Nanomaterials in carbohydrate biosensors

Magnetic Nanoseparation Technology for Efficient Control of Microorganisms and Toxins in Foods: A Review

Outbreaks of foodborne diseases mediated by food microorganisms and toxins remain one of the leading causes of disease and death worldwide. It not only poses a serious threat to human health and safety but also imposes a huge burden on health care and socioeconomics. Traditional methods for the removal and detection of pathogenic bacteria and toxins in various samples such as food and drinking water have certain limitations, requiring a rapid and sensitive strategy for the enrichment and separation of target analytes. Magnetic nanoparticles (MNPs) exhibit excellent performance in this field due to their fascinating properties. The strategy of combining biorecognition elements with MNPs can be used for fast and efficient enrichment and isolation of pathogens. In this review, we describe new trends and practical applications of magnetic nanoseparation technology in the detection of foodborne microorganisms and toxins. We mainly summarize the biochemical modification and functionalization methods of commonly used magnetic nanomaterial carriers and discuss the application of magnetic separation combined with other instrumental analysis techniques. Combined with various detection techniques, it will increase the efficiency of detection and identification of microorganisms and toxins in rapid assays.

A Review on the Role and Performance of Cellulose Nanomaterials in Sensors

Sensors and biosensors play a key role as an analytical tool for the rapid, reliable, and early diagnosis of human diseases. Such devices can also be employed for monitoring environmental pollutants in air and water in an expedited way. More recently, nanomaterials have been proposed as an alternative in sensor fabrication to achieve gains in performance in terms of sensitivity, selectivity, and portability. In this direction, the use of cellulose nanomaterials (CNM), such as cellulose nanofibrils (CNF), cellulose nanocrystals (CNC), and bacterial cellulose (BC), has experienced rapid growth in the fabrication of varied types of sensors. The advantageous properties are related to the supramolecular structures that form the distinct CNM, their biocompatibility, and highly reactive functional groups that enable surface functionalization. The CNM can be applied as hydrogels and xerogels, thin films, nanopapers and other structures interesting for sensor design. Besides, CNM can be combined with other materials (e.g., nanoparticles, enzymes, carbon nanomaterials, etc.) and varied substrates to advanced sensors and biosensors fabrication. This review explores recent advances on CNM and composites applied in the fabrication of optical, electrical, electrochemical, and piezoelectric sensors for detecting analytes ranging from environmental pollutants to human physiological parameters. Emphasis is given to how cellulose nanomaterials can contribute to enhance the performance of varied sensors as well as expand novel sensing applications, which could not be easily achieved using standard materials. Finally, challenges and future trends on the use of cellulose-based materials in sensors and biosensors are also discussed.

Universal Nanoplatform for Formaldehyde Detection Based on the Oxidase-Mimicking Activity of MnO2 Nanosheets and the In Situ Catalysis-Produced Fluorescence Species

Formaldehyde (HCHO) pollution is a scientific problem of general concern and has aroused wide attention. In this work, a fluorometric method for sensitive detection of formaldehyde was developed based on the oxidase-mimicking activity of MnO₂ nanosheets in the presence of o-phenylenediamine (OPD). The MnO₂ nanosheets were prepared by the bottom-up approach using manganese salt as the precursor, followed by the exfoliation with bovine serum albumin. The as-prepared MnO₂ nanosheets displayed excellent oxidase-mimicking activity, and can be used as the nanoplatform for sensing in fluorometric analysis. OPD was used as a typical substrate because MnO₂ nanosheets can catalyze the oxidation of OPD to generate yellow 2,3-diaminophenazine (DAP), which can emit bright yellow fluorescence at the wavelength of 560 nm. While in the presence of formaldehyde, the fluorescence was greatly quenched because formaldehyde can react with OPD to form Schiff bases that decreased the oxidation reaction of OPD to DAP. The main mechanism and the selectivity of the platform were studied. As a result, formaldehyde can be sensitively detected in a wide linear range of 0.8-100 μM with the detection limit as low as 6.2 × 10^-8 M. The platform can be used for the detection of formaldehyde in air, beer, and various food samples with good performance. This work not only expands the application of MnO₂ nanosheets in fluorescence sensing, but also provides a sensitive and selective method for the detection of formaldehyde in various samples via a new mechanism.

