**2.4 SPRi interaction monitoring**

All reactions were carried out at room temperature, in phosphate-buffered saline (PBS)/0.01%Tween 20. The flow rate in the chamber was 37 µL/min. Reflectivity was measured at 810 nm, at a fixed incidence angle (55°<<56°). After injection of serum (500 µL, 1/50 or 1/200 as indicated in the text), the biochip surface was rinsed with running buffer (10 min) to remove unbound ligands and specific binding was quantified by measuring the change in reflectivity (R) obtained after 10 min washing. The chip was regenerated using 0.1 M HCl-Glycine (pH 2.3) solution for 10 min and stabilized in the running buffer (10 min). Every twelve injections, a cleaning step was performed by injection of 1% SDS (sodium dodecyl sulphate) in water for 10 min followed by running buffer for 20 min. Saturation with NIS (1/25 in PBS), PLL-PEG or PVP as indicated in the text was realized after each cleaning step.
