A team of researchers from the University of Montreal have created the world’s smallest thermometer. The thermometer is based off of the properties of RNA molecules and is 20,000 times smaller than a strand of human hair. The programmable DNA thermometer will enable temperatures to be measured at the nano level.

Over 60 years ago, scientists had discovered that DNA molecules fold under high temperatures. “In recent years, biochemists also discovered that biomolecules such as proteins or RNA (a molecule similar to DNA) are employed as nanothermometers in living organisms and report temperature variation by folding or unfolding,” says senior author Prof Alexis Vallée-Bélisle. “Inspired by those natural nanothermometers, which are typically 20,000x smaller than a human hair, we have created various DNA structures that can fold and unfold at specifically defined temperatures.”

The main reason for using DNA molecules to construct the nanothermometer was due to the ease with which DNA molecules could be manipulated. The team used the unique properties of DNA to customize the design of the thermometer. DNA is found in abundance in all living things including both plants and animals. DNA contains biological information and hence is known as the building block of life.

“DNA is made from four different monomer molecules called nucleotides: nucleotide A binds weakly to nucleotide T, whereas nucleotide C binds strongly to nucleotide G,” explains David Gareau, first author of the study. “Using these simple design rules we are able to create DNA structures that fold and unfold at a specifically desired temperature. By adding optical reporters to these DNA structures, we can therefore create five nm-wide thermometers that produce an easily detectable signal as a function of temperature,” adds Arnaud Desrosiers, co-author of this study.

By placing the bases in the correct sequence in the correct order, the team was able to construct DNA strands that can coil and recoil in a particular way at varying temperatures. The team responded in Nano Letters optimistically about the thermometer as it can respond to minute temperature changes over small temperature intervals (±0.05 °C) or a more linear response over a wide temperature range (from 25 to 90 °C).

Future Of Nanotechnology

Thermometers haven’t seen much innovation and remain the most common tool for measuring body temperature. The most common method to record body temperature is by placing it under the tongue in the user’s mouth, where it will react accordingly to the body’s temperature. The mercury thermometers do pose some problems such as mercury poisoning due to leakage in case of breakage, and they may not be the most accurate.

This discovery could significantly change all of that as these DNA-based nanothermometers may be used in electronic based devices to monitor temperature at a cellular level.

“There are still many unanswered questions in biology,” Vallee-Belisle said. “For example, we know that the temperature inside the human body is maintained at 37° Celsius, but we have no idea whether there is a large temperature variation at the nanoscale inside each individual cell,” Vallee-Belisle pointed out.

These nanothermometers open many doors for research on nanotechnology and molecular technology. The use of nanotechnology in medicine can improve drug delivery methods, help detect symptoms quicker and make room for newer medicinal techniques such as precision medicine, using nanobots to repair cell tissues functioning similarly to antibodies.

One question that the team is determined to answer is that whether DNA strands are able to withstand higher temperatures or not. This question can only be answered with time as the team has only started its research into the fascinating and somewhat mysterious world of nanotechnology.