Development of fentanyl-specific monoclonal antibody (mAb) to antagonize the pharmacological effects of fentanyl.

Fentanyl, a critical component of opioid analgesics, poses a severe threat to public health, exacerbating the drug problem due to its potential fatality. Herein, we present two novel haptens designed with different attachment sites conjugated to keyhole limpet hemocyanin (KLH), aiming to develop an efficacious vaccine against fentanyl. KLH-Fent-1 demonstrated superior performance over KLH-Fent-2 in antibody titer, blood-brain distribution, and antinociceptive tests. Consequently, we immunized mice with KLH-Fent-1 to generate fentanyl-specific monoclonal antibodies (mAbs) using the hybridoma technique to compensate for the defects of active immunization in the treatment of opioid overdose and addiction. The mAb produced by hybridoma 9D5 exhibited the ability to recognize fentanyl and its analogs with a binding affinity of 10-10 M. Subsequently, we developed a human IgG1 chimeric mAb to improve the degree of humanization. Pre-treatment with murine and chimeric mAb significantly reduced the analgesic effect of fentanyl and altered its blood-brain biodistribution in vivo. Furthermore, in a mouse model of fentanyl-induced respiratory depression, the chimeric mAb effectively reversed respiratory depression promptly and maintained a certain level during the week. The development of high-affinity chimeric mAb gives support to combat the challenges of fentanyl misuse and its detrimental consequences. In conclusion, mAb passive immunization represents a viable strategy for addressing fentanyl addiction and overdose.

The NLRP3 inflammasome: a vital player in inflammation and mediating the anti-inflammatory effect of CBD.

BACKGROUND: The NLRP3 inflammasome is a vital player in the emergence of inflammation. The priming and activation of the NLRP3 inflammasome is a major trigger for inflammation which is a defense response against adverse stimuli. However, the excessive activation of the NLRP3 inflammasome can lead to the development of various inflammatory diseases. Cannabidiol, as the second-most abundant component in cannabis, has a variety of pharmacological properties, particularly anti-inflammation. Unlike tetrahydrocannabinol, cannabidiol has a lower affinity for cannabinoid receptors, which may be the reason why it is not psychoactive. Notably, the mechanism by which cannabidiol exerts its anti-inflammatory effect is still unclear. METHODS: We have performed a literature review based on published original and review articles encompassing the NLRP3 inflammasome and cannabidiol in inflammation from central databases, including PubMed and Web of Science. RESULTS AND CONCLUSIONS: In this review, we first summarize the composition and activation process of the NLRP3 inflammasome. Then, we list possible molecular mechanisms of action of cannabidiol. Next, we explain the role of the NLRP3 inflammasome and the anti-inflammatory effect of cannabidiol in inflammatory disorders. Finally, we emphasize the capacity of cannabidiol to suppress inflammation by blocking the NLRP3 signaling pathway, which indicates that cannabidiol is a quite promising anti-inflammatory compound.

Development of new matrix reference materials for quantitative urine analysis in drug tests.

Accurate quantitative analyses require standardized methods to control and improve the analytical process in the laboratory. The availability of urine reference materials (RMs) may offer a feasible option to improve the accuracy of urine analysis and to control matrix effects. This paper presents the complete process of the development of matrix RMs in urine, including sample preparation, homogeneity, and stability studies, as well as uncertainty assessment. A freeze-drying process was developed, and freeze-dried human and pig urine samples were prepared and verified to have comparable homogeneity to liquid samples and higher stability than liquid human, pig, and artificial urine samples at 4℃ or room temperature and under extreme conditions. A total of 21 authentic urine samples from August 2022 were measured with freeze-dried RMs and spiked urine samples, and the reliability of the quantification of the RMs was compared. The freeze-dried human urine matrix RM appeared to be an excellent tool for daily quality control, as it showed high stability and gave the most consistent results with spiked samples.

A mini-invasive surgical technique for Carlevale IOL implantation: case series study and description of concomitant surgery.