Glycan Nanobiosensors

This review paper comprehensively summarizes advances made in the design of glycan nanobiosensors using diverse forms of nanomaterials. In particular, the paper covers the application of gold nanoparticles, quantum dots, magnetic nanoparticles, carbon nanoparticles, hybrid types of nanoparticles, proteins as nanoscaffolds and various nanoscale-based approaches to designing such nanoscale probes. The article covers innovative immobilization strategies for the conjugation of glycans on nanoparticles. Summaries of the detection schemes applied, the analytes detected and the key operational characteristics of such nanobiosensors are provided in the form of tables for each particular type of nanomaterial.

Nanomaterials for Biosensing Lipopolysaccharide

Lipopolysaccharides (LPS) are endotoxins, hazardous and toxic inflammatory stimulators released from the outer membrane of Gram-negative bacteria, and are the major cause of septic shock giving rise to millions of fatal illnesses worldwide. There is an urgent need to identify and detect these molecules selectively and rapidly. Pathogen detection has been done by traditional as well as biosensor-based methods. Nanomaterial based biosensors can assist in achieving these goals and have tremendous potential. The biosensing techniques developed are low-cost, easy to operate, and give a fast response. Due to extremely small size, large surface area, and scope for surface modification, nanomaterials have been used to target various biomolecules, including LPS. The sensing mechanism can be quite complex and involves the transformation of chemical interactions into amplified physical signals. Many different sorts of nanomaterials such as metal nanomaterials, magnetic nanomaterials, quantum dots, and others have been used for biosensing of LPS and have shown attractive results. This review considers the recent developments in the application of nanomaterials in sensing of LPS with emphasis given mainly to electrochemical and optical sensing.

Advances in nanomaterial application in enzyme-based electrochemical biosensors: a review

Electrochemical enzyme-based biosensors are one of the largest and commercially successful groups of biosensors. Integration of nanomaterials in the biosensors results in significant improvement of biosensor sensitivity, limit of detection, stability, response rate and other analytical characteristics. Thus, new functional nanomaterials are key components of numerous biosensors. However, due to the great variety of available nanomaterials, they should be carefully selected according to the desired effects. The present review covers the recent applications of various types of nanomaterials in electrochemical enzyme-based biosensors for the detection of small biomolecules, environmental pollutants, food contaminants, and clinical biomarkers. Benefits and limitations of using nanomaterials for analytical purposes are discussed. Furthermore, we highlight specific properties of different nanomaterials, which are relevant to electrochemical biosensors. The review is structured according to the types of nanomaterials. We describe the application of inorganic nanomaterials, such as gold nanoparticles (AuNPs), platinum nanoparticles (PtNPs), silver nanoparticles (AgNPs), and palladium nanoparticles (PdNPs), zeolites, inorganic quantum dots, and organic nanomaterials, such as single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), carbon and graphene quantum dots, graphene, fullerenes, and calixarenes. Usage of composite nanomaterials is also presented.

