Variety Of Analytes Research Articles

A Damped Double Dipole Antenna for UHF RFID Sensing in the Frequency Domain

Ultrahigh frequency (UHF) radio frequency identification (RFID) tags provide an inexpensive framework for distributed sensing, yet for the most cost-effective implementation, it is necessary to consider antenna design in concert with the capabilities of responsive materials that can be coupled to the tag response. Materials, such as functionalized carbon nanotubes (CNTs), have been engineered to change in resistance when exposed to a variety of analytes and have been incorporated in RFID tags to create low-cost sensors that work at a fixed reader–tag separation distance. This article presents a damped double dipole antenna design enabling UHF RFID tags that are able to sense changes in resistance of a sensing element (with a conductivity similar to that of printed CNT networks) regardless of reader–tag distance within the far-field read range. Simulations of the proposed design show two methods of operation, either by comparing the damping between two resonant peaks or by shifting the resonant frequency of the RFID tag. The first method is validated experimentally with surface mount resistors, showing a relative change in the effective antenna transmission coefficient, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\tau _{e}$ </tex-math></inline-formula> , of 0.2 for a 35% change in resistance of the sensing element.

Solid electrolyte gas sensors based on mixed potential principle – A review

The development of kinetically controlled potentiometric solid electrolyte gas sensors, called shortly mixed potential sensors (MPS) started with the discovery of kinetic limitations of equilibrium establishment on poisoned oxygen sensors based on yttria stabilized zirconia (YSZ) equipped with platinum electrodes. The decades of development of these sensors generated a broad knowledge on the signal establishing and influencing processes at the interface between gas, electrode and electrolyte as well as on a variety of possible materials for improved sensitivity, selectivity and long-term stability. Furthermore, this knowledge was extended by approaches directed on electrochemical dynamic conditioning of such sensors and the coupling with other physical quantities like temperature and light. The broad knowledge enabled an extended field of applications in automotive, food, medical, electric and chemical industries. The variety of analytes to be addressed by these sensors beside the most prominent ones like CO, hydrocarbons (HC), NOx, NH3 and H2 is constantly increasing. The present review gives an overview on the historical development, the basics of theory of operation, the analytes and materials as well as applications. Regarding the publications, the work continues the overview given in former review articles.

New pores, new tricks.

Over the past three decades, biological nanopores have been developed for the rapid, low-cost, and portable sequencing of nucleic acids. A wide range of new applications are now been explored, including the sequencing of proteins, and the real-time identification of molecules in complex biological samples. All these applications, however, require developing nanopores with bespoke size, shape, and biophysical properties that can tackle the specific challenges associated with molecular recognition and transport for such a wide variety of analytes. Here I will describe the efforts in our laboratory to control the capture and transport of molecules across nanopores, to identify tiny differences in proteins and to engineer nanopores to recognize molecules in a complex biological sample.

Plurisubharmonic functions and real submanifolds of [formula omitted

We give an estimate for the volume of an analytic variety (or more generally the mass of a positive closed current) close to a real submanifold M. Applications are given to the Hausdorff measure of the intersection of the variety with M and the exponential integrability of plurisubharmonic functions on M.

Water-soluble pillar[6]arene bearing pyrene on alternating methylene bridges for direct spermine sensing.

This paper describes the design and synthesis of a conjugate, which is composed of a percarboxylated water-soluble pillar[6]arene and three fluorescent pyrene chromophores on alternating methylene bridges. The optical characteristics are investigated. This conjugate is capable of encapsulating polycationic guest spermine, which results in an enhancement in the fluorescence intensity of pyrene. This host-pyrene conjugate is used for direct sensing of spermine, which shows selectivity towards a variety of biological analytes. The detection of spermine is demonstrated in live cells.

3-Aminophenylboronic Acid Conjugation on Responsive Polymer and Gold Nanoparticles for Qualitative Bacterial Detection.

