Enhancing the Contrast of Tumor Imaging for Image-Guided Surgery Using a Tumor-Targeting Probiotic with the Continuous Expression of a Biomarker

Abstract

Tumor recurrence commonly results from tumor-positive resection margins and metastatic lesions. The complete removal of tumor-positive margins is particularly essential in clinics. Thus, we designed a strategy based on Escherichia coli Nissle 1917 (EcN) nitroreductase (NTR) with a polyethylene glycol (PEG) polymer coating (PC-EcN-NTR) to specifically target and colonize in tumors for high-contrast tumor imaging by providing a large amount of NTR as biomarkers in situ. NTR is a favorable biomarker for tumor detection and imaging. The nfsB-encoding plasmid with a 16S promoter was transfected into EcN for the continuous and stable expression of NTR (E. coli. NfsB). PC-EcN-NTR can accumulate and proliferate for a long time in tumors to substantially express NTR. When the NTR-activated fluorescence (FL) probe was sprayed on the tumor, the tumor region showed fluorescence signals within 5 min. Compared to the tumor without colonization with bacteria, the PC-EcN-NTR-colonized tumors displayed 3.15× enhanced fluorescence signals. Furthermore, the fluorescence signals of the whole tumor can last at least 3 h, which is suitable for a long and meticulous surgical operation. More importantly, in the PC-EcN-NTR-harboring tumor, obvious FL appeared even at the very edge (approximately 200 μm away from the edge) of the tumor tissue. A TCF-Based near-infrared-II fluorescent probe (probe 2) was designed and synthesized. Results similar to those of probe 1 were observed when probe 2 was used for in vivo tumor imaging, which further proved the generality of the enhancing ability of the tumor-targeting probiotic. This strategy will hopefully guide the surgical resection of tumors via monitoring intense NTR activity. It may spur the use of tumor-targeting probiotic and enzyme-activated fluorescent probes for the processes of tumor diagnosis and image-guided surgery.

Engineered live bacteria as disease detection and diagnosis tools

“…Bacteria-enabled fluorescence imaging is a promising method for cancer detection and surgical resection, as tumor-selective fluorescent bacteria enable easy determination of tumor boundaries [ 206 ]. A strategy based on E. coli Nissle 1917 (EcN) nitroreductase (NTR) with a polyethylene glycol (PEG) polymer coating (PC-EcN-NTR) was developed to enhance in vivo fluorescence imaging of tumors and image-guided surgery [ 207 ]. E. coli was genetically engineered to constitutively overexpress NTR for fluorescence probe activation.…”

A Red-Emission Fluorescent Probe with Large Stokes Shift for Detection of Viscosity in Living Cells and Tumor-Bearing Mice

“…To date, a large number of viscosity-sensitive fluorescent probes based on cyanine, BODIPY, naphthylamine, porphyrin, and other fluorescent dyes have been reported [5]. Moreover, 2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5 dihydro-furan (TCF) as an excellent electron-absorbing fluorophore has attracted significant attention due to its good photostability and super-resolution imaging [27][28][29][30]. Although a variety of TCF-based fluorescent probes have been reported for biological imaging [31][32][33][34], to our knowledge, the study of TCF-based viscosity-sensitive probes is very limited [35][36][37].…”

Cancer-Associated Fibroblast Mimetic AIE Probe for Precision Imaging-Guided Full-Cycle Management of Ovarian Cancer Surgery

“…6−8 High-contrast imaging between tumor tissue and normal tissue is the basis for fluoroscopic surgical navigation. 9,10 The main contrast agents used to achieve high contrast imaging of tumor tissue include passively targeted fluorescent probes and actively targeted fluorescent probes. 11−15 In addition, reducing the nonspecific clearance of probes may also improve imaging quality.…”

“…Visual tracking of these tiny and hidden ovarian cancer lesions promises more precise removal of the lesions and less damage from surgery. Fluorescence imaging has the characteristics of real-time imaging, high sensitivity, nonradioactive, and high spatial resolution, which has a broad application prospect in the surgery navigation of tumors. – High-contrast imaging between tumor tissue and normal tissue is the basis for fluoroscopic surgical navigation. , The main contrast agents used to achieve high contrast imaging of tumor tissue include passively targeted fluorescent probes and actively targeted fluorescent probes. – In addition, reducing the nonspecific clearance of probes may also improve imaging quality. Probes modified with polyethylene glycol have good passive targeting and can also be given active targeting by modifying the targeting moiety, but they are rapidly cleared by the liver after sustained administration, a phenomenon known as “accelerated blood clearance”. , Fortunately, the advent of cell membrane coating technology can simultaneously confer active targeting, passive targeting, and reduced nonspecific clearance of probes. , Due to the natural negative charge property of cell membranes, the formation of protein crowns in the blood by the probe can be avoided, enabling long circulation and facilitating the passive targeting function. – Also, the cell membrane expresses specific proteins, such as CD47, which function to reduce the clearance of the substance by the immune system. , In addition, there are many active proteins on the cell membrane that act as ligands to specifically target receptor proteins that are highly expressed on cancer cells, thus enabling active targeting. , Therefore, cell membrane mimetic probes have great potential in the field of surgical navigation.…”