A novel composite film derived from cysteic acid and PDDA-functionalized graphene: Enhanced sensing material for electrochemical determination of metronidazole

Novel N-doped carbon dots derived from citric acid and urea: fluorescent sensing for determination of metronidazole and cytotoxicity studies

Blue emitting nitrogen-doped carbon dots were synthesized using citric acid and urea through the hydrothermal method, and the fluorescence quantum yield was 35.08%. We discovered that N-CDs featured excellent robust fluorescence stability and chemical resistance. For metronidazole detection, our N-CDs exhibited quick response time, high selectivity and sensitivity, and low cytotoxicity. Specifically, our N-CDs could detect metronidazole in the linear range of 0-179 μM, and the LOD was 0.25 μM. Furthermore, metronidazole efficaciously quenches the fluorescence of N-CDs, possibly owing to the inner filter effect. Lastly, we have employed our N-CDs to detect metronidazole in commercial metronidazole tablets with high accuracy. Overall, the newly prepared fluorescence sensor, N-CDs, demonstrated a huge potential to detect metronidazole in a simple, efficient, sensitive, and rapid manner.

Triple-Helix Molecular Switch Triggered Cleavage Effect of DNAzyme for Ultrasensitive Electrochemical Detection of Chloramphenicol

The abuse of chloramphenicol (CAP) in animal-derived products leads to serious food safety problems, so the sensitive and accurate determination of CAP residues has great noteworthiness for public health. Herein, we present a novel electrochemical aptasensor that incorporates a poly(diallyldimethylammonium chloride) functionalized graphene/Ag@Au nanosheets (PDDA-Gr/Ag@Au NSs) composite modified electrode and a DNAzyme signal amplification effect triggered by a triple-helix molecular switch (THMS) for detecting CAP. The PDDA-Gr/Ag@Au NSs composite has the advantages of high surface area, great conductivity, and dispersibility and has successfully improved the electrochemical performance of the electrode. Specific interaction with CAP will cause the signal transduction probe (STP) to be released from the THMS. After that, the DNAzyme will be activated with the help of Pb²⁺ and remove the immobilized signal probe on the electrode surface. The signal change was recorded by square wave voltammetry (SWV) and led to an accurate quantification of CAP. With all these features, the proposed sensing strategy yielded a satisfactory analytical performance with linearity between 1 pM and 1 μM and a limit of detection of 18.6 fM. Furthermore, the aptasensor shows excellent specificity for CAP in the presence of other antibiotics and resists interference with other common metal ions. Importantly, the performance is not diminished when the constructed aptasensor is applied to measuring CAP in milk powder. This THMS-based method is easy to design, and alteration to different targets can be achieved by simply replacing the aptamer sequence in the THMS. Therefore, this method shows significant prospects as a flexible platform for accurate monitoring of antibiotic residues in foodstuffs.

Advances of Drugs Electroanalysis Based on Direct Electrochemical Redox on Electrodes: A Review

The strong development of mankind is inseparable from the proper use of drugs, and the electroanalytical research of drugs occupies an important position in the field of analytical chemistry. This review mainly elaborates the research progress of drugs electroanalysis based on direct electrochemical redox on various electrodes for the recent decade from 2011 to 2021. At first, we summarize some frequently used electrochemical data processing and electrochemical mechanism research derivation methods in the literature. Then, according to the drug therapeutic and application/usage purposes, the research progress of drugs electrochemical analysis is classified and discussed, where we focus on drugs electrochemical reaction mechanism. At the same time, the comparisons of electrochemical sensing performance of the drugs on various electrodes from recent studies are listed, so that readers can more intuitively compare and understand the electroanalytical sensing performance of each modified electrode for each of the drug. Finally, this review discusses the shortcomings and prospects of the drugs electroanalysis based on direct electrochemical redox research.

