Aminopeptidase N Activatable Fluorescent Probe for Tracking Metastatic Cancer and Image-Guided Surgery via in Situ Spraying

Fluorescent probe applications and prospects in gastrointestinal cancer: A bibliometric analysis

BACKGROUND

Gastrointestinal tumors, as one of the most common cancers worldwide, pose a significant threat to human health. In this context, the advent of fluorescence probe technology has offered new perspectives and methods for the diagnosis and surgical treatment of gastrointestinal tumors. However, there is currently a lack of systematic bibliometric analysis on the research concerning gastrointestinal cancer and fluorescence probes.

METHOD

This study retrieved and comprehensively analyzed 1816 documents from the Web of Science database using the Cite Space tool, exploring the spatiotemporal distribution, author and subject category distribution, research themes, and keywords in this field.

RESULTS

As of February 3, 2024, a total of 1816 records were retrieved, encompassing nine document types. Original research papers dominated the dataset, accounting for 89.922 %, followed by review articles at 6.773 %. We conducted a comprehensive analysis from various perspectives including countries, authors, institutions, keywords, journals, and references. Our findings reveal a strengthening trend in research on gastrointestinal cancer and fluorescent probes since 2010, with primary focus on drug delivery, endoscopy techniques, and genomic hybridization.

CONCLUSION

In recent years, there has been a growing interest in the design, application, and quantitative analysis techniques of fluorescent probes, marking a notable frontier in this field. Our research findings offer fundamental insights and aid in identifying potential collaborators for future endeavors in this area.

Glutathione and viscosity double-locked response fluorescent probe for imaging and surgical navigation of hepatocellular carcinoma

Early diagnosis and precise treatment of hepatocellular carcinoma (HCC) are crucial for human health. Therefore, addressing the potential markers of HCC, glutathione (GSH) and viscosity, we constructed a fluorescent probe (PG-V) activated cascadically by GSH/viscosity. PG-V possessed excellent photophysical properties and biocompatibility, and could specifically illuminate tumor tissue, achieving fluorescence imaging of HCC, and imaging-guided tumor resection.

Activatable Fluorescence and Bio/Chemiluminescence Probes for Aminopeptidases: From Design to Biomedical Applications

Aminopeptidases are exopeptidases that catalyze the cleavage of amino acid residues from the N-terminal fragment of protein or peptide substrates. Owing to their function, they play important roles in protein maturation, signal transduction, cell-cycle control, and various disease mechanisms, notably in cancer pathology. To gain better insights into their function, molecular imaging assisted by fluorescence and bio/chemiluminescence probes has become an indispensable method to their superiorities, including excellent sensitivity, selectivity, and real-time and noninvasive imaging. Numerous efforts are made to develop activatable probes that can effectively enhance efficiency and accuracy as well as minimize the side effects. This review is classified according to the type of aminopeptidases, summarizing some recent works on the design, work mechanism, and sensing, imaging, and theranostic performance of their activatable probe. Finally, the current challenges are outlined in developing activatable probes for aminopeptidases and provide possible solutions for future advancements.

Unlocking lysosomal acidity to activate membranolytic module for accurately cancer theranostics

Chemotherapy drug efflux, toxic side effects, and low efficacy against drug-resistant cells have plagued safe and efficient cancer theranostics. However, the materials or methods that resolve these defects all-in-one are scarce. Here, a new cancer theranostics strategy is proposed by utilizing changes in lysosomal acidity in cancer cells to activate the membranolytic model to overcome these obstacles together. Therefore, a simple fluorescent anthracene derivative Lyso-Mito is developed, which has a perfect pKa (4.62) value that falls between the pH of lysosomes in cancer and normal cells. Lyso-Mito itself can precisely target and convert the pH perturbation of lysosomes in cancer cells to fluorescent response and membranolytic module activity to accomplish the low drug efflux, weak toxic side effects, and low drug-resistant cancer diagnosis and treatment without linking other functional units or any additional assistance. Hereby, a new cancer theranostics strategy of integrating organelle microenvironment and the membranolytic model is realized.

Dual-Locked Fluorescent Probes Activated by Aminopeptidase N and the Tumor Redox Environment for High-Precision Imaging of Tumor Boundaries

Clear delineation of tumor margins is essential for accurate resection and decreased recurrence rate in the clinic. Fluorescence imaging is emerging as a promising alternative to traditional visual inspection by surgeons for intraoperative imaging. However, traditional probes lack accuracy in tumor diagnosis, making it difficult to depict tumor boundaries accurately. Herein, we proposed an offensive and defensive integration (ODI) strategy based on the "attack systems (invasive peptidase) and defense systems (reductive microenvironment)" of multi-dimensional tumor characteristics to design activatable fluorescent probes for imaging tumor boundaries precisely. Screened out from a series of ODI strategy-based probes, ANQ performed better than traditional probes based on tumor unilateral correlation by distinguishing between tumor cells and normal cells and minimizing false-positive signals from living metabolic organs. To further improve the signal-to-background ratio in vivo, derivatized FANQ, was prepared and successfully applied to distinguish orthotopic hepatocellular carcinoma tissues from adjacent tissues in mice models and clinical samples. This work highlights an innovative strategy to develop activatable probes for rapid diagnosis of tumors and high-precision imaging of tumor boundaries, providing more efficient tools for future clinical applications in intraoperative assisted resection.

Probing metalloenzyme dynamics in living systems: Contemporary advances in fluorescence imaging tools and applications

Metalloenzymes are essential to cellular function, and their overexpression or enhanced activation are potential therapeutic targets. However, the study of metalloenzymes in vitro presents various challenges, leading many to develop tools to study them in their native cellular environment. Small-molecule fluorescence probes are commonly used to monitor metalloenzyme function, activity, and distribution in situ. These include probes that are activity-based (fluorescence is mediated by enzyme activity) or binding-based (fluorescence is mediated by interactions with the enzyme upon binding its metal cofactor). We discuss recent innovations that overcome key design challenges, such as the rapid diffusion of activity-based probes, the difficulty of probing redox-active enzymes, the selectivity of binding-based probes, and the poor penetration depth of fluorescence, and describe novel applications of these tools.

Clearly fluorescent delineating ER+ breast tumor incisal edge and identifying tiny metastatic tumor foci at high resolution

Fluorescence-image guided surgery (FGS) can intraoperatively provide real-time visualization of a tumor incisal edge and high-resolution identification of tumor foci to improve treatment outcomes. In this contribution, we report a fluorescent probe NB-TAM based on intramolecularly folded photoinduced electron transfer (PET), which displayed a prominent turn-on response in the near-infrared (NIR) window upon specific interaction with the estrogen receptor (ER). Significantly, NB-TAM could delineate a clear tumor incisal edge (tumor-to-normal tissue ratio > 5) in a 70-min time window, and was successfully used to guide the facile and precise resection of ER+ breast tumors in mice. To our surprise, NB-TAM was found to be capable of identifying very tiny lung metastatic ER+ breast tumor foci (0.4 × 0.3 mm), and this ultrahigh resolution was essential to effectively promote tumor resection precision and early diagnosis of tiny tumors. These results clearly elucidate the promising application of NB-TAM as a diagnostic agent for intraoperative fluorescence imaging of ER+ breast cancer.

