Variety Of Analytes Research Articles

Structure-fragmentation study of pentacyclic triterpenoids using electrospray ionization quadrupole time-of-flight tandem mass spectrometry (ESI-QTOFMS/MS).

Pentacyclic triterpenoids are secondary plant metabolites widespread in fruit peel, leaves, and stem bark. Due to their important biological activities, these compounds are widely screened using advance analytical techniques like electrospray ionization (ESI) mass spectrometry. Over the past few decades, the practice of ESI has been refined into a versatile ionization technique for a wide variety of analytes differing in their chemical makeup, size, complexity, and bimolecular stability. The structure-fragmentation relationships (SFRs) of 16 pentacyclic triterpenoids were studied using a positive ion ESI quadrupole time-of-flight mass spectrometry (ESI-QqTOFMS/MS) hybrid instrument. ESI-QqTOFMS (positive ion mode) showed the presence of the protonated molecules [M + H]+ of most of analyzed compounds. Low-energy collision-induced dissociation MS/MS analysis of these molecules indicated multiple losses of water molecules and the loss of the formic acid moiety [M + H - HCOOH]+ and other substituents as the predominant pathway for further fragmentation. Key product ions were identified which resulted from the retro-Diels-Alder cleavage of the ring system. SFRs of all the compounds analyzed were also developed. We developed a fragmentation pattern of pentacyclic triterpenoids using the ESI-QqTOFMS/MS technique. It was concluded that the formation of key product ions and loss of characteristic neutrals can give detailed insight into structural information about the basic structure and attached substituents.

Benzimidazole appended optical sensors for ionic species: Compilation of literature reports from 2017 to 2022

Rigorous advancement in the area of generation of optical (colorimetric/fluorescent) chemosensors has seen brilliant success as vibrant tools for the selective and sensitive tracking of analytes (cations and/or anions etc.) since the advent of supramolecular chemistry. Several benzimidazole derivatives and their impending significance in field of molecular recognition have been reported in this literature review, which point to the vitality of the chemosensing area. The present review delivers comprehensions into different benzimidazole based derivatives with varied structural modulations by pyridine, coumarin, pyrazole, pyrene, carbazole and Schiff base functionalities for optical detection of a variety of analytes (metal ions and/or anions). The discussed literature reports will excavate new avenues and enable research fraternities to develop superlative chemosensors with enhanced sensitivity and selectivity. This review highlights the development of various benzimidazole appended optical chemosensors for various metal ions and anions since 2017.

Deep Learning‐Assisted Visualized Fluorometric Sensor Array for Biogenic Amines Detection

Comprehensive SummaryBiogenic amines (BAs) are important biomarkers for monitoring food quality and assisting in the diagnosis of disease. Facial, portable, accurate and high‐throughput BAs detection is still challenging by the specific sensor compounds development or the complicated instrument operation. Deep learning (DL) algorithms are blooming for their superiority on the nonlinear and multidimensional data analysis, which endow the great advantage for the artificial intelligence assisted large sample analysis of the environmental or daily health monitoring. In this work, we developed a deep learning‐assisted visualized fluorometric array‐based sensing method. Two commercial fluorescent dyes were selected and combined into sensor arrays. Variation in the alkalinity of BAs causes significant and distinct fluorescence changes of the dyes. In conjunction with pattern recognition by the pretrained CNN models, the sensor array clearly differentiates seven BAs with 99.29% prediction accuracy and allows rapid single and multi‐component quantification with a volume fraction range from 200 cm3/m3 to 2500 cm3/m3. This method also provides a new way for meat freshness monitoring. We envision that this novel analytical method for BAs can be used as an alternative and promising tool for the detection of a wider variety of analytes.

Raman Studies on Surface-Imprinted Polymers to Distinguish the Polymer Surface, Imprints, and Different Bacteria.

