At the University of Montreal scientists have created a DNA-based thermometer that is so tiny that it can be inserted into cells to read the temperature inside. The inspiration came from seeing naturally occurring molecules being used to sense the temperature in the biological world. Such molecules fold and unfold at specific temperatures and so their shape tells how hot their nearby environment is.
The thermometers are only 5 nanometers in diameter and are created from nucleotides by relying on the idea that adenine binds weakly to thymine, while cytosine and guanine form a stronger bond. The molecular thermometers can be made in quantity, each folding and unfolding at different temperatures, providing the necessary resolution for detailed studies. An optical reporter attached to the molecule can be used to detect the shape of the molecules and so know the temperature nearby.
From the study abstract in journal Nano Letters:
Using structural modifications or inexpensive DNA stabilizers, we show that we can tune the transition midpoints of DNA thermometers from 30 to 85 °C. Using multimeric switch architectures, we are able to create ultrasensitive thermometers that display large quantitative fluorescence gains within small temperature variation (e.g., > 700% over 10 °C). Using a combination of thermoswitches of different stabilities or a mix of stabilizers of various strengths, we can create extended thermometers that respond linearly up to 50 °C in temperature range. Here, we demonstrate the reversibility, robustness, and efficiency of these programmable DNA thermometers by monitoring temperature change inside individual wells during polymerase chain reactions.