Fluorescent Probes for Disease Diagnosis

The identification and detection of disease-related biomarkers is essential for early clinical diagnosis, evaluating disease progression, and for the development of therapeutics. Possessing the advantages of high sensitivity and selectivity, fluorescent probes have become effective tools for monitoring disease-related active molecules at the cellular level and in vivo. In this review, we describe current fluorescent probes designed for the detection and quantification of key bioactive molecules associated with common diseases, such as organ damage, inflammation, cancers, cardiovascular diseases, and brain disorders. We emphasize the strategies behind the design of fluorescent probes capable of disease biomarker detection and diagnosis and cover some aspects of combined diagnostic/therapeutic strategies based on regulating disease-related molecules. This review concludes with a discussion of the challenges and outlook for fluorescent probes, highlighting future avenues of research that should enable these probes to achieve accurate detection and identification of disease-related biomarkers for biomedical research and clinical applications.

A microenvironment-sensitive red emissive probe with a large Stokes shift for specific recognition and quantification of serum albumin in complex biofluids and live cells

Human serum albumin (HSA) is regarded as a useful biomarker for rapid medical diagnosis of various disorders mainly related to the kidneys and liver. Hence, it is crucial to identify and monitor the HSA level in complex biofluids (urine and blood samples) using a simple approach. Herein, we have designed and synthesized an intramolecular charge transfer (ICT) based environment-sensitive fluorescent molecular probe, (E)-2-(3-(2-(5-methoxy-1H-indol-3-yl)vinyl)-5,5-dimethylcyclohex-2-en-1-ylidene)malononitrile (DCI-MIN), that can selectively interact with HSA in PBS buffer solution and exhibit a ∼78-fold enhancement in fluorescence intensity with a significant Stokes shift (∼126 nm), which is important to avoid interference from the excitation light. The significant red fluorescence response can be attributed to the suppression of free intramolecular rotation of the DCI-MIN probe inside the hydrophobic binding cavity of HSA and the low polar microenvironment present within HSA. According to the 3σ/slope method, the detection limit was found to be 1.01 nM (0.0671 mg L-1) in aqueous solutions, which is significantly lower than the normal level of HSA in healthy urine and blood serum, indicating its high sensitivity. DCI-MIN has the ability to exhibit useful applications, including the detection and quantification of HSA concentration in complex biofluids (human urine and blood samples) as well as the imaging of serum albumin in living cells.

Bienzyme-Locked Activatable Fluorescent Probes for Specific Imaging of Tumor-Associated Mast Cells

Tumor-associated mast cells (TAMCs) have been recently revealed to play a multifaceted role in the tumor microenvironment. Noninvasive optical imaging of TAMCs is thus highly desired to gain insights into their functions in cancer immunotherapy. However, due to the lack of a single enzyme that is specific to mast cells, a common probe design approach based on single-enzyme activation is not applicable. Herein, we reported a bienzyme-locked molecular probe (THCMC) based on a photoinduced electron transfer-intramolecular charge-transfer hybrid strategy for in vivo imaging of TAMCs. The bienzyme-locked activation mechanism ensures that THCMC exclusively turns on near-infrared (NIR) fluorescence only in the presence of both tryptase and chymase specifically coexpressed by mast cells. Thus, THCMC effectively distinguishes mast cells from other leukocytes, including T cells, neutrophils, and macrophages, a capability lacking in single-locked probes. Such a high specificity of THCMC allows noninvasive tracking of the fluctuation of TAMCs in the tumor of living mice during cancer immunotherapy. The results reveal that the decreased intratumoral signal of THCMC after combination immunotherapy correlates well with the reduced population of TAMCs, accurately predicting the inhibition of tumor growth. Thus, this study not only presents the first NIR fluorescent probe specific for TAMCs but also proposes a generic bienzyme-locked probe design approach for in vivo cell imaging.

Recent Advances of Aminopeptidases-Responsive Small-Molecular Probes for Bioimaging

Aminopeptidases, enzymes with critical roles in human body, are emerging as vital biomarkers for metabolic processes and diseases. Aberrant aminopeptidase levels are often associated with diseases, particularly cancer. Small-molecule probes, such as fluorescent, fluorescent/photoacoustics, bioluminescent, and chemiluminescent probes, are essential tools in the study of aminopeptidases-related diseases. The fluorescent probes provide real-time insights into protein activities, offering high sensitivity in specific locations, and precise spatiotemporal results. Additionally, photoacoustic probes offer signals that are able to penetrate deeper tissues. Bioluminescent and chemiluminescent probes can enhance in vivo imaging abilities by reducing the background. This comprehensive review is focused on small-molecule probes that respond to four key aminopeptidases: aminopeptidase N, leucine aminopeptidase, Pyroglutamate aminopeptidase 1, and Prolyl Aminopeptidase, and their utilization in imaging tumors and afflicted regions. In this review, the design strategy of small-molecule probes, the variety of designs from previous studies, and the opportunities of future bioimaging applications are discussed, serving as a roadmap for future research, sparking innovations in aminopeptidase-responsive probe development, and enhancing our understanding of these enzymes in disease diagnostics and treatment.

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.

Ultrasensitive Optical Detection and Elimination of Residual Microtumors with a Postoperative Implantable Hydrogel Sensor for Preventing Cancer Recurrence

In vivo optical imaging of trace biomarkers in residual microtumors holds significant promise for cancer prognosis but poses a formidable challenge. Here, a novel hydrogel sensor is designed for ultrasensitive and specific imaging of the elusive biomarker. This hydrogel sensor seamlessly integrates a molecular beacon nanoprobe with fibroblasts, offering both high tissue retention capability and an impressive signal-to-noise ratio for imaging. Signal amplification is accomplished through exonuclease I-mediated biomarker recycling. The resulting hydrogel sensor sensitively detects the biomarker carcinoembryonic antigen with a detection limit of 1.8 pg mL-1 in test tubes. Moreover, it successfully identifies residual cancer nodules with a median diameter of less than 2 mm in mice bearing partially removed primary triple-negative breast carcinomas (4T1). Notably, this hydrogel sensor is proven effective for the sensitive diagnosis of invasive tumors in post-surgical mice with infiltrating 4T1 cells, leveraging the role of fibroblasts in locally enriching tumor cells. Furthermore, the residual microtumor is rapidly photothermal ablation by polydopamine-based nanoprobe under the guidance of visualization, achieving ≈100% suppression of tumor recurrence and lung metastasis. This work offers a promising alternative strategy for visually detecting residual microtumors, potentially enhancing the prognosis of cancer patients following surgical interventions.

Photoinduced Cuproptosis with Tumor-Specific for Metastasis-Inhibited Cancer Therapy

Cuproptosis is a novel form of regulated cell death which guarantees to increase the efficacy of existing anticancer treatments that employ traditional apoptotic therapeutics. However, reducing the amount of undesirable Cu ions released in normal tissue and maximizing Cu-induced cuproptosis therapeutic effects at tumor sites are the major challenges. In this study, exploiting the chemical properties of copper ionophores and the tumor microenvironment, a novel method is developed for controlling the valence of copper ions that cause photoinduced cuproptosis in tumor cells. CJS-Cu nanoparticles (NPs) can selectively induce cuproptosis after cascade reactions through H2 O2 -triggered Cu2+ release, photoirradiation-induced superoxide radical (∙O2 - ) generation, and reduction of Cu2+ to Cu+ by ∙O2 - . The generated reactive oxygen species can result in glutathione depletion and iron-sulfur cluster protein damage and further augmented cuproptosis. CJS-Cu NPs effectively suppressed tumor growth and downregulated the expression of metastasis-related proteins, contributing to the complete inhibition of lung metastasis. Ultimately, this study suggests novel avenues for the manipulation of cellular cuproptosis through photochemical reactions.

