Could a machine for detecting molecules in space be used to identify bacteria that cause stomach ulcers? This is the question that Dr Geraint ‘Taff’ Morgan and his colleagues, Professors Ejaz Huq and Phil Prewett, from Oxford MicroMedical Ltd are trying to solve.
Their work centres on the study of stable isotopes, which are different forms of an atom that have varying amount of neutrons and protons in their nuclei. The majority of elements exist in multiple forms – for example, an oxygen atom can naturally occur with 16, 17 or 18 protons and neutrons within its nucleus and is denoted as 16O, 17O and 18O respectively. The isotopes of higher numbers are heavier and behave in a slightly different manner to their lighter counterparts.
Isotopes vary in their abundance across the world in predictable patterns. Most elements have one isotope that is most abundant – 99.7% of naturally occurring oxygen atoms are 16O, for instance. The way isotopes behave in nature is predictable and you can model the ratio of isotopes across the globe. This means that the isotope ratios can be measured, allowing assumptions to be made about a material’s geographic origins.
For example, by measuring the hydrogen and oxygen isotope composition of two different pieces of beef, you can determine if they came from cows of the same region. This property means that claims about where certain meats may come from in your supermarket can be backed up or refuted.
Isotope ratios are measured by machines called mass spectrometers (known by many scientists as ‘Mass Specs’). The European Space Agency’s Rosetta probe, which travelled for 10 years and over 6 billion kilometres to study the Churyumov–Gerasimenko comet, contained a mini mass spectrometer tucked away within its Philae lander, which was released and made contact with the comet in November 2014.
Taff and Ejaz were part of the team from The Open University and Rutherford Appleton Laboratory (RAL Space) that developed and built the mass spectrometers, which represented a significant design challenge. Mass spectrometers in research laboratories are frequently large and delicate objects, making fitting one into a spacecraft smaller than a shoebox a difficult puzzle to solve. Previous attempts to reduce their size have impacted on the accuracy and precision of the instruments, which would not do when measuring trace levels of molecules on a speeding comet in the far reaches of the solar system.
Taff and Ejaz helped the team strip off any unnecessary parts of the machine and produce mass spectrometers with the job of measuring the isotope ratio of the icy core of the comet. Unfortunately, the Philae lander bounced twice when making contact with the comet and ended up landing on its side, preventing the sample drill from making contact with the surface.
However, when the lander first struck the comet, the impact created a large enough dust cloud, allowing particles from the surface to be collected and analysed. The measurements taken indicated the presence of water, some carbon dioxide and a complex series of molecules made up of hydrogen, carbon, sulphur, oxygen and nitrogen. These results, which showed that the so-called ‘building blocks of life‘ are present on a comet, were published in the journal Science.
From their experiences working on the probe, Taff and Ejaz were able to transfer the concepts to other projects closer to home. One such application was in the field of medical microbiology. The team are using the technology to detect whether a patient is infected with the stomach ulcer-causing bacteria, Helicobacter pylori.
The current method used to determine H. pylori infection is the urea breath test (UBT). The UBT works by a patient swallowing a small amount of urea labelled with the carbon-13 isotope, which the H. pylori bacteria metabolise, releasing isotopically labelled carbon dioxide that can then be detected in the patient’s breath.
H. pylori bacteria live within the lining of our stomachs, protected from the immune system by the mucus lining of the stomach walls. It is understood that some stomach cancers are the result of prolonged infection with this bacteria. Risk of infection is increased by lack of hygiene and overcrowding, and there is a higher prevalence in low-income economies.
While the UBT is a great diagnostic tool for H. pylori infection, it is quite expensive and often unavailable to those in the regions that need it the most. Taff and colleagues have come up with a portable mass spectrometer that can detect the shift in isotope ratios in a patient’s breath for a fraction of the cost of the commercially available kits.
“In reality most people who need the commercial test, (mainly those in low-income countries) don’t have access to it as it is expensive,” Taff explains.
Initially funded by the European Space Agency Business Incubation Centre Harwell (ESA BIC) and more recently by Innovate UK, the machine that he and his team have developed is an affordable and portable device, approximately the size of a shoebox and manufactured at a price feasible to these areas.
Other applications that Taff is working on involve the monitoring of air quality in British submarines, detecting prostate cancer through a ‘sniff-test’ method, investigating the chemical signatures that bedbugs release in hotel rooms, and working with the world’s largest perfume company to help them optimise their products in Paris.
Isotope analysis has many applications and implications across many fields of research. The techniques and machines involved are allowing for many previously unknown questions and problems to be solved, with the transfer of space technology and know-how actively being encouraged by ESA, the UK Space Agency and the Science and Technology Facilities Council.