 Metasurfaces are a promising technology for developing new generations of surface plasmid polariton, SPP, based biological or chemical sensors. These devices can be used to detect changes in their environment by altering their electromagnetic properties. This paper reviews several types of metasurfaces with negative values of effective refractive index, including freestanding, electromagnetically symmetric plasmonic slabs, multilayers, and two-dimensional wallpaper geometries such as split-ring resonators and fishnet structures. Additionally, the authors discuss how these structures can be used to achieve multifunctionality, as well as the limitations imposed by surface-bound intrinsic electromagnetic noise. This article was authored by Dragan Tanyskovic, Zoran Jackson, Slobodom Dukovic, and others.