A Golgi-Targeting And Dual Color "Turn-On" Probe For Spatially Precise Imaging Of Furin

Cancer is one of the leading causes of death worldwide.Early diagnosis of cancer is important for reducing the mortality rate of cancer.In clinic,existing methods for cancer diagnosis mainly rely on the morphological analysis of tissues(histopathology),cells(cytology),or detection of cancer-related biomarkers(e.g.,enzymes,proteins,or metabolites associating with the stages of cancer).However,at early stage of cancer,low abundance of these examination indicators challenges the accuracy and reliability of cancer detection.Therefore,it is of great urgency and interest to develop new methods to improve the detection accuracy for the early cancer diagnosis.Among the methods abovementioned,measuring the levels of cancer-related biomarkers is one promising approach for the early diagnosis of cancer.Furin,known as a tumor-overexpressing protein convertase mainly located in the trans-Golgi apparatus,can serve as an essential indicator for distinguishing tumor cells from normal cells.Furin imaging could be used intuitively for the early detection of cancer.In the past decade,several imaging modalities have been used for furin imaging(or detection),including positron emission tomography(PET),magnetic resonance imaging(MRI),and molecular fluorescence imaging.Among these imaging modals,molecular fluorescence imaging is advantageous in furin detection due to its high resolution,high selectivity,simple apparatus,and noninvasive capabilities.The reported fluorescence probes for furin detection commonly used the Arg-Val-Arg-Arg(RVRR)peptide sequence as the specific substrate for furin cleavage.Although these probes are able to roughly indicate the location of furin(i.e.,Golgi apparatus)by using their high affinity to furin and fluorescence "Turn-On",they are not equipped with another organelle-targeting warhead for additionally precise furin imaging.Moreover,previous works usually used merely monochromatic fluorescence for furin detection.Herein,we report a Golgi-targeting and dual color"Turn-On" probe Q-RVRR-DCM for imaging furin with high spatial precision.By integrating the principles of Forster resonance energy transfer and intramolecular charge transfer,the probe was designed non-fluorescent.Upon furin cleavage,Q-RVRR-DCM was converted into Q-RVRR and DCM-NH2,turning the dual fluorescence color "On" at 420 and 640 nm without spectral crosstalk.In furin-overexpressing HCT-116 cells,Q-RVRR-DCM showed not only furin-specific,dual color "Turn-On" fluorescence but also superior co-localization with Golgi tracker than that single color "Turn-On" probe RVRR-DCM.We envision that,with the excellent properties of Golgi-targeting and dual fluorescence color "Turn-On",our furin probe Q-RVRR-DCM could be applied for accurate early diagnosis of cancer in the near future.