Polyvinylpyrrolidone-assisted synthesis of highly water-stable cadmium-based metal-organic framework nanosheets for the detection of metronidazole

Recently, much effort has been dedicated to ultra-thin two-dimensional metal–organic framework (2D MOF) nanosheets due to their outstanding properties, such as ultra-thin morphology, large specific surface area, abundant modifiable active sites, etc. However, the preparation of high-quality 2D MOF nanosheets in good yields still remains a huge challenge. Herein, we report 2D cadmium-based metal–organic framework (Cd-MOF) nanosheets prepared in a one-pot polyvinylpyrrolidone (PVP)-assisted synthesis method with high yield. The Cd-MOF nanosheets were characterized with good stability and dispersion in aqueous systems, and were highly selective and sensitive to the antibiotic metronidazole (MNZ) with low limit of detection (LOD: 0.10 μM), thus providing a new and promising fluorescent sensor for rapid detection of MNZ in aqueous solution.

Except PVP was added for Cd-MOF nanosheets, the preparation process of bulk and Cd-MOF nanosheets was similar.

A sensitive electrochemical detection of metronidazole in synthetic serum and urine samples using low-cost screen-printed electrodes modified with reduced graphene oxide and C60

Monitoring the concentration of antibiotics in body fluids is essential to optimizing the therapy and minimizing the risk of bacteria resistance, which can be made with electrochemical sensors tailored with appropriate materials. In this paper, we report on sensors made with screen-printed electrodes (SPE) coated with fullerene (C60), reduced graphene oxide (rGO) and Nafion (NF) (C60-rGO-NF/SPE) to determine the antibiotic metronidazole (MTZ). Under optimized conditions, the C60-rGO-NF/SPE sensor exhibited a linear response in square wave voltammetry for MTZ concentrations from 2.5 × 10-7 to 34 × 10-6 mol/L, with a detection limit of 2.1 × 10-7 mol/L. This sensor was also capable of detecting MTZ in serum and urine, with recovery between 94% and 100%, which are similar to those of the standard chromatographic method (HPLC-UV). Because the C60-rGO-NF/SPE sensor is amenable to mass production and allows for MTZ determination with simple principles of detection, it fulfills the requirements of therapeutic drug monitoring programs.

Carbon-Based Nanomaterials: Promising Antiviral Agents to Combat COVID-19 in the Microbial-Resistant Era

Therapeutic options for the highly pathogenic human severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causing the current pandemic coronavirus disease (COVID-19) are urgently needed. COVID-19 is associated with viral pneumonia and acute respiratory distress syndrome causing significant morbidity and mortality. The proposed treatments for COVID-19 have shown little or no effect in the clinic so far. Additionally, bacterial and fungal pathogens contribute to the SARS-CoV-2-mediated pneumonia disease complex. The antibiotic resistance in pneumonia treatment is increasing at an alarming rate. Therefore, carbon-based nanomaterials (CBNs), such as fullerene, carbon dots, graphene, and their derivatives constitute a promising alternative due to their wide-spectrum antimicrobial activity, biocompatibility, biodegradability, and capacity to induce tissue regeneration. Furthermore, the antimicrobial mode of action is mainly physical (e.g., membrane distortion), characterized by a low risk of antimicrobial resistance. In this Review, we evaluated the literature on the antiviral activity and broad-spectrum antimicrobial properties of CBNs. CBNs had antiviral activity against 13 enveloped positive-sense single-stranded RNA viruses, including SARS-CoV-2. CBNs with low or no toxicity to humans are promising therapeutics against the COVID-19 pneumonia complex with other viruses, bacteria, and fungi, including those that are multidrug-resistant.

