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%RNP, from several hundred adsorbed nanoparticles
are collected in a single SPRI adsorption measurement. Analysis of
Δ%RNP 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%RNP 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%RNP distributions obtained for three different types of
genetically encoded gas-filled protein nanostructures derived from
bacteria.