Characterizing Single Polymeric and Protein Nanoparticles with Surface Plasmon Resonance Imaging Measurements

Near-infrared surface plasmon resonance imaging (SPRI) microscopy is used to detect and characterize the adsorption of single polymeric and protein nanoparticles (PPNPs) onto chemically modified gold thin films in real time. The single-nanoparticle SPRI responses, Δ%R_NP, from several hundred adsorbed nanoparticles are collected in a single SPRI adsorption measurement. Analysis of Δ%R_NP frequency distribution histograms is used to provide information on the size, material content, and interparticle interactions of the PPNPs. Examples include the measurement of log-normal Δ%R_NP distributions for mixtures of polystyrene nanoparticles, the quantitation of bioaffinity uptake into and aggregation of porous NIPAm-based (N-isopropylacrylamide) hydrogel nanoparticles specifically engineered to bind peptides and proteins, and the characterization of the negative single-nanoparticle SPRI response and log-normal Δ%R_NP distributions obtained for three different types of genetically encoded gas-filled protein nanostructures derived from bacteria.