High Contrast Bioimaging of Tumor and Inflammation with a Bicyclic Dioxetane Chemiluminescent Probe

The link between inflammation and the evolution of cancer is well established. Visualizing and tracking both tumor proliferation and the associated inflammatory response within a living organism are vital for dissecting the nexus between these two processes and for crafting precise treatment modalities. We report the creation and synthesis of an advanced NIR chemiluminescence probe that stands out for its exceptional selectivity, extraordinary sensitivity at nanomolar concentrations, swift detection capabilities, and broad application prospects. Crucially, this probe has been successfully utilized to image endogenous ONOO- across different inflammation models, including abdominal inflammation triggered by LPS, subcutaneous inflammatory conditions, and tumors grafted onto mice. These findings highlight the significant promise of chemiluminescence imaging in enhancing our grasp of the intricate interplay between cancer and inflammation and in steering the development of potent, targeted therapeutic strategies.

Activatable Near-Infrared Versatile Fluorescent and Chemiluminescent Dyes Based on the Dicyanomethylene-4H-pyran Scaffold: From Design to Imaging and Theranostics

Activatable fluorescent and chemiluminescent dyes with near-infrared emission have indispensable roles in the fields of bioimaging, molecular prodrugs, and phototheranostic agents. As one of the most popular fluorophore scaffolds, the dicyanomethylene-4H-pyran scaffold has been applied to fabricate a large number of versatile activatable optical dyes for analytes detection and diseases diagnosis and treatment by virtue of its high photostability, large Stokes shift, considerable two-photon absorption cross-section, and structural modifiability. This review discusses the molecular design strategies, recognition mechanisms, and both in vitro and in vivo bio-applications (especially for diagnosis and therapy of tumors) of activatable dicyanomethylene-4H-pyran dyes. The final section describes the current shortcomings and future development prospects of this topic.

Exploration of aminopeptidase N as new biomarker for early diagnosis of thyroid cancer

False-positive diagnosis and overdiagnosis are ongoing issues in clinical diagnosis of thyroid cancer. Identifying new disease markers is crucial for early diagnosis and improved treatment. Aminopeptidase N (APN) is a promising biomarker for cancer diagnosis due to its critical roles in tumor invasion, metastasis, angiogenesis, and other processes. However, its potential as biomarker for thyroid cancer diagnosis needs further investigation. This study developed an ultra-sensitive near-infrared fluorescence probe, LAN-apn, to investigate the expression level of APN in thyroid cancer and evaluate its potential as biomarker of thyroid cancer. LAN-apn could accurately and sensitively determine APN through fluorescence method (DL = 0.069 ng/mL) and colorimetric method (DL = 4.5 ng/mL). In addition, LAN-apn allowed for successful fluorescence imaging of APN in thyroid cancer cells and thyroid cancer tumors both in vivo and in vitro, and confirmed that APN was significantly upregulated in thyroid cancer. Therefore, APN may become a new biomarker for thyroid cancer diagnosis, and LAN-apn could be used as a new imaging tool for the study of APN-thyroid cancer relationship and the early diagnosis of thyroid cancer.

Dual Tumor-Selective β-Carboline-Based Fluorescent Probe for High-Contrast/Rapid Diagnosis of Clinical Tumor Tissues

Given that precise/rapid intraoperative tumor margin identification is still challenging, novel fluorescent probes HY and HYM, based on acidic tumor microenvironment (TME) activation and organic anion transporting polypeptide (OATPs)-mediated selective uptake, were constructed and synthesized. Both of them possessed acidic pH-activatable and reversible fluorescence as well as large Stokes shift. Compared with HY, HYM had a higher (over 9-fold) enhancement in fluorescence with pH ranging from 7.6 to 4.0, and the fluorescence quantum yield of HYM (ΦF = 0.49) at pH = 4.0 was 8-fold stronger than that (ΦF = 0.06) at pH = 7.4. Mechanism research demonstrated that acidic TME-induced protonation of the pyridine N atom on β-carbolines accounted for the pH-sensitive fluorescence by influencing the intramolecular charge transfer (ICT) effect. Furthermore, HYM selectively lit up cancer cells and tumor tissues not only by "off-on" fluorescence but also by OATPs (overexpressed on cancer cells)-mediated cancer cellular internalization, offering dual tumor selectivity for precise visualization of tumor mass and intraoperative guidance upon in situ spraying. Most importantly, HYM enabled rapid and high-contrast (tumor-to-normal tissue ratios > 6) human tumor margin identification in clinical tumor tissues by simple spraying within 6 min, being promising for aiding in clinical surgical resection.

NIR Light-Activated Mitochondrial RNA Cross-Linking Strategy for H2S Monitoring and Prolonged Colorectal Tumor Imaging

Molecular diffusion and leakage impede the long-term retention of probes/drugs and may cause potential adverse effects in theranostic fields. Spatiotemporally manipulating the organelle-immobilization behavior of probes/drugs for prolonged tumor retention is indispensable to achieving effective cancer diagnosis and therapy. Herein, we propose a rational strategy that could realize near-infrared light-activated ribonucleic acids (RNAs) cross-linking for prolonged tumor retention and simultaneously endogenous hydrogen sulfide (H2S) monitoring in colorectal tumors. Profiting from efficient singlet oxygen (1O2) generation from Cy796 under 808 nm light irradiation, the 1O2-animated furan moiety in Cy796 could covalently cross-link with cytoplasmic RNAs via a cycloaddition reaction and realize organelle immobilization. Subsequently, specific thiolysis of Cy796 assisted with H2S resulted in homologous product Cy644 with reduced 1O2 generation yields and enhanced absolute fluorescence quantum yields (from 7.42 to 27.70%) with blue-shifted absorption and emission, which avoided the molecular oxidation fluorescence quenching effect mediated by 1O2 and validated fluorescence imaging. Furthermore, studies have demonstrated that our proposed strategy possessed adequate capacity for fluorescence imaging and endogenous H2S detection in HCT116 cells, particularly accumulated at the tumor sites, and retained long-term imaging with excellent biocompatibility. The turn-on fluorescence mode and turn-off 1O2 generation efficiency in our strategy successfully realized a diminished fluorescence cross-talk and oxidation quenching effect. It is adequately envisioned that our proposed strategy for monitoring biomarkers and prolonged tumor retention will contribute tremendous dedication in the clinical, diagnostic, and therapeutic fields.

