How to measure and control the temperature inside living cells
August 7, 2013
A team of researchers working on DARPA’s Quantum-Assisted Sensing and Readout (QuASAR) program recently demonstrated sub-degree temperature measurement and control at the nanometer scale inside living cells. The QuASAR team is led by researchers from Harvard University.
The technology might open the door to a number of defense and medical applications: better thermal management of electronics, monitoring the structural integrity of high-performance materials, cell-specific treatment of disease and new tools for medical research.
To measure temperature, the researchers used imperfections engineered into diamond, known as nitrogen-vacancy (NV) color centers, as nanoscale thermometers. Each NV center can capture an electron, such that the center behaves like an isolated atom trapped in the solid diamond. Changes in temperature cause the lattice structure of the diamond to expand or contract, similar to the way the surface of a bridge does when exposed to hot or cold weather.
These shifts in the lattice induce changes in the spin properties of the trapped atoms, which researchers measure using a laser-based technique. The result is that scientists can now monitor sub-degree variations over a large range of temperatures in both organic and inorganic systems at length scales as low as 200 nanometers. For a sense of scale, see here.
The QuASAR team also demonstrated control and mapping of temperature gradients at the subcellular level by implanting gold nanoparticles into a human cell alongside the diamond sensors.
The 100-nanometer-diameter nanoparticles were then heated using a separate laser.
By varying the power of the heating laser and the concentration of gold nanoparticles, the researchers were able to modify and characterize (using the diamond sensors) the local thermal environment around the cell.
The temperature-measurement techniques have several potential applications and could lead to additional areas of study:
- It could provide insight into organic and inorganic systems, like heat dissipation in integrated circuits and thermal properties of musculoskeletal restoration or inflammation following physical exertion;
- Because the techniques have been shown to be effective up to temperatures of 600 degrees Kelvin, they could allow for monitoring of nanoscale cracking and degradation caused by temperature gradients in materials and components operating at high temperatures;
- The intrinsic chemical inertness of diamond may allow for direct microscopic monitoring and control of chemical reactions.