Genetically encoded red fluorescent copper(I) sensors for cellular copper(I) imaging.

•We develop a novel family of genetically encoded copper(I) sensors for in vivo usage.•The sensors’ optical response to copper(I) and other metal ions is characterized.•These sensors demonstrate a good sensitivity and specificity toward copper(I).•A series of proof-of-principle experiments is performed to prove the viability of these sensors in in vivo copper(I) imaging.