Folate conjugated, SERS-active gold nanoparticles for selective targeting of human cancer cells

One of the most interesting applications of Surface Enhanced Raman Scattering (SERS), ever since its discovery, has been the spectroscopic study and detection of biomolecules [1,2]. More recently, the application of SERS-active nanostructures as spectroscopic antennas inside biological cells has proved to be a simple way to perform spectroscopic imaging of both healthy and damaged living tissues [3]: an interesting task for biophysicists is indeed to find ways to distinguish between healthy and cancer cells. Moreover, much interest has lately risen around the concept of “theranostics”, i.e. combining diagnostics with therapy, the latter to perform selectively on cancer cells without damaging the healthy tissue [4]. Plasmonics-based theranostics is often performed combining SERS and photothermal bleaching. We will here present a biocompatible system based on gold nanoparticles (Nps) functionalized with the Raman active bifunctional linker 4-aminothiophenol and further conjugated with folic acid, a biomolecule with an essential role in cell reproduction (see Fig. 1., (a)). Our system can be considered a nanobiovector, as it is capable of targeting a specific kind of cell and locate in its proximity and/or inside it. Folic acid receptors are more frequent in cancer cells, as they reproduce more quickly [5]. For this reason, our nanovector targets cancer cells much more efficiently (Fig. 1., (b)). After presenting the system characterization, we will illustrate the interaction of our nanobiovector with different cell cultures. Proofs of selective targeting and eventual internalization in cells will be shown. The presence of SERS-active Nps allows not only to perform Raman imaging, but also the implementation of a SERS-based screening method that allows for a precise single cell diagnosis