FAP and keloid: More recently, Pu et al. developed another NIRprobe (FNP1) for imaging FAPα activity in fibrotic keloid cells.59 The probe was comprised of a hemicyanine dyeconjugated to the peptide substrate Cbz-Gly-Pro via a self-immolativePABA linker, which rendered the probe silent until FAPα cleavedthe bond between the PABA linker and the proline residue to releasethe hemicyanine scaffold with a 45-fold fluorescence increase at 710nm.