Because of their sensitive and selective responses to a wide variety of analytes, colorimetric sensors have gained widespread acceptance in recent years. Gold nanoparticles (AuNPs) are widely employed in visual sensor strategies due to their high stability and ease of use. Combining AuNPs with a responsive polymer can result in distinct surface plasmon resonance (SPR) changes that can be utilized as colorimetric biosensors. The purpose of this research is to develop a colorimetric-based sensor through the utilization of the optical properties of gold nanoparticles (AuNPs) crosslinked with pH-responsive polymers poly (acrylic acid) (PAA) conjugated to 3-aminophenyl boronic acid (APBA). The polymer (PAA) was synthesized via RAFT polymerization. The inversed Turkevic method was used to produce AuNPs, which were subsequently used in a self-assembly process using poly (acrylic acid)-aminophenyl boronic acid (PAA-APBA) to create the self-assembled AuNPs-APBA-PAA. The particle size, zeta potential, and reversibility of the polymer-modified gold nanoparticles were determined using a transmission electron microscope (TEM), a particle size analyzer (PSA), and an Ultraviolet-Visible spectrophotometer (UV-Vis spectrophotometer). Visual, UV-Vis spectrophotometer and TEM observations confirmed the system's ability to identify bacteria. Statistical analysis was performed using a one-way analysis of variance using Excel software. Using UV-Vis spectrophotometry, the particle size of AuNPs was determined to be 25.7 nm, and the maximum absorbance occurred at 530 nm. AuNPs PAA APBA colloid exhibited an absorbance maximum of 532 nm, a zeta potential of -41.53, and a pH transition point between 4 and 5. At E. coli concentrations of 4.5 x 107 CFU/mL, the color of the system sensors changed from red to blue after 15 hours of incubation, whereas at S. aureus concentrations of 1.2 x 109 CFU/mL, the color changed to purple immediately after mixing. The TEM confirmed that the detection mechanism is based on the boronate-polyol bonding of saccharides on the outer membranes of Escherichia coli and Staphylococcus aureus. The use of APBA in conjunction with pH-responsive PAA polymers containing AuNPs to detect E. coli and S. aureus bacteria induces a maximum wavelength transition, followed by a color change from red to blue. By the process of de-swelling of the responsive polymer, which induces the aggregation of the AuNPs, the established sensor system is able to alter the color. The conjugated polymer and gold nanoparticle-based sensor system demonstrated a promising method for bacterial detection.

Aptamer-functionalized two-photon SiO2@GQDs hybrid-based signal amplification strategy for targeted cancer imaging.

Targeted imaging is playing an increasingly important role in the early detection and precise diagnosis of cancer. This need has motivated research into sensory nanomaterials that can be constructed into imaging agents to serve as biosensors. Graphene quantum dots (GQDs) as a valuable nanoprobe show great potential for use in two-photon biological imaging. However, most as-prepared GQDs exhibit a low two-photon absorption cross-section, narrow spectral coverage, and "one-to-one" signal conversion mode, which greatly hamper their wide application in sensitive early-stage cancer detection. Herein, a versatile strategy has been employed to fabricate an aptamer Sgc8c-functionalized hybrid as a proof-of-concept of the signal amplification strategy for targeted cancer imaging. In this study, GQDs with two-photon imaging performance, and silica nanoparticles (SiO2 NPs) as nanocarriers to provide amplified recognition events by high loading of GQD signal tags, were adopted to construct a two-photon hybrid-based signal amplification strategy. Thus, the obtained hybrid (denoted SiO2@GQDs) enabled extremely strong fluorescence with a quantum yield up to 0.49, excellent photostability and biocompatibility, and enhanced bright two-photon fluorescence up to 2.7 times that of bare GQDs (excitation at 760 nm; emission at 512 nm). Moreover, further modification with aptamer Sgc8c showed little disruption to the structure of the SiO2@GQDs-hybrid and the corresponding two-photon emission. Hence, SiO2@GQDs-Sgc8c showed specific responses to target cells. Moreover, it could be used as a signal-amplifying two-photon nanoprobe for targeted cancer imaging with high specificity and great efficiency, which exhibits a distinct green fluorescence compared to that of GQDs-Sgc8c or SiO2@GQDs. This signal amplification strategy holds great potential for the accurate early diagnosis of tumors and offers new tools for the detection a wide variety of analytes in clinical application.

