Establishment of Molecular Design Strategy To Obtain Activatable Fluorescent Probes for Carboxypeptidases

Visualization of Intraoperative Pancreatic Leakage (ViP): The IDEAL Stage I First-in-human, Single-arm Clinical Pilot Trial of SmartPAN

Background

The invisible fluid leaking from a partially resected pancreas is associated with complications including postoperative pancreatic fistula (POPF), calling for strategies to visualize intraoperative leakage. This single-arm, monocentric trial aims to evaluate the usefulness and safety of SmartPAN, a hydrogel that reacts to alkali pancreatic fluids by changing color and thus enables the surgeon to take immediate action to close leakage.

Methods

Patients awaiting partial pancreatic resection for any indication were recruited to receive intraoperative SmartPAN application. Trial endpoints covered SmartPAN usability and safety according to reports completed by surgeons after each operation, laboratory measurements of nonbiodegradable compounds in body fluids, and clinical evaluations over 30 days of follow-up.

Results

In total 42 patients were recruited to the trial and 29 received partial pancreatic resection with SmartPAN application according to protocol. All 16 attending surgeons rated SmartPAN as easy to learn and use, mostly agreeing that it was useful and that they intended to use it frequently. No adverse effects or complications were associated with SmartPAN, nor were its compounds detected in blood or abdominal fluids. Positive leakage response was detected in 10/29 surgeries. POPF developed in 7 patients, including 2 intraoperatively detected leakages, thereof 1 with targeted closure as well as 5 with no leakage detected.

Conclusion

This study represents the first-in-human clinical trial of SmartPAN and the precursor to randomized controlled trials. The outcomes support SmartPAN's clinical usability and safety and showcase the device's potential to intraoperatively visualize precursors of POPF.

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.

Advancement of fluorescent aminopeptidase probes for rapid cancer detection-current uses and neurosurgical applications

Surgical resection is considered for most brain tumors to obtain tissue diagnosis and to eradicate or debulk the tumor. Glioma, the most common primary malignant brain tumor, generally has a poor prognosis despite the multidisciplinary treatments with radical resection and chemoradiotherapy. Surgical resection of glioma is often complicated by the obscure border between the tumor and the adjacent brain tissues and by the tumor's infiltration into the eloquent brain. 5-aminolevulinic acid is frequently used for tumor visualization, as it exhibits high fluorescence in high-grade glioma. Here, we provide an overview of the fluorescent probes currently used for brain tumors, as well as those under development for other cancers, including HMRG-based probes, 2MeSiR-based probes, and other aminopeptidase probes. We describe our recently developed HMRG-based probes in brain tumors, such as PR-HMRG, combined with the existing diagnosis approach. These probes are remarkably effective for cancer cell recognition. Thus, they can be potentially integrated into surgical treatment for intraoperative detection of cancers.

Evaluation of pancreatic chymotrypsin activity for on-site prediction of clinically relevant postoperative pancreatic fistula

OBJECTIVES

Although the risk of complications due to postoperative pancreatic fistula (POPF) have been evaluated based on the amylase level in drained ascitic fluid, this method has much room for improvement regarding diagnostic accuracy and facility of the measurement. This study aimed to investigate the clinical value of measuring pancreatic chymotrypsin activity for rapid and accurate prediction of POPF after pancreaticoduodenectomy.

METHODS

In 52 consecutive patients undergoing pancreaticoduodenectomy, the chymotrypsin activity in pancreatic juice was measured by calculating the increase in fluorescence intensity during the first 5 min after activation with an enzyme-activatable fluorophore. The predictive value for clinically relevant POPF (CR-POPF) was compared between this technique and the conventional method based on the amylase level.

RESULTS

According to receiver operating characteristic analyses, pancreatic chymotrypsin activity on postoperative day (POD) 3 measured with a multiplate reader had the highest predictive value for CR-POPF (area under the curve [AUC], 0.752; P < 0.001), yielding 77.8 % sensitivity and 68.8 % specificity. The AUC and sensitivity/specificity of the amylase level in ascitic fluid on POD 3 were 0.695 (P = 0.053) and 77.8 %/41.2 %, respectively. Multivariable analysis identified high pancreatic chymotrypsin activity on POD 3 as an independent risk factor for CR-POPF. Measurement of pancreatic chymotrypsin activity with a prototype portable fluorescence photometer could significantly predict CR-POPF (AUC, 0.731; P = 0.010).

