All solid-state miniaturized potentiometric sensors for flunitrazepam determination in beverages

Eu-MOF-based highly sensitive and selective luminescence probe for trace, in situ and visual detection of flunitrazepam

Flunitrazepam, as an emerging new psychoactive substance classified as a third-generation drug that is more harmful and camouflaged, is gradually proliferating globally. Maliciously used as a criminal tool in homicide and rape cases, it has already caused serious harm to public safety and social stability. Owing to its special molecular structure, low concentration level and rapid metabolic process in the human body, accurate detection of flunitrazepam remains a major challenge, especially for real sample and on-site detection. In this paper, a lanthanide MOF (Eu-MOF) based on bi-ligand was constructed as a luminescence probe and used for the first time to detect trace amounts of flunitrazepam. The 'antenna effect' promotes strong luminescence of Eu-MOF, while the lower LUMO orbital energy level of flunitrazepam allows it to accept electrons from the electron donor leading to quenching of Eu-MOF luminescence. The probe has a high sensitivity and can detect flunitrazepam in the range of 0-800 μM with a detection limit as low as 73 nM. Moreover, flunitrazepam was detected in urine from real samples as well as in a variety of beverages to further validate its accuracy and practicality. The reported Eu-MOF represents one of the pioneering luminescence probes for the detection of flunitrazepam, which offers great promise for the on-site or on-line analysis of flunitrazepam.

Recent advances in nanomaterial-based solid-contact ion-selective electrodes

Solid-contact ion-selective electrodes (SC-ISEs) are advanced potentiometric sensors with great capability to detect a wide range of ions for the monitoring of industrial processes and environmental pollutants, as well as the determination of electrolytes for clinical analysis. Over the past decades, the innovative design of ion-selective electrodes (ISEs), specifically SC-ISEs, to improve potential stability and miniaturization for in situ/real-time analysis, has attracted considerable interest. Recently, the utilisation of nanomaterials was particularly prominent in SC-ISEs due to their excellent physical and chemical properties. In this article, we review the recent applications of various types of nanostructured materials that are composed of carbon, metals and polymers for the development of SC-ISEs. The challenges and opportunities in this field, along with the prospects for future applications of nanomaterials in SC-ISEs are also discussed.

Flunitrazepam induces neurotoxicity in zebrafish through microbiota-gut-brain axis

The abuse of psychoactive substances has led to their frequent detection in the environment, with unknown effects on the nervous system. In this study, zebrafish were exposed to benzodiazepine drug flunitrazepam (FLZ, 0.2 and 5 μg/L) for 30 days to assess its neurotoxicity. Results revealed that FLZ disrupted the balance of gut microbiota and caused an increase in pathogenic bacteria, such as Paracoccus and Aeromonas, leading to pathological damage to the intestine. The upregulation of intestinal pro-inflammatory factors, IL-1β and TNF-α, by 2.4 and 6.3 times, respectively, along with the downregulation of tight junction proteins, Occludin and zonula occludens 1 (ZO-1), by 80 % and 50 %, increased in intestinal permeability. Moreover, untargeted metabolomics demonstrated that FLZ interfered with intestinal nucleotide metabolism and amino acid biosynthesis. FLZ could also increase the levels of lipopolysaccharide (LPS) and malondialdehyde (MDA) in the brain by 0.9 and 3.4 times, respectively, leading to pathological changes in brain tissue. Furthermore, FLZ significantly disturbed nucleotide metabolism and amino acid biosynthesis and metabolism pathways in the brain. Correlation analysis between gut microbiota and neurochemicals confirmed that FLZ can induce neurotoxicity through the microbiota-gut-brain axis. These findings elucidate the molecular mechanisms of psychoactive drugs on microbiota-gut-brain axis and provide a theoretical basis for the ecological environmental risk assessment of various psychoactive substances.

All-solid-state chip utilizing molecular imprinted polymer for erythromycin detection in milk samples: Printed circuit board-based potentiometric system

Detection of erythromycin (ERY) residues in commercial milk samples is crucial for the safety assessment. Herein, a printed circuit board was patterned as a feasible miniaturized potentiometric sensor for ERY determination in dairy samples. The proposed chip design fits to a 3.5-mm female audio plug to facilitate the potential measurements of working electrode versus reference one in this all-solid-state system. The sensor utilizes molecular imprinted polymer (MIP) for the selective recognition of the studied drug in such challenging matrix. The electrode stability is achieved through the addition of poly (3,4-ethylenedioxythiophene) nano-dispersion on its surface. The proposed device detects down to 6.6 × 10-8 M ERY with a slope of 51 mV/decade in the 1 × 10-7-1 × 10-3 M range. The results display high accuracy (99.9% ± 2.6) with satisfactory relative standard deviation for repeatability (1.6%) and reproducibility (5.0%). The effect of common antibiotic classes, namely, amphenicols, beta-lactams, fluoroquinolones, sulfonamides, and tetracyclines, can be neglected as evidenced by their calculated binding capacities towards the proposed MIP. The calculated selectivity coefficients also show a good electrode performance in the presence of naturally present inorganic ions allowing its application to different milk samples.