A Redox Conjugated Polymer-Based All-Solid-State Reference Electrode

This work reports the design, synthesis, and characterization of a novel redox-active conjugated polyaniline containing quinone moiety as a solid state reference electrode. The union of electro-active quinone with π-conjugated polyaniline was created by the first chemical synthesis of para-dimethoxybenzene-functionalized aniline as a monomer using a palladium-mediated coupling. The successful polymerization of the as-prepared monomer was accomplished without acid additives. Its post-polymerization modification with strong Lewis acid boron tribromide furnished unique poly (aniline quinone/hydroquinone) with desired properties for all-solid-state reference electrode (RE) applications. The electrochemical responses from the conjugated polyaniline backbone in this unique polymer have been “suppressed” by the quinone pendant. The resulting poly (aniline quinone) showed a quasi-reversible redox process from the redox behavior of the pendant quinone. The stable electrode potential of this poly (aniline quinone/hydroquinone) suggested that it was a single phase in which the amounts of totally reduced and totally oxidized species could be maintained at a constant in various solvents and electrolytes. Its electrochemical stability was excellent with 95% peak current retention after continuous cyclic voltammetric testing. The aniline and quinone moieties in poly (aniline quinone/hydroquinone) render it to have both hydrophilic and hydrophobic compatibility. It showed excellent behavior as a reference electrode in aqueous and non-aqueous media and can be used in both non-zero current and zero-current conditions, providing a stable potential with a maximum potential drift of ~4.7 mV over ten consecutive days.

Rational design of fluorescent probe for Hg2+ by changing the chemical bond type

Two kinds of fluorescent probes DFBT and DFABT, and their corresponding water-soluble compounds WDFBT and WDFABT, based on the trimers containing a benzo[2,1,3]thiadiazole moiety and two fluorene moieties are synthesized. Their luminescent behavior towards Hg²⁺ ions and other various metal ions in organic and water solutions are studied in detail via absorption and emission spectroscopy. All these probes show a selective “on–off-type” fluorescent response to Hg²⁺ ions in solution over other metal ions with a maximum detection limit of 10⁻⁷ M. Importantly, the probe type can be changed from irreversible to reversible by altering the bridge mode between the functional units from C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C triple bond to C–C single bond. Their detection mechanisms towards Hg²⁺ are studied in detail via mass spectrometry and Job plots, which are attributed to irreversible chemical reaction for DFABT and WDFABT and a reversible coordination reaction for DFBT and WDFBT respectively. Our research results about this kind of organic fluorescent probe provide valuable information to the future design of practical Hg²⁺ fluorescent probes.

Two kinds of fluorescent probes for Hg²⁺ with different detection mechanism have been realized by simply changing the chemical bond.

Nitrogen-doped carbon quantum dots for fluorescence detection of Cu2+ and electrochemical monitoring of bisphenol A

Nitrogen-doped carbon dots were applied in the fluorescence detection of Cu²⁺ and electrochemical detection of BPA.

Investigation into the ring-substituted polyanilines and their application for the detection and adsorption of sulfur dioxide

It has been demonstrated in this study that the substituents on the monomer aniline benzene ring are able to introduce the significant differences to the resulting polyaniline's collective properties. We systematically evaluated the structural perturbation effects of two substituents (methyl and methoxy) of aniline monomer through the electrochemical method. Our results showed that the methoxy group induces the less structural perturbation than the methyl counterpart, because of its partial double bond restriction. The morphologies are different for the polyaniline and the ring-substituted polyanilines, in which substituted polyanilines feature the larger porosities with the addition of these side groups. The influential effects of the methoxy side group have been further illustrated and amplified by its superior sensing performance towards the environmentally-significant sulfur dioxide gas, evaluated through the construction of the quartz crystal microbalance (QCM)-based gas sensor with these polyaniline materials. The as-constructed gas sensor's sensitivity, selectivity and stability in terms of its SO₂ responses have been evaluated in details. The methoxy-substituted polyaniline was tested to show the unique gas sensing properties for the sulfur dioxide at the low concentrations (50-250 ppm) and function as the adsorbing material at the high concentrations (500-1250 ppm). Thus it can be used both as sensing material as well as a novel filter and/or storage reservoir for the removal of sulfur dioxide pollutant from the environments.