Technological development of mucoadhesive film containing poloxamer 407, polyvinyl alcohol and polyvinylpyrrolidone for buccal metronidazole delivery

Aim: This work aimed to develop a mucoadhesive film composed of a triblock copolymer (poloxamer 407), polyvinyl alcohol and polyvinylpyrrolidone for buccal modified delivery of metronidazole. Materials & methods: Three film formulations containing different polymer amounts were prepared by solvent casting. They were characterized as physicochemical, mechanical and mucoadhesive properties, and in vitro metronidazole release profiles. Results: Films displayed physicochemical, mechanical and mucoadhesive characteristics dependent of polymeric composition and drug presence. They could rapidly swell and promote the fast drug release (80% in 20 min) that was governed by Fickian diffusion. The films showed total disintegration in less than 90 s and total drug release in 30 min. Conclusion: Therefore, the formulations represent a promising alternative for modifying of buccal metronidazole delivery for pharmaceutical applications.

Application of Nanostructured Carbon-Based Electrochemical (Bio)Sensors for Screening of Emerging Pharmaceutical Pollutants in Waters and Aquatic Species: A Review

Pharmaceuticals, as a contaminant of emergent concern, are being released uncontrollably into the environment potentially causing hazardous effects to aquatic ecosystems and consequently to human health. In the absence of well-established monitoring programs, one can only imagine the full extent of this problem and so there is an urgent need for the development of extremely sensitive, portable, and low-cost devices to perform analysis. Carbon-based nanomaterials are the most used nanostructures in (bio)sensors construction attributed to their facile and well-characterized production methods, commercial availability, reduced cost, high chemical stability, and low toxicity. However, most importantly, their relatively good conductivity enabling appropriate electron transfer rates-as well as their high surface area yielding attachment and extraordinary loading capacity for biomolecules-have been relevant and desirable features, justifying the key role that they have been playing, and will continue to play, in electrochemical (bio)sensor development. The present review outlines the contribution of carbon nanomaterials (carbon nanotubes, graphene, fullerene, carbon nanofibers, carbon black, carbon nanopowder, biochar nanoparticles, and graphite oxide), used alone or combined with other (nano)materials, to the field of environmental (bio)sensing, and more specifically, to pharmaceutical pollutants analysis in waters and aquatic species. The main trends of this field of research are also addressed.

Efficient preparation of nitrogen-doped fluorescent carbon dots for highly sensitive detection of metronidazole and live cell imaging

Herein, nitrogen-doped carbon dots (N-CDs) emitting blue fluorescence were prepared using L-tartaric acid and triethylenetetramine through a simple and quick microwave-assisted method. The synthesized N-CDs displayed excitation-dependent fluorescence behavior, and their maximum excitation and emission wavelengths were 350 and 425 nm, respectively. The obtained N-CDs, which featured excellent fluorescence properties with a high fluorescence quantum yield of 31%, were applied to detect metronidazole (MNZ), which can effectively quench the fluorescence intensity of N-CDs due to the inner filter effect. This phenomenon was used as basis to develop a label-free fluorescent method for rapid MNZ determination, with the limit of detection of 0.22 μM and corresponding linear range of 0.5-22 μM. Hence, we had established a fluorescence method for MNZ detection and applied it to detect MNZ in real samples with satisfactory results. Finally, N-CDs with superior biocompatibility were applied for cell imaging and MNZ detection by the changes in fluorescence intensity.

An Ultrasensitive Non-Enzymatic Sensor for Quantitation of Anti-Cancer Substance Chicoric Acid Based on Bimetallic Nanoalloy with Polyetherimide-Capped Reduced Graphene Oxide