Government surveillance and facial recognition system in the context of modern technologies and security challenges

The challenges to privacy resulting from the use of modern and constantly improving data processing technologies pose a significant threat not only at the personal level, but also at the national level. The proliferation of biometric systems, and specifically facial recognition technologies in our everyday lives, has prompted the need to foster a public discussion regarding the associated societal and ethical concerns. Modern information and communication technologies allow organizations to process data on an extremely large scale and at an increasing speed. This thesis is reaffirmed by the exceptional economic strength of companies that process and store personal data on a worldwide scale (Alphabet, also known as Google or Meta, the company that owns Facebook and Instagram), or by the recent acknowledgment of this issue by several countries and the European Union. This paper highlights the state-of-the-art in data processing technology and centers on the numerous difficulties in handling data. It focuses on ethical, technical and legal concerns regarding facial recognition systems and also emphasizes the technologies available and their capacity for handling the larger volume and variety of personal data processing and Big Data Analytics.

Titania Nanosheet as a Matrix for Surface-Assisted Laser Desorption/Ionization Mass Spectrometry Analysis and Imaging.

Surface-assisted laser desorption/ionization (SALDI) acts as a soft desorption/ionization technique, which has been widely recognized in small-molecule analysis owing to eliminating the requirement of the organic matrix. Herein, titania nanosheets (TiO2 NSs) were applied as novel substrates for simultaneous analysis and imaging of low-mass molecules and lipid species. A wide variety of representative analytes containing amino acids, bases, drugs, peptides, endogenous small molecules, and saccharide-spiked urine were examined by the TiO2 NS-assisted LDI mass spectrometry (MS). Compared with conventional organic matrices and substrates [Ag nanoparticles (NPs), Au NPs, carbon nanotubes, carbon NPs, CeO2 microparticles, and P25 TiO2], the TiO2 NS-assisted LDI MS method shows higher sensitivity and less spectral interference. Repeatability was evaluated with batch-to-batch relative standard deviations for 5-hydroxytryptophan, glucose-spiked urine, and glucose with addition of internal standard, which were 17.4, 14.9, and 2.8%, respectively. The TiO2 NS-assisted LDI MS method also allows the determination of blood glucose levels in mouse serum with a linear range of 0.5-10 mM. Owing to the nanoscale size and uniform deposition of the TiO2 NS matrix, spatial distributions of 16 endogenous small molecules and 16 lipid species from the horizontal section of the mouse brain tissue can be visualized at a 50 μm spatial resolution. These successful applications confirm that the TiO2-assisted LDI MS method has promising prospects in the field of life science.

Advances in Ultra-small Fluorescence Nanoprobes for Detection of Metal Ions, Drugs, Pesticides and Biomarkers.

Identification of trace level chemical species (drugs, pesticides, metal ions and biomarkers) plays key role in environmental monitoring. Recently, fluorescence assay has shown significant advances in detecting of trace level drugs, pesticides, metal ions and biomarkers in real samples. Ultra-small nanostructure materials (metal nanoclusters (NCs), quantum dots (QDs) and carbon dots (CDs)) have been integrated with fluorescence spectrometer for sensitive and selective analysis of trace level target analytes in various samples including environmental and biological samples. This review summarizes the properties of metal NCs and ligand chemistry for the fabrication of metal NCs. We also briefly summarized the synthetic routes for the preparation of QDs and CDs. Advances of ultra-small fluorescent nanosensors (NCs, QDs and CDs) for sensing of metal ions, drugs, pesticides and biomarkers in various sample matrices are briefly discussed. Additionally, we discuss the recent challenges and future perspectives of ultra-small materials as fluorescent sensors for assaying of wide variety of target analytes in real samples.

