Fiber-optic control and thermometry of single-cell thermosensation logic

Thermal activation of transient receptor potential (TRP) cation channels is one of the most striking examples of temperature-controlled processes in cell biology. As the evidence indicating the fundamental role of such processes in thermosensation builds at a fast pace, adequately accurate tools that would allow heat receptor logic behind thermosensation to be examined on a single-cell level are in great demand. Here, we demonstrate a specifically designed fiber-optic probe that enables thermal activation with simultaneous online thermometry of individual cells expressing genetically encoded TRP channels. This probe integrates a fiber-optic tract for the delivery of laser light with a two-wire microwave transmission line. A diamond microcrystal fixed on the fiber tip is heated by laser radiation transmitted through the fiber, providing a local heating of a cell culture, enabling a well-controlled TRP-assisted thermal activation of cells. Online local temperature measurements are performed by using the temperature-dependent frequency shift of optically detected magnetic resonance, induced by coupling the microwave field, delivered by the microwave transmission line, to nitrogen—vacancy centers in the diamond microcrystal. Activation of TRP channels is verified by using genetically encoded fluorescence indicators, visualizing an increase in the calcium flow through activated TRP channels

HgCdTe quantum wells grown by molecular beam epitaxy

CdxHg₁₋xTe-based (x = 0 – 0.25) quantum wells (QWs) of 8 – 22 nm in thickness were grown on (013) CdTe/ZnTe/GaAs substrates by molecular beam epitaxy. The composition and thickness (d) of wide-gap layers (spacers) were x ∼ 0.7 mol.frac. and d ∼ 35 nm, respectively, at both sides of the quantum well. The thickness and composition of epilayers during the growth were controlled by ellipsometry in situ. It was shown that the accuracy of thickness and composition were ∆x = ± 0.002, ∆d = ± 0.5 nm. The central part of spacers (10 nm thick) was doped by indium up to a carrier concentration of ∼10¹⁵ cm⁻³ . A CdTe cap layer 40 nm in thickness was grown to protect QW. The compositions of the spacer and QWs were determined by measuring the Е₁ and Е₁+∆₁ peaks in reflection spectra using layer-by-layer chemical etching. The galvanomagnetic investigations (the range of magnetic fields was 0 – 13 T) of the grown QW showed the presence of a 2D electron gas in all the samples. The 2D electron mobility µe = (2.4 – 3.5)×10⁵ cm² /(V·s) for the concentrations N = (1.5 – 3)×10¹¹ cm⁻² (x < 0.11) that confirms a high quality of the grown QWs