CONCLUSION

Measurement of pancreatic chymotrypsin activity enabled accurate and rapid prediction of CR-POPF after pancreaticoduodenectomy. This can help surgeons to implement appropriate drain management at the patient's bedside without delay.

Modular Design Platform for Activatable Fluorescence Probes Targeting Carboxypeptidases Based on ProTide Chemistry

Carboxypeptidases (CPs) are a family of hydrolases that cleave one or more amino acids from the C-terminal of peptides or proteins and play indispensable roles in various physiological and pathological processes. However, only a few highly activatable fluorescence probes for CPs have been reported, and there is a need for a flexibly tunable molecular design platform to afford a range of fluorescence probes for CPs for biological and medical research. Here, we focused on the unique activation mechanism of ProTide-based prodrugs and established a modular design platform for CP-targeting florescence probes based on ProTide chemistry. In this design, probe properties such as fluorescence emission wavelength, reactivity/stability, and target CP can be readily tuned and optimized by changing the four probe modules: the fluorophore, the substituent on the phosphorus atom, the linker amino acid at the P1 position, and the substrate amino acid at the P1' position. In particular, switching the linker amino acid at position P1 enabled us to precisely optimize the reactivity for target CPs. As a proof-of-concept, we constructed probes for carboxypeptidase M (CPM) and prostate-specific membrane antigen (also known as glutamate carboxypeptidase II). The developed probes were applicable for the imaging of CP activities in live cells and in clinical specimens from patients. This design strategy should be useful in studying CP-related biological and pathological phenomena.

A peptides-based biosensor with target-triggered charge-switchable property for simple and sensitive detection of Granzyme B

Granzyme B (GrB) is a serine protease released by natural killer cells and cytotoxic T lymphocytes during immune responses, which not only plays a role in tumor diagnosis but also provides valuable guidance during tumor treatment. In this work, we have designed a charge-switching peptide to fabricate an electrochemical biosensor for quantitative analysis of GrB. Specifically, the designed zwitterionic peptide is in an electrically neutral state before activation, and a door lock structure (proline) is constructed by utilizing the selectivity of carboxypeptidase A (CPA) to the carboxy-terminus of the peptide chain. The door lock is opened when the target is present, allowing CPA to hydrolyze the peptide. At this time, the peptide will convert from neutral to positive, triggering the assembly of a positively charged peptide layer on the electrode surface, resulting in a signal change. Studies have shown that the biosensor has good analytical performance, with a detection range of 0.01 pM-8 pM and a detection limit as low as 3.5 fM. Moreover, the developed biosensor has been effectively applied to the analysis of clinical samples, demonstrating its ability to monitor tumor progression and treatment with clinical applications.

Discovery of Potential Antituberculosis Agents Targeted Methionine Aminopeptidase 1 of Mycobacterium tuberculosis by the Developed Fluorescent Probe

Tuberculosis (TB) is a chronic systemic infectious disease caused by Mycobacterium tuberculosis (M. tuberculosis). Methionine aminopeptidase 1 (MtMET-AP1) is a hydrolase that mediates the necessary post-translational N-terminal methionine excision (NME) of peptides during protein synthesis, which is necessary for bacterial proliferation and is a potential target for the treatment of tuberculosis. Based on the functional characteristics of MtMET-AP1, we developed an enzymatic activated near-infrared fluorescent probe DDAN-MT for rapid, highly selective, and real-time monitoring of endogenous MtMET-AP1 activity in M. tuberculosis. Using the probe DDAN-MT, a visually high-throughput screening technique was established, which obtained three potential inhibitors (GSK-J4 hydrochchloride, JX06, and lavendustin C) against MtMET-AP1 from a 2560 compounds library. More importantly, these inhibitors could inhibit the growth of M. tuberculosis H37Ra especially (MICs < 5 μM), with low toxicities on intestinal bacteria strains and human cells. Therefore, the visual sensing of MtMET-AP1 was successfully performed by DDAN-MT, and MtMET-AP1 inhibitors were discovered as potential antituberculosis agents.

