SERS-based monitoring of the intracellular pH in endothelial cells:the influence of the extracellular environment and tumour necrosis factor-alpha

The intracellular pH plays an important role in various cellular processes. In this work, we describe a method for monitoring of the intracellular pH in endothelial cells by using surface enhanced Raman spectroscopy (SERS) and 4-mercaptobenzoic acid (MBA) anchored to gold nanoparticles as pH-sensitive probes. Using the Raman microimaging technique, we analysed changes in intracellular pH induced by buffers with acid or alkaline pH, as well as in endothelial inflammation induced by tumour necrosis factor-alpha (TNF alpha). The targeted nanosensor enabled spatial pH measurements revealing distinct changes of the intracellular pH in endosomal compartments of the endothelium. Altogether, SERS-based analysis of intracellular pH proves to be a promising technique for a better understanding of intracellular pH regulation in various subcellular compartments.This work was supported by the National Center of Science (grant PRELUDIUM DEC-2012/05/N/ST4/00218) and by the European Union from the resources of the European Regional Development Fund under the Innovative Economy Programme (grant coordinated by JCET-UJ, no. POIG.01.01.02-00-069/09). We also thank the University of Edinburgh School of Chemistry for the Neil Campbell Travel Award for supporting LJ. We also thank Joanna Jalmuzna from the Department of Mathematics and Computer Sciences, Jagiellonian University in Krakow for fitting the calibration curve using Gnuplot software