Silver Criterion Human Practices

Choosing a diagnostic track

Attending a Royal Society conference ('Synthetic Biology: Does industry get it?') at the start of our project highlighted the diversity of synthetic biology applications. However, we were particularly excited by the medical applications. We reviewed the conference for our general university newspaper to explain synthetic biology, through examples, to a non-science specialist readership. You can read the article here. Understanding of the current medical applications of synthetic biology guided our initial diagnostics track choice, which was corroborated by the results of our initial survey of the public, where more than half of the 200 surveyed wanted a synthetic biology solution for disease diagnosis.

Image 1: The team at the Royal Society conference in London

Dialogue with experts, stakeholders and industry informed our decision to focus on acute congenital Chagas disease

Further research led us to neglected tropical diseases (NTDs) because this is where we felt our diagnostic would have most impact (FINDdx, 2015). Chagas disease was chosen after identification of the cruzipain protease as a potential unexplored disease biomarker. Many other parasitic diseases use specific proteases in their infection mechanism giving scope for the development of an adaptable modular diagnostic device with common input and output modules by variable cleavage sequence.

After communication with experts researching the use of cruzipain as a drug target we realised that there was some difficulty in quantifying a cruzipain blood concentration, due to variable parasite concentration (Emilio Malchiodi, personal communication). This made it difficult to ascertain our expected output through modelling. In response to this we designed a split protease based amplification system to increase sensitivity of our detector circuitry.

A PLOS analysis (Albert Picado, 2017) identified a point of care test for congenital Chagas disease as the number one need in Latin America and a priority for the world health organisation and Ministry of Health. However this disease still seemed to be a lower priority for researchers, so we therefore decided to tailor our design to a congenital diagnostic to meet this unmet need (Table 1). Currently there is a 10 month wait for children born to infected mothers for diagnosis. This causes the child to miss the critical window for detection, when parasite concentrations are highest a few weeks after birth (this occurs due to the unsuitability of antibody based rapid diagnostic tests and lack of medical infrastructure (PATH, 2016)).

Problem	Our Solution
Lack of medical infrastructure in the worst affected areas compromises follow up and results distribution	A rapid point of care test, optimised through modelling
Antibody based tests cannot be used due to presence of maternal antibodies	A non-antibody based test
Blood smear analysis requires training, and PCR tests require specialised equipment	A simple test that does not require specialised equipment or training, using blood clotting as an easily visible output

Table 1: Evaluation of key problems producing demand for a congenital diagnostic and how our kit seeks to solve these

Surveys to Latin American Teams

3 Latin American teams (AQA_Unesp, Amazonas, and TEC CEM) kindly translated and distributed a survey that we created to help us understand public perception and acceptance of our diagnostic kit design, in areas that it would be used. This was very important to us as the healthcare system in these areas is not the same as in the UK, and so it was necessary to gain the insight of locals in order to make sure our solution was relevant and could be applied to our target users. Our consultations with HeLEX highlighted how key an understanding of the infrastructure and culture of the affected areas is, in making a successful product.

441 people were surveyed in total, and these results informed our decisions to develop a test to be carried out in a medical facility rather than a home test (Figure 1). 28% and 14% of those surveyed were uncomfortable with use of bacteria living in and being used in production of our device, therefore synthetic biology is an acceptable approach.