De Rham Comparison and Poincaré Duality for Rigid Varieties

Over any smooth algebraic variety over a p-adic local field k, we construct the de Rham comparison isomorphisms for the étale cohomology with partial compact support of de Rham \({\mathbb {Z}}_p\)-local systems, and show that they are compatible with Poincaré duality and with the canonical morphisms among such cohomology. We deduce these results from their analogues for rigid analytic varieties that are Zariski open in some proper smooth rigid analytic varieties over k. In particular, we prove finiteness of étale cohomology with partial compact support of any \({\mathbb {Z}}_p\)-local systems, and establish the Poincaré duality for such cohomology after inverting p.

Picomolar or beyond Limit of Detection Using Molecularly Imprinted Polymer-Based Electrochemical Sensors: A Review

Over the last decades, molecularly imprinted polymers (MIPs) have emerged as selective synthetic receptors that have a selective binding site for specific analytes/target molecules. MIPs are synthetic analogues to the natural biological antigen-antibody system. Owing to the advantages they exhibit, such as high stability, simple synthetic procedure, and cost-effectiveness, MIPs have been widely used as receptors/sensors for the detection and monitoring of a variety of analytes. Moreover, integrating electrochemical sensors with MIPs offers a promising approach and demonstrates greater potential over traditional MIPs. In this review, we have compiled the methods and techniques for the production of MIP-based electrochemical sensors along with the applications of reported MIP sensors for a variety of analytes. A comprehensive in-depth analysis of recent trends reported on picomolar (pM/10-12 M)) and beyond picomolar concentration LOD (≥pM) achieved using MIPs sensors is reported. Finally, we discuss the challenges faced and put forward future perspectives along with our conclusion.

A -adic monodromy theorem for de Rham local systems

We study horizontal semistable and horizontal de Rham representations of the absolute Galois group of a certain smooth affinoid over a$p$-adic field. In particular, we prove that a horizontal de Rham representation becomes horizontal semistable after a finite extension of the base field. As an application, we show that every de Rham local system on a smooth rigid analytic variety becomes horizontal semistable étale locally around every classical point. We also discuss potentially crystalline loci of de Rham local systems and cohomologically potentially good reduction loci of smooth proper morphisms.

Electrodeposition of Metal Nanoparticles inside Carbon Nanopipettes for Sensing Applications.

Conductive nanopipettes offer promising confined spaces to enable advanced electrochemical sensing applications in small spaces. Herein, a series of metal-decorated carbon nanopipettes (CNPs) were developed, in which Au, Ag, and Pt are modified at the inner walls of CNPs by a simple electrodeposition method. The fabricated tips show good sensing performances for a variety of important analytes, such as glucose, hydrogen peroxide, and chloride and hydrogen ions in biological and catalytic systems. This simple and effective approach can be further extended to prepare other functionalized nanopipette electrodes toward more versatile and powerful measurements in electrochemical sensing and imaging applications.

Hydrogel-Based Biosensors.

There is an increasing interest in sensing applications for a variety of analytes in aqueous environments, as conventional methods do not work reliably under humid conditions or they require complex equipment with experienced operators. Hydrogel sensors are easy to fabricate, are incredibly sensitive, and have broad dynamic ranges. Experiments on their robustness, reliability, and reusability have indicated the possible long-term applications of these systems in a variety of fields, including disease diagnosis, detection of pharmaceuticals, and in environmental testing. It is possible to produce hydrogels, which, upon sensing a specific analyte, can adsorb it onto their 3D-structure and can therefore be used to remove them from a given environment. High specificity can be obtained by using molecularly imprinted polymers. Typical detection principles involve optical methods including fluorescence and chemiluminescence, and volume changes in colloidal photonic crystals, as well as electrochemical methods. Here, we explore the current research utilizing hydrogel-based sensors in three main areas: (1) biomedical applications, (2) for detecting and quantifying pharmaceuticals of interest, and (3) detecting and quantifying environmental contaminants in aqueous environments.