Molecularly imprinted polymers (MIPs) are widely used as robust biomimetic recognition layers in sensing devices targeting a wide variety of analytes including microorganisms such as bacteria. Assessment of imprinting success and selectivity toward the target is of great importance in MIP quality control. We generated Escherichia coli-imprinted poly(styrene-co-DVB) as a model system for bacteria-imprinted polymers via surface imprinting using a glass stamp with covalently immobilized E. coli. Confocal Raman Microscopy was successfully employed to visualize bacteria, imprints, and polymer and to distinguish them from each other. The method has proven highly feasible for assessing if imprinting had been successful. In addition, we developed a method for selectivity investigation of bacteria MIPs based on combining Confocal Raman Microscopy and Partial Least Squares Discriminant Analysis (PLS-DA). The Raman spectra of E. coli and Bacillus cereus were acquired on E. coli-imprinted poly(styrene-co-DVB) and used to establish a PLS-DA model for differentiating between the bacteria species. Model validation demonstrated a correct classification of 95% of Raman spectra, indicating sufficient accuracy of the model for future use in MIP selectivity studies. Simultaneous differentiation of 3 bacteria species (E. coli, B. cereus, and Lactococcus lactis) on E. coli-imprinted poly(styrene-co-DVB) proved more difficult, which might be due to the limited depth resolution of the confocal Raman microscope resulting in the presence of interfering signals from the polymer substrate. It might be possible to overcome this obstacle by selective enhancement of the Raman signals originating from bacteria surfaces, such as tip enhanced Raman spectroscopy.

Versatile potentiometric metabolite sensing without dioxygen interference

The field of electrochemical biosensors has been dominated by amperometric and voltammetric sensors; however, these are limited greatly in their signal dependence on electrode size. Open circuit potentiometric sensors are emerging as an alternative due to their signal insensitivity to electrode size. Here, we present a second-generation biosensor that uses a modified chitosan hydrogel to entrap a dehydrogenase or other oxidoreductase enzyme of interest. The chitosan is modified with a desired electron mediator such that in the presence of the analyte, the enzyme will oxidize or reduce the mediator, thus altering the measured interfacial potential. Using the above design, we demonstrate a swift screening method for appropriate enzyme-mediator pairs based on open circuit potentiometry, as well as the efficacy of the biosensor design using two dehydrogenase enzymes (FADGDH and ADH) and peroxidase. Using 1,2-naphthoquinone as the mediator for FADGDH, dynamic ranges from 0.1 to 50 mM glucose are achieved. We additionally demonstrate the ease of fabrication and modification, a lifetime of ≥28 days, insensitivity to interferents, miniaturization to the microscale, and sensor efficacy in the presence of the enzyme's natural cofactor. These results forge a foundation for the generalized use of potentiometric biosensors for a wide variety of analytes within biologically-relevant systems where oxygen can be an interferent.

Recent progress in the design of G-quadruplex–based electrochemical aptasensors

Aptamer-based electrochemical sensors are now developed for the detection of a wide variety of analytes including ions, low-molecular-weight molecules, proteins, and living cells. An aptamer-based sensor is an analytical device whose bio-sensing element (i.e. the aptamer) is immobilized on a transducer surface. Aptasensors have attracted great attention because of their high selectivity, sensitivity, and stability; they could be miniaturized and are of low production cost and offer extraordinary flexibility in the design of their assemblies. This review will emphasize recent developments of aptasensors using aptamers that are able to adopt the particular G-quadruplex (G4) conformations, which are secondary DNA structures formed from guanine-rich sequences. Indeed, G4 exhibits notable recognition properties inherent to their particular structuration. • G4 is involved in the design of electrochem for the sensitive detection of a wide variety of analytes.