High-precision detection and navigation surgery of colorectal cancer micrometastases

Surgical resection is an effective treatment for colorectal cancer (CRC) patients, whereas occult metastases hinder the curative effect. Currently, there is no effective method to achieve intraoperatively diagnosis of tumor-positive lymph nodes (LNs). Herein, we adopt a near-infrared-II (NIR-II) organic donor-pi-acceptor-pi-donor probe FE-2PEG, which exhibits bright fluorescence over 1100 nm, excellent photostability, blood circulation time, and biocompatibility, to achieve high-performance bioimaging with improved temporal and spatial resolution. Importantly, the FE-2PEG shows efficient passive enrichment in orthotopic CRC, metastatic mesenteric LNs, and peritoneal metastases by enhanced permeability and retention effect. Under NIR-II fluorescence-guided surgery (FGS), the peritoneal micrometastases were resected with a sensitivity of 94.51%, specificity of 86.59%, positive predictive value (PPV) of 96.57%, and negative predictive value of 79.78%. The PPV still achieves 96.07% even for micrometastases less than 3 mm. Pathological staining and NIR-II microscopy imaging proved that FE-2PEG could successfully delineate the boundary between the tumor and normal tissues. Dual-color NIR-II imaging strategy with FE-2PEG (1100 ~ 1300 nm) and PbS@CdS quantum dots (> 1500 nm) successfully protects both blood supply and normal tissues during surgery. The NIR-II-based FGS provides a promising prospect for precise intraoperative diagnosis and minimally invasive surgery of CRC.

Tumor Microenvironment-Responsive Hydrogel for Direct Extracellular ATP Imaging-Guided Surgical Resection with Clear Boundaries

Most solid tumors are clinically treated using surgical resection, and the presence of residual tumor tissues at the surgical margins often determines tumor survival and recurrence. Herein, a hydrogel (Apt-HEX/Cp-BHQ1 Gel, termed AHB Gel) is developed for fluorescence-guided surgical resection. AHB Gel is constructed by tethering a polyacrylamide hydrogel and ATP-responsive aptamers together. It exhibits strong fluorescence under high ATP concentrations corresponding to the TME (100-500 µm) but shows little fluorescence at low ATP concentrations (10-100 nm) such as those in normal tissues. AHB Gel can rapidly (within 3 min) emit fluorescence after exposure to ATP, and the fluorescence signal only occurs at sites exposed to high ATP, resulting in a clear boundary between the ATP-high and ATP-low regions. In vivo, AHB Gel exhibits specific tumor-targeting capacity with no fluorescence response in normal tissue, providing clear tumor boundaries. In addition, AHB Gel has good storage stability, which is conducive to its future clinical application. In summary, AHB Gel is a novel tumor microenvironment-targeted DNA-hybrid hydrogel for ATP-based fluorescence imaging. It can enable the precise imaging of tumor tissues, showing promising application in fluorescence-guided surgeries in the future.

Activatable probes with potential for intraoperative tumor-specific fluorescence-imaging guided surgery

Owing to societal development and aging population, the impact of cancer on human health and quality of life has increased. Early detection and surgical treatment are the most effective approaches for most cancer patients. As the scope of conventional tumor resection is determined by auxiliary examination and surgeon experience, there is often insufficient recognition of tiny tumors. The ability to detect such tumors can be improved by using fluorescent tumor-specific probes for surgical navigation. This review mainly describes the design principles and mechanisms of activatable probes for the fluorescence imaging of tumors. This type of probe is nonfluorescent in normal tissue but exhibits obvious fluorescence emission upon encountering tumor-specific substrates, such as enzymes or bioactive molecules, or changes in the microenvironment, such as a low pH. In some cases, a single-factor response does not guarantee the effective fluorescence labeling of tumors. Therefore, two-factor-activatable fluorescence imaging probes that react with two specific factors in tumor cells have also been developed. Compared with single biomarker testing, the simultaneous monitoring of multiple biomarkers may provide additional insight into the role of these substances in cancer development and aid in improving the accuracy of early cancer diagnosis. Research and progress in this field can provide new methods for precision medicine and targeted therapy. The development of new approaches for early diagnosis and treatment can effectively improve the prognosis of cancer patients and help enhance their quality of life.

Precise tumor delineation in clinical tissues using a novel acidic tumor microenvironment activatable near-infrared fluorescent contrast agent

Tumor selective near-infrared (NIR) fluorescent contrast agents has the potential to greatly enhance the efficiency and precision of tumor surgery by enabling real-time tumor margin identification for tumor resection guided by imaging. However, the development of these agents is still challenging. In this study, based on the acidic tumor microenvironment (TME), we designed and synthesized a novel pH-sensitive NIR fluorescent contrast agent OBD from β-carboline. The fluorescence quantum yield of OBD exhibited a notable increase at pH 3.6, approximately 12-fold higher compared to its value at pH 7.4. After cellular uptake, OBD lighted up the cancer cells with high specificity and accumulated in the mitochondria. Spraying OBD emitted selective fluorescence in xenograft tumor tissues with tumor-to-normal tissue ratios (TNR) as high as 11.18, implying successful image-guided surgery. Furthermore, OBD was also shown to track metastasis in spray mode. After simple topical spray, OBD rapidly and precisely visualized the tumor margins of clinical colon and liver tissues with TNR over 4.2. Therefore, the small-molecule fluorescent contrast agent OBD has promising clinical applications in tumor identification during surgery.

Biomedical applications of magnetosomes: State of the art and perspectives

Magnetosomes, synthesized by magnetotactic bacteria (MTB), have been used in nano- and biotechnological applications, owing to their unique properties such as superparamagnetism, uniform size distribution, excellent bioavailability, and easily modifiable functional groups. In this review, we first discuss the mechanisms of magnetosome formation and describe various modification methods. Subsequently, we focus on presenting the biomedical advancements of bacterial magnetosomes in biomedical imaging, drug delivery, anticancer therapy, biosensor. Finally, we discuss future applications and challenges. This review summarizes the application of magnetosomes in the biomedical field, highlighting the latest advancements and exploring the future development of magnetosomes.

Unveiling the Crucial Roles of O2•- and ATP in Hepatic Ischemia-Reperfusion Injury Using Dual-Color/Reversible Fluorescence Imaging

Hepatic ischemia-reperfusion injury (HIRI) is mainly responsible for morbidity or death due to graft rejection after liver transplantation. During HIRI, superoxide anion (O2•-) and adenosine-5'-triphosphate (ATP) have been identified as pivotal biomarkers associated with oxidative stress and energy metabolism, respectively. However, how the temporal and spatial fluctuations of O2•- and ATP coordinate changes in HIRI and particularly how they synergistically regulate each other in the pathological mechanism of HIRI remains unclear. Herein, we rationally designed and successfully synthesized a dual-color and dual-reversible molecular fluorescent probe (UDP) for dynamic and simultaneous visualization of O2•- and ATP in real-time, and uncovered their interrelationship and synergy in HIRI. UDP featured excellent sensitivity, selectivity, and reversibility in response to O2•- and ATP, which rendered UDP suitable for detecting O2•- and ATP and generating independent responses in the blue and red fluorescence channels without spectral crosstalk. Notably, in situ imaging with UDP revealed for the first time synchronous O2•- bursts and ATP depletion in hepatocytes and mouse livers during the process of HIRI. Surprisingly, a slight increase in ATP was observed during reperfusion. More importantly, intracellular O2•-─succinate dehydrogenase (SDH)─mitochondrial (Mito) reduced nicotinamide adenine dinucleotide (NADH)─Mito ATP─intracellular ATP cascade signaling pathway in the HIRI process was unveiled which illustrated the correlation between O2•- and ATP for the first time. This research confirms the potential of UDP for the dynamic monitoring of HIRI and provides a clear illustration of HIRI pathogenesis.

