Imaging and Localisation of Nanoparticles in Tissue Using Surface Enhanced Spatially Offset Raman Spectroscopy

In fifteen words or less, explain the significance of this contribution (Novel Aspect).: Describes the localisation of nanoparticles in 3D using SESORS

Abstract Text:

In recent years, Raman based techniques have been used extensively in bioanalytical research applications with the ultimate goal of creating platforms for medical diagnostics. Surface enhanced spatially offset Raman spectroscopy (SESORS) is a powerful analytical technique that has emerged in an attempt to combine the signal enhancements offered by surface enhanced Raman scattering (SERS) with the subsurface probing in turbid media offered by spatially offset Raman spectroscopy (SORS). Using SESORS it is possible to non-invasively retrieve subsurface spectra that originate from highly specific biofunctional SERS active nanotags inside diffusely scattering objects such as mammalian tissue.

 

In this work we explore whether SESORS can be used to determine the location of an object within tissue. To address this question multiple experimental factors pertaining to the optical set-up in imaging experiments using an in-house built point-collection based spatially offset Raman spectroscopy (SORS) system were investigated to determine those critical to the 3-dimensional positioning capability of SESORS. Here we report the effects of the spatial offset magnitude and geometry on locating nanoparticles (NPs) as an imaging target through tissue and outline experimental techniques to allow for the correct interpretation of SESORS images to ascertain the correct location of NPs in the 2-dimensional x, y-imaging plane at depth. Additionally, building on these principles, the concept of ‘ratiometric SESORS imaging’ is introduced for the location of buried inclusions in 3-dimensions. Together these principles are vital in developing a methodology for the location of SERS active inclusions in 3-dimensions. This approach utilises the relationship between the magnitude of the spatial offset, the probed depth and ratiometric analysis of the NP and tissue Raman intensities, to ultimately image and spatially discriminate between two distinct NP flavours buried at different depths within a 3-dimensional model for the first time.  This research demonstrates how to accurately identify multiple objects at depth in tissue and their location using SESORS which addresses a key capability in moving SESORS closer to use in biomedical applications.