Exploiting effective therapies to fight tumor growth is an important part of modern cancer research. The anti-cancer activities of many plant-derived substances are well known, in part because the substances are often extensively distributed. Chicoric acid, a phenolic compound widely distributed in many plants, has drawn widespread attention in recent years because of its extraordinary anti-cancer activities. However, traditional methods for quantifying chicoric acid are inefficient and time-consuming. In this study, an ultrasensitive non-enzymatic sensor for the determination of chicoric acid was developed based on the use of an Au@Pt-polyetherimide-reduced graphene oxide (PEI-RGO) nanohybrid-modified glassy carbon electrode. Owing to the considerable conductivity of PEI-functionalized RGO and the efficient electrocatalytic activity of Au@Pt nanoalloys, the designed sensor exhibited a high capacity for chicoric acid measurement, with a low detection limit of 4.8 nM (signal-to-noise ratio of 3) and a broad linear range of four orders of magnitude. With the advantages provided by the synergistic effects of Au@Pt nanocomposites and PEI-RGO, the developed sensor also revealed exceptional electrochemical characteristics, including superior sensitivity, fast response, acceptable long-term stability, and favorable selectivity. This work provides a powerful new platform for the highly accurate measurement of chicoric acid quantities, facilitating further research into its potential as a cancer treatment.

A Non-Enzymatic Sensor Based on Trimetallic Nanoalloy with Poly (Diallyldimethylammonium Chloride)-Capped Reduced Graphene Oxide for Dynamic Monitoring Hydrogen Peroxide Production by Cancerous Cells

Catching cancer at an early stage is necessary to make it easier to treat and to save people's lives rather than just extending them. Reactive oxygen species (ROS) have sparked a huge interest owing to their vital role in various biological processes, especially in tumorigenesis, thus leading to the potential of ROS as prognostic biomarkers for cancer. Herein, a non-enzymatic biosensor for the dynamic monitoring of intracellular hydrogen peroxide (H2O2), the most important ROS, via an effective electrode composed of poly (diallyldimethylammonium chloride) (PDDA)-capped reduced graphene oxide (RGO) nanosheets with high loading trimetallic AuPtAg nanoalloy, is proposed. The designed biosensor was able to measure H2O2 released from different cancerous cells promptly and precisely owing to the impressive conductivity of RGO and PDDA and the excellent synergistic effect of the ternary alloy in boosting the electrocatalytic activity. Built upon the peroxidase-like activity of the nanoalloy, the developed sensor exhibited distinguished electrochemical performance, resulting in a low detection limit of 1.2 nM and a wide linear range from 0.05 μM to 5.5 mM. Our approach offers a significant contribution toward the further elucidation of the role of ROS in carcinogenesis and the effective screening of cancer at an early stage.

Label-free and highly selective electrochemical aptasensor for detection of PCBs based on nickel hexacyanoferrate nanoparticles/reduced graphene oxides hybrids

In consideration of the urgent need to determine polychlorinated biphenyls (PCBs) in the environment, a label-free and highly selective electrochemical aptasensor was constructed for determining PCBs based on nickel hexacyanoferrate nanoparticles (NiHCF NPs)/reduced graphene oxides (rGO) hybrids. NiHCF NPs/rGO hybrids with small size of about 5 nm NiHCF NPs were synthesized for the first time by in situ co-deposition of NiHCF NPs on rGO surface. In the hybrids, rGO with large area and good conductivity can supply more space for loading NiHCF NPs and improve the conductivity of the hybrids. NiHCF NPs that can be used to be act as a signal probe exhibit a couple of well-defined peaks with highly reversible redox ability and good stability. Here, PCB77 as a model molecule, the anti-PCB77 aptamer was anchored on the NiHCF NPs/rGO hybrids by covalent bonding reaction. The design aptasensor for detecting PCB77 exhibits a favorable linear response from 1.0 to 100.0 ng/L with a low detection limit of 0.22 ng/L. Meanwhile, it displays good selectivity for PCB77 detection due to the specificity and high affinity of aptamer to PCB77. Additionally, the application of the aptasensor was evaluated in real environmental samples.