Application of Paper-Based Microfluidic Analytical Devices (µPAD) in Forensic and Clinical Toxicology: A Review

The need for providing rapid and, possibly, on-the-spot analytical results in the case of intoxication has prompted researchers to develop rapid, sensitive, and cost-effective methods and analytical devices suitable for use in nonspecialized laboratories and at the point of need (PON). In recent years, the technology of paper-based microfluidic analytical devices (μPADs) has undergone rapid development and now provides a feasible, low-cost alternative to traditional rapid tests for detecting harmful compounds. In fact, µPADs have been developed to detect toxic molecules (arsenic, cyanide, ethanol, and nitrite), drugs, and drugs of abuse (benzodiazepines, cathinones, cocaine, fentanyl, ketamine, MDMA, morphine, synthetic cannabinoids, tetrahydrocannabinol, and xylazine), and also psychoactive substances used for drug-facilitated crimes (flunitrazepam, gamma-hydroxybutyric acid (GHB), ketamine, metamizole, midazolam, and scopolamine). The present report critically evaluates the recent developments in paper-based devices, particularly in detection methods, and how these new analytical tools have been tested in forensic and clinical toxicology, also including future perspectives on their application, such as multisensing paper-based devices, microfluidic paper-based separation, and wearable paper-based sensors.

Point-of-care electrochemical sensor for selective determination of date rape drug "ketamine" based on core-shell molecularly imprinted polymer

Misuse of illicit drugs is a serious problem that became the primary concern for many authorities worldwide. Point-of-care (POC) diagnostic tools can provide accurate and fast screening information that helps to detect illicit drugs in a short time. A portable, disposable and reproducible core-shell molecularly imprinted polymer (MIP) screen-printed sensor was synthesized as a POC analyzer for the assay of the date rape drug "ketamine hydrochloride" in different matrices. Firstly, the screen-printed electrode substrate was modified electrochemically with polyaniline (PANI) as an ion-to-electron transducer interlayer to improve the potential signal stability. Secondly, core-shell MIP was prepared, the core consisting of silica nanoparticles prepared by Stober's method, while the MIP shell was synthesized onto silica nanoparticles surface by copolymerizing methacrylic acid functional monomer and the crossing agent; ethylene glycol dimethacrylate in the presence of ketamine as a template molecule. Finally, the core-shell MIP was incorporated into the PVC membrane as an ionophore and drop-casted over PANI modified screen-printed carbon electrode. The imprinting process and the morphology of MIP were examined using scanning electron microscopy, Fourier-transform infrared and X-ray photoelectron spectroscopic methods. The sensor exhibited a short response time within 3-5 s in a pH range (2.0-5.0). The potential profile indicated a linear relationship in a dynamic concentration range of 1.0 × 10^-6 M to 1.0 × 10^-2 M with a slope of 54.7 mV/decade. The sensor was employed to determine ketamine in biological matrices and beverages.

Two fabricated carbon paste electrodes for novel potentiometric determination of probenecid in dosage form and human plasma

Solid contact ion selective electrodes are extensively utilized owing to their marvelous performance over traditional liquid contact ones. The main drawback of those solid contact electrodes is aqueous layer formation which affects their constancy. Herein and to overcome this common drawback, a carbon paste electrode containing poly(3,4-ethylenedioxythiophene) was constructed and used for determination of probenecid at variant pH values. This modification decreased the potential drift down to 0.8 mV/h and improved its stability over 30 days. A Nernstian slope of - 57.8 mV/decade associated with a linear range of 1.0 × 10^-6-1.0 × 10^-2 mol/L was obtained. The modified carbon paste electrode successfully detected up to 8.0 × 10^-7 mol/L probenecid. Results of this modified carbon paste electrode were also compared to unmodified one.

Wearable Electronic Finger for Date Rape Drugs Screening: From "Do-It-Yourself" Fabrication to Self-Testing

In-house digital fabrication of low-cost sensors that can on-site and rapidly detect adulteration of alcoholic beverages with sedation drugs (known as date rape drugs, (DRDs)) and analgesics is of great importance for everyday consumers and supervisory authorities. DRDs and analgesics are administrated in spirits for "drug-facilitated sexual assault" crimes and for the reduction of the following day hangover caused by low-quality spirits, respectively. This work describes, a novel "do-it-yourself" wearable 3D printed electrochemical finger (e-finger), which enables direct, rapid, and multianalyte self-testing of the main DRDs (flunitrazepam, scopolamine, ketamine) and paracetamol via direct immersing into a spirit shot. The oxygen interference on flunitrazepam detection was alleviated by dissolving an effervescent tablet of vitamin C in the spirit shot, as ascorbic acid serves as a scavenger for dissolved oxygen. The e-finger can be printed in-house at any size by anyone with access to a low-cost domestic 3D printer using a simple, fast, and low-cost printing procedure. The e-finger is addressed by a smartphone-based miniature potentiostat and allows on-the-spot self-checking of the quality and safety of alcoholic spirits, via a single calibration-free voltammetric measurement, readily performed even by untrained end users. The e-finger is a new powerful screening tool in the hands of supervisory authorities to conduct on-site forensic investigations. More importantly, it paves the way toward in-house e-production of "ready-to-use" reliable self-testing devices.