Caged Luciferase Inhibitor-Based Bioluminescence Switching Strategy Enables Efficient Detection of Serum APN Activity and the Identification of Its Roles in Metastasis of Non-Small Cell Lung Cancer

Bioluminogenic probes emerged as powerful tools for imaging and analysis of various bioanalyses, but traditional approaches would be limited to the low sensitivity during determine the low activity of protease in clinical specimens. Herein, we proposed a caged luciferase inhibitor-based bioluminescence-switching strategy (CLIBS) by using a cleavable luciferase inhibitor to modulate the activity of luciferase reporter to amplify the detective signals, which led to the enhancement of detection sensitivity, and enabled the determination of circulating Aminopeptidase N (APN) activity in thousands of times diluted serum. By applying the CLIBS to serum samples in non-small cell lung cancer (NSCLC) patients from two clinical cohorts, we revealed that, for the first time, higher circulating APN activities but not its concentration, were associated with more NSCLC metastasis or higher metastasis stages by subsequent clinical analysis, and can serve as an independent factor for forecasting NSCLC patients' risk of metastasis.

Orderly Self-Assembly of Organic Fluorophores for Sensing and Imaging

Fluorescence imaging utilizing traditional organic fluorophores is extensively applied in both cellular and in vivo studies. However, it faces significant obstacles, such as low signal-to-background ratio (SBR) and spurious positive/negative signals, primarily due to the facile diffusion of these fluorophores. To cope with this challenge, orderly self-assembled functionalized organic fluorophores have gained significant attention in the past decades. These fluorophores can create nanoaggregates via a well-ordered self-assembly process, thus prolonging their residency time within cells and in vivo settings. The development of self-assembled-based fluorophores is an emerging field, and as such, in this review, we present a summary of the progress and challenges of self-assembly fluorophores, focusing on their development history, self-assembly mechanisms, and biomedical applications. We hope that the insights provided herein will assist scientists in further developing functionalized organic fluorophores for in situ imaging, sensing, and therapy.

Emission Wavelength-Tunable Bicyclic Dioxetane Chemiluminescent Probes for Precise In Vitro and In Vivo Imaging

Chemiluminescent probes have become increasingly popular in various research areas including precise tumor imaging and immunofluorescence analysis. Nevertheless, previously developed chemiluminescence probes are mainly limited to studying oxidation reaction-associated biological events. This study presents the first example of bioimaging applicable bicyclic dioxetane chemiluminescent probes with tunable emission wavelengths that range from 525 to 800 nm. These newly developed probes were able to detect the analytes of β-Gal, H2O2, and superoxide with high specificity and a limit of detection of 77 mU L-1, 96, and 28 nM, respectively. The bioimaging application of the probes was verified in ovarian and liver cancer cells and macrophage cells, allowing the detection of the content of β-Gal, H2O2, and superoxide inside the cells. The high specificity allowed us to image the xenografted tumor in mice. We expect that our probes will receive extensive applications in recording complex biomolecular events using noninvasive imaging techniques.

Tyrosinase-activated Nanocomposites for Double-Modals Imaging Guided Photodynamic and Photothermal Synergistic Therapy

Tyrosinase (TYR) is an important biomarker of melanoma. The exploration of fluorescent pr-obes-based composites is beneficial to build an integrative platform for the diagnosis and treatment of melanoma. Herein, a multifunctional nanocomposite IOBOH@BSA activated by TYR is developed for selective imaging and ablation of melanoma. The chemical structure of IOBOH enables the fluorescence (FL) imaging activated by TYR, photoacoustic (PA) imaging, and photodynamic-photothermal activity by regulating the balance between radiative decay and non-radiative decay. IOBOH combined with bovine serum albumin (IOBOH@BSA) presents the response to TYR and realizes FL imaging with mitochondria-targeting in melanoma. Moreover, IOBOH@BSA shows excellent photothermal ability and is applied for PA imaging. After IOBOH@BSA is activated by TYR, the singlet oxygen generation increases obviously. IOBOH@BSA can realize TYR-activated imaging and photodynamic-photothermal therapy of melanoma. The development of TYR-activated multifunctional nanocomposites promotes the precise imaging and improves the therapeutic effect of melanoma.

Fluorescent dyes based on rhodamine derivatives for bioimaging and therapeutics: recent progress, challenges, and prospects

Since their inception, rhodamine dyes have been extensively applied in biotechnology as fluorescent markers or for the detection of biomolecules owing to their good optical physical properties. Accordingly, they have emerged as a powerful tool for the visualization of living systems. In addition to fluorescence bioimaging, the molecular design of rhodamine derivatives with disease therapeutic functions (e.g., cancer and bacterial infection) has recently attracted increased research attention, which is significantly important for the construction of molecular libraries for diagnostic and therapeutic integration. However, reviews focusing on integrated design strategies for rhodamine dye-based diagnosis and treatment and their wide application in disease treatment are extremely rare. In this review, first, a brief history of the development of rhodamine fluorescent dyes, the transformation of rhodamine fluorescent dyes from bioimaging to disease therapy, and the concept of optics-based diagnosis and treatment integration and its significance to human development are presented. Next, a systematic review of several excellent rhodamine-based derivatives for bioimaging, as well as for disease diagnosis and treatment, is presented. Finally, the challenges in practical integration of rhodamine-based diagnostic and treatment dyes and the future outlook of clinical translation are also discussed.

Cell-Membrane-Localizing Fluorescence Probes for Aminopeptidase N

Aminopeptidase N (APN), a transmembrane ectoenzyme, plays multifunctional roles in cell survival and migration, angiogenesis, blood pressure regulation, and viral uptake. Abnormally high levels of the enzyme can be found in some tumors and injured liver and kidney. Therefore, noninvasive detection methods for APN are in demand for diagnosing and studying the associated diseases, leading to two dozen activatable small-molecule probes reported up to date. All of the known probes, however, analyze the enzyme activity by monitoring fluorescent molecules inside cells, despite the enzymatic reaction taking place on the outer cell membrane. In this case, different cell permeability and enzyme kinetics can cause false signal data. To address this critical issue, we have developed two cell-membrane-localizing APN probes whose enzymatic products also localize the outer cell membrane. The probes selectively respond to APN with ratiometric fluorescence signal changes. A selected probe, which has two-photon imaging capability, allowed us to determine the relative APN levels in various organ tissues for the first time: 4.3 (intestine), 2.1 (kidney), 2.7 (liver), 3.2 (lung), and 1.0 (stomach). Also, a higher APN level was observed from a HepG2-xenograft mouse tissue in comparison with the normal tissue. Furthermore, we observed a significant APN level increase in the mouse liver of a drug (acetaminophen)-induced liver injury model. The probe thus offers a reliable means for studying APN-associated biology including drug-induced hepatotoxicity simply by ratiometric imaging.

