Fabrication of bioluminescent capsules and live-cell imaging

The plasma membrane of living cells is an interface of material transfers and an antenna for outer signals. This chapter provides a guide on how to fabricate bioluminescent capsules for illuminating intracellular signaling and cargo protein delivery. The capsule consists of four components, which are, in consecutive order: a secretion peptide (SP), a host luciferase body (leader), a guest protein or peptide (cargo), and a membrane localization signal (MLS). Any guest protein, including a luciferase or a fluorescent protein, may be sandwiched between the host luciferase body and MLS and may be deliverable to the plasma membrane (PM), where the capsule waits for outer signals and to quickly release the embedded luciferase in response to a specific signal. The present strategy provides an efficient molecular vehicle for cargo proteins and imaging of intracellular molecular events in living cells without substrate-derived demerits of luciferases.