A carbonylative coupling approach to alkyl stationary phases with variable embedded carbamate groups for high-performance liquid chromatography

A highly efficient carbonylative coupling method for the preparation of alkyl stationary phases with variable numbers of carbamate groups was established. The effectiveness of such method was verified through elemental analysis, X-ray photoelectron spectroscopy and solid-state 13C nuclear magnetic resonance spectroscopy of three as-synthesized stationary phases bearing different alkyl chains and different numbers of carbamate groups (octadecyl/one carbamate group, C18C; docosyl/three carbamate groups, C22C3; triacontyl/two carbamate groups, C30C2). The comparative evaluation of these stationary phases using a great variety of analytes, including three sets of isomers of alkylbenzenes, two sets of standard mixtures of polycyclic aromatic hydrocarbons (SRM 1647e and 869b), nine polychlorinated biphenyls, fiveteen N-substituted ureas, ten sulfonylureas, five xanthines and some other phytonutrients, revealed their remarkable applicability in reversed-phase liquid chromatography. Notably, the intercalated carbamate groups rendered the resultant stationary phases compatible with 100% aqueous mobile phase. The suppression of silanol activity was positively related to the number of polar groups embedded in the bonded selector, and the smallest peak tailing factor (1.14) for amitriptyline was obtained by C22C3. The molecular shape-related selectivity was found to be more closely related to the length of the selector's aliphatic chain, as supported by the lowest αTBN/BaP value (0.31) by C30C2. These carbamate-embedded alkyl stationary phases constituted another class of polar-embedded stationary phases possessing a single type of functional ligand.

Investigation of Vaping Fluids Recovered From New York State E-Cigarette or Vaping Product Use-Associated Lung Injury Patients.

E-cigarette or vaping product use-associated lung injury (EVALI) is a serious pulmonary condition that is associated with the extended use of certain vaping products. EVALI was first characterized in the summer of 2019 and has since been reported in all 50 U.S. states. From August 2019 through June 2021, the New York State Department of Health has reported more than 197 confirmed cases emanating from all regions of the state. The Wadsworth Center at the New York State Department of Heath received vaping cartridges recovered from EVALI patients for chemical analysis of their contents. Untargeted analytical methods using gas chromatography-mass spectrometry and liquid chromatography-high-resolution mass spectrometry as well as targeted analyses for a variety of analytes including cannabinoids, pesticides, vitamin E acetate (VEA) and mycotoxins were used to characterize the composition of the vaping fluids and several commercial vaping fluid additives. From the analyses of the 284 e-cigarette devices recovered from patients, 82 were found to be nicotine-containing pods, and 202 devices containing cannabis oil, apparently from unauthorized or black-market dealers. The fluids from the cannabis-oil cartridges tended to have lower levels of THCs (Δ9-tetrahydrocannabinol + Δ8-tetrahydrocannabinol) and total cannabinoids compared with those of commercially produced formulations and contained significant levels of diluents including VEA, medium-chain triglycerides, polyethylene glycol, and castor oil. VEA was the diluent most frequently detected, which was present in 132 (65.3%) of the vaping fluids that contained cannabis oil. When present, VEA ranged from 2.0 to 67.8% of the total mass of the oil with a mean content of 37.0%. In some cases, two or three diluents were detected in the same sample. The ratio of VEA to THCs varied widely, from 0.07 to 5.34. VEA and specifically the high ratios of VEA to THCs in black-market vaping fluids may be causative in EVALI. The safety of additional components and additives that are present in vaping fluids are likewise of concern.

Perspective on Nanofiber Electrochemical Sensors: Design of Relative Selectivity Experiments.

The use of nanofibers creates the ability for non-enzymatic sensing in various applications and greatly improves the sensitivity, speed, and accuracy of electrochemical sensors for a wide variety of analytes. The high surface area to volume ratio of the fibers as well as their high porosity, even when compared to other common nanostructures, allows for enhanced electrocatalytic, adsorptive, and analyte-specific recognition mechanisms. Nanofibers have the potential to rival and replace materials used in electrochemical sensing. As more types of nanofibers are developed and tested for new applications, more consistent and refined selectivity experiments are needed. We applied this idea in a review of interferant control experiments and real sample analyses. The goal of this review is to provide guidelines for acceptable nanofiber sensor selectivity experiments with considerations for electrocatalytic, adsorptive, and analyte-specific recognition mechanisms. The intended presented review and guidelines will be of particular use to junior researchers designing their first control experiments, but could be used as a reference for anyone designing selectivity experiments for non-enzymatic sensors including nanofibers. We indicate the importance of testing both interferants in complex media and mechanistic interferants in the selectivity analysis of newly developed nanofiber sensor surfaces.

