Surface-Enhanced, Spatially Offset Raman Spectroscopy (SESORS) in Tissue Analogues

Surface-enhanced, spatially offset Raman spectroscopy (SESORS) combines the remarkable enhancements in sensitivity afforded by surface-enhanced Raman spectroscopy (SERS) with the non-invasive, subsurface sampling capabilities of spatially offset Raman spectroscopy. Taken together, these techniques show great promise for in vivo Raman measurements. Herein, we present a step forward for this technique, demonstrating SESORS through tissue analogues of six known and varied thicknesses, with a large number of distinct spatial offsets, in a backscattering optical geometry. This is accomplished by spin-coating SERS-active nanoparticles (NPs) on glass slides and monitoring the relative spectral contribution from the NPs and tissue sections, respectively, as a function of both the tissue thickness and the spatial offset of the collection probe. The results show that SESORS outperforms SERS alone for this purpose, the NP signal can be attained at tissue thicknesses of >6.75 mm, and greater tissue thicknesses require greater spatial offsets to maximize the NP signal, all with an optical geometry optimized for utility. This demonstration represents a step forward toward the implementation of SESORS for non-invasive, in vivo analysis.