By Oli Usher, on 3 July 2014
“I joined UCL in 1998. I remember saying in the job interview, ‘in two years, I’ll achieve electrochemistry in the gas phase’. Fifteen years later I think I might have achieved it,” says Daren Caruana, a UCL Chemist.
“On the bright side, though, I still have my job.”
Electrochemistry is the study and manipulation of matter based on the behaviour of its electrons. It covers a huge range of phenomena, from electroplating cutlery with silver to glucose testing of blood samples for people with diabetes. Electrochemistry needs to be done in an electrically conductive liquid, which brings with it complications – it means the sample isn’t clean, and the solvent can often be toxic or corrosive.
There is, however, no reason why the same type of chemistry cannot be done within a gas, which would eliminate many of these problems.
But the gas has to be electrically conducting, which rules out air.
Fortunately – as anyone who remembers high school chemistry should remember – flames conduct electricity.
Unfortunately for Caruana, turning theory into practice when it involves flammable gases is not entirely straightforward. Hence his plans falling a little behind schedule.
One early experiment using hydrogen gas exploded, showering the entire room with shards of glass – except for his research assistant who was standing right next to the equipment. (The assistant, a devout Catholic, wrote to the Pope to report this possible miracle. Caruana served a term as deputy Departmental Safety Officer as penance.)
After years of finessing the technique of electrochemistry in flames, Caruana’s current project is to use it to test people with tuberculosis.
When infected with the disease, some people are highly contagious as they breathe out a constant stream of bacteria, while others are not. Currently the only way to test this is to make them breathe on agar, and wait and see if any bacteria reproduce. But his plan is to build a relatively cheap electrochemical device that will give a near-instant diagnosis.
In his lab, Caruana has a prototype (built entirely in-house by Dr Matt Li), a Heath Robinson-esque contraption of Perspex, screws, circuit boards and a great deal of Blu-Tack. But in time this should be possible to shrink down to the size of a desktop computer.
In the device, the patient’s breath is blown in a narrow stream through the flame, and one-by-one, the bacteria are incinerated. Different types of bacteria have different properties which can be clearly detected by the electrical properties they display as they pass through the flame, either because they have a different chemical makeup or different physical properties. For instance, Mycobacterium tuberculosis, the pathogen that causes TB, has a tough outer shell. This means that it visibly pops in a tiny explosion when it passes through the flame.
For safety reasons the current tests with the equipment are concentrating on non-infectious bacteria with similar properties to TB. But, in partnership with Prof Ibrahim Abubakar, Prof Timothy McHugh and Dr Marc Lipman from the Royal Free Hospital and UCL Business he hopes to continue the development, including tests on live TB bacteria. The aim is to have a commercial device ready to roll out to health centres around the country in the next three to five years.