Nanotechnology in Glycomics: Applications in Diagnostics, Therapy, Imaging, and Separation Processes

This review comprehensively covers the most recent achievements (from 2013) in the successful integration of nanomaterials in the field of glycomics. The first part of the paper addresses the beneficial properties of nanomaterials for the construction of biosensors, bioanalytical devices, and protocols for the detection of various analytes, including viruses and whole cells, together with their key characteristics. The second part of the review focuses on the application of nanomaterials integrated with glycans for various biomedical applications, that is, vaccines against viral and bacterial infections and cancer cells, as therapeutic agents, for in vivo imaging and nuclear magnetic resonance imaging, and for selective drug delivery. The final part of the review describes various ways in which glycan enrichment can be effectively done using nanomaterials, molecularly imprinted polymers with polymer thickness controlled at the nanoscale, with a subsequent analysis of glycans by mass spectrometry. A short section describing an active glycoprofiling by microengines (microrockets) is covered as well.

Colorimetric Logic Gate for Pyrophosphate and Pyrophosphatase via Regulating the Catalytic Capability of Horseradish Peroxidase

By regulating the catalytic capability of horseradish peroxidase (HRP), an artful colorimetric assay platform for pyrophosphate (PPi) and pyrophosphatase (PPase) was unprecedentedly designed. In this work, Cu(I), generated by reducing Cu(II) in the presence of ascorbate, could inhibit HRP's catalytic capability of transforming colorless 3,3',5,5'-tetramethylbenzidine (TMB) into blue oxidized TMB (oxTMB). The robust coordination between PPi and Cu(II) is able to discourage the reduction of Cu(II) to Cu(I) effectively, thus restoring the original catalytic capability of HRP and regenerating blue-colored oxTMB. Upon PPase introduction, PPi would be hydrolyzed into orthophosphate, which could release Cu(II) free from the Cu(II)-PPi complex, and thus in turn allows the catalytic capability of HRP to be inhibited by Cu(I). HRP was activated or deactivated to different degrees depending on PPi or PPase levels, which could be indicated by using HRP-triggered catalytic system as a signal amplifier, thus paving a way for PPi and PPase sensing. Based on the colorimetric sensor for PPi and PPase, an "INH" logic gate was rationally constructed. With the merits of high sensitivity and selectivity, cost-effectiveness, and simplification, our proposed analytical system has also been verified to have potential to be utilized for enzyme inhibitor screening and diagnosis of PPase-related diseases.

Catalyst-Free Cycloaddition Reaction for the Synthesis of Glyconanoparticles

A new conjugation method for the immobilization of carbohydrates on nanomaterials was demonstrated simply by mixing perfluorophenyl azide-functionalized silica nanoparticles (SNPs), an amine-derivatized carbohydrate, and phenylacetaldehyde under ambient conditions without any catalyst. The density of carbohydrates on the glyconanoparticles was determined using the quantitative ¹⁹F NMR (¹⁹F qNMR) technique; for example, the density of d-mannose (Man) on Man-SNPs was 2.5 ± 0.2 × 10^-16 nmol/nm². The glyconanoparticles retained their binding affinity and selectivity toward cognate lectins. The apparent dissociation constant of the glyconanoparticles was measured by a fluorescence competition assay, where the binding affinity of Man-SNPs was almost 4 orders of magnitude higher than that of Man with concanavalin A. Moreover, even with a ligand density of 2.6 times lower than Man-SNPs synthesized by the copper-catalyzed azide-alkyne cycloaddition, the binding affinity of Man-SNPs prepared by the current method was more than 4 times higher.

A fluorescent ELISA based on the enzyme-triggered synthesis of poly(thymine)-templated copper nanoparticles

Inspired by the ALP-triggered hydrolysis of the substrate ascorbic acid 2-phosphate as well as the product ascorbate-controlled generation of polyT-CuNPs with bright red fluorescence, we have developed a novel, selective and sensitive fluorescence turn-on assay for ALP activity sensing. Based on the conventional ELISA platform and commercially available antibody-ALP conjugates, an unconventional fluorescent ELISA system has been rationally developed and successfully applied in the quantitative measurement of model antigen proteins using fluorescence spectroscopy and a naked-eye readout under ultraviolet light.

