All imaging agents were individually dissolved in PBS with or without 1% (w/v) bovine serum albumin (BSA) purchased from Sigma-Aldrich. The imaging agents, mixed with 30% glycerol, and Chameleon® Duo fluorescent protein ladder (LI-COR) were loaded (7 μl) in 4–20% criterion TGX Stain-Free protein gel obtained from Bio-Rad. The gel was run for 40 min at 100 V, and then imaged with the Odyssey CLx (LI-COR) in 700- and 800-nm channels (Fig. 1). Fluorescence quantification of each lane was performed using FIJI [20 (link)].