A major barrier towards achieving affordability of diagnostic systems for low-resource settings is the lack of purchasing price parity between the countries where tests are manufactured and those where the tests are needed. Synthetic biology can be used to circumvent the classical manufacturing chain by enabling a complete production pathway
amenable to in-country manufacture for the most expensive portion of the test - the functional protein.
Fusion proteins have been designed for this purpose with 3 core elements: 1) the central assay protein (e.g. enzyme, binding protein or peptide); 2) a visualising protein (e.g. fluorescent protein) to facilitate visual monitoring of the production and isolation without requiring a laboratory infrastructure; 3) an affinity peptide which is fundamental to effective interfacing between the biological component and the transduction system in the diagnostic and plays a key role in simplifying isolation and purification. These affinity peptides can be designed for affordable and abundant material such as silica or paper.
The fusion proteins can then be used directly in the diagnostic assay, enabling the detection of both small molecule and nucleic acid analytes. With the continued challenge of infectious diseases and the rising rates of non-communicable diseases in the Global South, a system that is applicable across a range of analytes will be critical to changing the paradigm of diagnostic testing in low-resource settings.