Light controlled reversible Michael addition of cysteine: a new tool for dynamic site-specific labeling of proteins

Cysteine-based Michael addition is a widely employed strategy for covalent conjugation of proteins, peptides, and drugs. The covalent reaction is irreversible in most cases, leading to a lack of control over the process. Utilizing spectroscopic analyses along with X-ray crystallographic studies, we demonstrate Michael addition of an engineered cysteine residue in human Cellular Retinol Binding Protein II (hCRBPII) with a coumarin analog that creates a non-fluorescent complex. UV-illumination reverses the conjugation, yielding a fluorescent species, presumably through a retro-Michael process. This series of events can be repeated between a bound and non-bound form of the cysteine reversibly, resulting in the ON-OFF control of fluorescence. The details of the mechanism of photoswitching was illuminated by recapitulation of the process in light irradiated single crystals, confirming the mechanism at atomic resolution.

Multiplex substrate profiling by mass spectrometry for proteases

Proteolysis is a central regulator of many biological pathways and the study of proteases has had a significant impact on our understanding of both native biology and disease. Proteases are key regulators of infectious disease and misregulated proteolysis in humans contributes to a variety of maladies, including cardiovascular disease, neurodegeneration, inflammatory diseases, and cancer. Central to understanding a protease's biological role, is characterizing its substrate specificity. This chapter will facilitate the characterization of individual proteases and complex, heterogeneous proteolytic mixtures and provide examples of the breadth of applications that leverage the characterization of misregulated proteolysis. Here we present the protocol of Multiplex Substrate Profiling by Mass Spectrometry (MSP-MS), a functional assay that quantitatively characterizes proteolysis using a synthetic library of physiochemically diverse, model peptide substrates, and mass spectrometry. We present a detailed protocol as well as examples of the use of MSP-MS for the study of disease states, for the development of diagnostic and prognostic tests, for the generation of tool compounds, and for the development of protease-targeted drugs.

Intraoperative visualisation of pancreatic leakage (ViP): study protocol for an IDEAL Stage I Post Market Clinical Study

INTRODUCTION

Pancreatic resections are an important field of surgery worldwide to treat a variety of benign and malignant diseases. Postoperative pancreatic fistula (POPF) remains a frequent and critical complication after partial pancreatectomy and affects up to 50% of patients. POPF increases mortality, prolongs the postoperative hospital stay and is associated with a significant economic burden. Despite various scientific approaches and clinical strategies, it has not yet been possible to develop an effective preventive tool. The SmartPAN indicator is the first surgery-ready medical device for direct visualisation of pancreatic leakage already during the operation. Applied to the surface of pancreatic tissue, it detects sites of biochemical leak via colour reaction, thereby guiding effective closure and potentially mitigating POPF development.

METHODS AND ANALYSIS

The ViP trial is a prospective single-arm, single-centre first in human study to collect data on usability and confirm safety of SmartPAN. A total of 35 patients with planned partial pancreatectomy will be included in the trial with a follow-up of 30 days after the index surgery. Usability endpoints such as adherence to protocol and evaluation by the operating surgeon as well as safety parameters including major intraoperative and postoperative complications, especially POPF development, will be analysed.

ETHICS AND DISSEMINATION

Following the IDEAL-D (Idea, Development, Exploration, Assessment, and Long term study of Device development and surgical innovation) framework of medical device development preclinical in vitro, porcine in vivo, and human ex vivo studies have proven feasibility, efficacy and safety of SmartPAN. After market approval, the ViP trial is the IDEAL Stage I trial to investigate SmartPAN in a clinical setting. The study has been approved by the local ethics committee as the device is used exclusively within its intended purpose. Results will be published in a peer-reviewed journal. The study will provide a basis for a future randomised controlled interventional trial to confirm clinical efficacy of SmartPAN.

TRIAL REGISTRATION NUMBER

German Clinical Trial Register DRKS00027559, registered on 4 March 2022.

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

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.