Nanoscale zero-valent metals: a review of synthesis, characterization, and applications to environmental remediation

Engineered nanoscale zero-valent metals (NZVMs) representing the forefront of technologies have been considered as promising materials for environmental remediation and antimicrobial effect, due to their high reducibility and strong adsorption capability. This review is focused on the methodology for synthesis of bare NZVMs, supported NZVMs, modified NZVMs, and bimetallic systems with both traditional and green methods. Recent studies have demonstrated that self-assembly methods can play an important role for obtaining ordered, controllable, and tunable NZVMs. In addition to common characterization methods, the state-of-the-art methods have been developed to obtain the properties of NZVMs (e.g., granularity, size distribution, specific surface area, shape, crystal form, and chemical bond) with the resolution down to subnanometer scale. These methods include spherical aberration corrected scanning transmission electron microscopy (Cs-corrected STEM), electron energy-loss spectroscopy (EELS), and near edge X-ray absorption fine structure (NEXAFS). A growing body of experimental data has proven that nanoscale zero-valent iron (NZVI) is highly effective and versatile. This article discusses the applications of NZVMs to treatment of heavy metals, halogenated organic compounds, polycyclic aromatic hydrocarbons, nutrients, radioelements, and microorganisms, using both ex situ and in situ methods. Furthermore, this paper briefly describes the ecotoxicological effects for NZVMs and the research prospects related to their synthesis, modification, characterization, and applications.

Full Spectrum Visible LED Light Activated Antibacterial System Realized by Optimized Cu2O Crystals

Assisted by three-dimensional printing technology, we proposed and demonstrated a full spectrum visible light activated antibacterial system by using a combination of 500 nm sized Cu2O crystals and light-emitting diode (LED) lamps. Further improved antibacterial ratios were achieved, for the first time, with pure Cu2O for both Gram-positive bacteria and Gram-negative bacteria among all of the six different color LED lamps. For practical antibacterial applications, we revealed that the nonwoven fabric could act as excellent carrier for Cu2O crystals and provide impressive antibacterial performance. Furthermore, integrated with our self-developed app, the poly(ethylene terephthalate) film loaded with Cu2O crystals also showed significant antibacterial property, thus making it possible to be applied in field of touch screen. The present research not only provided a healthier alternative to traditional ultraviolet-based sterilization but also opened an auto-response manner to decrease the rate of microbial contamination on billions of touch screen devices.

Nitrogen-doped carbon nanoparticle modulated turn-on fluorescent probes for histidine detection and its imaging in living cells

In this work, nitrogen-doped carbon nanoparticle (N-CNP) modulated turn-on fluorescent probes were developed for rapid and selective detection of histidine. The as synthesized N-CNPs exhibited high fluorescence quantum yield and excellent biocompatibility. The fluorescence of N-CNPs can be quenched selectively by Cu(II) ions with high efficiency, and restored by the addition of histidine owing to the competitive binding of Cu(II) ions and histidine that removes Cu(II) ions from the surface of the N-CNPs. Under the optimal conditions, a linear relationship between the increased fluorescence intensity of N-CNP/Cu(II) ion conjugates and the concentration of histidine was established in the range from 0.5 to 60 μM. The detection limit was as low as 150 nM (signal-to-noise ratio of 3). In addition, the as-prepared N-CNP/Cu(II) ion nanoprobes showed excellent biocompatibility and were applied for a histidine imaging assay in living cells, which presented great potential in the bio-labeling assay and clinical diagnostic applications.

