A NIR fluorescent probe for Vanin-1 and its applications in imaging, kidney injury diagnosis, and the development of inhibitor

Discovering a New Drug Against Acute Kidney Injury by Using a Tailored Photoacoustic Imaging Probe

Acute kidney injury (AKI) has become an increasing concern for patients due to the widespread clinical use of nephrotoxic drugs. Currently, the early diagnosis of AKI is still challenging and the available therapeutic drugs cannot meet the clinical demand. Herein, this work has investigated the key redox couple involved in AKI and develops a tailored photoacoustic (PA) imaging probe (AB-DiOH) which can reversibly respond to hypochlorite (ClO-)/glutathione (GSH) with high specificity and sensitivity. This probe enables the real-time monitoring of AKI by noninvasive PA imaging, with better detection sensitivity than the blood test. Furthermore, this probe is utilized for screening nephroprotective drugs among natural products. For the first time, astragalin is discovered to be a potential new drug for the treatment of AKI. After oral administration, astragalin can be efficiently absorbed by the animal body, alleviate kidney injury, and meanwhile induce no damage to other normal tissues. The treatment mechanism of astragalin has also been revealed to be the simultaneous inhibition of oxidative stress, ferroptosis, and cuproposis. The developed PA imaging probe and the discovered drug candidate provide a promising new tool and strategy for the early diagnosis and effective treatment of AKI.

Engineering Cyanine- and Hemicyanine-Based Probes for Optical Imaging of Kidney Diseases

Molecular optical probes play pivotal roles in in vivo imaging of biomarkers associated to kidney diseases. Relying on structural tunability and high fluorescence quantum yields, versatile optical probes have been constructed on cyanine or hemicyanine-based scaffold in recent years. This review summaries the recent progress on the development of optical probes for imaging of kidney diseases, particularly through near-infrared fluorescence, chemiluminescence and photoacoustic imaging modalities. The chemical design and sensing mechanisms are discussed along with applications in the detection of renal cell carcinoma and acute kidney injury. This progress provides insights and directions for the development of next generation kidney-targeted probes and for pushing their further applications in preclinical and clinical research.

A high-affinity fluorescent probe for human uridine-disphosphate glucuronosyltransferase 1A9 function monitoring under environmental pollutant exposure

Uridine-disphosphate glucuronosyltransferase 1A9 (UGT1A9), an important detoxification and inactivation enzyme for toxicants, regulates the exposure level of environmental pollutants in the human body and induces various toxicological consequences. However, an effective tool for high-throughput monitoring of UGT1A9 function under exposure to environmental pollutants is still lacking. In this study, 1,3-dichloro-7-hydroxy-9,9-dimethylacridin-2(9H)-one (DDAO) was found to exhibit excellent specificity and high affinity towards human UGT1A9. Remarkable changes in absorption and fluorescence signals after reacting with UGT1A9 were observed, due to the intramolecular charge transfer (ICT) mechanism. Importantly, DDAO was successfully applied to monitor the biological functions of UGT1A9 in response to environmental pollutant exposure not only in microsome samples, but also in living cells by using a high-throughput screening method. Meanwhile, the identified pollutants that disturb UGT1A9 functions were found to significantly influence the exposure level and retention time of bisphenol S/bisphenol A in living cells. Furthermore, the molecular mechanism underlying the inhibition of UGT1A9 by these pollutant-derived disruptors was elucidated by molecular docking and molecular dynamics simulations. Collectively, a fluorescent probe to characterize the responses of UGT1A9 towards environmental pollutants was developed, which was beneficial for elucidating the health hazards of environmental pollutants from a new perspective.

Tailored Zwitterionic Hemicyanine Reporters for Early Diagnosis and Prognostic Assessment of Acute Renal Failure

Drug-induced renal failure (DIRF) poses a serious medical complication with high mortality risk. However, early diagnosis or prognosis of DIRF remain challenging, as current methods rely on detecting late-stage biomarkers. Herein we present a library of zwitterionic unimolecular hemicyanines (ZCs) available for constructing activatable reporters to detect DIRF since its initial stage. Zwitterionic properties of these probes are achieved through interspersedly integrating alkyl sulfonates and quaternary ammonium cations onto hemicyanine skeleton, which result in record low plasma protein binding (<5 %) and remarkable renal clearance efficiencies (≈96 %). An activatable reporter ZCRR is further developed by masking the optimal candidate ZC6 with a tetrapeptide specifically cleavable by caspase-8, an initiating indicator of apoptosis. In living mice with cisplatin-induced DIRF, systematically administered ZCRR efficiently accumulates in kidneys and responds to elevated caspase-8 for near-infrared fluorescence signals 'turn-on', enabling sensitive detection of intrarenal apoptosis 60 h earlier than clinical methods, and precise evaluation of apoptosis remediation effects by different medications on DIRF mice. As it's urinary excretable, ZCRR also allows for remote detection of DIRF and predicting renoprotective efficacy through in vitro optical urinalysis. This study thus presents unimolecular renal clearable scaffolds that are applicable to developing versatile activatable reporters for renal diseases management.

