Itlc sg paper strips

Radiolabeling of UBI_29–41-Cy5-N₃ with ^99mTc was performed according
to a previous procedure.^{32 (link)} In short, to
5 μL of UBI_29–41-Cy5-N₃ (15 μM
in PBS), 4 μL of SnCl₂·2H₂O (0.44
mg/mL saline, Technescan PYP, Mallinckrodt Medical B.V. Petten), 4
μL of NaOH (0.1 M), and 100 μL of a freshly eluted ^99mTc-Na-pertechnetate solution (1000 MBq/mL, Mallinckrodt
Medical B.V.) were added, and the mixture was gently stirred in a
shaking water bath for 1 h at 37 °C.^{32 (link)} After 1 h, the reaction mixture was purified by size-exclusion chromatography
with sterile PBS as the mobile phase using Sephadex G-25 desalting
columns (PD-10, GE Healthcare Europe GmbH). Fractions containing ^99mTc-UBI_29–41-Cy5-N₃, counted
for radioactivity in a dose-calibrator, were collected and directly
used for labeling of bacteria. The stability of ^99mTc-labeling
was determined after incubation of 10 μL of tracer at rt in
1 mL of PBS or fetal-calf serum (20%, v/v, FCS, Life Technologies
Inc.), and samples were analyzed at various intervals until 24 h.
The release of radioactivity was determined by instant thin-layer
chromatography (ITLC) on 1 × 7 cm ITLC-SG paper strips (Agilent
Technologies) with PBS as the mobile phase. A schematic depiction
of ^99mTc-UBI_29–41-Cy5-N₃ is
shown in Figure S7.