Polymeric agents for activatable fluorescence, self-luminescence and photoacoustic imaging

Numerous polymeric agents have been widely applied in biology and medicine by virtue of the facile chemical modification, feasible nano-engineering approaches and fine-tuned pharmacokinetics. To endow polymeric imaging agents with ability to monitor and measure subtle molecular or cellular alterations at diseased sites, activatable polymeric probes that can elicit signal changes in response to biomolecular interactions or the analytes of interest have to be developed. Herein, this review aims to provide a systemic interpretation and summarization of the design methodology and imaging utility of recently emerged activatable polymeric probes. An introduction of activatable probes allowing for precise imaging and classification of polymeric imaging agents is reported first. Then, we give a detailed discussion of the contemporary design approaches toward activatable polymeric probes in diverse imaging modes for the detection of various stimuli and their imaging applications. Finally, current challenges and future advances are discussed and highlighted.

Development of a fluorescent probe library enabling efficient screening of tumour-imaging probes based on discovery of biomarker enzymatic activities

Fluorescent probes that can selectively detect tumour lesions have great potential for fluorescence imaging-guided surgery. Here, we established a library-based approach for efficient screening of probes for tumour-selective imaging based on discovery of biomarker enzymes. We constructed a combinatorial fluorescent probe library for aminopeptidases and proteases, which is composed of 380 probes with various substrate moieties. Using this probe library, we performed lysate-based in vitro screening and/or direct imaging-based ex vivo screening of freshly resected clinical specimens from lung or gastric cancer patients, and found promising probes for tumour-selective visualization. Further, we identified two target enzymes as novel biomarker enzymes for discriminating between tumour and non-tumour tissues. This library-based approach is expected to be an efficient tool to develop tumour-imaging probes and to discover new biomarker enzyme activities for various tumours and other diseases.

Efficient methodology to develop tumor-imaging fluorescent probes based on screening with our newly constructed probe library for aminopeptidase/protease (380 probes) and clinical samples has been established.

SmartPAN: in vitro and in vivo proof-of-safety assessments for an intra-operative predictive indicator of postoperative pancreatic fistula

Pancreatic surgery is complicated by untreated fluid leakage, but no tenable techniques exist to detect and close leakage sites during surgery. A novel hydrogel called SmartPAN has been developed to meet this need and is here assessed for safety before trials on human patients. Firstly, resazurin assays were used to test the cytotoxic effects of SmartPAN's active bromothymol blue (BTB) indicator and its solution of phosphate-buffered saline (PBS) on normal (HPDE: Human Pancreatic Duct Epithelial) or carcinomic (FAMPAC) human pancreatic cells. Cells incubated with BTB showed no significant reduction in cell viability below threshold safety levels. However, PBS had a mild cytotoxic effect on FAMPAC cells. Secondly, SmartPAN's pathological effects were evaluated in vivo by applying 4 mL SmartPAN to a porcine (Sus scrofa domesticus) model of pancreatic resection. There were no significant differences in macroscopic and microscopic pathologies between pigs treated with SmartPAN or saline. Thirdly, measurements using HPLC-MS/MS demonstrate that BTB does not cross into the bloodstream and was eliminated from the body within two days of surgery. Overall, SmartPAN appears safe in the short-term and ready for first-in-human trials because its components are either biocompatible or quickly neutralized by dilution and drainage.

Fundamentals and developments in fluorescence-guided cancer surgery

Fluorescence-guided surgery using tumour-targeted imaging agents has emerged over the past decade as a promising and effective method of intraoperative cancer detection. An impressive number of fluorescently labelled antibodies, peptides, particles and other molecules related to cancer hallmarks have been developed for the illumination of target lesions. New approaches are being implemented to translate these imaging agents into the clinic, although only a few have made it past early-phase clinical trials. For this translational process to succeed, target selection, imaging agents and their related detection systems and clinical implementation have to operate in perfect harmony to enable real-time intraoperative visualization that can benefit patients. Herein, we review key aspects of this imaging cascade and focus on imaging approaches and methods that have helped to shed new light onto the field of intraoperative fluorescence-guided cancer surgery with the singular goal of improving patient outcomes.

