Heavy-atom engineered hypoxia-responsive probes for precisive photoacoustic imaging and cancer therapy

Photoacoustic agents combining photodynamic therapy(PDT) and photothermal therapy(PTT) functions have emerged as potent theranostic agents for combating cancer. The molecular approaches for enhancing the near-infrared(NIR)-absorption and maximizing non-radiative energy transfer are essential for effective photoacoustic imaging(PAI) and therapy applications. In addition, such molecules with high specificity and affinity to cancer cells are urgently needed, which would further decrease the side effect during treatments. In this study, we applied a heavy-atom engineering strategy and introduced p-aminophenol,-thio, and-seleno moieties into NIR heptamethine cyanine(Cy7) skeleton(Cy7-X-NH_(2), X = O, S, Se) to significantly increase photothermal conversion efficiency for PTT and promote intersystem crossing for PDT.Additionally, we designed a series of nitroreductase(NTR)-activated photoacoustic probes(Cy7-X-NO_(2),X = O, S, Se), and target hypoxic tumors with NTR overexpression. Our prostate cancer targeting probe,Cy7-Se-NO_(2)-KUE, exhibited specific tumor photoacoustic signals and effective tumor killing through outstanding synergistic PTT/PDT in vivo. These findings highlighted a versatile strategy for cancer photoacoustic diagnosis and enhanced phototherapy.

Membrane dual-targeting probes:A promising strategy for fluorescence-guided prostate cancer surgery and lymph node metastases detection

Fluorescence-guided surgery(FGS)with tumor-targeted imaging agents,particularly those using the near-infrared wavelength,has emerged as a real-time technique to highlight the tumor location and margins during a surgical procedure.For accurate visualization of prostate cancer(PCa)boundary and lymphatic metastasis,we developed a new approach involving an efficient self-quenched near-infrared fluorescence probe,Cy-KUE-OA,with dual PCa-membrane affinity.Cy-KUE-OA specifically targeted the prostate-specific membrane antigen(PSMA),anchored into the phospholipids of the cell membrane of PCa cells and consequently showed a strong Cy7-de-quenching effect.This dual–membrane-targeting probe allowed us to detect PSMA-expressing PCa cells both in vitro and in vivo and enabled clear visualization of the tumor boundary during fluorescence-guided laparoscopic surgery in PCa mouse models.Furthermore,the high PCa preference of Cy-KUE-OA was confirmed on surgically resected patient specimens of healthy tissues,PCa,and lymph node metastases.Taken together,our results serve as a bridge between preclinical and clinical research in FGS of PCa and lay a solid foundation for further clinical research.

A novel nitroreductase-enhanced MRI contrast agent and its potential application in bacterial imaging

Nitroreductases(NTRs) are known to be able to metabolize nitro-substituted compounds in the presence of reduced nicotinamide adenine dinucleotide(NADH) as an electron donor. NTRs are present in a wide range of bacterial genera and, to a lesser extent, in eukaryotes hypoxic tumour cells and tumorous tissues, which makes it an appropriate biomarker for an imaging target to detect the hypoxic status of cancer cells and potential bacterial infections. To evaluate the specific activation level of NTR, great efforts have been devoted to the development of fluorescent probes to detect NTR activities using fluorogenic methods to probe its behaviour in a cellular context; however, NTR-responsive MRI contrast agents are still by far underexplored. In this study, para-nitrobenzyl substituted T_1-weighted magnetic resonance imaging(MRI)contrast agent Gd-DOTA-PNB(probe 1) has been designed and explored for the possible detection of NTR.Our experimental results show that probe 1 could serve as an MRI-enhanced contrast agent for monitoring NTR activity. The in vitro response and mechanism of the NTR catalysed reduction of probe 1 have been investigated through LC–MS and MRI. Para-nitrobenzyl substituted probe 1 was catalytically reduced by NTR to the intermediate para-aminobenzyl substituted probe which then underwent a rearrangement elimination reaction to Gd-DOTA, generating the enhanced T1-weighted MR imaging. Further, LC–MS and MRI studies of living Escherichia coli have confirmed the NTR activity detection ability of probe 1 at a cellular level. This method may potentially be used for the diagnosis of bacterial infections.

Fluorogen-activating proteins: beyond classical fluorescent proteins

Fluorescence imaging is a powerful technique for the real-time noninvasive monitoring of protein dynamics. Recently, fluorogen activating proteins(FAPs)/fluorogen probes for protein imaging were developed. Unlike the traditional fluorescent proteins(FPs), FAPs do not fluoresce unless bound to their specific small-molecule fluorogens. When using FAPs/fluorogen probes, a washing step is not required for the removal of free probes from the cells, thus allowing rapid and specific detection of proteins in living cells with high signal-to-noise ratio. Furthermore, with different fluorogens, living cell multi-color proteins labeling system was developed. In this review, we describe about the discovery of FAPs, the design strategy of FAP fluorogens, the application of the FAP technology and the advances of FAP technology in protein labeling systems.

A Pseudopaline Fluorescent Probe for the Selective Detection of Pseudomonas aeruginosa

The rise of resistance to all known antibiotics is a global crisis.In addition to novel treatment options,there is an urgent need to develop rapid,specific,sensitive,and reliable diagnostic methods to detect pathogenic bacteria in clinical samples and reduce the overuse and misuse antibiotics.Pseudopaline,a metallophore produced by the human pathogen Pseudomonas aeruginosa,transports divalent metal ions via a dedicated active transport system,making it an ideal carrier for a second functional moiety.