Chemiluminescence (CL) is an advantageous detection tool for in vivo imaging because of the high signal-to-noise ratio of its optical-signal readout, which does not require an external excitation source. Conjugated polymers (CPs) are now used as an energy acceptor in CL nanoparticles to enhance the CL. Here, we demonstrate CL from the direct oxidation of CP backbones in conjugated-polymer nanoparticles (CPNs) by hypochlorite. Such CL CPNs completely avoid the involvement of small-molecule CL donors. The strategy greatly simplifies CL-probes preparation and increases the stability of CL nanoprobes by overcoming the leakage problem of CL donors in nanoparticles. Hypochlorite can oxidize the vinylene bond (CC) in polyfluorene-vinylene (PFV)/polyphenylenevinylene (PPV) via π 2 −π 2 cycloaddition to form a PFV-or PPVdioxetane intermediate that is unstable and can spontaneously degrade into PFV-or PPV-aldehyde and generate photons. The dioxetane-intermediate formation was confirmed by UV−vis-absorption, fluorescence, nuclear-magnetic-resonance ( 1 H NMR), and Fourier-transform infrared (FT-IR) spectroscopy. The CL quantum yield (QY) of the brightest CL probe, -9H-fluorene-2,7-vinylene)-co-(1-methoxy-4-(2-ethylhexyloxy)-2,5-phenylenevinylene)] (90:10 mol ratio, CPN-PFV-co-MEHPV), was 17.79 einsteins/mol (namely, photons per particle). CPN-PFV-co-MEHPV was size-stable, noncytotoxic, selective, and sensitive for hypochlorite detection. The linear range and the LOD of CPN-PFV-co-MEHPV for ClO − detection are 2−30 and 0.47 μM. Thus, CPN-PFV-co-MEHPV was successfully applied for in vivo imaging of endogenously produced ClO − in living animals. We expect that the represented strategy could be extended to construct other CL nanoprobes for bioimaging and disease diagnosis by simply optimizing and transforming CP backbones; such CL CPNs will have a profound impact on the field of bioimaging.

A simple, sensitive, and biological safety POCL–GOx–alginate/Ca gel system to detect and image local concentration of glucose in tumor periphery.

The abnormally expressed peptidases in human tissues are associated with many kinds of cancers. Monitoring of endogenous peptidase activity could allow us for pathophysiology elucidation and early clinical diagnosis. Herein, we developed a general strategy for bioluminescence (BL) sensing of peptidase activity in vivo based on tumor-targeting probiotics. The probiotic that harbored a luciferase-encoding plasmid was used to target and colonize tumor and provide luciferase for BL imaging. The peptide-based probes Lc and GPc were applied to track leucine aminopeptidase (LAP) and dipeptidyl peptidase IV (DPPIV) activity, respectively, by simply adding l-leucine and Gly-Pro dipeptides at the N-terminus of d-cysteine, which were specifically controlled by peptidase cleavage and released free d-cysteine to conduct a subsequent click condensation reaction with 2-cyano-6-hydroxybenzothiazole (HCBT) to produce firefly luciferin in situ, giving rise to a strong BL signal. Neither gene modification of cells of interest nor complicated synthesis was required in this BL system. Encouraged by these advantages, we successfully used our probes to monitor LAP and DPPIV activities in vitro and in vivo, respectively. A good linearity between BL and peptidase was obtained in the concentration range of 2.5–40.0 mU/mL with a limit of detection (LOD) of 1.1 mU/mL (55 ng/mL) for LAP and 2.0–40.0 mU/mL with a LOD of 0.78 mU/mL (1.15 ng/mL) for DPPIV, respectively. Additionally, approximately 5-fold (LAP) and 10-fold (DPPIV) differences in the BL signal before and after treatment with a specific inhibitor were also obtained for in vivo BL imaging. All these results reflected the potential application value of our probes in BL sensing of peptidase activity. We envision that our strategy may be a useful approach for monitoring a wide range of peptidases in tumors, especially in primary tumors.

Hypochlorite acid (ClO-) is one of the major reactive oxygen species (ROS) in colon cancer providing an effective target for the colonic tumor in vivo imaging. For detection of ClO-...