High Resolution Surface Plasmon Resonance Imaging for Single Cells
Alexander W. Peterson, Michael W. Halter, Alessandro Tona, Anne L. Plant
Background Surface plasmon resonance imaging (SPRI) is a label-free technique that can image refractive index changes at an interface. We have previously shown that SPRI can be used to study the dynamics of cell-substratum interactions. However, characterization of spatial resolution in 3 dimensions is necessary to quantitatively interpret SPR images. Spatial resolution is complicated by the asymmetric propagation length of surface plasmons in the x and y dimensions leading to image degradation in one direction. Inferring the distance of intracellular organelles and other subcellular features from the interface by SPRI is complicated by uncertainties regarding the detection of the evanescent wave decay into cells. This study provides an experimental basis for characterizing the resolution of an SPR imaging system in the lateral and distal dimensions and demonstrates a novel approach for resolving sub-micrometer cellular structures by SPRI. The SPRI resolution here is distinct in its ability to visualize subcellular structures that are in proximity to a surface, which is comparable with that of total internal reflection fluorescence (TIRF) microscopy but has the advantage of no fluorescent labels. Results An SPR imaging system was designed that uses an inverted microscope body and a high numerical aperture objective lens to image cells. A digital light projector is used to pattern the angle of the incident excitation on the sample. Cellular components such as focal adhesions, nucleus, and cellular secretions are visualized. The point spread function of polymeric nanoparticle beads indicates near-diffraction limited spatial resolution. To characterize the z-axis response, we used micrometer scale polymeric beads with a refractive index similar to cells as reference materials to determine the detection limit of the SPR field as a function of distance from the substrate. Multi-wavelength measurements of these microspheres show that it is possible to ta
, Halter, M.
, Tona, A.
and Plant, A.
High Resolution Surface Plasmon Resonance Imaging for Single Cells, BMC Cell Biology, [online], https://doi.org/10.1186/1471-2121-15-35
(Accessed November 30, 2021)