Figure 2: Schistosoma biosensor work-flow.

S. mansoni cercariae are shed from infected snails and mechanically-transformed to produce S. mansoni cercarial transformation fluid (SmCTF) samples, which were lyophilised. Whole-cell biosensors are treated with either reconstituted SmCTF biological samples or a control protease from a commercially sourced panel. Whole-cell biosensors are washed and labelled. Labelled cells are analysed via flow cytometry. Proteolytic cleavage of the biosensor via the activity of SmCTF-derived cercarial elastase prevents cell labelling, thus resulting in a ‘loss of colour’ biosensor output (+detection of S. mansoni). Labelled cells indicate that the biosensor was not proteolytically cleaved thus resulting in a ‘gain of colour’ biosensor output (−detection of S. mansoni).