Abstract

As a macroscopic system containing millions of billions of molecules, a cell can be described, in many of its aspects, in terms of thermodynamic parameters, including temperature in the first place. Activation of a broad family of transient receptor potential (TRP) cation channels by temperature variations[1-3] is one of the most striking examples of temperature-controlled processes in cell biology. With the evidence indicating the fundamental role of such cellular processes in thermosensation building at a fast pace[4], adequately accurate and delicate tools that would allow heat receptor logic behind thermosensation to be examined on a single-cell level are in great demand. Here, we confront this challenge by demonstrating a fiber-optic probe (Fig.1a) that enables thermal activation with simultaneous online thermometry of individual cells with genetically encoded TRP channels in a cell culture. The fiber probe integrates a fiber-optic tract for the delivery of laser light with a microwave transmission line[5], implemented as a pair of copper wires, running along either side of the fiber. A diamond microcrystal attached to the tip of the fiber and heated by laser radiation transmitted through the fiber provides a local heating of the cell culture, enabling a well-controlled TRPA-assisted thermal activation of cells. Online local temperature measurements are performed by using the temperature-dependent frequency shift of optically detected magnetic resonance[6], which is induced by coupling the microwave field, delivered by the microwave transmission line, to nitrogen--vacancy (NV) centers in diamond on the tip of the fiber probe. Activation of TRPA channels is independently verified(Fig.1b) by using genetically encoded fluorescence indicators, visualizing an increase in the calcium flow through activated TRPA channels.

© 2015 IEEE