Effective reduction of non-specific binding of blood cells in a microfluidic chip for isolation of rare cancer cells

The high purity of target cells enriched from blood samples plays an important role in the clinical detection of diseases. However, non-specific binding of blood cells in the isolated cell samples can complicate downstream molecular and genetic analysis. In this work, we report a simple solution to non-specific binding of blood cells by modifying the surface of microchips with a multilayer nanofilm, with the outmost layer containing both PEG brushes for reducing blood cell adhesion and antibodies for enriching target cells. This layer-by-layer (LbL) polysaccharide nanofilm was modified with neutravindin and then conjugated with a mixture of biotinylated PEG molecules and biotinylated antibodies. Using EpCAM-expressing and HER2-expressing cancer cells in blood as model platforms, we were able to dramatically reduce the non-specific binding of blood cells to approximately 1 cell per mm2 without sacrificing the high capture efficiency of the microchip. To support the rational extension of this approach to other applications for cell isolation and blood cell resistance, we conducted extensive characterization on the nanofilm formation and degradation, antifouling with PEG brushes and introducing functional antibodies. This simple, yet effective, approach can be applied to a variety of microchip applications that require high purity of sample cells containing minimal contamination from blood cells.

A highly sensitive metronidazole sensor based on a Pt nanospheres/polyfurfural film modified electrode

A sensitively electrochemical metronidazole sensor basing on a Pt nanospheres/polyfurfural modified glassy carbon electrode.

Petal-like graphene–Ag composites with highly exposed active edge sites were designed and constructed for electrochemical determination of metronidazole

The petal-like graphene–Ag composites with highly exposed active edge sites were constructed, which served as both the electrocatalyst and the current amplifier for electrochemical detection of metronidazole.

Signal amplification biosensor based on DNA for ultrasensitive electrochemical determination of metronidazole

The biosensor (PDDA-GN/DNA/GCE) showed remarkable signal amplification performance toward the reduction of metronidazole, and was applied to determinate metronidazole in urine and lake water samples with satisfactory results.

Synergetic catalysis based on the proline tailed metalloporphyrin with graphene sheet as efficient mimetic enzyme for ultrasensitive electrochemical detection of dopamine

In this paper, linking with the butoxycarbonyl (BOC) protection of proline, a new tailed metalloporphyrin with many useful active functions, nickel (II) 5-[4-N-(tert-Butoxycarbonyl)-l-prolinecoxylpropyloxy]phenyl-10,15,20-triphenylporphyrin (NiTBLPyP), was designed and synthesized. And the NiTBLPyP polymer (poly(NiTBLPyP)) was successfully obtained via a low-cost electrochemical method and exploited as an efficient mimic enzyme. Subsequently, a noncovalent nanohybrid of poly(NiTBLPyP) with graphene (rGO) sheet (rGO-poly(NiTBLPyP)) was prepared through π-π stacking interaction for the ultrasensitive and selective detection of DA. The nanohybrid was characterized by UV-vis spectroscopy, Fourier transform infrared spectra, Raman spectroscopy, scanning electron microscopy and electrochemical impedance spectroscopy. Due to the excellent electrocatalytic ability of poly(NiTBLPyP) film and aromatic π-π stacking interaction between poly(NiTBLPyP and rGO sheet, the obtained rGO-poly(NiTBLPyP) film exhibited a great synergistic amplification effect toward dopamine oxidation. Under optimum experimental conditions, the logarithm of catalytic currents showed a good linear relationship with that of the dopamine concentration in the range of 0.01-200 μM with a low detection limit of 1.40 nM. With good sensitivity and selectivity, the present method was applied to the determination of DA in real sample and the results was satisfactory. Thus, the rGO-poly(NiTBLPyP) film is one of the promising mimetic enzyme for electrocatalysis and relevant fields.

