X-Gal, a SERRS inactive precursor and a common marker for galactosidase enzymes, was introduced to macrophage cells along with metal nanoparticles. On incubation, enzymatic activity of galactosidase on X-Gal produces a SERRS active trans-alkene dimerised product. This product adsorbs onto the delivered citrate capped gold nanoparticles producing a distinctive SERRS signal. Using SERRS mapping to evaluate the formation of this product, enzyme activity was assessed, not only across a cell population, but also at sub-cellular levels. The authors note that the SERRS activity in this study may not reflect the only sites of galactosidase activity, but rather the sites where both galactosidase and the nanoparticles are co-located. Nevertheless, approaches towards sub-cellular analysis of enzyme activity are important.
Advances in targeted nanoparticle uptake combined with the multiplexing capability of SERRS make this an interesting approach to sub-cellular studies of biochemical activity.
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Analysis of intracellular enzyme activity by surface enhanced Raman scattering
Ross Stevenson, Sarah McAughtrie, Laura Senior, Robert J. Stokes, Helen McGachy, Laurence Tetley, Paola Nativo, James M. Brewer, James Alexander, Karen Faulds and Duncan Graham
Analyst, 2013, Advance Article