm), gold side down, using an optical adhesive (NOA 81, Norland Products, NJ, USA), followed by UV curing for ∼50 min using a UV lamp (UVP B-100AP, AnalytikJena, Germany). The mica was then carefully detached to obtain the molecularly smooth and clean gold layer. 23 To deposit OH-, COOH-, C 6 H 5 -, CH 3 -, and NH 2 -functionalized SAMs onto the prepared gold surfaces, the following alkanethiol solutions (1 mM in ethanol) were prepared: 11-hydroxy-1-undecanethiol (97%), 10-carboxy-1-decanethiol (95%), 2-phenylethanethiol (98%), 1-undecanethiol (98%), and 11-amino-1undecanethiol hydrochloride (99%), respectively, purchased from Sigma-Aldrich (St Louis, MO, USA). Specifically, the prepared gold surfaces were separately immersed in each target alkanethiol solution for ∼18 h. Finally, each SAM-coated disk was weakly sonicated to remove unbound and/or loosely bound molecules, followed by drying with N 2 blowing.

All reagents used were of analytical grade. Sodium hyaluronate (M W = 7.46 KDa) was purchased from Lifecore Biomedical (USA). AG 50W -X8 resin was purchased from Bio-Rad (USA). Dimethyl sulfoxide (DMSO), Tetrabutylammonium fluoride hydrate (TBA-F), 11-Amino-1-undecanethiol hydrochloride (AT), N-hydroxysulfosuccinimide (NHS), 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride (EDC), 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT), hydrogen nicotinamide adenine dinucleotide (NADH), pyruvate, haemoglobin from bovine blood and Drabkin's reagent were acquired from Sigma-Aldrich (Italy). Fluorescein-5-thiosemicarbazide and Cy5.5 hydrazide were purchased from Life Technologies Ltd (UK). Cell Culture reagents and culture medium were purchased from Biochrom (Germany). The water used was distilled and ultrapurified (Milli-Q system).

Microscope coverslip slides (22 mm  50 mm, no. 1.5 thickness) were obtained from Menzel-Gläser, Germany. Gold wire (99.997% trace metals basis) and chromium chips (99.5% trace metals basis) used for the thermal evaporation were purchased from Sigma-Aldrich. The 30% hydrogen peroxide solution and 95% concentrated sulfuric acid used for preparation of the piranha solution were supplied by VWR Chemicals, UK. For preparation of the gold etchant solution, 32% ammonia solution, HPLC purity ethanol, and cysteamine, obtained from Sigma-Aldrich, were used. 1-Octadecanethiol (98%) and HEPES were also obtained from Sigma-Aldrich. Chemicals used for the gold nanostructures functionalization, i.e. 11-amino-1-undecanethiol hydrochloride, glutaraldehyde (25%), Na,Na-bis(carboxymethyl)-L-lysine triuoroacetate salt (AB-NTA), and nickel sulfate were supplied by Sigma-Aldrich. All chemicals were used as received.