Novel electrochemical sensing platform based on a molecularly imprinted polymer decorated 3D nanoporous nickel skeleton for ultrasensitive and selective determination of metronidazole

A novel electrochemical sensor has been developed by using a composite element of three-dimensional (3D) nanoporous nickel (NPNi) and molecularly imprinted polymer (MIP). NPNi is introduced in order to enhance the electron-transport ability and surface area of the sensor, while the electrosynthesized MIP layer affords simultaneous identification and quantification of the target molecule by employing Fe(CN)6(3-/4-) as the probe to indicate the current intensity. The morphology of the hybrid film was observed by scanning electron microscopy, and the properties of the sensor were examined by cyclic voltammetry and electrochemical impedance spectroscopy. By using metronidazole (MNZ) as a model analyte, the sensor based on the MIP/NPNi hybrid exhibits great features such as a remarkably low detection limit of 2 × 10(-14) M (S/N = 3), superb selectivity in discriminating MNZ from its structural analogues, and good antiinterference ability toward several coexisting substances. Moreover, the proposed method also demonstrates excellent repeatability and stability, with relative standard deviations of less than 1.12% and 1.4%, respectively. Analysis of MNZ in pharmaceutical dosage form and fish tissue is successfully carried out without assistance of complicated pretreatment. The MIP/NPNi composite presented here with admirable merits makes it a promising candidate for developing electrochemical sensor devices and plays a role in widespread fields.

Multiple signal amplified electrochemiluminescent immunoassay for Hg2+ using graphene-coupled quantum dots and gold nanoparticles-labeled horseradish peroxidase

A multiple signal amplification strategy was designed for an ultrasensitive competitive immunoassay for Hg(2+). This strategy was achieved using graphene conjugated with a large number of CdSe quantum dots to enhance the basal signal and enormous horseradish peroxidase (HRP) labeled with gold nanoparticles (AuNPs) to consume the coreactant H2O2 generated in situ. The immunosensor was constructed by immobilization of coating antigen on poly(diallyldimethylammonium chloride)-graphene-CdSe composites (PDDA-GN-CdSe), and a strong electrochemiluminescence (ECL) signal was obtained. When the immunosensor was immersed in antibody-AuNPs-HRP composites, the ECL signal greatly decreased, which was ascribed to the bound enzyme on the electrode surface. The self-produced coreactant H2O2 was consumed by o-phenylenediamine in the presence of enzyme, effectively decreasing the ECL intensity from the quantum dots. The Hg(2+) in solution and the corresponding coating antigen competed for the limited antibody, and thus, the ECL intensity was linearly dependent on the logarithm of the mercury(II) concentration from 0.2 to 1000 ng mL(-1) with a detection limit of 0.06 ng mL(-1). The immunoassay exhibited good stability and accuracy and acceptable reproducibility, indicating that it provides a promising approach for the detection of trace mercury and other small molecular compounds in environmental samples.

Molecularly imprinted polymer decorated nanoporous gold for highly selective and sensitive electrochemical sensors

Electrochemical nanosensors based on nanoporous gold leaf (NPGL) and molecularly imprinted polymer (MIP) are developed for pharmaceutical analysis by using metronidazole (MNZ) as a model analyte. NPGL, serving as the loading platform for MIP immobilization, possesses large accessible surface area with superb electric conductivity, while electrochemically synthesized MIP thin layer affords selectivity for specific recognition of MNZ molecules. For MNZ determination, the hybrid electrode shows two dynamic linear range of 5 × 10(-11) to 1 × 10(-9) mol L(-1) and 1 × 10(-9) to 1.4 × 10(-6) mol L(-1) with a remarkably low detection limit of 1.8 × 10(-11) mol L(-1) (S/N = 3). In addition, the sensor exhibits high binding affinity and selectivity towards MNZ with excellent reproducibility and stability. Finally, the reliability of MIP-NPGL for MNZ detection is proved in real fish tissue samples, demonstrating the potential for the proposed electrochemical sensors in monitoring drug and biological samples.

Hierarchical polystyrene@reduced graphene oxide–Pt core–shell microspheres for non-enzymatic detection of hydrogen peroxide

A non-enzymatic electrochemical sensor based on polystyrene@reduced graphene oxide (RGO)–Pt core–shell microspheres was developed for sensitive detection of hydrogen peroxide (H₂O₂).