PURPOSE: To examine the feasibility and outcomes of a modified technique for the implantation of scleral fixated Carlevale intraocular lens (IOL) (I71 FIL SSF. Soleko IOL Division, Pontecorvo, Italy), and to analyze the occurrence of adverse events. METHODS: This is a retrospective observational study conducted revising patients charts from 2018 to 2023. Thirty-five eyes of 33 patients were included. Patients requiring IOL explantation had either IOL dislocation or opacification. The implantation of the Carlevale IOL was performed with the subconjunctival positioning of the anchors without any scleral flap. All maneuvers were performed transconjunctivally. The anatomical outcomes considered were IOL positioning, and the absence of postoperative complications. The functional outcomes analyzed were best correctedvisual acuity (BCVA) and refraction. RESULTS: In all the cases, the IOL was well positioned and centered postoperatively. No cases of conjunctival erosion were recorded. The best corrected visual acuity (BCVA) was 0.9±0.6 logMar (mean±standard deviation) preoperatively and 0.5±0.5 logMar (mean±standard deviation) postoperatively. The mean preoperative spherical equivalent was +6.8±7.7 dioptres, while postoperatively it was -1.1±1.6 dioptres. The most frequent procedure associated to secondary IOL implantation was posterior vitrectomy (25 eyes, 71.4%), which was performed with 25-gauge transconjunctival cannulas in the ciliary sulcus. The follow-up period was 24.5±16.9 months (mean±standard deviation). CONCLUSION: The described mini-invasive technique for Carlevale IOL implantation is safe and effective. It can be recommended either as a stand-alone operation or associated to concurrent surgical procedures.

In-sample stability and postsampling analysis of 21 illicit drugs, their metabolites and cotinine in wastewater.

A thorough understanding of the degradation of chemical biomarkers in wastewater after the sampling is critical in the surveillance of illicit drug use based on the back-calculation technique. Herein, three temperatures, eight groups of matrices, and acidification were applied to simulate the preservation condition of 21 illicit drugs, their metabolites, and cotinine for a 240-day stability study. It was proved that the temperature, matrices, and acidification play vital roles in their stability in wastewater. Most of them demonstrated high stability (transformation rates < 20%) during room temperature for 45 days, and the transformation rates decreased while the storage temperature reduced. The stability of the target compounds such as cocaine (COC), 6-monoacetylmorphine (6-MAM), and amphetamine (AM) is influenced by matrices. Acidification prevented the majority of analytes from transforming, making it a feasible solution for preservation after sampling. A model that combined the effects of temperature and matrix was developed to back-calculate the concentration of target compounds during the postsampling process. The feasibility of this model was validated by correcting the loss of COC and 6-MAM from 24.2% and 16.2% to 2.98% and 2.77%. This study simulated a typical large-scale sampling and storage scenario. The effect of the temperature, pH, and matrix on in-sample stability and the postsampling analysis of selected target compounds was investigated for the first time in this study.

Magnetic Liposomes Infused with GPCR-Expressing Cell Membrane for Targeted Extraction Using Minimum Organic Solvent: An Investigative Study of Trace THC in Sewage.

Trace analysis of lipophilic substances in complex environmental, food, or biological matrices has proven to be a challenge, on account of their high susceptibility to adsorption by particulate matter and liquid-solid interfaces. For this purpose, liquid-liquid extraction (LLE) is often employed as the separation method, which uses water-immiscible organic solvents. As an alternative, magnetic solid-phase extraction (MSPE) allows for adsorption, separation, and recovery of analytes from large volumes of aqueous samples with minimum usage of organic solvents. However, the poor selectivity hampers its performance in various scenarios, especially in sewage samples where complicated and unpredictable interference exists, resulting in block of the active adsorption sites of the sorbent. To this end, we propose receptor-affinity MSPE employing magnetic liposomes decorated with cell membranes expressing G-protein-coupled receptor as the sorbents. Application of the novel sorbent CM@Lip@Fe infused with CB1 cannabinoid receptors was demonstrated for the targeted extraction and enrichment of tetrahydrocannabinol from sewage matrix. Thanks to the high affinity and molecular selectivity of the ligand-receptor interactions, a limit of quantitation of 5.17 ng/L was achieved coupled with HPLC-MS/MS in unfiltered raw sewage, featuring minimum usage of organic solvents, fivefold enhanced sensitivity, low sorbent dosage (75 mg/L of sewage), and high efficiency as major advantages over conventional LLE. This work establishes a framework for efficient separation of specific molecules from complex media, thus promising to extend and refine standard LLE as the clean-up procedure for trace analysis.

Cucurbituril-protected dual-readout gold nanoclusters for sensitive fentanyl detection.