Enzyme-Instructed Aggregation/Dispersion of Fluorophores for Near-Infrared Fluorescence Imaging In Vivo

Near-infrared (NIR) fluorescence is a noninvasive, highly sensitive, and high-resolution modality with great potential for in vivo imaging. Compared with "Always-On" probes, activatable NIR fluorescent probes with "Turn-Off/On" or "Ratiometric" fluorescent signals at target sites exhibit better signal-to-noise ratio (SNR), wherein enzymes are one of the ideal triggers for probe activation, which play vital roles in a variety of biological processes. In this review, we provide an overview of enzyme-activatable NIR fluorescent probes and concentrate on the design strategies and sensing mechanisms. We focus on the aggregation/dispersion state of fluorophores after the interaction of probes and enzymes and finally discuss the current challenges and provide some perspective ideas for the construction of enzyme-activatable NIR fluorescent probes.

Near-Infrared Persistent Luminescence Nanoprobe for Ultrasensitive Image-Guided Tumor Resection

Near-infrared (NIR) fluorescence imaging poses significant superiority over traditional medical imaging for tumor resection, thus having attracted widely attention. However, for tiny tumor residues, it requires relative high sensitivity to determine. Here, based on persistent luminescence nanoparticles (PLNPs), an ultrasensitive nanoprobe with extraordinary tumor imaging result is developed to guide surgical removal. Persistent luminescence (PersL) is quenched in normal tissue by the outer layer of MnO2 , and is recovered due to the degradation of MnO2 in tumor microenvironment, significantly improving the sensitivity of tumor imaging. Combined with the absence of background fluorescence in imaging of PLNPs, ultrahigh sensitivity is achieved. In orthotopic breast cancer model, the intraoperative tumor-to-normal tissue (T/NT) signal ratio of the nanoprobe is 58.8, about 9 times that of downconversion nanoparticles. The T/NT ratio of residual tumor (<2 mm) remains 12.4, considerably high to distinguish tumor tissue from normal tissue. Besides, multiple-microtumor, 4T1 liver-implanted tumor and lung metastasis models are built to prove that this ultrasensitive nanoprobe is feasible to recognize tumor residues. Notably, PersL imaging takes only 1.5 min, appropriate to be applied for intraoperative imaging. Overall, an ultrasensitive and convenient imaging for recognizing residual tumor tissue is introduced, holding promise for complete surgical removal.

Supramolecular Host-Guest Strategy for the Accelerating Detection of Nitroreductase

Identifying nitroreductase (NTR) with fluorescent techniques has become a research hotspot, due to its good sensitivity and selectivity toward the early-stage cancer diagnosis and monitoring. Herein, a host-guest reporter (NAQA⊂Zn-MPPB) is successfully achieved by encapsulating the NTR probe NAQA into a new NADH-functioned metal-organic cage Zn-MPPB, which makes the reporter for ultrafast detection of NTR within dozens of seconds in solution. The host-guest strategy fuses the Zn-MPPB and NAQA to form a pseudomolecule material, which changes the reaction process of NTR and NAQA from a double substrates mechanism to a single substrate one, and accelerates the reduction efficiency of NAQA. This advantage make the new host-guest reporter exhibit a linear relationship between emission changes and NTR concentration, and it shows better sensitively toward NTR than that of NAQA. Additionally, the positively charged water-soluble metal-organic cage can encapsulate NAQA in the cavity, promote it to dissolve in an aqueous environment, and facilitate their accumulation into tumor cells. As expected, such host-guest reporter displays a fast and high efficiently imaging capability toward NTR in tumor cells and tumor-bearing mice, and flow cytometry assay is conducted to corroborate the capability as well, implying the considerably potential of host-guest strategy for early tumor diagnosis and treatment.

Acidic tumor microenvironment-activatable fluorescent diagnostic probe for the rapid identification and resection of human tumors via spraying

A fluorescent diagnostic probe for real-time intraoperative image-guided tumor resection can significantly improve the efficiency and quality of oncological therapy, but their development is challenging. Herein, a novel fluorescent diagnostic probe called HLTC based on β-carboline was designed and synthesized. HLTC was found to show a ∼10-fold enhancement of fluorescence quantum field with pH from 7.4 to 4.0, indicating its imaging potential in acid environment which is a typical hallmark of the tumor microenvironment (TME). Following fluorescence microscopy imaging showed HLTC could emit specific signals in cancer cells and sections, by both one-photon excitation and two-photon excitation. Importantly, HLTC enabled the precise and rapid delineation of both transplanted tumor and clinical tumor tissues within several minutes of simple topical spray. The tumor-to-background ratio (TBR) was up to 10.2 ± 1.0 at clinical liver cancer tissues and 9.9 ± 0.3 at clinical colon cancer tissues, allowing precise tumor margin identification and the effective guidance of surgical tumor resection. Furthermore, CCK8 assay, pharmacokinetic evaluation, blood analysis and H&E staining were performed, which verified high biocompatibility and biosafety of HLTC at working concentration. These results reveal the exciting potential of this small-molecule fluorescent diagnostic probe for real-time fluorescence-based navigation during surgical tumor resection.

Application of nanotechnology in reversing therapeutic resistance and controlling metastasis of colorectal cancer

Colorectal cancer (CRC) is the most common digestive malignancy across the world. Its first-line treatments applied in the routine clinical setting include surgery, chemotherapy, radiotherapy, targeted therapy, and immunotherapy. However, resistance to therapy has been identified as the major clinical challenge that fails the treatment method, leading to recurrence and distant metastasis. An increasing number of studies have been attempting to explore the underlying mechanisms of the resistance of CRC cells to different therapies, which can be summarized into two aspects: (1) The intrinsic characters and adapted alterations of CRC cells before and during treatment that regulate the drug metabolism, drug transport, drug target, and the activation of signaling pathways; and (2) the suppressive features of the tumor microenvironment (TME). To combat the issue of therapeutic resistance, effective strategies are warranted with a focus on the restoration of CRC cells’ sensitivity to specific treatments as well as reprogramming impressive TME into stimulatory conditions. To date, nanotechnology seems promising with scope for improvement of drug mobility, treatment efficacy, and reduction of systemic toxicity. The instinctive advantages offered by nanomaterials enable the diversity of loading cargoes to increase drug concentration and targeting specificity, as well as offer a platform for trying the combination of different treatments to eventually prevent tumor recurrence, metastasis, and reversion of therapy resistance. The present review intends to summarize the known mechanisms of CRC resistance to chemotherapy, radiotherapy, immunotherapy, and targeted therapy, as well as the process of metastasis. We have also emphasized the recent application of nanomaterials in combating therapeutic resistance and preventing metastasis either by combining with other treatment approaches or alone. In summary, nanomedicine is an emerging technology with potential for CRC treatment; hence, efforts should be devoted to targeting cancer cells for the restoration of therapeutic sensitivity as well as reprogramming the TME. It is believed that the combined strategy will be beneficial to achieve synergistic outcomes contributing to control and management of CRC in the future.