Squaraine-Based Optical Sensors: Designer Toolbox for Exploring Ionic and Molecular Recognitions

Small molecule-based chromogenic and fluorogenic probes play an indispensable role in many sensing applications. Ideal optical chemosensors should provide selectivity and sensitivity towards a variety of analytes. Synthetic accessibility and attractive photophysical properties have made squaraine dyes an enticing platform for the development of chemosensors. This review highlights the versatility of modular assemblies of squaraine-based chemosensors and chemodosimeters that take advantage of the availability of various structurally and functionally diverse recognition motifs, as well as utilizing additional recognition capabilities due to the unique structural features of the squaraine ring.

Neurocraft: software for microscale brain network dynamics

The brain operates at millisecond timescales but despite of that, the study of its functional networks is approached with time invariant methods. Equally, for a variety of brain conditions treatment is delivered with fixed temporal protocols unable to monitor and follow the rapid progression and therefore the cycles of a disease. To facilitate the understanding of brain network dynamics we developed Neurocraft, a user friendly software suite. Neurocraft features a highly novel signal processing engine fit for tracking evolving network states with superior time and frequency resolution. A variety of analytics like dynamic connectivity maps, force-directed representations and propagation models, allow for the highly selective investigation of transient pathophysiological dynamics. In addition, machine-learning tools enable the unsupervised investigation and selection of key network features at individual and group-levels. For proof of concept, we compared six seizure-free and non seizure-free focal epilepsy patients after resective surgery using Neurocraft. The network features were calculated using 50 intracranial electrodes on average during at least 120 epileptiform discharges lasting less than one second, per patient. Powerful network differences were detected in the pre-operative data of the two patient groups (effect size = 1.27), suggesting the predictive value of dynamic network features. More than one million patients are treated with cardiac and neuro modulation devices that are unable to track the hourly or daily changes in a subject’s disease. Decoding the dynamics of transition from normal to abnormal states may be crucial in the understanding, tracking and treatment of neurological conditions. Neurocraft provides a user-friendly platform for the research of microscale brain dynamics and a stepping stone for the personalised device-based adaptive neuromodulation in real-time.

(Invited) Single Molecule Sensing Using Engineered Biological Nanopores

A specially engineered biological nanopore directly resolves a large variety of analytes including inorganic ions, small molecules, nucleic acids or even proteins. This high resolution enables the biological nanopore as an ideal sensor to directly monitor single molecule analytes, which include but not limited to the probing of carcinogenic DNA damages, cisplatin modifications to DNA and small molecule interactions with ion channels. O6-carboxymethyl guanine, which is a highly carcinogenic base damage related to the development of rectum cancer, were identified by a nanopore sequencing assay with no ambiguity. By taking a tetrachloroaurate(III) as an atomic adaptor inside a biological nanopore, we report a novel concept of nanopore fabrication with a bio-inorganic interface, which immediately discriminate between cysteine, homocysteine and glutathione via direct nanopore readouts. Emerging optical single channel recording (oSCR) techniquesand its simplified form DiffusiOptoPhysiology (DOP) has also significantly improved the measurement throughput of nanopore via fluorescence microscopy instead of a patch clamp which lacks a desired throughput. Figure 1

Surface-enhanced Raman scattering of CoTiO3@Ag nanofibers for high-performance sensing applications

