Coexistence and collaboration: engineering encapsulation for whole-cell biosensors

The emerging field of biosensors exploits the abilities of cells to identify specific molecules, presenting improved sensitivity, specificity, and limit of detection. Whole-cell biosensors (WCB) are organisms specifically engineered to detect a target analyte and express a reporter in response. In biomanufacturing, they can be used for monitoring of key substrate and metabolite concentrations or strain engineering, while in medicine, they can be used to diagnose disease or report on human-microbe interactions. Many applications require WCB to coexist with mammalian cells where a key challenge is to keep separate cell populations viable while still allowing them to interact. In this review, we highlight key considerations when encapsulating WCB to engineer controlled microenvironments that enable collaboration and coexistence of different populations.