Real-Time Microscale Temperature Imaging by Stimulated Raman Scattering.

Abstract

Microscale thermometry of aqueous solutions is essential to understand the dynamics of local heat generation and dissipation in chemical and biological systems. A wide variety of fluorescent probes have been developed to map temperature changes with submicrometer resolution, but they often suffer from the uncertainty associated with microenvironment-dependent fluorescent properties. In this work, we develop a label-free ratiometric stimulated Raman scattering (SRS) microscopy technique to quantify microscale temperature by monitoring the O-H Raman stretching modes of water. By tracking the ratio changes of the hydrogen-bonding O-H band and the isosbestic band, we can directly quantify the temperature of water-based environments in real time without exogenous contrast agents. We demonstrate real-time measurement of localized intracellular and extracellular temperature changes due to laser absorption. This high-speed nonlinear optical imaging technique has the potential for in situ microscale imaging of thermogenesis in both chemical and biological systems.