Can we measure the temperature of human cells? A young scientist explains

As part of our series exploring the edges of scientific research, we caught up with World Economic Forum Young Scientist Pierre Karam, a chemistry professor at the American University of Beirut, who is integrating biosensors into smartphones in order to monitor and control waterborne and infectious diseases in resource-limited settings.

I am trying to develop a tiny thermometer. I know this might not sound very impressive at first, but the technology that we are currently using is almost identical to the thermometer that was assembled by Ferdinand II, the Grand Duke of Tuscany, in 1654. Ferdinand II filled a glass tube with alcohol and used it to measure temperature changes.

Science and technology have advanced a lot since then - and much of the work nowadays is being conducted at microscale- and nanoscale levels. These scales are much smaller than the tip of a thermometer itself, which makes it impossible to measure accurately any temperature changes. For example, a human cell is a few microns in diameter. If you want to measure the temperature in the sub-cellular compartments or to understand how potentially a drug might affect cell metabolism, it is impossible to do it with current technology. Our work is trying to solve this pressing question.

We are trying to exploit the unique fluorescent properties of conjugated polymers. These polymers were initially developed to fabricate flexible and cheap organic solar cells. They have a very poor water solubility - but what was considered an undesirable property has turned out to be ideal for our application. So we use their low solubility at room temperature to our advantage. Any change in temperature affects their solubility, which in turn translates to a change in their colour.

We are trying to take the thermometer that your parents use when you are sick to measure your body temperature and shrink it using science to the point that you cannot see it anymore with your own eyes. When it becomes really tiny, we use it to measure the temperature of one of the smallest parts of your body. This is important because when we understand what is happening inside those tiny parts of your body, we can develop good medication that can make you get better faster.

Working in a country with limited resources, like Lebanon, makes it challenging at many levels. We are lucky to be at the American University of Beirut, which makes every conceivable effort to make it easier for us. However, supplies take a considerable amount of time to be shipped, so often we need to be creative, using or modifying whatever we can get our hands on.

It still amazes me to know that people think a molecule that is synthetically produced in a lab is not identical, or is even of lesser value, than the same molecule that is produced ‘naturally’.

Just like many discoveries, developing the nano-thermometer was a pure coincidence. One afternoon, while performing an experiment, I made a random observation that did not mean much at that time. Later that night - like every night - I was analyzing my data in my head and planning for the next day, while dozing into a deep sleep. This is when I recalled reading a manuscript, a few weeks earlier, about an innovative way to measure temperature in solution. I somehow connected the results that I had obtained that day to the published work, and I speculated that what I had might be able to report temperature changes. Excited, I dressed and went to my lab and tried the experiment that night. It was a great success from the first go. Funnily enough, the ratio that I first used turned out to be the optimal one.