I hope you are all doing well. I’m writing from Belfast after having all the ESRs in here last week for the 3rd Summer School. It was really nice to have you all here to discuss about our projects and check everyone else’s progress in the project. Not only that, but we also had the chance to learn more about software development with the talks programmed for the week. Many topics were discussed: security in the cloud, programming, smartphone app development, business entrepreneurship… So I would like to thank everyone involved in the organization for the great job, especially Karen. I really enjoyed learning how to design an app using Thunkable, a user-friendly platform that would allow you to program simple operations in a smartphone app.
On Wednesday I had the chance to discuss a bit deeper about my specific project in front of everyone else in the FoodSmartphone consortium, in an amazing scenario in Bushmills.
As you might already know from previous blogs, I am working in the development of an assay that would permit to detect Mycobacterium bovis in dairy samples. This is something really important to reduce the cases of zoonotic tuberculosis in the EU. Despite a strict regulation being applied with regards to this matter, more than 1000 new cases of zoonotic tuberculosis happened in the EU in 2016 according to the WHO. These are mainly caused by consumption of raw milk that has been contaminated with the bacteria. The main reason why this still happens is because the only tests being run nowadays are practiced in the animals, but not in the finished food product. Since the tuberculin tests are only run once a year in the animal, there is a big chance that the bacteria reaches the commercial raw milk in the event of a cow getting infected. Plus, numerous wildlife animals carry the disease and can pass it to the herd, such as badgers in the UK. This is a huge problem, as controlling the disease in wildlife animals is not as simple as doing so in farm animals.
Considering the severity of the disease caused by this bacteria in humans, there is no wonder why developing a food test is required. To do that, an immunochemical assay is planned, using gold nanoparticles as signal generators instead of commonly used enzymatic assays. Before trying the immunochemical approach, a PCR-based approach was explored, but many issues were observed regarding the background noise. This is why using antibodies as biorecognition elements has been chosen as the technique to work with. This approach allows to detect less than 10000 cfu/ml in buffered solutions, which is within the EU regulatory limits (less than 20000 cfu/ml total count in plate). Now the idea is trying to enhance the signal as much as possible using the properties of gold nanomaterials, which as I might have explain before possess very interesting properties related to the plasmonic effect.
Especial attention must be paid at the validation process: as important as developing an analytical assay is to validate it and make sure it works in field conditions. For the most basic validation process (single laboratory validation study), both inclusivity and exclusivity tests must be run. That means testing different positive samples (50 if available) and non-target samples (30 if possible). This will guarantee that no false negatives or false positives are obtained in this test. Finally, a reference method must be used too, this way one can ensure that the samples that are being tested are exactly as expected. Culture-based methods are usually chosen as reference for this kind of contaminants, resulting in a pure isolate. However, Mycobacterium bovis is a dangerous pathogen that needs to be inactivated by gamma-irradiation if one wants to work with it in the lab in a safe manner. This process damages the genomic structure of the bacteria, keeping the epitopes and surface structures unaltered. Thus, the bacteria will no longer grow, which means it is safe to use, but at the same time culture-based methods won’t be a possible choice as reference. This is why PCR is chosen as reference method for this kind of assay.
Of course there are still a few things to optimize before moving to the validation step, but it is interesting to keep all these steps in mind to know at what stage of the biosensor development we currently are.
I will keep you up to date! Hopefully this project will lead to smartphones being used to test how safe our food is!
Enjoy the coming of the summer! J
See you soon,