The implementation of sensor platforms that provide high detection sensitivities is crucial for the design of new analytical devices for diagnostic, drug discovery, and environmental monitoring applications. Surface-plasmon resonance (SPR) is a label-free optical-detection technique that allows real-time, quantitative analysis and provides an outstanding performance. However, ongoing research is needed for the improvement of detection sensitivities of plasmonic sensors. For instance, localized SPR (LSPR), a method based on the use of gold or silver nanoparticles as local resonators, has shown to enhance the plasmonic effect. Further advantages can be obtained by ‘‘nanostructuring’’ the metallic thin films of the SPR interface; nanostructured metallic surfaces promote the coupling of light with surface-plasmon polariton (SPP) modes, which induce an electric-field enhancement that results in a signal improvement. Moreover, the detection sensitivity of the technique relies critically on the immobilization efficiency of the biocapturing elements on the sensor surface. For this purpose, sensor platforms designed with ‘‘nanopatterned’’ bioadhesive–nonadhesive regions have already shown to produce a drastic increase in the performance, thanks to a better control of the biomolecular-probe immobilization. In this work, we studied the effect of 2D crystalline organothiol nanoarrays on the SPR imaging (SPRi) sensitivity. The organothiol nanoarray consisted of bioadhesive carboxylic ((COOH)) ‘‘nanospots’’ distributed in a matrix of polyethylene oxide (PEO), which is a nonadhesive material known to be unsusceptible to protein and cell adhesion. Such a nanostructured surface has already shown potential for the improvement of the immobilization efficiency of proteins on surfaces.

In the present study, the SPRi detection sensitivity of nanoarrayed surfaces for the Human IgG – anti-Human IgG immunoreaction is compared to that of uniformly functionalized carboxylic surfaces. For the same concentration of analyte, the detection sensitivity improved by a factor of five, when a 2D crystalline nanoarrayed surface was used instead of a uniformly bioadhesive surface. This amplification effect could not be observed in a random arrangement of ‘‘nanodomains’’ of the same dimensions and density.