Ghana generates over 3000 tons of plastic waste daily, with an estimated 250,000 tons of plastic waste generated dumped into the Atlantic Ocean annually (3).

Ghana’s water bodies contain levels of heavy metals such as cadmium, mercury and lead 400, 180, and 15 times over the WHO limit (2).

We wanted to create a cell-free biosensor to combine with our bioremediation device to provide a way to quickly detect the target metals cadmium, lead, arsenic or mercury (commonly detected heavy metals in Ghana’s River waters). These biosensors are transcription-only which minimises the device’s necessary components effectively increasing usability and also reducing cost.

Through a literature search, we found the target protein metallothioneins which are metal-chelating proteins. We synthesised and then extracted the metallothioneins, these proteins were then immobilised into a cellulose hydrogel to create our cell-free bioremediation device. The hydrogel is able to take in water which allows the metallothioneins to chelate the toxic heavy metals out of the water and keep them in the hydrogel.

We used mutated varieties of the PETase enzyme which can break down and covert polyethylene terephthalate (PET) plastic into more usable monohydroxyethyl terephthalate (MHET). These were synthesised these enzymes and then immobilised onto silica beads. These beads could then be placed in water to break down PET.