Functionalized Au-NPs were stabilized by adding 20 μl of 10% bovine serum albumin (BSA), followed by gentle shaking for 30 min at room temperature. Unbound oligonucleotides were removed by three times centrifugation (9.300 ×g for 10 min) through a discontinuous glycerol gradient in 2 ml Eppendorf tubes. The gradient consisted of 800 μl PBS containing 30% glycerol (w/v) and

1% BSA (w/v), overlaid with 1 ml of functionalized Au-NPs. The small molecule library screening pellet was finally resuspended in 1 ml of PBS containing 1% BSA, 0.05% Tween 20, 20% glycerol and 0.02% NaN3. In some experiments Au-NPs were functionalized with BSA instead of antibody. Absorption spectra were recorded with a UV-1601 spectrophotometer (Shimadzu Corporation, Kyoto, Japan) equipped with software package UVProbe (Shimadzu) and quartz cells

(200 μl) with 10 mm path length. Nickel electron microscopy grids coated with pioloform were glow discharged and coated with poly-l-lysine. Au-NPs functionalized with antibodies or KU-60019 solubility dmso with BSA were allowed to settle on the coated grids. After 10 min, the grids were washed in PBS and free protein-binding sites were blocked for 15 min with 0.1% BSA in PBS. Grids with bound Au-NPs were then incubated with the secondary antibody (goat anti-rabbit IgG, conjugated with 5 nm Au-NPs), diluted 1:10 in PBS-0.1% BSA. After 30 min the grids were washed three times for 5 min each with PBS. The grids were fixed in 2.5% glutaraldehyde in PBS for 10 min. Finally, samples were washed twice with MilliQ water (Millipore, Billerica, MA, USA) for 1 min, air-dried and examined with a JEOL JEM-1200EX transmission electron microscope (JEOL, Tokyo, Japan) operating at 60 kV. For detection of cytokines by Nano-iPCR, two methods were used differing in the mode of anchoring the antibodies to plastic surface. In Nano-iPCR next I biotinylated antibody was attached to immobilized extravidin, whereas in Nano-iPCR II the antibody was directly bound to the plate. One hundred microliter aliquotes of extravidin

(1–2 μg/ml in 100 mM borate buffer, pH 9.5) were added into each well of real-time 96-well plate or real-time tube strip (Eppendorf, Hamburg, Germany) and incubated for 1 h at 37 °C. After adsorption of the protein, the wells were washed with PBS containing 0.05% Tween 20 (TPBS) and the remaining binding sites were blocked by 2 h incubation at 37 °C with TPBS supplemented with 2% BSA. The wells were then washed three times with 200 μl of TPBS, followed by addition of 100 μl biotinylated anti-SCF or anti-IL-3 antibody (1 μg/ml in TPBS-1% BSA). After incubation for 1 h at 37 °C, unbound antibody was rinsed out and 100 μl sample aliquotes were probed for the presence of SCF or IL-3.