**5. Conclusions**

We reported the development of Fluc-based PCA using purified probes for the first time. However, the stabilities of the probes were low due to the split forms. The problem might be overcome by using another enzyme with a highly stable structure.

Furthermore, we developed a unique PPI assay, called FlimPIA, wherein the catalytic reaction of Fluc is divided into two half-reactions. FlimPIA has several advantages, especially in vitro. Our next challenge is to improve the response in cellulo.
