Polymer films with size-selected silver nanoparticles as plasmon resonance-based transducers for protein sensing

Transducers based on the phenomenon of localised surface plasmon resonance (LSPR) are fabricated using silver nanoparticles (NPs) imbedded into thin poly (methyl methacrylate) films. The particles are produced by magnetron sputtering, size selected with a precision ≤ 10% of the diameter and deposited on the films in vacuum. Immersion of NPs is controlled by post-deposition thermal annealing providing very good adhesion, in particular, resistance against following wet chemical procedures. LSPR properties of silver NPs are exploited for protein detection using a classical antibody-antigen scheme through covalent attachment of antibody molecules to the particles, followed by incubation with antigen (chicken egg albumin). Atomic force microscopy studies reveal that antibodies are predominantly attached to NPs providing binding sites for the antigens of interest. Specific changes in the LSPR band are observed for each step of protein incubation on NPs. Thus, the transducers demonstrate good sensitivity and selectivity in detection. Flexibility of polymer substrates paves a way for making devices of required configuration.