The goal of the present project is the development of novel nanostructured cross-sensor reactive arrays (CRSA) based on SERS and the different affinity of peptides and proteins to interact with different metallorganic complexes. This sensor concept will be universal for the ultrasensitive detection and identification of metallic cations and peptides/proteins. Briefly, we shall fabricate micron-sized, composite nanomaterials as follows. Gold nanoparticles will be first deposited on silica or polymer microspheres via layer by layer self-assembly, and subsequent epitaxial growth will be carried out with silver (using novel methods recently developed in our lab) to generate discrete, highly SERS active surfaces. These composite particles will be functionalized with organic ligands with high affinity for metals (thiolated porphyrins and terpyridines). In a first step, quantitative multiplex ultrasensitive detection of metals will be aimed. In a second step, each microsphere coupled with one ligand and a given metal will be fabricated as a sensing element for the CRSA. These sensing elements will be organized into solid supports (the actual CRSA) and tested for the identification of different protein species, especially those related with pathogenic states or drug abuse, by combining SERS spectroscopy with chemometric methods (i.e. principal component analysis, hierarchical cluster analysis and partial least squares). The final product is intended to be mounted on a conventional glass slide with ability for drawing a rapid and accurate conclusion on the health condition of a patient, or environmental risk in a time scale of seconds.