British invention leads the world in explosive trace detection

selective antibodiesUntil now the accurate detection of small molecules of explosive material or other contraband chemicals has been extremely difficult. However, all that looks set to change thanks to the expertise of the team at Selective Antibodies, led by its Managing Director, Professor Colin Self.

It was through his role as the head of a large NHS department of clinical biochemistry that Professor Self realised there was a need for more accurate testing solutions.

“Through my role with the Department of Clinical Biochemistry the critical importance of rapid, accurate and robust diagnostic testing systems was very clear to me,” he said. “This led to a desire to improve the systems that were available. Through this came the development of the positive selective antibody dipstick systems. Its application into many sectors within and outside of medicine, including the very important one of security – where rapid and unambiguous results were needed – was clear.”

The professor’s previous diagnostic work had been responsible for one of the first profitable biotechnology companies to come out of Cambridge, and Self said he saw the need for rapid high performance tests for a class of substances that existing systems had difficulty with – the small molecule.

“The very large group of compounds includes medicaments, drugs of abuse, hormones, toxins, CBRNe agents of critical importance in the human and veterinary clinical areas, the food and drink sectors, environmental control as well as the forensic and security sectors. So small molecules are worth the focus. Selective Antibodies Ltd is aimed at this area – with the focus on providing the most user friendly, rapid testing systems possible,” said Self.

He points out that there was a need to develop molecule detection technology, as existing systems weren’t good enough. Self felt that the most convenient system for the detection of small molecules would be a dipstick system. Through this system, substances to be tested could be captured and detected by antibodies – an application of an existing idea from another type of test.

Self said, “The pregnancy test is a wonderful example of the power and simplicity of the approach, offering a standard of analysis unobtainable in even the most sophisticated laboratories within the lifetime of many practising doctors. The problem was that this level of convenience was not readily available for small molecule detection. It has been the aim of Selective Antibodies Ltd to change that.”

Dipstick systems for pregnancy testing are very well established and offer high quality of result, Self explained, with the advantage that they show up as a line on a blank background to indicate a positive result. Previously, this has been difficult to achieve for small molecular weight substances such as explosives. The professor said that instead, negative systems had been used, meaning a disappearing line was indicative of a positive result.

The Selective Antibody technology has been developed to reverse this, so that the positive presence of the small molecular weight explosive is seen as a positive line – just like a pregnancy test.  This brings a number of advantages, according to Self, not least the fact that the tests are intuitive – more explosive results in more of a red line. It’s as if the explosive is actually being seen on the stick.

So, how does it work?

“The use of the dipstick is very simple indeed,” said Self. “In its simplest form, a stick is taken and placed into the sample to be tested. If positive, a red line is seen to rapidly appear in the test zone.  This may be read by eye for ‘yes/no’ for a semi-quantitative measurement, or by means of a simple hand-held reader if quantification, documentation, storage or data transference is required down to parts per billion levels. The technology is simply in the stick.”

He explained how it works: “The test zone on the stick is formed by a secondary antibody that can bind to a primary antibody that can itself bind to the explosive. As the primary antibody is attached to red gold particles, binding of the primary antibody in the test zone results in a clear red line. If explosive is present the primary and secondary antibodies bind, giving the line. In the absence of explosive the unbound primary antibody binds to a blocking substance that prevents its subsequent binding to the secondary antibody in the test line.  Simply put, if explosive is present a line is seen, if explosive is absent no line is seen.”

There is a wide range of real-world applications for this technology:

  • Rapid positive detection of explosives and CBRN agents
  • Detection of therapeutic and illicit drugs
  • Detection of hormones and other biomarkers of use in human and veterinary medicine
  • Environmental testing
  • Rapid testing of food and drink
  • Authentication testing

Due to the simplicity of the technology, the devices can be used by a range of skilled, semi-skilled and even unskilled workers, including first responders, forensic scientists, law enforcement officers, quality assurance personnel, human and veterinary staff and even private individuals who may use one of the tests at home.

Selective Antibodies has been able to develop its unique product thanks to funding from competitive programmes such as LINK Awards, Governmental contracts and EU programmes. This new excellent product for explosive testing has come as a result of a competitive three-year European Framework VII Security programme programme of €4.4m that  Selective Antibodies recently completed.

So, what can we expect next from the professor and the team at Selective Antibodies?

Self said, “The future for Selective Antibodies Ltd is now firmly rooted in the development of rapid, easy to use and understand diagnostic testing areas, with the team at Selective Antibodies seeing food security as a major opportunity for this rapid testing capability.” Another real opportunity that stands out is roadside testing for drugs of abuse by the police giving the potential for the first time for an arrest-able offence to be proven.


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