Surface-enhanced Raman scattering (SERS) has proven to be a powerful fingerprinting technique for the ultra-sensitive detection of a variety of biological and chemical analytes. Hence, the development of facile, low-cost, and reliable SERS-active substrates is essential for practical applications. In this study, electrospun CoTiO3@Ag nanofibers annealed at different temperatures were developed and explored for SERS detection using R6G as a probe. The results showed that with increasing annealing temperature, more Ag nanoparticles grew on the surface of the CoTiO3 nanofibers, leading to a maximum SERS effect achieved at 700 °C. The substrate showed good reusability during repeated SERS detection of R6G and RhB without appreciable loss of activity. High sensitivity over a range of R6G concentrations (10-9–10-3 M) and good uniformity (RSD = 12.3%) were also observed for the prepared substrate. Moreover, when the individual nanofibers were assembled into helically bundled CoTiO3@Ag nanofibers, the SERS effect was increased by a factor of 9.27. This further enhancement was attributed to the interparticle plasmonic couplings and consequently increased number of hot spots, as demonstrated by FEM simulations of bundled CoTiO3@Ag nanofibers with different spacings. These findings demonstrate that elegant manipulation of the nanofibers can effectively boost the resulting SERS performance.

Good Formal Structures for Flat Meromorphic Connections, III: Irregularity and Turning Loci

Given a formal at meromorphic connection over an excellent scheme over a field of characteristic zero, in a previous paper we established existence of good formal structures and a good Deligne–Malgrange lattice after suitably blowing up. In this paper, we reinterpret and refine these results by introducing some related structures. We consider the turning locus , which is the set of points at which one cannot achieve a good formal structure without blowing up. We show that when the polar divisor has normal crossings, the turning locus is of pure codimension 1 within the polar divisor, and hence of pure codimension 2 within the full space; this had been previously established by André in the case of a smooth polar divisor. We also construct an irregularity sheaf and its associated b-divisor , which measure irregularity along divisors on blowups of the original space; this generalizes another result of André on the semicontinuity of irregularity in a curve fibration. One concrete consequence of these refinements is a process for resolution of turning points which is functorial with respect to regular morphisms of excellent schemes; this allows us to transfer the result from schemes to formal schemes, complex analytic varieties, and nonarchimedean analytic varieties.

A counterexample to an optimistic guess about étale local systems

In p-adic Hodge theory, it is known that if a Galois representation is de Rham, then it becomes semistable after extension of the base field. Liu and Zhu asked whether a corresponding result holds in the relative setting: given an \'etale local system on a quasi-compact rigid analytic variety (for example, a projective scheme) over a p-adic field, does it become semistable after a finite extension of the base field? We give a counterexample.

Progress and challenges in diagnosis and treatment of rejection following liver transplantation.

Liver biopsy remains the most widely utilized method for diagnosis of allograft rejection following liver transplantation. However, associated risks and limitations present an opportunity for emerging noninvasive diagnostic techniques to improve upon the current standard of care. This review evaluates progress toward development of new noninvasive methods for the monitoring and diagnosing of allograft rejection. Recent studies investigate the potential of a variety of analytes. Quantification of dd-cfDNA and of DSA show potential to indicate status of allograft rejection and aid in immunosuppression modulation. Moreover, mRNA microarray profiling of differentially expressed genes, as well as characterization of cytokine responses and immunophenotypic shifts following liver transplantation, may predict and recognize rejection events. Noninvasive methods are not yet ready to replace liver biopsy as the standard of care for diagnosis of allograft rejection, though several assays and biomarkers have shown promising preliminary results. As noninvasive techniques become validated in clinical settings, their integration with current diagnostic methods is likely to foster increased sensitivity, specificity, and reliability of diagnosis.

Biomimetic Sensors to Detect Bioanalytes in Real-Life Samples Using Molecularly Imprinted Polymers: A Review.

Molecularly imprinted polymers (MIPs) come with the promise to be highly versatile, useful artificial receptors for sensing a wide variety of analytes. Despite a very large body of literature on imprinting, the number of papers addressing real-life biological samples and analytes is somewhat limited. Furthermore, the topic of MIP-based sensor design is still, rather, in the research stage and lacks wide-spread commercialization. This review summarizes recent advances of MIP-based sensors targeting biological species. It covers systems that are potentially interesting in medical applications/diagnostics, in detecting illicit substances, environmental analysis, and in the quality control of food. The main emphasis is placed on work that demonstrates application in real-life matrices, including those that are diluted in a reasonable manner. Hence, it does not restrict itself to the transducer type, but focusses on both materials and analytical tasks.

