Fig. 4. On-chip immunoaffinity capture assay validation.

(A) Representative zoom-in images of the substrate after each functionalisation step: bilayer formation, NeutrAvidin incubation, and biotinylated antibody incubation. Scale bars: 5 μm. (B) The number of localisations after each functionalisation step. (C) Validation of the immunoaffinity functionalisation using streptavidin functionalised AuNPs (AuNP-SAv) and biotinylated liposomes as positive and negative controls, respectively. Scale bars: 10 μm. (D) Dose response for different concentrations of streptavidin-functionalised 20 nm gold nanoparticles. Each data point corresponds to the mean of scans covering an area of 0.2 mm² over multiple different channels within each chip (N = 3). Error bars represent the standard deviation over the mean.