Recent advances on emerging nanomaterials for diagnosis and treatment of inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic idiopathic inflammatory disorder that affects the entire gastrointestinal tract and is associated with an increased risk of colorectal cancer. Mainstream clinical testing methods are time-consuming, painful for patients, and insufficiently sensitive to detect early symptoms. Currently, there is no definitive cure for IBD, and frequent doses of medications with potentially severe side effects may affect patient response. In recent years, nanomaterials have demonstrated considerable potential for IBD management due to their diverse structures, composition, and physical and chemical properties. In this review, we provide an overview of the advances in nanomaterial-based diagnosis and treatment of IBD in recent five years. Multi-functional bio-nano platforms, including contrast agents, near-infrared (NIR) fluorescent probes, and bioactive substance detection agents have been developed for IBD diagnosis. Based on a series of pathogenic characteristics of IBD, the therapeutic strategies of antioxidant, anti-inflammatory, and intestinal microbiome regulation of IBD based on nanomaterials are systematically introduced. Finally, the future challenges and prospects in this field are presented to facilitate the development of diagnosis and treatment of IBD.

Vanin-1-Activated Chemiluminescent Probe: Help to Early Diagnosis of Acute Kidney Injury with High Signal-to-Noise Ratio through Urinalysis

Acute kidney injury (AKI) is a common medical condition with high morbidity and mortality. Although urinalysis provides a noninvasive and convenient diagnostic method for AKI at the molecular level, the low sensitivity of current chemical probes used in urinalysis hinders the time diagnosis of AKI. Herein, we achieved the sensitive and early diagnosis of AKI by the development of a chemiluminescent probe CL-Pa suitable for detection of urinary Vanin-1. Vanin-1 is considered as an early and sensitive biomarker for AKI, while few chemical probes have been applied to for its efficient detection. By virtue of the low autofluorescence interference during urine imaging in the chemiluminescence model, CL-Pa could realize the monitoring of the up-regulated urinary Vanin-1 with a high signal-to-noise ratio (∼588). Importantly, under the help of CL-Pa, the up-regulation of urinary Vanin-1 of cisplatin-induced AKI mice at 12 h post cisplatin injection was detected, which was much earlier than clinical biomarkers (sCr and BUN) and change of kidney histology (48 h post cisplatin injection). Furthermore, using this probe, the fluctuation of urinary Vanin-1 of mice with different degrees of AKI was monitored. This study demonstrated the ability of CL-Pa in sensitively detecting drug-induced AKI through urinalysis and suggested the great potential of CL-Pa for early diagnosis of AKI and evaluate the efficiency of anti-AKI drugs clinically.

Dual-Channel Recognition of Human Serum Albumin and Glutathione by Fluorescent Probes with Site-Dependent Responsive Features

Design of chemical probes with high specificity and responses are particularly intriguing. In this work, a fluorescent probe (M-OH-SO₃) with dual-channel spectral responses toward human serum albumin (HSA) is presented. By employing dinitrobenzenesulfonate as a recognition site as well as a fluorescence quencher, probe M-OH-SO₃ displayed weak fluorescence, which, nevertheless, exhibits extensive yellow (575 nm) and red (660 nm) fluorescence emissions toward HSA under excitations at 400 and 500 nm, respectively. Interestingly, M-OH-SO₃ displayed the best performance toward HSA with distinctly higher selectivity than that of its counterparts M-SO₃, M-H-SO₃, and M-F-SO₃, which were prepared simply by modulating the functional group at the ortho position of the dicyanoisophorone core. Molecular docking results revealed that M-OH-SO₃ possesses the lowest binding energy among the tested derivatives and accordingly the strongest binding affinity. Probe M-OH-SO₃ showed a good linear relationship toward HSA in a range of 0.5-18 μM with a limit of detection of 35 nM. Cell imaging results demonstrated that probe M-OH-SO₃ could visualize the variation HSA levels in hepatocarcinoma cells. In addition, probe M-OH-SO₃ could also be employed for the recognition of glutathione through the cleavage of the dinitrobenzenesulfonate group along with an enhancement of emission at 575 nm. The site-dependent properties inspired a novel paradigm for design of fluorescent probes with optimized selectivity and responses.

