Activatable imaging probes for cancer-linked NAD(P)H:quinone oxidoreductase-1 (NQO1): Advances and future prospects

A near-infrared fluorescent probe with two-photon excitation for in situ imaging of NQO1 in human colorectum cancer tissue

Colorectum cancer has become one of the most fatal cancer diseases, in which NAD(P)H: quinone oxidoreductase 1 (NQO1) plays a role in intracellular free radical reduction and detoxification and has been linked to colorectum cancer and chemotherapy resistance. Therefore, rational design of optical probe for NQO1 detection is urgent for the early diagnosis of colorectum cancer. Herein, we have developed a novel two-photon fluorescent probe, WHFD, which is capable of selectively detecting of intracellular NQO1 with two-photon (TP) absorption (800 nm) and near-infrared emission (620 nm). Combination with a substantial Stokes shift (175 nm) and biocompatibility, we have assessed its suitability for in vivo imaging of endogenous NQO1 activities from HepG2 tumor-bearing live animals with high tissue penetration up to 300 μm. Particularly, we for the first time used the probe to image NQO1 activities from human colorectum cancer samples by using TP microscopy, and proving our probe possesses reliable diagnostic performance to directly in situ imaging of cancer biomarker and can clearly distinguish the boundary between human colorectum cancer tissue and their surrounding normal tissue, which shows great potential for the intraoperative navigation.

NQO1-activated multifunctional theranostic probe for imaging-guided mitochondria-targeted photodynamic therapy and boosting immunogenic cell death

NAD(P)H: quinine oxidoreductase (NQO1) is overexpressed in many types of cancer cells, and have been used as a biomarker for cancer diagnosis and targeted therapy. The development of activatable theranostic agents is highly desirable for precise cancer diagnosis and therapy. Herein, a NQO1-activated near-infrared multifunctional theranostic probe I-HCy-Q is successfully developed for imaging guided photodynamic therapy. The NIR fluorescence (λex/em = 685/703 nm) and capacity of reactive oxygen species generation are sensitive controllable by the level of NQO1, the linear detection range of NQO1 and limit of detection are 0.05-1.5 μg/mL and 5.66 ng/mL, respectively. On the one hand, I-HCy-Q can monitor the activity of NQO1 and distinguish the NQO1 positive cancer cells; on the other hand, the capacity of mitochondria-targeted photodynamic therapy makes I-HCy-Q an effective inducer of apoptosis and immunogenic cell death. Attribute to its complementary advantages, I-HCy-Q holds potential for the imaging and treatment of tumors in complex organisms.

Activity-Based Fluorescence Diagnostics for Cancer

Fluorescence imaging is one of the most promising approaches to achieve intraoperative assessment of the tumor/normal tissue margins during cancer surgery. This is critical to improve the patients' prognosis, and therefore various molecular fluorescence imaging probes have been developed for the identification of cancer lesions during surgery. Among them, "activatable" fluorescence probes that react with cancer-specific biomarker enzymes to generate fluorescence signals have great potential for high-contrast cancer imaging due to their low background fluorescence and high signal amplification by enzymatic turnover. Over the past two decades, activatable fluorescence probes employing various fluorescence control mechanisms have been developed worldwide for this purpose. Furthermore, new biomarker enzymatic activities for specific types of cancers have been identified, enabling visualization of various types of cancers with high sensitivity and specificity. This Review focuses on recent advances in the design, function and characteristics of activatable fluorescence probes that target cancer-specific enzymatic activities for cancer imaging and also discusses future prospects in the field of activity-based diagnostics for cancer.

Mitochondria-targetable small molecule fluorescent probes for the detection of cancer-associated biomarkers: A review

Cancer represents a global threat to human health, and effective strategies for improved cancer early diagnosis and treatment are urgently needed. The detection of tumor biomarkers has been one of the important auxiliary means for tumor screening and diagnosis. Mitochondria are crucial subcellular organelles that produce most chemical energy used by cells, control metabolic processes, and maintain cell function. Evidence suggests the close involvement of mitochondria with cancer development. As a consequence, the identification of cancer-associated biomarker expression levels in mitochondria holds significant importance in the diagnosis of early-stage diseases and the monitoring of therapy efficacy. Small-molecule fluorescent probes are effective for the identification and visualization of bioactive entities within biological systems, owing to their heightened sensitivity, expeditious non-invasive analysis and real-time detection capacities. The design principles and sensing mechanisms of mitochondrial targeted fluorescent probes are summarized in this review. Additionally, the biomedical applications of these probes for detecting cancer-associated biomarkers are highlighted. The limitations and challenges of fluorescent probes in vivo are also considered and some future perspectives are provided. This review is expected to provide valuable insights for the future development of novel fluorescent probes for clinical imaging, thereby contributing to the advancement of cancer diagnosis and treatment.

A bioluminescent probe for NQO1 overexpressing cancer cell imaging in vitro and in vivo

A bioluminescent probe NQO1-Luc toward NQO1 was constructed, which exhibits high selectivity and sensitivity toward NQO1 in vitro and adequate capability of distinguishing NQO1-overexpressing tumors in vivo.

Enzyme-activated near-infrared fluorogenic probe with high-efficiency intrahepatic targeting ability for visualization of drug-induced liver injury

Hepatotoxicity is a serious problem faced by thousands of clinical drugs, and drug-induced liver injury (DILI) caused by chronic administration or overdose has become a major biosafety issue. However, the near-infrared (NIR) fluorescent probes currently used for liver injury detection still suffer from poor liver targeting ability and low sensitivity. Enzyme-activated fluorogenic probes with powerful in situ targeting ability are the key to improving the imaging effect of liver injury. Herein, we rationally designed a leucine aminopeptidase (LAP) activated fluorogenic probe hCy-CA-LAP, which greatly improved the hepatocyte-targeting capability by introducing a cholic acid group. The probe hCy-CA-LAP is converted into a high-emission hCy-CA fluorophore in the presence of LAP, showing high selectivity, high sensitivity and low detection limit (0.0067 U mL-1) for LAP, and successfully realizes the sensitive detection of small fluctuations of LAP in living cells. Moreover, the probe can achieve effective in situ accumulation in the liver, thereby achieving precise imaging and evaluation of two different types of drug-induced hepatotoxicity in vivo. Therefore, the probe hCy-CA-LAP may be a potential tool for exploring the roles of LAP and evaluating the degree of DILI.