Figure 1.
(a) Scheme of the instrument set for angular interrogation of SPR sensors utilizing the attenuated total internal reflection method. Two different SPR structures with different characteristic propagation and penetration lengths were used in this study: (b) cSPR is composed of a layer of gold comprised between the glass substrate (prism) and the cover medium (PBS or DMEM plus cells) and (c) LRSPR is composed of a layer of Cytop polymer deposited on the glass substrate, onto which a thin layer of gold is sputtered, creating a RI symmetry supporting long range plasmon waves.
Figure 2.
Experimental spectra recorded for cSPR sensors and LRSPR sensors at different cell coverage values.
(a) cSPR spectra and (b) LRSPR spectra. The arrows indicate the evolution of the spectra. (c) Micrographs of three different cell coverage values of round 3T3 cells. Scale bar is 100 µm.
Figure 3.
Comparison of cSPR and LRSPR spectra parameters for the two experimental schemes.
Dependence of θres (a) and Rmin (b) with respect to the cell coverage (round cells). The inset in (a) represents Δθres/HWHM, the slope of which is the figure of merit of the sensor. It was found that FOM = 1.30%−1 and FOM = 7.39%−1 for cSPR and LRSPR, respectively, yielding a 5.7-fold enhancement in the case of LRSPR. Dependence of Δθres (c), and Rmin (d) with respect to the cell spreading. The error bars represent the standard errors.
Figure 4.
Typical reflectivity spectra of cSPR and LRSPR upon cellular spreading.
(a) cSPR spectra and (b) LRSPR spectra. The cell seeding density was of 150 cells/mm2. The arrows show the evolution of the spectra. The insets show a close-up of the minimum of intensity. The coverage values were inferred from the curve in Figure S2.
Figure 5.
Comparison of cSPR parameters from experimental studies to those predicted by the averaged-intensity cSPR model.
Dependence of θres (a) and Rmin (b) with respect to the cell coverage. Dependence of θres (c), and Rmin (d) with respect to the spreading of cells. The simulations are plotted in dashed curves (ncell = 1.35: diamond, ncell = 1.36: squares, ncell = 1.37: triangles). Fitting the linear parts in (a) yielded ncell = 1.3483 (by quadratic extrapolation of the slopes). Error bars represent the standard errors.
Figure 6.
Comparison of LRSPR parameters from experimental studies to those predicted by the effective-RI LRSPR model.
Dependence of θres (a) and Rmin (b) with respect to the cell coverage. Dependence of θres (c) and Rmin (d) with respect to the spreading of cells. The simulations are plotted in dashed curves (ncell = 1.35: diamond, ncell = 1.36: squares, ncell = 1.37: triangles). The linear fitting in (a) yielded ncell = 1.360. Error bars represent the standard errors.