An "AND" Molecular Logic Gate as a Super-Enhancers for De Novo Designing Activatable Probe and Its Application in Atherosclerosis Imaging

Developing activatable fluorescent probes with superlative fluorescence enhancement factor (F/F0 ) to improve the signal-to-noise (S/N) ratio is still an urgent issue. "AND" molecular logic gates are emerging as a useful tool for enhanced probes selectivity and accuracy. Here, an "AND" logic gate is developed as super-enhancers for designing activatable probes with huge F/F0 and S/N ratio. It utilizes lipid-droplets (LDs) as controllable background input and sets the target analyte as variable input. The fluorescence is tremendously quenching due to double locking, thus an extreme F/F0 ratio of target analyte is obtained. Importantly, this probe can transfer to LDs after a response occurs. The target analyte can be directly visualized through the spatial location without a control group. Accordingly, a peroxynitrite (ONOO- ) activatable probe (CNP2-B) is de novo designed. The F/F0 of CNP2-B achieves 2600 after reacting with ONOO- . Furthermore, CNP2-B can transfer from mitochondria to lipid droplets after being activated. The higher selectivity and S/N ratio of CNP2-B are obtained than commercial probe 3'-(p-hydroxyphenyl) fluorescein (HPFin vitro and in vivo. Therefore, the atherosclerotic plaques at mouse models are delineated clearly after administration with in situ CNP2-B probe gel. Such input controllable "AND" logic gate is envisioned to execute more imaging tasks.

Membrane-tethered activation design of a photosensitizer boosts systemic antitumor immunity via pyroptosis

Pyroptotic immunogenic cell death presents an emerging targeting pathway for cancer immunotherapy. We report a novel membrane-tethered activation design of a photosensitizer (PS) that boosts systemic anti-tumor immunity to primary and distant tumors via pyroptosis induction. The membrane-tethered PS is designed by installing a new phenylbenzopyrylium PS with zwitterionic lipid anchors and a target-cleavable caging moiety. This design affords excellent membrane tethering and enzymatic activation of the PS, exerting specific phototoxicity to cancer cells and inducing effective pyroptosis. Our design demonstrates prolonged circulation, long-lasting fluorogenic imaging and persistent photodynamic therapy of immunogenic 'cold' tumors in vivo, eliciting potent immunity toward local and abscopal tumors via promoted maturation of dendritic cells and recruitment of cytotoxic T lymphocytes. This design affords a promising approach for enhancing systemic antitumor immunity for cancer immunotherapy.

An edoplasmic reticulum-targeted NIR fluorescent probe with a large Stokes shift for hypoxia imaging

Hypoxia is closely linked to various diseases, including solid tumors. The level of nitroreductase (NTR) is usually abnormally upregulated in hypoxic conditions, which can be a biomarker of hypoxia. Herein, the first endoplasmic reticulum-targeting NIR fluorescent probe, ISO-NTR, was developed for highly selective and sensitive detection of NTR. It shows a large Stokes shift (185 nm) and a 5-fold increases in fluorescence intensity. Meanwhile, the ISO-NTR probe with a dicyanoisophorone derivative has excellent endoplasmic reticulum targeting in living systems with high Pearson's correlation coefficients (R_r = 0.9489). Molecular docking calculations and high binding energy between the probe and NTR (-10.78 kcal·mol^-1) may explain the high selectivity of ISO-NTR. Additionally, it has been successfully applied to NTR imaging in vitro and vivo due to its good sensitivity, high selectivity and large Stokes shift, which may provide an effective method for studying the physiological and pathological functions of NTR in living systems. This probe could be developed as a potential imaging tool to further explore the pathogenesis of hypoxia-related diseases in endoplasmic reticulum stress.

Dual factor coactivatable fluorescent nanosensor with boosted cytoplasmic biomarker accessibility toward selective tumor imaging

Fluorescent nanosensor-based tumor imaging holds great promise in cancer diagnosis and treatment assistance, yet the signal contrast is heavily hampered by the unspecific/unwanted activation at microscopic regions with a highly restricted local abundance of biomarkers. Herein, we developed an activation boosting strategy by the integration and manipulation of dual-factor coactivation of sensing and lysosome escape facilitated the rise of cytosolic biomarker accessibility. By employing hybrid DNA probes on gold nanoquenchers, ATP sensing initiated conformation switch of the corresponding aptamer units triggered the exposure of a hidden toehold in a loop structure. Sequentially, miRNA-21 sensing was triggered by toehold-mediated strand displacement and detachment of the binding complexes. The application of lysosomotropic agent chloroquine at optimized time interval facilitated the release of nanosensors into the cytosol and a ∼10.5-fold increment of intracellular fluorescence in vitro, while coactivation improved the cancer-to-normal cell signal ratio by ∼5.9 times. The synergy effects led to a high tumor-to-normal tissue ratio value of ∼7.9 in the in vivo imaging results. This strategy establishes a new paradigm of fluorescent nanosensors for selective and specific tumor imaging.

Tuning the Cellular Uptake and Retention of Rhodamine Dyes by Molecular Engineering for High-Contrast Imaging of Cancer Cells

Probes allowing high-contrast discrimination of cancer cells and effective retention are powerful tools for the early diagnosis and treatment of cancer. However, conventional small-molecule probes often show limited performance in both aspects. Herein, we report an ingenious molecular engineering strategy for tuning the cellular uptake and retention of rhodamine dyes. Introduction of polar aminoethyl leads to the increased brightness and reduced cellular uptake of dyes, and this change can be reversed by amino acetylation. Moreover, these modifications allow cancer cells to take up more dyes than normal cells (16-fold) through active transport. Specifically, we further improve the signal contrast (56-fold) between cancer and normal cells by constructing activatable probes and confirm that the released fluorophore can remain in cancer cells with extended time, enabling long-term and specific tumor imaging.

An aminopeptidase N-based color-convertible fluorescent nano-probe for cancer diagnosis

Specific cancer diagnosis at an early stage plays a significant role in preventing cancer metastasis and reducing cancer mortality. Thus, exploring specific and sensitive fluorescent probes to realize early cancer diagnosis is an urgent need in clinic. Aminopeptidase N (APN/CD13), overexpressed in numerous malignant tumors, is an important tumor biomarker associated with cancer progression, invasion, and metastasis. In this study, a novel fluorescent molecule APN-SUB, capable of monitoring APN in real time, is encapsulated in a pH-responsive block copolymer (termed APN-SUB nanoprobe) for cancer diagnosis. APN-SUB contains a fluorophore center and a trigger moiety (leucine group), which is covalently conjugated on the fluorophore with an amide bond. The hydrolysis of the amide bond in APN-SUB activated by APN leads to a red shift of maximum fluorescence emission wavelength from 495 nm to 600 nm, realizing dual-color transformation from green to red. Moreover, the APN-SUB nanoprobe with pH-responsiveness is prepared to improve the accumulation and the release rate in the tumor region. It is worth noting that the APN-SUB nanoprobe exhibits good performance for APN imaging, namely, superior limit of detection (0.14 nU mL^-1), excellent selectivity and strong photostability. More importantly, the APN-SUB nanoprobe can be successfully employed as a color-convertible fluorescent probe for cancer diagnosis by tracking the activity of APN with high specificity and sensitivity in vivo, demonstrating its potential value for cancer diagnosis.

