**2.2 Materials**

200 Electropolymerization

for probe immobilization and surface plasmon resonance imaging (SPRi) for ligand detection. The biological model consists in antigen-antibody interactions, where probes are peptides used as antigens and ligands are antibodies (Ab) contained in serum samples. Our data suggest that modification of the peptide conformation is the main parameter involved in the decrease of the signal observed upon successive uses of the chip. This conformational change leads to both a progressive reduction of the signal due to a decrease of the peptide reactivity with Ab, and the selection of Ab with the highest affinity. This phenomenon can be evaluated and must be taken into account in the analysis of the data resulting from

Polyvinylpyrrolidone (PVP, MW 360 kDa) was obtained from Sigma-Aldrich (St Quentin Fallavier, France). Poly(L-Lysine)-PEG (PLL(20KDa) grafted with PEG(2 Kda) having 3.5 Lys units/PEG chains = PLL-PEG) was purchased from SurfaceSolutionS (Zurich,

Peptides were synthesized by Altergen (Bischheim, France) with a pyrrole-modified NH2 terminus as previously described (Villiers et al., 2009). Two peptides are derived from the structural protein core of hepatitis C virus of the genotype 1b (HCV), one from ovalbumine, one from hen egg lysozyme, nine from hepatitis D virus (HDV) of various genotypes. Full sequences can be found on the ExPASy server (http://ca.expasy.org/) under different

Peptide Original protein Accession number Amino acids number C131 HCV P26663 131-150 C20 HCV P26663 20-40 Ova75 Ovalbumine P01012 75-96 HEL101 Lysozyme P00698 101-120 HDV1 HDV P0C6M9 155-172 HDV2 HDV P0C6M9 174-195 HDV3 HDV P0C6M9 189-211 HDV4 HDV P0C6M9 65-80 HDV5 HDV P0C6M9 1-18 HDV6 HDV Q70E23 155-172 HDV7 HDV A1IVP7 155-172 HDV8 HDV Q70E23 174-195 HDV9 HDV A1IVP7 174-195 HDV10 HDV Q70E23 189-211 (aa 195: X=W) HDV11 HDV A1IVP7 189-211

Rabbit immune serums against different peptides were prepared by NeoMPS (Strasbourg, France). Human serums from healthy donors as non immune serum (NIS) were purchased from the Etablissement Français du Sang (La Tronche, France). Human serums from HDV infected patients were provided by Drs E. Gordien and S. Brichler (Hôpital Avicenne, Paris,

samples screening.

**2.1 Reagents** 

Switzerland).

**2. Materials and methods** 

accession numbers (Table 1).

Table 1. Peptides used in the study

Glass prisms coated with a 50 nm gold layer were obtained from Genoptics-HORIBA Scientific (Chilly-Mazarin, France). Electrodeposition was performed using an Omnigrid Micro robotic arrayer (Genoptics-HORIBA Scientific). Surface Plasmon Resonance (SPR) signals were monitored using a surface plasmon resonance imager (SPRi-Plex from Genoptics-HORIBA Scientific). Measurements were performed using SPRi dedicated software (Genoptics-HORIBA Scientific). Sample injections were ensured by a 231XL sampling injector coupled to a 832 temperature regulator (Gilson, Roissy, France).