Activatable molecular probes for fluorescence-guided surgery, endoscopy and tissue biopsy

The real-time, dynamic optical visualization of lesions and margins ensures not only complete resection of the malignant tissues but also better preservation of the vital organs/tissues during surgical procedures. Most imaging probes with an "always-on" signal encounter high background noise due to their non-specific accumulation in normal tissues. By contrast, activatable molecular probes only "turn on" their signals upon reaction with the targeted biomolecules that are overexpressed in malignant cells, offering high target-to-background ratios with high specificity and sensitivity. This review summarizes the recent progress of activatable molecular probes in surgical imaging and diagnosis. The design principle and mechanism of activatable molecular probes are discussed, followed by specific emphasis on applications ranging from fluorescence-guided surgery to endoscopy and tissue biopsy. Finally, potential challenges and perspectives in the field of activatable molecular probe-enabled surgical imaging are discussed.

Fluorescent molecular probe-based activity and inhibition monitoring of histone deacetylases

Extensive studies in recent decades have revealed that gene expression regulation is not limited to genetic mutations but also to processes that do not alter the genetic sequence. Post-translational histone modification is one of these processes in addition to DNA or RNA modifications. Histone modifications are essential in controlling histone functions and play a vital role in cellular gene expression. The reversible histone acetylation, regulated by histone acetyltransferases (HATs) and histone deacetylases (HDACs), is an example of such modifications. HDACs are involved in the deacetylation of histones and lead to the termination of gene expression. Although this cellular process is essential, upregulation of HDACs is found in numerous cancers. Therefore, research related to the activity and inhibition monitoring of HDACs is necessary to gain profound knowledge of these enzymes and evaluate the success of the therapeutic approach. In this perspective, methodology derived from fluorescent molecular probes is one of the preferable methods. Herein, we describe fluorescent probes developed to target HDACs by considering their activity and inhibition characteristics.

Applying an intraoperative predictive indicator for postoperative pancreatic fistula: randomized preclinical trial

Leaking pancreatic fluid can contribute to postoperative pancreatic fistula (POPF), which can complicate pancreatic surgery. Surgeons lack reliable tools to identify pancreatic leaks, so a novel hydrogel indicator called SmartPAN was developed for intraoperative application. In this preclinical efficacy assessment study, SmartPAN was capable of detecting sites associated with biochemical leak and POPF-related symptoms, thereby guiding effective closure. Thus, SmartPAN may help to reduce POPF development in upcoming clinical trials.

In vivo imaging via a red-emitting fluorescent probe to diagnosing liver cancer or drug-induced liver disease

Leucine aminopeptidase (LAP) as an important proteolytic enzyme, has been mainly found in hepatobiliary cells, and overexpressed in hepatoma cells. Herein, a new highly selective red-emitting fluorescent probe (DCDHF-Ala) for LAP has been synthesized based on 2-dicyanomethyldiene-3-cyano-2, 5-dihydrofuran (DCDHF) as fluorophore, and alanine (Ala) as the detection group. More importantly, it's the first time to use Ala as a reactive group for LAP. DCDHF-Ala has a low detection limit (0.20 U/L), excellent water solubility and cell membrane permeability. In addition, the probe has been successfully applied to fluorescent imaging in cells and zebrafish. It's especially worth mentioning that, DCDHF-Ala has a high biosafety and enables a real-time detection of LAP levels in mice model. What's the most important is that DCDHF-Ala may be an effective tool to qualitatively monitor the upregulation of LAP induced by liver injury and liver cancer.

Review on the recent progress in the development of fluorescent probes targeting enzymes

Enzymes are very important for biological processes in a living being, performing similar or multiple tasks in and out of cells, tissues and other organisms at a particular location. The abnormal activity of particular enzyme usually caused serious diseases such as Alzheimer's disease, Parkinson's disease, cancers, diabetes, cardiovascular diseases, arthritis etc. Hence, nondestructive and real-time visualization for certain enzyme is very important for understanding the biological issues, as well as the drug administration and drug metabolism. Fluorescent cellular probe-based enzyme detectionin vitroandin vivohas become broad interest for human disease diagnostics and therapeutics. This review highlights the recent findings and designs of highly sensitive and selective fluorescent cellular probes targeting enzymes for quantitative analysis and bioimaging.