Effect of spacer alkyl chain length on retention among three imidazolium stationary phases under various modes in high performance liquid chromatography

The properties of ionic liquids (ILs) greatly influenced the retention of solutes on IL-functionalized stationary phases. In this work, three IL-functionalized stationary phases (Sil-C4Im, Sil-C7Im, and Sil-C10Im) were prepared by modifying silica gel with three ionic liquid silane reagents differing in spacer alkyl chain lengths, which refers to the alkyl chain between the imidazolium and the sulfur atom. The preparation was proved through a range of characterization techniques, including elemental analysis (EA), Fourier transform infrared spectroscopy (FT-IR), and thermogravimetric analysis (TGA). The effects of chromatographic conditions, such as acetonitrile content, salt concentration, pH, and column temperature, were studied to explore the retention mechanism of three stationary phases, which indicates that three IL-stationary phases provide interactions with solutes in reverse-phase liquid chromatography (RPLC), hydrophilic interaction liquid chromatography (HILIC), and ion exchange chromatography (IEC). The column efficiency is 83,686 plates/m for aminobenzoic acid, and the column also has excellent repeatability of retention time with relative standard deviations (RSDs) between 0.24% and 0.34% (n = 12). A variety of analytes, including five nucleosides and nucleobases, six alkylbenzenes, two polycyclic aromatic hydrocarbons (PAHs), and four inorganic anions, were separated well on three IL-functionalized stationary phases. It was found that the spacer alkyl chain length influenced selectivity by comparing the retention of the three IL-functionalized stationary phases.

Porous hydrogel scaffolds integrating Prussian Blue nanoparticles: A versatile strategy for electrochemical (bio)sensing

Hydrogels have emerged as promising porous soft materials from which to develop a wide range of biosensing platforms due to the possibility to easily engineer their properties and to effectively immobilize enzymes and nanomaterials in their matrix. Despite their attractive properties, the ability to form stable hydrogel films integrating well–dispersed catalytic nanomaterials and enzymes on electrode surfaces is still required to enable their implementation into electrochemical biosensors. Here, we report a facile approach to prepare hydrogel films embedding Prussian Blue nanoparticles (PBNPs) and different enzymes on electrode surfaces for electrochemical biosensing. A one-pot strategy was employed for the synthesis, under mild conditions, of PBNPs and the simultaneous immobilization of enzymes in a highly functionalized carboxymethyl cellulose matrix, yielding homogeneous hydrogel composites. Highly porous hydrogel films were successfully prepared by drop casting the hydrogel composites on the surface of flexible screen–printed electrodes (SPEs). Due to the high loading of well–dispersed PBNPs, the hydrogel films demonstrated good electrocatalytic activity for both the oxidation of NADH and the reduction of hydrogen peroxide resulting in high detection sensitivity. Two amperometric biosensors for the rapid detection of glucose and ethanol in serum were realized by employing hydrogel composites integrating glucose oxidase and alcohol dehydrogenase. By combining the unique features of hydrogels on flexible electrochemical strips, our approach holds great promise for the development of portable electrochemical (bio)sensors, which are easy to fabricate and versatile for the detection of a variety of analytes.

Plasmon-Tuned Particles for the Amplification of Surface-Enhanced Raman Scattering from Analytes.

