Chemical Probing in Cells by Intrinsic SERS Spectra

13 Chemical Probing in Cells by Intrinsic SERS Spectra 

Since the metallic NPs after delivery to cells are mostly present in endosomes, the majority of SERS intracellular studies provide information about the composition of endosomal structures or their local environment. SERS spectra from cellular compartments in different types of cells using Ag and Au NPs, both free and carrying RRMs, are obtained. 

In the case of intrinsic intracellular SERS studies without RRMs, there is no analytically significant SERS response of intrinsic molecules (Chourpa et al. 2008). A particularly high number of NPs per cell should be used to obtain intrinsic SERS spectra. Typical SERS intrinsic spectra from cells of the immortalized rat renal proximal tubule cells are shown in Fig. 6.3 as an example (Kneipp et al. 2006). The spectra obtained after 120 min incubation with Au NPs provided the best SERS 

V stretching 5 deformation p rocking y-j- twisting y wagging sym symmetrical asym asymmetrical Pro proline, Tyr tyrosine Phe phenylalanine A adenine T thymine C cytosine G guanine (adapted with permission from Kneipp et al. 2006. Cop5oight 2006 American Chemical Society) 

In fact, the possibility of obtaining molecular structural information from the target analyte inside the cell is the most important characteristic of SERS. Until now this has not been possible by any other techniques. On the other hand, the limitation of intracellular SERS spectroscopy exists due to the complex matrix of molecules present in the cell that can produce SERS. Consequentiy, very complicated SERS spectra are acquired from the cells. Such SERS spectra provide only general information about the types of molecules present inside the cell. Therefore, in order to obtain a specific and known SERS spectmm from cells functionalization of the SERS tags with a RRM is required. 

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