Orientation of capture antibodies on gold nanoparticles to improve the sensitivity of ELISA-based medical devices

The sensitivity of ELISA-based devices strongly depends on the right orientation of antibodies on the sensor surface. The aim of this work was to increase the analytical performance of a commercial ELISA-based medical device (VIDAS (R)), thanks to the specific orientation of antibodies on gold nanostructured disposables. For this purpose, fPSA VIDAS (R) assay was used as model and the disposable providing the antigen binding surface (SPR (R)) was functionalized with gold nanostructures coated with monovalent half-fragment antibodies (reduced IgG, rIgG). The functionalization of polystyrene SPRs (R) with gold nanostructures was achieved through a one-step incubation of gold dispersions in a mixture of non-toxic solvents. Five different concentrations of gold nanoparticles (NPs) were tested with a maximum fluorescence enhancement for NPs density around 3-8 *103 NPs/ mu m2 (752 +/- 11 RFV vs 316 +/- 5 RFV of bare SPRs (R)). The comparison of the dose-response curve obtained with commercial and gold coated-SPRs (R) revealed a significant improvement (p < 0.0001) of the analytical sensitivity of the VIDAS (R) system using nanostructured disposables. This improved version of SPRs (R) allows to distinguish small variations of fPSA concentrations opening the way to the application of this biomarker to other kinds of cancer as recently described in the literature.