Cell Imaging by Spontaneous and Amplified Raman Spectroscopies

Figure 4

Schematic representation of the experiment with red blood cell on a SERS substrate: the SERS signal is peaked at the SERS substrate z = 0 in (a) (red points) and is associated with SERS spectra corresponding to lipids and proteins not masked by Hb as shown in (b). In particular, this is achieved with spatially resolved signals revealing sensitivity to the local membrane environment with capability of reconstructing the membrane SERS map of the RBC, in close correlation with the actual morphology of the cell scanned (see optical image in the inset in (b)). In a twin experiment with a normal coverslip as substrate (not shown), the Raman signal is ascribable only to Hb: the spontaneous Raman intensity (integrated between 1400 and 1600 cm⁻¹) versus the axial distance denotes a broad bell-shaped curve (orange points) to be contrasted to the sharp and localized curve obtained on SERS substrate (red points in (a)). In this case, Raman imaging reveals only the spectral signature of Hb in all the RBC volume with no contribution from membrane, as represented in (c).