Observing hydrogen sulfide in the endoplasmic reticulum of cancer cells and zebrafish by using an activity-based fluorescent probe

A crucial endogenous signaling chemical, hydrogen sulfide, is involved in many physiological actions. In this work, we created the fluorescent probe ER-Nap-NBD using a naphthalimide fluorophore as the signal reporter, a 7-nitro-1,2,3-benzoxadiazole amine as the responsive moiety, and a sulfonamide part for endoplasmic reticulum targeting. ER-Nap-NBD could be detected the H₂S levels in solution and in living systems (cells and zebrafish).

A NIR fluorescent probe for the detection of renal damage based on overrepresentation of alanine aminopeptidase enzyme

Kidney damage generates changes at the phenotypic and genotypic levels that allow its monitoring using different biomarkers in blood, urine or serum. Among these biomarkers, kidney failure causes the urine overrepresentation of the alanine aminopeptidase (APN) enzyme. Here, we describe the design of a molecular probe (NB-ALA) based on the Nile Blue fluorophore (NB), which can detect the APN enzyme in urine by simple fluorometric measurements.

Aminopeptidase N-Responsive Conjugates with Tunable Charge-Reversal Properties for Highly Efficient Tumor Accumulation and Penetration

Tumor enzyme-responsive charge-reversal carriers can induce efficient transcytosis and lead to efficient tumor infiltration and potent anticancer efficacy. However, the correlations of molecular structure with charge-reversal property, tumor penetration, and drug delivery efficiency are unknown. Herein, aminopeptidase N (APN)-responsive conjugates were synthesized to investigate these correlations. We found that the monomeric unit structure and the polymer chain structure determined the enzymatic hydrolysis and charge-reversal rates, and accordingly, the transcytosis and tumor accumulation and penetration of the APN-responsive conjugates. The conjugate with moderate APN responsiveness balanced the in vitro transcytosis and in vivo overall drug delivery process and achieved the best tumor delivery efficiency, giving potent antitumor efficacy. This work provides new insight into the design of tumor enzyme-responsive charge-reversal nanomedicines for efficient cancer drug delivery.

Highly Bright Near-Infrared Chemiluminescent Probes for Cancer Imaging and Laparotomy

Near-infrared (NIR) chemiluminescence imaging holds potential for sensitive imaging of cancer due to its low background; however, few NIR chemiluminophores are available, which share the drawback of low chemiluminescence quantum yields (Φ_CL ). Herein, we report the synthesis of NIR chemiluminophores for cancer imaging and laparotomy. Molecular engineering of the electron-withdrawing group at the para-position of the phenol-dioxetane leads to a highly bright NIR chemiluminophore (DPT), showing the Φ_CL (4.6×10^-2  Einstein mol^-1 ) that is 3 to 5-fold higher than existing NIR chemiluminophores. By caging the phenol group of DPT with a cathepsin B (CatB) responsive moiety, an activatable chemiluminescence probe (DPT_CB ) is developed for real-time turn-on detection of deeply buried tumor tissues in living mice. Due to its high brightness, DPT_CB permits accurate chemiluminescence-guided laparotomy.

Chemosensor with Ultra-High Fluorescence Enhancement for Assisting in Diagnosis and Resection of Ovarian Cancer

Fluorescence imaging-guided diagnostics is one of the most promising approaches for facile detection of tumors in situ owing to its simple operation and non-invasiveness. As a crucial biomarker for primary ovarian cancers, β-galactosidase (β-gal) has been demonstrated to be the significant molecular target for visualization of ovarian tumors. Herein, a membrane-permeable fluorescent chemosensor (namely, LAN-βgal) was synthesized for β-gal-specific detection using the d-galactose residue as a specific recognition unit and LAN-OH (Φ_F = 0.47) as a fluorophore. After β-gal was digested, the fluorescence of the initially quenched LAN-βgal (Φ_F < 0.001) was enhanced by up to more than 2000-fold, which exceeded the fluorescence enhancement of other previously reported probes. We also demonstrated that the chemosensor LAN-βgal could visualize endogenous β-gal and distinguish ovarian cancer cells from normal ovarian cells. Further, the chemosensor LAN-βgal was successfully applied to visualize the back tumor-bearing mouse model and peritoneal metastatic ovarian cancer model in vivo. More importantly, through in situ spraying, the proposed chemosensor was successfully employed to assist in the surgical resection of ovarian cancer tumors due to its high tumor-to-normal (T/N) tissue fluorescence ratio of 218. To the best of our knowledge, this is the highest T/N tissue fluorescence ratio ever reported. We believe that the LAN-βgal chemosensor can be utilized as a new tool for the clinical diagnosis and treatment of ovarian cancer.

An enzyme activated fluorescent probe for LTA4H activity sensing and its application in cancer screening

Early diagnosis of cancer is an efficient strategy to prevent tumor progression and improve the survival rate of patients. However, to discovery of reliable tumor-specific biomarkers remains a great challenge. Leukotriene A4 hydrolase (LTA₄H) is a bifunctional zinc metalloenzyme with epoxide hydrolase activity and aminopeptidase activity, which plays important roles in allergic and inflammatory reactions and showed strong relevance with carcinoma progression. We thus sought to investigate the possibility of application LTA₄H activity detection in cancer diagnosis. To achieve this, we herein develop an enzyme activated fluorescent probe for LTA₄H activity sensing by incorporating the specific recognition unit of LTA₄H with a red-emitting fluorophore. The acquired probe (named as ADMAB) showed high sensitivity and specificity toward LTA₄H in vitro. By further application of ADMAB in living cells, significantly elevated LTA₄H activity in cancer cell lines was observed when compared with normal cell lines and in vivo tracing A549 tumor in nude mice was also realized by ADMAB. Meanwhile, the wound-healing assay further revealed the importance of LTA₄H in tumor metastasis. Moreover, the LTA₄H activity in human serum sample was successfully detected by ADMAB and significantly elevated LTA₄H activity in patients diagnosed with cancer was firstly found, which demonstrated ADMAB to be a useful tool for cancer diagnosis and LTA₄H related biological study.

Colon Adenocarcinoma Quantitative Proteomics Reveals Dysregulation in Key Cancer Signaling Pathways and a Candidate Protein Marker Panel

Colorectal cancer (CRC) is reportedly the second leading cause of cancer death worldwide. By the end of the decade, there will likely be more than one million fatalities worldwide from this cancer, with an estimated 2.2 million additional cases. We need new ways of thinking about cancer research. One approach is to deploy systems science using quantitative proteomics to obtain postgenomic and functional insights into cancer. The present study compares the tissue proteome of CRC (n = 10) with the matched peritumoral controls (n = 10) in samples obtained from the Indian subcontinent. When compared with the controls, a list of 22 substantially altered protein candidates was identified, which were associated with the growth, survival, and metastasis of the tumor. A list of the unique peptides from top significant proteins, including olfactomedin-4, alanyl aminopeptidase, and grancalcin was further validated using a parallel reaction monitoring-based targeted proteomics approach. In addition, biological pathway analysis showed perturbation in key biological processes, including dysregulation in purine metabolism, MYC targets in cancer, DNA repair, and replication, and leukocyte transendothelial migration, among others. The protein panel reported herein is also shown to be dysregulated in CRC and warrants further research toward understanding pathobiology, diagnostics, and therapeutics development in CRC.