A large number of cases showed that fentanyl (FEN) has become the main cause of death from illegal drug overdose owing to its potent effect on respiratory depression, which has emerged as a grave threat to public health and safety. However, traditional analytical methods require cost-prohibitive equipment, complex pretreatment procedures, and technically trained experts, thus highlighting the urgent need to develop a cost-effective, straightforward, and highly sensitive method to detect FEN. This work demonstrated a dual-readout sensor FGGC-AuNCs@Q7 for FEN detection, which is based on the molecular recognition and self-assembly between the macrocycle cucurbit[7]uril (Q7) and FEN, accompanying spontaneous visual Tyndall effect and fluorescence optical responses of the gold nanoclusters within seconds. A detection limit of 1 ng mL-1 and a linear range of 9 to 148 000 ng mL-1 were achieved for fluorescence detection on FEN, with favorable selectivity in the presence of other illicit drugs or common interferents. The proposed method has been proved by its satisfactory application for the analysis of human urine.

Machine Learning-Assisted Rapid Screening of Four Types of New Psychoactive Substances in Drug Seizures.

Over the past few years, new psychoactive substances (NPS) have become a global health and social problem because of their wide variety, constant structural renewal, vague legal definitions, and rapid adaptation to legal restrictions. The rapid structural modifications of NPS have posed significant challenges for the screening and identification of these new substances using traditional mass spectrometric techniques based on reference substances or a mass spectral database. Here, we propose supervised machine learning (ML) classification models such as k-nearest neighbors, support vector machine, random forest, and multigrained cascade forest for the rapid screening of NPS using mass spectrometric data. This approach utilizes ML methods to learn the statistical probability distributions of mass spectral data for NPS and non-NPS. Four classification ML models were generated and evaluated using a data set comprising 567 LC-MS and 732 GC-MS spectra. Through cross validation, we achieved an F1 score of 0.35-0.97. These algorithms were applied in conjunction with mass spectrometry techniques for the detection of six seizures including electronic cigarette oil and suspected powdered substances netted in drug trafficking cases. The models provided warning signals for synthetic cannabinoids, synthetic cathinones, and fentanyl. Thus, an early warning system was successfully established, which provided a useful method for reliable and effective identifications of unknown NPS.

Assessment of abuse potential of carfentanil.

Carfentanil, as a fentanyl analogue, is a potent synthetic opioid. It has been controlled in many countries, and its emergence has been highlighted by many recent reports. However, although discriminative stimulus effects of carfentanil in rats had been reported, its abuse potential has not been fully evaluated. In this study, we evaluated the abuse potential of carfentanil via the tests of conditioned place preference (CPP), drug self-administration and naloxone-precipitated opioid withdrawal assay, compared with fentanyl and heroin. Carfentanil exhibited significant place preference at a minimum dose of 1 µg/kg in mice, whereas fentanyl and heroin induced significant place preference at the minimum doses of 100 µg/kg and 1000 µg/kg, respectively. In the drug-substitution test in heroin self-administered rats (50 µg/kg/infusion), carfentanil and fentanyl acquired significant self-administrations above saline levels from 0.05-0.1 and 0.1-10.0 µg/kg/infusion, respectively. Carfentanil induced the maximum number of infusions at 0.1 µg/kg, whereas fentanyl and heroin at 1 and 25 µg/kg, respectively. In short, carfentanil showed the highest potency to induce CPP and self-administration. Furthermore, repeated treatment with escalating doses of carfentanil, fentanyl or heroin induced typical withdrawal symptoms in mice, including a greater number of jumping and weight loss than saline group. This indicated that carfentanil could produce physical dependence similar to fentanyl and heroin. Taken together, the present study demonstrated the higher abuse potential of carfentanil compared with fentanyl and heroin. The rank order of abuse potential for these compounds is carfentanil > fentanyl > heroin.

The relationship between dietary fibre and stroke: A meta-analysis.