Magnetic Particle Spectroscopy with One-Stage Lock-In Implementation for Magnetic Bioassays with Improved Sensitivities.

In recent years, magnetic particle spectroscopy (MPS) has become a highly sensitive and versatile sensing technique for quantitative bioassays. It relies on the dynamic magnetic responses of magnetic nanoparticles (MNPs) for the detection of target analytes in the liquid phase. There are many research studies reporting the application of MPS for detecting a variety of analytes including viruses, toxins, nucleic acids, and so forth. Herein, we report a modified version of the MPS platform with the addition of a one-stage lock-in design to remove the feedthrough signals induced by external driving magnetic fields, thus capturing only MNP responses for improved system sensitivity. This one-stage lock-in MPS system is able to detect as low as 781 ng multi-core Nanomag50 iron oxide MNPs (micromod Partikeltechnologie GmbH) and 78 ng single-core SHB30 iron oxide MNPs (Ocean NanoTech). We first demonstrated the performance of this MPS system for bioassay-related applications. Using the SARS-CoV-2 spike protein as a model, we have achieved a detection limit of 125 nM (equal to 5 pmole) for detecting spike protein molecules in the liquid phase. In addition, using a streptavidin-biotin binding system as a proof-of-concept, we show that these single-core SHB30 MNPs can be used for Brownian relaxation-based bioassays while the multi-core Nanomag50 cannot be used. The effects of MNP amount on the concentration-dependent response profiles for detecting streptavidin were also investigated. Results show that by using a lower concentration/ amount of MNPs, concentration-response curves shift to a lower concentration/amount of target analytes. This lower concentration-response indicates the possibility of improved bioassay sensitivities by using lower amounts of MNPs.

Ultrasensitive and Selective Protein Recognition with Nanobody‐Functionalized Synthetic Nanopores

The development of flexible and reconfigurable sensors that can be readily tailored toward different molecular analytes constitutes a key goal and formidable challenge in biosensing. In this regard, synthetic nanopores have emerged as potent physical transducers to convert molecular interactions into electrical signals. Yet, systematic strategies to functionalize their surfaces with receptor proteins for the selective detection of molecular analytes remain scarce. Addressing these limitations, a general strategy is presented to immobilize nanobodies in a directional fashion onto the surface of track-etched nanopores exploiting copper-free click reactions and site-specific protein conjugation systems. The functional immobilization of three different nanobodies is demonstrated in ligand binding experiments with green fluorescent protein, mCherry, and α-amylase (α-Amy) serving as molecular analytes. Ligand binding is resolved using a combination of optical and electrical recordings displaying quantitative dose-response curves. Furthermore, a change in surface charge density is identified as the predominant molecular factor that underlies quantitative dose-responses for the three different protein analytes in nanoconfined geometries. The devised strategy should pave the way for the systematic functionalization of nanopore surfaces with biological receptors and their ability to detect a variety of analytes for diagnostic purposes.

Non-archimedean hyperbolicity and applications

Abstract Inspired by the work of Cherry, we introduce and study a new notion of Brody hyperbolicity for rigid analytic varieties over a non-archimedean field K of characteristic zero. We use this notion of hyperbolicity to show the following algebraic statement: if a projective variety admits a non-constant morphism from an abelian variety, then so does any specialization of it. As an application of this result, we show that the moduli space of abelian varieties is K-analytically Brody hyperbolic in equal characteristic 0. These two results are predicted by the Green–Griffiths–Lang conjecture on hyperbolic varieties and its natural analogues for non-archimedean hyperbolicity. Finally, we use Scholze’s uniformization theorem to prove that the aforementioned moduli space satisfies a non-archimedean analogue of the “Theorem of the Fixed Part” in mixed characteristic.