Researchers have developed low-cost, biodegradable biosensors for global health applications in resource-limited settings.

The biosensors, called AL-PHA beads, have been designed to recognise specific proteases – enzymes that play complex roles in human health and disease. By detecting the activities of different proteases, researchers can gain important insights into a broad range of diseases.  

The beads are made from PHAs, a family of microbially produced biopolymers that are biodegradable and can potentially be used as more environmentally friendly plastics. In recent years, researchers have developed new methods to engineer PHAs for a number of different industrial and biomedical applications, including enzyme production, diagnostics, vaccines and tissue engineering.

The new findings published in Materials Today describe for the first time how specially engineered PHA beads can be used as protease biosensors for global health applications in resource-limited settings.

Detecting schistosomiasis

In their proof-of-concept study, the team, led by researchers at Imperial’s Section of Structural and Synthetic Biology, developed a library of over 20 AL-PHA beads to detect important global health proteases. The fluorescent biosensors include fusion proteins which are designed to only be recognised by specific disease-associated proteases. When this happens, the beads lose their fluorescence, which can in turn be measured by researchers.

The team and collaborators set out to first investigate whether the AL-PHA beads could detect Schistosoma mansoni – a water-borne parasite and one of the principal causative agents of the neglected tropical disease schistosomiasis. Current estimates suggest that 779 million people are at risk of infection, leading to an annual mortality upwards of 280,000 people in sub-Saharan Africa alone. The work was undertaken as part of the Water Infrastructure for Schistosomiasis-Endemic Regions (WISER) project, which is funded by the UK Government's Global Challenges Research Fund (GCRF) through the Engineering and Physical Sciences Research Council (EPSRC).

Using S. mansoni derived samples containing soluble cercarial antigens, the biosensors were able to successfully detect protease activity specific to the organism that causes schistosomiasis in humans. 

Professor Michael Templeton, Principal Investigator of WISER, commented: “With further development, we believe that the beads could potentially detect the organism in water samples. This would be a game-changer for being able to assess the infection risk associated with individual water bodies (e.g. lakes, rivers) and allow us to monitor the effects of schistosomiasis prevention strategies on this risk.”  

Cancer clues

The team, with support from the Cancer Research UK Imperial Centre also engineered AL-PHA beads to recognise different types of cancer-associated protease activity. The beads successfully recognised metalloproteinases including MMPs, ADAMs and ADAMTSs, suggesting that they could be used to support cancer diagnostics and extracellular vesicle (EV) research.

Joint first author Dr Richard Kelwick explains: “Cancer cells produce many different kinds of proteases that can sometimes promote tumour growth and spread (metastasis).”

“Detecting the activities of cancer-associated proteases, including metalloproteinases, can lead to important insights into cancer biology that might, in the future, lead to new approaches for early-stage cancer detection in patients.”

Advancing applications of PHAs

The current study represents the latest exciting advance in PHA beads technology. It builds on the groundbreaking work of Professor Alexander Steinbüchel and colleagues who, in 1995, were the first to demonstrate that phasins could be used to display fusion proteins on the surface of PHAs beads. More recently, Professor Bernd Rehm, Professor George Guo-Qiang Chen and other researchers have also extended functionalised PHAs applications.

Commenting on the wider context of the research, Professor Paul Freemont said: “While PHA beads technology was first developed over 20 years ago, we are really excited to have extended its application into potential global healthcare applications.”

“The use of synthetic biology to design new biosensors for resource-poor environments is a fantastic endeavour and I am confident that some of these approaches will make a real-world difference.”

Next steps

The researchers are now hoping to build on the proof-of-concept findings and further develop their low-cost, biodegradable biosensors by improving the fusion protein designs. They will also look to test the beads against a wider range of samples to ensure greater accuracy.

Commenting on the wider implications of the research, Dr Kelwick added: “We envision that, with further development, AL-PHA beads could be used as a platform for implementation as low-cost global health protease biosensors for use in resource-limited settings.”

“We also humbly suggest that our research might inspire others to develop their own AL-PHA biosensors, or other kinds of PHAs-based biotechnologies, for global health applications.”

‘AL-PHA beads: Bioplastic-based protease biosensors for global health applications’ by Richard J.R. Kelwick, Alexander J. Webb, Yizhou Wang, Amelie Heliot, Fiona Allan, Aidan M. Emery, Michael R. Templeton and Paul S. Freemont is published in Materials Today

This research has been supported by The Cancer Research UK Imperial Centre Development Fund, BBSRC, EPSRC, Imperial’s Confidence in Concept programme as well as the UKRI Global Challenges Research Fund through their support for the WISER project