Enzyme biomarker test could detect disease and infection

What is it about?

Proteases, a type of enzyme, play a range of important roles in humans and living microorganisms. The involvement of proteases in all life functions has highlighted their crucial role in the progression of many diseases and in microorganism growth. For example, protease can be found highly elevated in the urine of patients with diabetic kidney disease, or at the sites of infected wounds. Similarly in animals, an elevation of proteases can reveal diseases, i.e. increased protease activity in cow milk can be an indication of bovine mastitis caused by microorganisms such as Staphylococcus aureus and Streptococcus ubris. In food, proteases produced by bacteria contaminated in meat and dairy products can led to rancidity, and decreased shelf life and quality. Current protease detection methods are costly, time-consuming and are not always effective. In this work, Dr Cao and his team have developed a gold nanoparticles-based nanosensor which has resulted in sensitive, fast and cost effective protease detection in milk and urine. The developed approach offers a cheaper and faster alternative to the tests currently used for protease detection in milk and urine. The test is based on a chemical reaction that causes a change of colour where proteases are present. It is well known that gold nanoparticles can speed up an oxidization of tetramethylbenzidine (TMB) to generate an oxidised blue-coloured product. However, the team found that when gold nanoparticles are covered with casein (a molecule present substantially in milk), the casein acts as a surface barrier whereby when TMB is added, the oxidization reaction is slow resulting in only a slight colour change. Where proteases are present, they ‘eat’ the casein resulting in a much faster reaction for the oxidization of TMB, causing a fast generation of blue colour.

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Why is it important?

Using this approach, proteases could be detected within 90 minutes without complicated or expensive read-out equipment. In addition, the ‘ingredients’ for making the nanosenor are readily available and cheap. Gold nanoparticles can be produced in abundance with little restriction on storage requirements making it a durable and cheap substance. Casein is also easily accessed, readily found in milk. Not only is the test cheap to produce, but it can be used anywhere and is not reliant on laboratory conditions. Eliminating the need to carry out tests in a laboratory setting is life-changing. As well as being cost-effective, it means faster diagnosis.

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