Fluorescence Probes for Imaging Basic Carboxypeptidase Activity in Living Cells with High Intracellular Retention

Basic carboxypeptidases (basic CPs) cleave the C-terminal basic amino acid of peptides, and their activity is upregulated in some types of cancers. Therefore, detecting the activity of basic CPs in living cells would be important not only for studying the physiological functions of these enzymes but also for visualization of cancerous tissues. Here, we report two fluorescein diacetate (FDA)-based activatable fluorescence probes, named 5ArgAF-FDA and 5LysAF-FDA, in which the substrate amino acid arginine or lysine is conjugated to the benzene moiety via an azoformyl linker. In live-cell fluorescence imaging of CPM, one of the seven basic CPs, 5ArgAF-FDA showed a larger intracellular fluorescence increase than did 5LysAF-FDA within a few minutes. This increase was inhibited by coincubation with 2-mercaptomethyl-3-guanidinoethylthiopropanoic acid (MGTA), an inhibitor of basic CPs. When 5ArgAF-FDA was applied to a coculture of two breast cancer cell lines with different CPM activities, the fluorescence increase in individual cells was correlated with the expression level of CPM, suggesting that 5ArgAF-FDA has the ability to distinguish cell lines having different levels of CPM activity, owing to its high intracellular retention. We believe these probes will be useful for imaging cancers with upregulated basic CP activity.

Recent Progress in Small Spirocyclic, Xanthene-Based Fluorescent Probes

The use of fluorescent probes in a multitude of applications is still an expanding field. This review covers the recent progress made in small molecular, spirocyclic xanthene-based probes containing different heteroatoms (e.g., oxygen, silicon, carbon) in position 10'. After a short introduction, we will focus on applications like the interaction of probes with enzymes and targeted labeling of organelles and proteins, detection of small molecules, as well as their use in therapeutics or diagnostics and super-resolution microscopy. Furthermore, the last part will summarize recent advances in the synthesis and understanding of their structure-behavior relationship including novel computational approaches.

SmartPAN: A novel polysaccharide-microsphere-based surgical indicator of pancreatic leakage

Postoperative pancreatic fistula is a major surgical complication that can follow pancreatic resection. Postoperative pancreatic fistula can develop as a consequence of leaking pancreatic fluid, which calls for an intraoperative indicator of leakage. But suitable indicators of pancreatic leakage have yet to be found. This study details the evidence-based development and early efficacy assessments of a novel pancreatic leakage indicator (SmartPAN), following the IDEAL framework of product development. We developed 41 SmartPAN prototypes by combining indicators of pancreatic fluid with a polysaccharide-microsphere matrix. The prototypes were assessed in vitro using porcine ( Sus scrofa domesticus) pancreatic tissue and ex vivo with human pancreatic fluid. From these initial tests, we chose a hydrogel-based compound that uses the pH indicator bromothymol blue to detect alkali pancreatic fluid. This prototype was then assessed in vivo for usability, effectiveness and reliability using a porcine model. Treatment groups were defined by SmartPAN-reaction at initial pancreatic resection: indicator-positive or negative. Indicator-positive individuals randomly received either targeted closure of leakage sites or no further closure. We assessed SmartPAN’s reliability and effectiveness by monitoring abdominal drainage for amylase and with relaparotomy after 48 h. SmartPAN responses were consistent between both surgical procedures and conformed to amylase measurements. In conclusion, we have developed the first surgery-ready indicator for predicting the occurrence of pancreatic leakage during pancreatic resection. SmartPAN can enable targeted prophylactic closure in a simple and reliable way, and thus may reduce the impact of postoperative pancreatic fistula by guiding peri- and post-operative management.

Chemical toolbox for 'live' biochemistry to understand enzymatic functions in living systems

In this review, we present an overview of the recent advances in chemical toolboxes that are used to provide insights into 'live' protein functions in living systems. Protein functions are mediated by various factors inside of cells, such as protein-protein interactions, posttranslational modifications, and they are also subject to environmental factors such as pH, redox states and crowding conditions. Obtaining a true understanding of protein functions in living systems is therefore a considerably difficult task. Recent advances in research tools have allowed us to consider 'live' biochemistry as a valid approach to precisely understand how proteins function in a live cell context.

Separation-Based Enzymomics Assay for the Discovery of Altered Peptide-Metabolizing Enzymatic Activities in Biosamples

We have developed a novel method to globally monitor the enzymatic activities of biological samples based on performing the global activity analysis on a proteome separated by native electrophoresis. The study of the alteration in peptide-metabolizing enzymatic activity in colorectal tumor specimens led us to the discovery of elevated thimet oligopeptidase activity, which contributed to the faster consumption of immune-stimulating peptide neurotensin.