Inelastic scattering from molecules because of vibrational modes produces unique Raman shifts, allowing these analytes to be detected with high specificity. Because Raman scattering is weak, surface-enhanced Raman scattering (SERS) has been used as a label-free technique for the detection of a variety of analytes at low concentrations. Using simple solution-based colloidal processing techniques, we have fabricated gold-coated carbon-black nanoparticles that show enhanced Raman activity. By varying the fabrication conditions, we create particles of different surface morphologies, allowing control over the peak wavelength for localized surface plasmon resonance (LSPR). By matching the LSPR wavelength to the incident laser wavelength, we get the highest signal from two model analytes, 4-nitrobenzenethiol (4-NBT) and Congo Red (CR). Our straightforward room-temperature-solution-based approach for making tunable SERS-active particles expands the range of incident radiation wavelengths that can be used for the detection of analytes using Raman scattering.

Rapid Determination of Non-Steroidal Anti-Inflammatory Drugs in Urine Samples after In-Matrix Derivatization and Fabric Phase Sorptive Extraction-Gas Chromatography-Mass Spectrometry Analysis.

Fabric phase sorptive extraction (FPSE) has become a popular sorptive-based microextraction technique for the rapid analysis of a wide variety of analytes in complex matrices. The present study describes a simple and green analytical protocol based on in-matrix methyl chloroformate (MCF) derivatization of non-steroidal anti-inflammatory (NSAID) drugs in urine samples followed by FPSE and gas chromatography-mass spectrometry (GC-MS) analysis. Use of MCF as derivatizing reagent saves substantial amounts of time, reagent and energy, and can be directly performed in aqueous samples without any sample pre-treatment. The derivatized analytes were extracted using sol-gel Carbowax 20M coated FPSE membrane and eluted in 0.5 mL of MeOH for GC-MS analysis. A chemometric design of experiment-based approach was utilized comprising a Placket-Burman design (PBD) and central composite design (CCD) for screening and optimization of significant variables of derivatization and FPSE protocol, respectively. Under optimized conditions, the proposed FPSE-GC-MS method exhibited good linearity in the range of 0.1-10 µg mL-1 with coefficients of determination (R2) in the range of 0.998-0.999. The intra-day and inter-day precisions for the proposed method were lower than &lt;7% and &lt;10%, respectively. The developed method has been successfully applied to the determination of NSAIDs in urine samples of patients under their medication. Finally, the green character of the proposed method was evaluated using ComplexGAPI tool. The proposed method will pave the way for simper analysis of polar drugs by FPSE-GC-MS.

Aptamer-functionalized 2D photonic crystal hydrogels for detection of adenosine.

Aptamer-functionalized two-dimensional photonic crystal (2DPC) hydrogels are reported for the detection of adenosine (AD). As a molecular recognition group, an AD-binding aptamer was covalently attached to 2DPC hydrogels. This aptamer selectively and sensitively binds AD, changing the conformation of the aptamer from a long single-stranded structure (AD-free conformation) to a short hairpin loop structure (AD-bound conformation). The AD-binding-induced changes of aptamer conformation reduced the volume of the 2DPC hydrogels and decreased the interparticle spacing of the 2DPC embedded in the hydrogel network. The particle spacing changes being dependent on AD concentration were determined by measuring 2DPC light diffraction using a simple laser pointer. The 2DPC hydrogel sensor showed a large particle spacing decrease of ~ 110nm in response to 1mM AD in phosphate-buffered saline (PBS). The linear range of determination of AD was 0.1nM to 1mM and the limit of detection was 0.09nM. The hydrogel sensor response for real samples was then validated in diluted fetal bovine serum (FBS) and human urine. The average % difference in particle spacing changes measured between diluted FBS and pure PBS was only 3.99%. In diluted human urine, the recoveries for the detection of AD were 95-101% and the relative standard deviations were 4.9-7.8%. The results demonstrate the potential applicability of the hydrogel sensor for real samples. This sensing concept, using the aptamer-functionalized 2DPC hydrogels, allows for a simple, sensitive, selective, and reversible detection of AD. It may enable sensor development for a wide variety of analytes by simply changing the aptamer recognition group.