Visual Identification of Trichosporon asahii, a Gut Yeast Associated with Obesity, Using an Enzymatic NIR Fluorescent Probe

Lipase found in the gut microbiota participates in the digestion and absorption of dietary fats. As such, the gut microbiota is involved in the regulation of the host metabolism, affecting the levels of lipids and free fatty acids, ultimately resulting in obesity. In this study, an enzymatic activatable near-infrared fluorescent probe, DDAO-C6, was developed for visually sensing endogenous lipase from gut microbes. Using DDAO-C6, a cultivated intestinal yeast strain was rapidly identified from human feces that exhibited high lipase expression and was identified as Trichosporon asahii Y2. We then determined that the colonization of the gut of mice with T. asahii Y2 increased lipase activity in the digestive tract and promoted obesity and hyperlipidemia when the mice were fed high fat diets. Above all, the present research resulted in a fluorescence visualization tool for the functional investigation of gut microbiota associated with obesity and disorders of lipid metabolism.

Endoplasmic Reticulum-Targeting Near-Infrared Fluorescent Probe for CYP2J2 Activity and Its Imaging Application in Endoplasmic Reticulum Stress and Tumor

CYP2J2 as an endoplasmic reticulum (ER)-expressed vital cytochrome P450 isoform participates in the metabolism of endogenous polyunsaturated fatty acids. Its abnormal expression and function are closely related to the progress of cancer and cardiovascular diseases. Herein, an ER-targeting near-infrared (NIR) fluorescent probe ER-BnXPI was developed for monitoring CYP2J2 activity, which possessed a high selectivity and sensitivity toward CYP2J2 among various CYP450 isoforms and exhibited excellent subcellular localization for ER. Then, the CYP2J2 variation behavior under the ER stress model was imaged by ER-BnXPI in living cells and successfully used for the in vivo imaging in different tumors that well distinguished tumor tissues from para-cancerous tissues. All these findings fully demonstrated that ER-BnXPI could be used as a promising tool for exploring the physiological function of CYP2J2 and provided some novel approach for the diagnosis and therapy of CYP2J2-related vascular inflammation and cancer.

A Bioluminescent Probe for Detecting Norepinephrine in Vivo

As a neurotransmitter, norepinephrine (NE) is critical for psychiatric conditions, neurodegenerative diseases, and pheochromocytoma. A real-time and noninvasive method for the detection of NE as a tracer to investigate the NE-relevant disease treatment process is urgently desirable. Herein, we successfully developed a turn-on NE bioluminescent probe (NBP), which was grounded on p-toluenethiol deprotectrf by nucleophilic substitution. Compared with other analytes, the NBP exhibited high sensitivity and selectivity in vitro. More importantly, the NBP provides a promising strategy for in vivo imaging of NE in living animals with noninvasive visualization and real-time features.

Optical substrates for drug-metabolizing enzymes: Recent advances and future perspectives

Drug-metabolizing enzymes (DMEs), a diverse group of enzymes responsible for the metabolic elimination of drugs and other xenobiotics, have been recognized as the critical determinants to drug safety and efficacy. Deciphering and understanding the key roles of individual DMEs in drug metabolism and toxicity, as well as characterizing the interactions of central DMEs with xenobiotics require reliable, practical and highly specific tools for sensing the activities of these enzymes in biological systems. In the last few decades, the scientists have developed a variety of optical substrates for sensing human DMEs, parts of them have been successfully used for studying target enzyme(s) in tissue preparations and living systems. Herein, molecular design principals and recent advances in the development and applications of optical substrates for human DMEs have been reviewed systematically. Furthermore, the challenges and future perspectives in this field are also highlighted. The presented information offers a group of practical approaches and imaging tools for sensing DMEs activities in complex biological systems, which strongly facilitates high-throughput screening the modulators of target DMEs and studies on drug/herb‒drug interactions, as well as promotes the fundamental researches for exploring the relevance of DMEs to human diseases and drug treatment outcomes.

Visual Analysis and Inhibitor Screening of Leucine Aminopeptidase, a Key Virulence Factor for Pathogenic Bacteria-Associated Infection

Leucine aminopeptidase (LAP) is a hydrolase for the hydrolysis of peptides or proteins containing a leucine residue at the N-terminal. It is also known to be a key virulence factor for the pathogenic abilities of various pathogens causing infectious diseases, which indicated a new insight into the diagnosis and therapy of pathogenic infections. A new fluorescent probe (S)-2-amino-N-(4-(((6,8-dichloro-9,9-dimethyl-7-oxo-7,9-dihydroacridin-2-yl)oxy)methyl)phenyl)-4-methylpentanamide (DDBL) containing DDAO as the fluorophore and leucine as the recognition group was developed for LAP. By real-time visual sensing of LAP, six bacteria with LAP expression were identified efficiently from human feces, as well as by sensitive visual analysis using native-PAGE specially stained with DDBL. Furthermore, a high throughput screening system established with DDBL was applied to identify a natural inhibitor (3-acetyl-11-keto-β-boswellic acid, AKBA), which could attenuate mouse sepsis induced by Staphylococcus aureus. Therefore, the visual sensing of LAP by DDBL suggested the application for target bacteria identification and LAP homolog analysis as well as potential inhibitor expounding for treatment of bacterial infections.