OBJECTIVE: An analysis was conducted to explore the relationship between dietary fibre intake and stroke risk. METHODS: PubMed, EMBASE, Cochrane Library, China National Knowledge Infrastructure (CNKI) and WanFang and Weipu databases were systematically searched to obtain peer-reviewed literature on the relationship between dietary fibre and stroke risk. The search time was as of 1 April 2023. Newcastle-Ottawa Scale (NOS) was used to evaluate the quality of the included studies. The pooled hazard ratio (HR) and 95% confidence interval (CI) were calculated using Stata 16.0. The Q test and I2 statistics were used to evaluate the heterogeneity and sensitivity analysis to explore potential bias. Meta-regression analysis was conducted to explore the relationship between total dietary intake quality and stroke risk. RESULTS: Sixteen high-quality studies, involving 855,671 subjects, met the inclusion criteria and were involved in the final meta-analysis. The results showed that higher total dietary fibre (HR: 0.81; 95% CI: 0.75-0.88), fruit fibre (HR: 0.88; 95% CI: 0.82-0.93), vegetable fibre (HR: 0.85; 95% CI: 0.81-0.89), soluble fibre (HR: 0.82; 95% CI: 0.72-0.93) and insoluble fibre (HR: 0.77; 95% CI: 0.66-0.89) had a positive effect on reducing the risk of stroke. However, cereal fibre (HR: 0.90; 95% CI: 0.81-1.00) was not statistically significant in reducing the risk of stroke. For different stroke types, higher total dietary fibre was associated with ischemic stroke (HR: 0.83; 95% CI: 0.79-0.88) and had a similar positive effect but was not found in haemorrhagic stroke (HR: 0.91; 95% CI: 0.80-1.03). Stroke risk decreased with increased total dietary fibre intake (ß=-0.006189, P=0.001). No potential bias from the individual study was found from sensitivity analysis. CONCLUSION: Increasing dietary fibre intake had a positive effect on reducing the risk of stroke. Different dietary fibres have various effects on stroke.

Teaching PCR for Simultaneous Sensing of Gene Transcription and Downstream Metabolites by Cucurbit[8]uril-Mediated Intervention of Polymerase Activity.

The target of typical PCR analysis is restricted to nucleic acids. To this end, we report here a novel strategy to simultaneously detect genetic and metabolic markers using commercial PCR kits with cucurbit[8]urils (CB[8]) implemented to manipulate the activity of Taq DNA polymerase. CB[8] binds with the nonionic surfactants and displaces them from the polymerase surface, resulting in decreased enzyme activity. Meanwhile, the inhibited enzyme can be reversibly activated when spermine, the downstream metabolite of ornithine decarboxylase (ODC), is present in the sample, which competitively binds to CB[8] and recovers polymerase activity. CB[8] was implemented in conventional PCR kits not only to reduce false-positive results but also to extend the detection range of PCR technology. With this novel method to detect ODC in cell lysates containing both the nucleotides and intracellular metabolites, positive results were only observed in highly active HEK 293T cells, whereas silent cells treated with ODC inhibitor showed negative readouts, therefore providing a simple but elegant dual-modality PCR method for precision diagnosis.

Label-free tumor cell screening based on IDO1-mediated tryptophan metabolism at single cell level.

Indoleamine 2,3-dioxygenase 1 (IDO1) plays a critical role in inflammatory and immunometabolism programming through catalyzing the oxidation of tryptophan (Trp) into downstream N-formylkynurenine. IDO1 is typically up-regulated in malignant tumors, making it a potential biomarker for cancer diagnosis. Here we show an effective strategy for tumor cell detection by integrating IDO1 activity assay with single cell-encapsulated droplets on a microfluidic platform for high-throughput bioanalysis. Mixed cells, as well as other cofactors, are encapsulated in individual droplets, which act as dynamic microreactors for IDO1-catalyzed oxidation of Trp. After pico-injection of a biosensing ensemble consisting of the macrocycle cucurbit [8]uril (Q8) and a fluorescent guest, rapid and robust screening of tumor cells by fluorescence signal is achieved in a few minutes reporting to Trp depletion, expanding the scope of conventional antibody-based detection of protein biomarkers. The results represent the first example of quantifying IDO1 enzymatic activity at the single cell level with a high-throughput performance, therefore promising warning signs and early diagnosis of tumor cells.

2-Fluorodeschloroketamine has similar abuse potential as ketamine.