Asymmetric and Reduced Xanthene Fluorophores: Synthesis, Photochemical Properties, and Application to Activatable Fluorescent Probes for Detection of Nitroreductase

Xanthene fluorophores, including fluorescein, rhodol, and rhodamines, are representative classes of fluorescent probes that have been applied in the detection and visualization of biomolecules. “Turn on” activatable fluorescent probes, that can be turned on in response to enzymatic reactions, have been developed and prepared to reduce the high background signal of “always-on” fluorescent probes. However, the development of activity-based fluorescent probes for biological applications, using simple xanthene dyes, is hampered by their inefficient synthetic methods and the difficulty of chemical modifications. We have, thus, developed a highly efficient, versatile synthetic route to developing chemically more stable reduced xanthene fluorophores, based on fluorescein, rhodol, and rhodamine via continuous Pd-catalyzed cross-coupling. Their fluorescent nature was evaluated by monitoring fluorescence with variation in the concentration, pH, and solvent. As an application to activatable fluorescent probe, nitroreductase (NTR)-responsive fluorescent probes were also developed using the reduced xanthene fluorophores, and their fluorogenic properties were evaluated.

Fluorescence Detection of Prostate Cancer by an Activatable Fluorescence Probe for PSMA Carboxypeptidase Activity

Prostate cancer (PCa) is a common malignant tumor among adult males, and convenient intraoperative detection of PCa would reduce the risk of leaving positive surgical margins, especially during nerve-sparing procedures. To achieve rapid, fluorescence-based visualization of PCa, we focused on the glutamate carboxypeptidase (CP) activity of prostate-specific membrane antigen (PSMA), a type II transmembrane glycoprotein that is attracting attention as a PCa biomarker. Based on our finding that aryl glutamate conjugates with an azoformyl linker are recognized by PSMA and have a sufficiently low LUMO (lowest unoccupied molecular orbital) energy level to quench the fluorophore through photoinduced electron transfer, we designed and synthesized a first-in-class activatable fluorescence probe for CP activity of PSMA. The developed probe allowed us to visualize the CP activity of PSMA in living cells and in clinical specimens from PCa patients and is expected to be useful for rapid intraoperative detection and diagnosis of PCa.

Novel Glycosylated Naphthalimide-Based Activatable Fluorescent Probe: A Tool for the Assessment of Hexosaminidase Activity and Intracellular Hexosaminidase Imaging

The development of effective detection methods for hexosaminidase is of great importance for the rapid screening of potential inhibitors in vitro and for the early diagnosis of related diseases ex vivo. In this study, the activatable fluorescent probes that are based on naphthalimide decorated with ethylene glycol units were synthesized using N-acetyl-β-d-glucosaminide as a hexosaminidase-responsive group. When exposed to this enzyme, the glucoside-linked naphthalimide moiety of 1c can be cleaved quickly with significant changes in both color (from colorless to yellow) and fluorescence (from blue to green). Probe 1c shows better water-solubility and fluorescence properties than common substrate 4-methylumbelliferyl N-acetyl-β-d-glucosaminide. Furthermore, the response mechanism of 1c to hexosaminidase was evaluated using HPLC analysis and TD-DFT calculations. Molecular docking was performed to investigate the interaction mode. In addition, 1c has successfully achieved the straightforward rapid discovery of effective hexosaminidase inhibitors. Fluorescence imaging experiments indicate that 1c has good cell safety and can be employed as a useful tool for detecting intracellular hexosaminidase activity.

Engineering of Electrochromic Materials as Activatable Probes for Molecular Imaging and Photodynamic Therapy

