Abstract:

The measurement of intracellular chemical concentrations and their changes during the cell cycle provides essential information for systems-biological models of cells. This information, however, is difficult to obtain at the single cell level – especially in living cells where chemical levels can change rapidly in response to external or internal events. It is even more difficult to measure such changes in a nondestructive and mostly non-invasive way. Here, I present our results in characterizing and distinguishing individual cells and subcellular structures by a technique called laser-tweezers Raman spectroscopy (LTRS). LTRS is a unique optical tool that characterizes molecular bonds through inelastic light scattering. I will discuss the principles of this technique on a few, select examples. I will also present our recent results on the development of nanoscale pH sensors based on functionalized silver nanoparticles and surface-enhanced Raman scattering (SERS).  The SERS spectrum from individual gold and silver nanoparticles (50-80 nm in diameter) functionalized with small molecules exhibits a characteristic response to binding events and changes in their local chemical environment. Measurements from nanoparticles incorporated into individual cells demonstrate that the nanoparticle sensors retain their robust signal and sensitivity to pH when incorporated into a cell.