(A) Gold Drop Sens electrodes were functionalized with polymer comprising of polyaniline (PANI) containing either 0.50 or 85% 2-aminobenzylamine (2- ABA). Following incubation with NHS-biotin and HRP-streptavidin, transducer surfaces were washed, incubated with ECL reagent and imaged. (B) The light signal emitted from the polymer-coated electrodes in (A) was plotted against the percentage of 2-ABA in the co-polymer (n=4; error bars show ± SEM). (C) Polytyramine was electropolymerised onto gold DropSens electrodes at a scan rate of either 0.1 V s-1 or 0.2 V s-1, followed by incubation in the presence or absence of NHS-biotin, followed by HRP-streptavidin. The overlay images display chemiluminescence (false green colour) superimposed onto the bright field image to show the location of the signal relative to the electrodes. (D) Impedance data from the electrodes in (C) were obtained in 2 mM K3[Fe(CN)6]/ K4[Fe(CN)6]. (E) Poly 3-(4-hydroxyphenyl) propanoic acid, as a 25 mM solution in either PBS or methanol, was electropolymerised onto gold DropSens electrodes using two cycles at a scan rate of 0.1 V s-1. The polymer-coated electrodes were incubated in the presence or absence of biotin hydrazide with EDC, followed by HRP-streptavidin. (F) Self-assembled monolayers of 4-ATP (4-aminothiophenol) were deposited upon gold or platinum electrodes which had been coated by screen printing (SPE; DropSens) or sputtering. (P4electrodes). The functionalised electrodes were then incubated in the presence or absence of NHS-biotin followed by HRP-streptavidin.