Electrochromic materials (EMs) are widely used color-switchable materials, but their applications as stimuli-responsive biomaterials to monitor and control biological processes remain unexplored. This study reports the engineering of an organic π-electron structure-based EM (dicationic 1,1,4,4-tetraarylbutadiene, 1²⁺) as a unique hydrogen sulfide (H₂S)-responsive chromophore amenable to build H₂S-activatable fluorescent probes (1²⁺-semiconducting polymer nanoparticles, 1²⁺-SNPs) for in vivo H₂S detection. We demonstrate that EM 1²⁺, with a strong absorption (500-850 nm), efficiently quenches the fluorescence (580, 700, or 830 nm) of different fluorophores within 1²⁺-SNPs, while the selective conversion into colorless diene 2 via H₂S-mediated two-electron reduction significantly recovers fluorescence, allowing for non-invasive imaging of hepatic and tumor H₂S in mice in real time. Strikingly, EM 1²⁺ is further applied to design a near-infrared photosensitizer with tumor-targeting and H₂S-activatable ability for effective photodynamic therapy (PDT) of H₂S-related tumors in mice. This study demonstrates promise for applying EMs to build activatable probes for molecular imaging of H₂S and selective PDT of tumors, which may lead to the development of new EMs capable of detecting and regulating essential biological processes in vivo.

Lighting-Up Tumor for Assisting Resection via Spraying NIR Fluorescent Probe of γ-Glutamyltranspeptidas

For the precision resection, development of near-infrared (NIR) fluorescent probe based on specificity identification tumor-associated enzyme for lighting-up the tumor area, is urgent in the field of diagnosis and treatment. Overexpression of γ-glutamyltranspeptidase, one of the cell-membrane enzymes, known as a biomarker is concerned with the growth and progression of ovarian, liver, colon and breast cancer compared to normal tissue. In this work, a remarkable enzyme-activated NIR fluorescent probe NIR-SN-GGT was proposed and synthesized including two moieties: a NIR dicyanoisophorone core as signal reporter unit; γ-glutamyl group as the specificity identification site. In the presence of γ-GGT, probe NIR-SN-GGT was transformed into NIR-SN-NH₂, the recovery of Intramolecular Charge Transfer (ICT), liberating the NIR fluorescence signal, which was firstly employed to distinguish tumor tissue and normal tissues via simple “spraying” manner, greatly promoting the possibility of precise excision. Furthermore, combined with magnetic resonance imaging by T2 weight mode, tumor transplanted BABL/c mice could be also lit up for first time by NIR fluorescence probe having a large stokes, which demonstrated that probe NIR-SN-GGT would be a useful tool for assisting surgeon to diagnose and remove tumor in clinical practice.

Quinone-Derived π-Extended Phenazines as New Fluorogenic Probes for Live-Cell Imaging of Lipid Droplets

We describe a new synthetic methodology for the preparation of fluorescent π-extended phenazines from the naturally-occurring naphthoquinone lapachol. These novel structures represent the first fluorogenic probes based on the phenazine scaffold for imaging of lipid droplets in live cells. Systematic characterization and analysis of the compounds in vitro and in cells led to the identification of key structural features responsible for the fluorescent behavior of quinone-derived π-extended phenazines. Furthermore, live-cell imaging experiments identified one compound (P1) as a marker for intracellular lipid droplets with minimal background and enhanced performance over the lipophilic tracker Nile Red.

The development of a novel AND logic based fluorescence probe for the detection of peroxynitrite and GSH

We have developed a novel AND logic based fluorescence probe for the simultaneous detection of ONOO^– and GSH (GSH-PF3).

We have developed a novel AND logic based fluorescence probe for the simultaneous detection of ONOO^– and GSH (GSH-PF3). The GSH-PF3 probe was synthesised over three steps starting from commercially available fluorescein. The probe was constructed by attaching the GSH reactive motif, 2,4-dinitrobenzenesulfonyl, to the previously reported boronate fluorescence based probe, PF3. GSH-PF3 produced only a small fluorescence response towards the addition of GSH or ONOO^– separately. However, when the probe was exposed to both analytes, there was a significant (40-fold) fluorescence enhancement. GSH-PF3 demonstrated an excellent selectivity towards both GSH and ONOO^–. In cellular imaging experiments the probe was shown to be cell permeable with no ‘turn-on’ response observed for the addition of either GSH or ONOO^– separately. However, in the presence of both analytes, a clear fluorescence response was observed in live cells. GSH-PF3 was further able to monitor the co-existence of metabolically produced ONOO^– and GSH by exogenous stimulation.

Recent progresses in small-molecule enzymatic fluorescent probes for cancer imaging

An overview of recent advances in small-molecule enzymatic fluorescent probes for cancer imaging, including design strategies and cancer imaging applications.