SPR chips were functionalized with initiator moieties by immersion in 5 mM ethanolic solution of ω-mercaptoundecyl bromoisobutyrate, overnight, and then rinsed with ethanol and used within one day for synthesis. PDMAEMA brush coated SPR chips were prepared in the same way as for silicon substrates. Quaternisation of PDMAEMA to generate PMETAC brushes was accomplished by immersing substrates in 100 mM iodomethane (in isopropanol), overnight, and rinsed with ethanol. SPR assays were carried out on a Biacore 1K+ and/or Biacore 3000 and X100. The flow rate of injections and running buffer was maintained constant throughout the experiment at a value of 10 µL min -1 . A change of 10 4 RU corresponding to 1 µg cm -2 of binding capacity was considered based on the literature 11 . Brush-coated SPR chips were mounted on plastic sensor chip supports, docked, and left to equilibrate with the respective running buffer until a stable baseline was obtained (normally, within 45 min). For each nucleic acid material, a set of concentrations ranging from 1 to 20 µg mL -1 was prepared by serial dilutions, with the buffer matching the running buffer to reduce RI drifts. All injections were carried out incrementally, starting from the lowest concentration. Upon equilibration, 50 µL of nucleic acid solutions were injected for 5 min, followed by a washing step with running buffer for 10 min. Prior to each subsequent injection, regeneration with 2 M NaCl and further equilibration were performed.