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.

Liposomes are small vesicles that can be used in various targeting applications as carrier vehicles. In this paper, we show that real-time surface plasmon resonance imaging microscopy (SPRI microscopy) can be used to detect diffraction patterns of these singular vesicles in water phase at room temperature and without any additives. The diffraction pattern intensities, related to the particle size, are shown to follow the log-normal distribution in a cumulative distribution function (CDF) that is very well in accordance with the normal size distribution of liposomes prepared with the extrusion method. In addition, this distribution is further analyzed to determine the number of gold nanoparticle (GNP) encapsulated liposomes in a set of liposomal adsorption events. Thus, we obtain the encapsulation efficiency and present a method to study the intrinsic properties of liposomes and other soft nanomaterials. (Figure Presented).

The specific binding and uptake of protein molecules to individual hydrogel nanoparticles is measured with real-time single-nanoparticle surface plasmon resonance imaging (SPRI) microscopy. Nanoparticles that adsorb onto chemically modified gold thin films interact with traveling surface plasmon polaritons and create individual point diffraction patterns in the SPRI microscopy differential reflectivity images. The intensity of each point diffraction pattern depends on the integrated refractive index of the nanoparticle; an increase in this single nanoparticle point diffraction intensity (Δ%RNP) is observed for nanoparticles that bind proteins. SPRI adsorption measurements can be used to measure an average increase in Δ%RNP that can be correlated with bulk dynamic light scattering measurements. Moreover, the distribution of Δ%RNP values observed for individual nanoparticles can be used to learn more about the nature of the protein-nanoparticle interaction. As a first example, the binding of the lectin Concanavalin A to 180 nm N-Isopropylacrylamide hydrogel nanoparticles that incorporate a small percentage of mannose sugar monomer units is characterized.