Thiazole derivative-modified upconversion nanoparticles for Hg(2+) detection in living cells

Mercury ion (Hg(2+)) is an extremely toxic ion, which will accumulate in human bodies and cause severe nervous system damage. Therefore, the sensitive and efficient monitoring of Hg(2+) in human bodies is of great importance. Upconversion nanoparticle (UCNPs) based nano probes exhibit no autofluorescence, deep penetration depth and chemical stability in biological samples, as well as a large anti-stokes shift. In this study, we have developed thiazole-derivative-functionalized UCNPs, and employed an upconversion emission intensity ratio of 540 nm to 803 nm (I540/I803) as a ratiometric signal to detect Hg(2+) in living cells showing excellent photo stability and high selectivity. Our nano probe was characterized using transmission electron microscopy (TEM) and powder X-ray diffraction (PXRD). The low cytotoxicity of our probe was confirmed by an MTT assay and the UCL test in HeLa cells was carried out by confocal microscopy. Our results demonstrated that organic-dye-functionalized UCNPs should be a good strategy for detecting toxic metal ions when studying cellular biosystems.

Carbohydrates in Supramolecular Chemistry

Carbohydrates are involved in a variety of biological processes. The ability of sugars to form a large number of hydrogen bonds has made them important components for supramolecular chemistry. We discuss recent advances in the use of carbohydrates in supramolecular chemistry and reveal that carbohydrates are useful building blocks for the stabilization of complex architectures. Systems are presented according to the scaffold that supports the glyco-conjugate: organic macrocycles, dendrimers, nanomaterials, and polymers are considered. Glyco-conjugates can form host-guest complexes, and can self-assemble by using carbohydrate-carbohydrate interactions and other weak interactions such as π-π interactions. Finally, complex supramolecular architectures based on carbohydrate-protein interactions are discussed.

A quadruplet electrochemical platform for ultrasensitive and simultaneous detection of ascorbic acid, dopamine, uric acid and acetaminophen based on a ferrocene derivative functional Au NPs/carbon dots nanocomposite and graphene

In this work, a new nanomaterial of thiol functional ferrocene derivative (Fc-SH) stabilized Au NPs/carbon dots nanocomposite (Au/C NC) coupling with graphene modified glassy carbon electrode (Fc-S-Au/C NC/graphene/GCE) was fabricated to serve as a quadruplet detection platform for ultrasensitive and simultaneous determination of ascorbic acid (AA), dopamine (DA), uric acid (UA) and acetaminophen (AC). The Au/C NC was synthesized by adding HAuCl4 into carbon nanodots solution without using any additional reductant and stabilizing agent. Then the Fc-SH was utilized as the protective and capping agent to modify the Au/C NC. Transmission electron microscopy (TEM), UV-Vis, Fourier-transform infrared (FT-IR), scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) were adopted to characterize the morphology and electrochemical properties of the materials and the electrodes. The Fc-S-Au/C NC/graphene/GCE exhibits a synergistic catalytic and amplification effects towards oxidation of AA, DA, UA and AC owing to the existence of the nanomaterial and electron mediator. When simultaneous detection of AA, DA, UA and AC, the oxidation peak potentials of the four compounds on the electrode can be well separated and the peak currents were linearly dependent on their concentrations. The quadruplet detection platform shows excellent linear range and ultrasensitive response to the four components, the detection limits were estimated to be as low as 1.00, 0.05, 0.12 and 0.10 μM (S/N = 3), and the modified electrode exhibits excellent stability and reproducibility. The proposed electrode has been successfully applied to detect of these four analytes in real samples with satisfactory results.

Affinity biosensors for tumor-marker analysis

The use of cancer biomarkers is emerging as one of the most promising strategies for early detection and management of cancer. Biosensors can provide advanced platforms for biomarker analysis with the advantages of being easy to use, inexpensive, rapid and offering multi-analyte testing capability. The intention of this article is to discuss recent advances and trends in affinity biosensors for cancer diagnosis, prognosis and even theragnosis. The different types of affinity biosensors will be reviewed in terms of molecular recognition element. Current challenges and trends for this technology will be also discussed, with a particular emphasis on recent developments in miRNA detection.

Recognition of saccharides in the NIR region with a novel fluorogenic boronolectin: in vitro and live cell labeling

The detection performance in solution and in live cells of a novel mono-boronic acid derivative of a near-infrared luminescent tricarbocyanine with OFF–ON response upon addition of saccharides.