2-Fluorodeschloroketamine (2-FDCK) as a substitute for ketamine has emerged among drug abusers in recent years. However, 2-FDCK has not been controlled or regulated in many countries, which may be partly related to the lack of evidence on its abuse potential. In this study, we evaluated the abuse potential of 2-FDCK via the tests of the conditioned place preference (CPP), locomotor sensitization, drug self-administration and drug discrimination using ketamine as a reference. 2-FDCK induced significant CPP at a minimum dose of 3 mg/kg in mice, an effect comparable with that of ketamine (3 mg/kg). Acute injections of 2-FDCK or ketamine at 30 mg/kg enhanced locomotor activity. Repeated treatments with this dose of 2-FDCK and ketamine induced locomotor sensitization after withdrawal. 2-FDCK readily induced self-administration with 0.5 mg/kg/infusion, the same dose for ketamine, and induced the highest seeking response at 1 mg/kg. Drug discrimination test showed that 2-FDCK dose-dependently substitute for ketamine with comparable ED50 to ketamine in substitution testing. Taken together, these results strongly suggested that 2-FDCK has an abuse potential comparable with ketamine.

Advances in Cryochemistry: Mechanisms, Reactions and Applications.

It is counterintuitive that chemical reactions can be accelerated by freezing, but this amazing phenomenon was discovered as early as the 1960s. In frozen systems, the increase in reaction rate is caused by various mechanisms and the freeze concentration effect is the main reason for the observed acceleration. Some accelerated reactions have great application value in the chemistry synthesis and environmental fields; at the same time, certain reactions accelerated at low temperature during the storage of food, medicine, and biological products should cause concern. The study of reactions accelerated by freezing will overturn common sense and provide a new strategy for researchers in the chemistry field. In this review, we mainly introduce various mechanisms for accelerating reactions induced by freezing and summarize a variety of accelerated cryochemical reactions and their applications.

Triplexed Tracking Labile Sulfur-Containing Species on a Single-Molecule "Nezha" Sensor.

Sulfur-containing species (SCS), especially sulfur dioxide-relevant species, play an essential role in ecological balance. Owing to the intrinsically labile and mobile characteristics of SCS, it is still considered to be an insurmountable challenge for multiplexed tracking dynamics of SCS with distinct molecular structure, valence state, and condensed state. To address this key problem, we proposed herein alternative versatile single-molecule sensors (VSMs) that intramolecularly integrate high affinity target-guided multiple recognition units into a single sensory molecule, clarified as molecular Nezha available in triplexed responses to gaseous sulfur dioxide, liquid sulfur trioxide, and aqueous bisulfite through ubiquitous charge transfer and nucleophilic addition. High-performance molecular Nezha remarkably facilitated promising applications in a quantitative visualization of SCS on lab-on-paper and tracking the dynamics transformation of SCS as well comprehensive evaluation of multiphase adsorption science of SCS on an advanced Zeolitic imidazolate framework-8 (ZIF-8).

Recent advances in the NEK7-licensed NLRP3 inflammasome activation: Mechanisms, role in diseases and related inhibitors.

The nucleotide-binding oligomerization domain (NOD)-like receptor containing pyrin domain 3 (NLRP3) inflammasome is a high-molecular-weight complex mediated by the activation of pattern-recognition receptors (PRRs) seed in innate immunity. Once NLRP3 is activated, the following recruitment of the adapter apoptosis-associated speck-like protein containing a caspase recruitment domain (CARD) (ASC) and procaspase-1 would be initiated. Cleavage of procaspase-1 into active caspase-1 then leads to the maturation of the precursor forms of interleukin (IL)-1ß and IL-18 into biologically active IL-1ß and IL-18. The activation of NLRP3 inflammasome is thought to be tightly associated with a regulator never in mitosis A (NIMA)-related kinase 7 (NEK7), apart from other signaling events such as K+ efflux and reactive oxygen species (ROS). Plus, the NLRP3 inflammasome has been linked to various metabolic disorders, chronic inflammation and other diseases. In this review, we firstly describe the cellular/molecular mechanisms of the NEK7-licensed NLRP3 inflammasome activation. Then we detail the potential inhibitors that can selectively and effectively modulate either the NEK7-NLRP3 complex itself or the related molecular/cellular events. Finally, we describe some inhibitors as promising therapeutic strategies for diverse diseases driven by NLRP3 inflammasome.

Impurity profiling of alfentanil hydrochloride by liquid chromatography/quadrupole time-of-flight high-resolution mass spectrometric techniques for drug enforcement.