A non-peptide probe for detecting chymotrypsin activity based on protection-deprotection strategy in living systems

Chymotrypsin (CHT) plays a vital role in the metabolism of organisms and affects cell proliferation and apoptosis. Abnormal levels of CHT will lead to a variety of diseases, such as inflammatory arthritis, diabetes, pharyngitis, indigestion, and pancreatic cancer. Therefore, it is significant to design an effective method for the detection of CHT in living systems. Here, we synthesized a specific deep-red non-peptide probe DT by effectively combining isophorone and p-hydroxybenzaldehyde for the detection of CHT using 3-phenylpropionate chloride as the recognition group based on a protection-deprotection strategy. The DT probe exhibited an emission range of 525-700 nm and showed excellent photostability, high sensitivity (LOD = 0.071 U mL^-1), and selectivity for CHT detection. The cellular experiments demonstrated that DT could sensitively recognize CHT activity in three cell lines and the content of CHT was much higher in P815 cells than in MCF-7 and 3T3 cells. Also, DT was successfully used to visualize the endogenous CHT in zebrafish. Notably, the DT probe provided an intuitive way to visualize endogenous CHT in mouse pancreas for the first time, demonstrating the potential for application in the future clinical diagnosis of pancreatic diseases. Therefore, the small-molecule probe DT is expected to be a useful molecular tool for CHT-related disease diagnosis and drug discovery.

2D Strategy for the Construction of an Enzyme-Activated NIR Fluorophore Suitable for the Visual Sensing and Profiling of Homologous Nitroreductases from Various Bacterial Species

Nitroreductases (NTRs) mediate the reduction of nitroaromatic compounds to the corresponding nitrite, hydroxylamine, or amino derivatives. The activity of NTRs in bacteria facilitates the metabolic activation and antibacterial activity of 5-nitroimidazoles. Therefore, NTR activity correlates with the drug susceptibility and resistance of pathogenic bacteria. As such, it is important to develop a rapid and visual assay for the real-time sensing of bacterial NTRs for the evaluation and development of antibiotics. Herein, an activatable near-infrared fluorescent probe (HC-NO2) derived from a hemicyanine fluorophore was designed and developed based on two evaluation factors, including the calculated partition coefficient (Clog P) and fluorescence wavelength. Using HC-NO2 as the special substrate of NTRs, NTR activity can be assayed efficiently, and then, bacteria can be imaged based on the detection of NTRs. More importantly, a sensitive in-gel assay using HC-NO2 has been developed to selectively identify NTRs and sensitively determine NTR activity. Using the in-gel assay, NTRs from various bacterial species have been profiled visually from the "fluorescence fingerprints", which facilitates the rapid identification of NTRs from bacterial lysates. Thus, various homologous NTRs were identified from three metronidazole-susceptible bacterial species as well as seven unsusceptible species, which were confirmed by the whole-genome sequence. As such, the evaluation of NTRs from different bacterial species should help improve the rational usage of 5-nitroimidazole drugs as antibiotics.

A NIR fluorescent probe for fatty acid amide hydrolase bioimaging and its application in development of inhibitors

Fatty acid amide hydrolase (FAAH) is primarily responsible for the inactivation of fatty acid ethanolamide (FAE) and is involved in a variety of biological functions related to diseases of the nervous system. Herein, we developed a highly selective and sensitive FAAH-activated near-infrared fluorescent probe named DAND and achieved the real-time detection and imaging of FAAH activity in complex biosystems. Moreover, a visual high-throughput screening method was established using DAND, piperine was identified as a novel inhibitor of FAAH. Based on the interaction of piperine with FAAH, a more potent FAAH inhibitor (11f) was designed and synthesized which possessed an IC₅₀ value of 0.65 μM. Furthermore, 11f could attenuate the liposaccharide (LPS)-induced activation of BV2 cells, exhibiting an excellent anti-inflammatory activity. These results indicated that DAND could be used as a promising molecular tool for exploring FAAH activity and for rapidly screening potential FAAH inhibitors. In addition, piperine and its derivatives could serve as potential candidate drugs for the treatment of neurodegenerative diseases in the future.