Barnstead e pure filtration system

β-Casein, trypsin (from bovine pancreas), anisole, poly(methyl methacrylate) (PMMA, MW ~ 996 kDa), poly(allylamine hydrochloride) (PAH, MW ~ 56 kDa), titanium(IV)bis(ammo-niumlactato)dihydroxide solution (TALH, 50 wt% in H₂O), trifluoroacetic acid (TFA, 99%), Super-DHB, and n-octadecyltri-chlorosilane (C18, 90%) were from Sigma-Aldrich (St. Louis, MO). Ethanol (200 proof) and acetonitrile (ACN) were from Fisher Scientific (Pittsburgh, OH). Phosphoric acid (85% w/w) was from EMD Millipore (Billerica, MA). Poly(-diallyldimethylammonium chloride) solution (PDDA, 20%) and carboxylated polystyrene nanospheres (0.2 μm, 2.6% solids) were from Polysciences, Inc. (Warrington, PA). BK7 glass substrates were from Corning (Painted Post, NY). Chromium and gold used for electron-beam evaporation were acquired as pellets of 99.99% purity from Kurt J. Lesker (Jefferson Hills, PA). Nanopure water (≥18 MΩ cm), purified through a Barnstead E Pure filtration system (Thermo Scientific, Rockford, IL), was used for all reagent preparations.

Gold(III) chloride trihydrate, trisodium citrate dihydrate, N-hydroxysuccinimide (NHS), 1- (3-(dimethylamino)propyl)-3-ethylcarbodiimide hydrochloride (EDC), 2-(2’-aminoethoxy) ethanol (AEE), Tween 20, 16- mercaptohexadecanoic acid (16-MHDA), 3,3’,5,5’-tetramethylbenzidine (TMB), horseradish peroxidase (HRP, Type VI), cholera toxin from Vibrio cholerae (CT), anticholera toxin antibody from rabbit (whole antiserum), and Protein A from Staphylococcus aureus were from Sigma-Aldrich (St. Louis, MO). Streptavidin and (+)-biotinyl-3,6,9-trioxaundecanediamine (BA) were from Thermo Scientific (Rockford, IL). 1-Oleoyl-2-palmitoyl-sn-glycero-3-phosphocholine (POPC) and 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-N-(biotinyl) sodium salt (biotin-PE) were from Avanti Polar Lipids (Alabaster, AL). Monosialoganglioside receptor GM₁ was from Matreya (Pleasant Gap, PA). Functionalized oligonucleotides were obtained from Integrated DNA Technologies (Coralville, IA), and their sequences are provided in Table 1. Detailed compositions of all buffers used (1× PBS, PBT, PCB, and MES) may be found in the Supporting Information. Nanopure water (≥18 MΩ·cm), purified through a Barnstead E-Pure filtration system (Thermo Scientific, Rockford, IL), was used for all reagent preparations.