RATIONALE: Fentanyl and its analogues play important roles in the hospital and clinic setting as anesthetics. However, illicitly manufactured fentanyl as well as the new psychoactive substances (NPS) account for 30% of all deaths in the United States. Since fentanyl derivatives and NPS are designed to produce similar effects, their related substances are similar or even have the same active groups. A comprehensive analysis of the related substances of alfentanil hydrochloride can provide a basis for the identification and supervision of fentanyl derivatives and NPS. METHODS: A liquid chromatography/quadrupole time-of-flight tandem mass spectrometry (LC/QTOF-MS/MS) method was developed for the separation and characterization of related substances in alfentanil hydrochloride. Degradation studies were conducted according to the ICH-prescribed stress conditions. The compounds were identified mainly through positive electrospray ionization QTOF high-resolution mass spectrometric measurements of the accurate masses of the precursor and product ions and their calculated elemental compositions. Their formation mechanisms were also discussed. RESULTS: Seventeen related substances were detected in alfentanil hydrochloride and its stressed samples. Among them, nine were process-related substances and the other eight were degradation products. The stress study results demonstrated that alfentanil hydrochloride was unstable under acid, alkaline, and oxidative stress conditions, while relatively stable under dry photolytic and thermal stress conditions. Alfentanil hydrochloride was most susceptible for degradation at the N-phenylpropanamide and piperidine sites. CONCLUSIONS: Process-related alfentanil hydrochloride compounds are useful for determination of synthetic routes and entangling of fentanyl analogues. The stress study results can provide a sound scientific basis for the waste water monitoring of alfentanil. These results are important for routine quality control in the manufacturing and storage of alfentanil hydrochloride, as well as for drug enforcement of fentanyl and its analogues.

Removal of Tetracycline in Sewage and Dairy Products with High-Stable MOF.

Serious environmental and human health problems caused by the abuse of antibiotics have attracted worldwide concern. Recently, metal-organic frameworks (MOFs) with high porosity have drawn wide attention for their effects in the adsorption and removal of pollutants from complex matrices. Herein, a high-stable metal organic framework (MOF), i.e., ((ZnCl2)3(L)2·DMF)n, where L=1,3,5-tris((pyridin-4-ylthio)methyl)benzene), MOF 1, was applied to adsorb and remove tetracycline from sewage and dairy products. The results showed that MOF 1 exhibited a strong performance in the adsorption of tetracycline. The effects of initial pH values, adsorbent dose, contact time and ionic strength of the adsorption performance of MOF 1 were investigated. The adsorption kinetics best fit the pseudo-second order model, and the adsorption isotherms matched the Langmuir adsorption model well. It was indicated that both chemical adsorption and physical adsorption play an important role in the adsorption process, and the adsorption of tetracycline was homogeneous and occurred on a monolayer on the surface of MOF 1. Additionally, the stability of MOF 1 and the details of the adsorption mechanism were also investigated. Thus, this study provides a new candidate for the application of MOFs-based adsorbents in the removal of antibiotics from sewage and dairy products.

Reversibly Switching the Charge State and Adsorption Location of A Single Potassium Atom on Ultrathin CuO Films.

Potassium (K) cations are spontaneously formed upon thermal deposition of low-coverage K onto an ultrathin CuO monolayer grown on Cu(110) and they were explored by low-temperature scanning tunneling microscopy (STM) and X-ray photoemission spectroscopy. The formed K cations are highly immobile and thermally stable. The local work function around an individual K cation decreases by 1.5±0.3 eV, and a charging zone underneath it is established within about 1.0 nm. The cationic and neutral states of the K atom are switchable upon application of an STM bias voltage pulse, which is simultaneously accompanied by an adsorption site relocation.

Displacement Induced Off-On Fluorescent Biosensor Targeting IDO1 Activity in Live Cells.

We show how the macrocyclic host cucurbit[8]uril (CB[8]) and a fluorescent dye form a biosensing ensemble while its cavity simultaneously traps tryptophan, the upstream substrate of IDO1 enzymes, therefore providing a label-free method to monitor the activity of IDO1 in real time. Incubation of malignant HeLa and HepG2 cells overexpressing IDO1 with the associative biosensor resulted in its spontaneous uptake and a fluorescence switch-on response in situ, which can be traced to the displacement of tryptophan from CB[8] upon IDO1-catalyzed oxidation. The results, for the first time, establish a supramolecular sensing concept for the detection of intracellular enzymatic activity in live cells, thus allowing direct cell-based analysis and inhibitor screening compatible with commercial instruments including microplate reader, fluorescent microscopy, and flow cytometry.