In-Situ Imaging of Azoreductase Activity in the Acute and Chronic Ulcerative Colitis Mice by a Near-Infrared Fluorescent Probe.

Azoreductase (AzoR) is an essential reductive enzyme which is closely associated with the intestinal disease such as ulcerative colitis (UC). To date, only a few fluorescent probes for detecting AzoR activity in bacteria or cells have been constructed successfully. It is still challenging to design fluorescent probes for in situ monitoring AzoR in vivo. In this paper, a near-infrared (NIR) fluorescent probe (Cy-Azo) based on hemicyanine is designed and synthesized. The emission of the probe is located at 735 nm in the NIR region, which is favorable for its application in vivo. In addition, Cy-Azo shows high sensitivity to AzoR activity with 17-fold fluorescence enhancement and is particularly selective to AzoR over other enzymes, ions, and amino acids. Meanwhile, a possible response mechanism (the azo group in Cy-Azo is reduced by AzoR and cleaved resulting in the production of Cy-NH2) was proposed and verified by HPLC, MS, and theory calculation. In addition, based on low cell cytotoxicity, Cy-Azo is successfully applied in visualizing the activity of AzoR in two cell lines (HCT116 and HepG2 cells) and three types of bacteria (E. coli, S. aureus, and P. aeruginosa). In particular, due to its NIR emission, the probe can monitor AzoR activity in acute and chronic UC mice models. To our knowledge this is the first fluorescent probe for detecting AzoR activity in vivo, which can provide much important information for the diagnosis and treatment of UC.

A rhodamine-deoxylactam based fluorescent probe for fast and selective detection of nitric oxide in living cells.

Nitric oxide (NO) plays vital roles in many physiological process and is closely related to many diseases. So far, a number of fluorescent probes have been constructed for the detection of NO successfully. However, the probes still suffer from long-time reaction and limited selectivity. Herein, a fluorescent probe named dRB-OPD is synthesized and used to recognize NO. The probe contains a deoxy-rhodamine B as fluorophore and o-phenylenediamino as reaction site. dRB-OPD shows fast response to NO within 40 s with 170-fold fluorescence enhancement. Moreover, the probe shows high selectivity towards NO over dehydroascorbic acid (DHA), ascorbic acid (AA), and methylglyoxal (MGO). Particularly, the probe can avoid the serious interference from cysteine (Cys) found in the rhodamine lactam-based fluorescent NO probes (RB-OPD). In addition, the probe is applied for the detection of exogenous and endogenous NO in the HepG2 and RAW 264.7 cells with satisfactory results.

A ratiometric fluorescent probe for peroxynitrite prepared by de novo synthesis and its application in assessing the mitochondrial oxidative stress status in cells and in vivo.

A ratiometric fluorescent probe Cy-NEt2 for detecting ONOO- is designed and prepared by de novo synthesis, which is a reliable, cheap and flexible route. The probe is applied for monitoring the level of mitochondrial ONOO- and assessing the lipopolysaccharide (LPS)-induced mitochondrial oxidative stress status in living cells and in vivo successfully.