Plasmonic nanoparticle aggregates for the ultrasenstive detection of analytes at ultra- low concentrations

Conferencia; Vebleo Fellow webminar Nanomedicine, Nanomaterials and Nanotechnology; 2021

The aim of this presentation is to show how the near and far field optical properties of noble metal nanoparticles, together with the capabilities of intermolecular interactions, can be used for the design and development of plasmonic sensors able to detect ultralow concentrations of analytes of interest in Medicine, Food Science and Environment. First, we will discuss how a strict stoichiometric control between the nanoparticle and the glue molecule concentration allows the formation of plasmonic dimers. The molecule in the gap acting as a host is able to detect and identify a guest molecule (methyl viologen) at ultra-low concentrations by SERS (Surface Enhanced Raman Scattering). The resulting dimers are stable in colloidal dispersions over several days, generating in this way nanostructures with highly reproducible SERS hot spots with Raman enhancements of the order of 108. Second, we will show how bio-molecular recognition events between functionalized plasmonic nanostructures can be used for the ultrasensitive detection of proteins of interest in Medicine and Food Science using both SERS as well as UV Vis spectroscopy. In that regard, we will explain a novel methodology developed by our group denoted as IDILA (Intensity Depletion Immuno-Linked Assay). That novel methodology principle relies on the controlled agglomeration of functionalized Ag nanospheres generated in the presence of a biotinylated immunoglobulin acting as linker between these nanoparticles and the inhibition of the agglomeration (dimer formation) in the presence of the specific antigen. This inhibition results in a change in the far field optical response (extinction spectra) that depends on the antigen concentration. The power to detect (sub) picomolar concentrations of antigens and the excellent analytical performance of this methodology over other techniques has been already reported for the detection of biomarkers of interest in Medicine (e.g. cytokines implicated in the pathogenesis of chronic inflammatory diseases) and Food Science (e.g. gluten proteins involved in celiac disease.