Advancements in biosensor technologies for fibrinogen detection in cardiovascular disorders

Rapid and accurate identification of cardiovascular diseases (CVDs) are crucial for timely medical interventions and improved patient outcomes. Fibrinogen (Fib) has emerged as a valuable biomarker for CVDs, playing a significant role in their early detection. Elevated levels of Fib are associated with an increased risk of developing CVD, highlighting its importance for more precise diagnosis and effective treatment strategies. In recent years, significant advancements have been made in developing biosensor-based approaches for detecting Fib, offering high sensitivity and specificity. This review aims to explore the impact of Fib on cardiovascular conditions, assess the current advancements, and discuss the future potential of biosensors in Fib research for diagnosing cardiovascular disorders. Furthermore, we evaluate various biosensor techniques, including optical, electrochemical, electronic, and gravimetric methods, in terms of their utility for measuring Fib in clinical samples such as serum, plasma, whole blood, and other body fluids. A comparative analysis of these techniques is conducted based on their performance characteristics. By providing a comprehensive overview of the relationship between Fib and cardiovascular ailments, this review aims to clarify the advancements in biosensor technology for Fib detection. The comparison of different biosensor techniques will aid researchers and clinicians in selecting the most suitable approach for their specific diagnostic needs. Ultimately, integrating biosensors into clinical practice has the potential to revolutionize the detection and management of CVDs, leading to improved patient care and outcomes.

Prediction of Self-Association and Solution Behavior of Monoclonal Antibodies Using the QCM-D Metric of Loosely Interacting Layer

Despite the increasing availability and success of monoclonal antibodies (mAb), early identification of candidate molecules with desirable developability attributes remains challenging due to self-association and poor solution behavior. Measuring these phenomena experimentally using the available methods is complicated in mAbs development. Quartz crystal microbalance with dissipation monitoring (QCM-D) detects a loosely interacting layer on top of the irreversibly adsorbed layer of molecules, providing information about the mAbs interaction. This work aimed to explore whether the characteristics of this layer can be used as a reliable self-association metric. QCM-D experiments showed a large frequency shift (Δf) associated with loosely interacting layers for omalizumab but a small or absent layer for tocilizumab. Accordingly, the viscosity of omalizumab increased exponentially at high concentrations compared to tocilizumab. Testing eight mAbs with different self-association behaviors revealed a strong rank order correlation between the mostly used metric of self-association, i.e., diffusion interaction parameter (kD-DLS), and Δf, indicating Δf's potential for predicting mAb solution behavior. The study also highlighted the robustness of the metric to impurities and temperature variations compared to the sensitive kD-DLS. Overall, we demonstrate that the loosely interacting layer provides valuable information about mAb self-association, predicting the colloidal stability and solution behavior in therapeutic development.

"Binding" or "Binding and Switching"? A Perspective on Resolving Conformational Changes of Surface-Attached Biomolecular Receptors

Understanding the structural reconfiguration of a biomolecular receptor remains a topic of particular interest to the biosensing community. This is because conformationally changing receptors are commonly employed in biosensors to harness their capability to bind specifically to their target. Often, such receptors are attached to surfaces so that binding can be transduced into a measurable response. Doing so, however, can impose constraints on the possible configurations they can adopt. Such constraints can ultimately influence, for example, their receptor-target binding models or their affinity, which is essential to provide the desired analytical performances in biosensors. Motivated by the idea of gaining further insights into the impact of surface attachment on conformationally switching receptors attached to surfaces, we explore here the various surface-based techniques capable of monitoring structural changes. We decided to narrow our survey to techniques that have been applied to the investigation of nucleic acids to provide an overview of their key features. We envision that this will bring a broader perspective of the field and the challenges ahead with the hopes of "finding the switch" in surface-attached biomolecular receptors.

Construction of a monoclonal molecular imprinted sensor with high affinity for specific recognition of influenza a virus subtype

Although molecular imprinting technology has been widely used in the construction of virus sensors, it is still a great challenge to identify subtypes viruses specifically because of their high similarity in morphology, size and structure. Here, a monoclonal molecular imprinted polymers (MIPs) sensor for recognition of H5N1 is constructed to permit the accurate distinguishing of H5N1 from other influenza A virus (IAV) subtypes. Firstly, H5N1 are immobilized on magnetic microspheres to produce H5N1-MagNPs, then the high affinity nanogel H5N1-MIPs is prepared by solid phase imprinting technique. When H5N1-MIPs is combined with MagNP-H5N1, different concentrations of H5N1 are added for competitive substitution. The quantitative detection of H5N1 is realized by the change of fluorescence intensity of supernatant. As expected, the constructed sensor shows satisfactory selectivity, and can identify the target virus from highly similar IAV subtypes, such as H1N1, H7N9 and H9N2. The sensor was highly sensitive, with a detection limit of 0.58 fM, and a selectivity factor that is comparable to that of other small MIPs sensors is achieved. In addition, the proposed sensor is cheap, with a cost of only RMB 0.08 yuan. The proposed monoclonal sensor provides a new method for the specific recognition of designated virus subtype, which is expected to be used for large-scale screening and accurate treatment of infected people.

Sensitivity-Enhancing Strategies of Graphene Field-Effect Transistor Biosensors for Biomarker Detection

The ultrasensitive recognition of biomarkers plays a crucial role in the precise diagnosis of diseases. Graphene-based field-effect transistors (GFET) are considered the most promising devices among the next generation of biosensors. GFET biosensors possess distinct advantages, including label-free, ease of integration and operation, and the ability to directly detect biomarkers in liquid environments. This review summarized recent advances in GFET biosensors for biomarker detection, with a focus on interface functionalization. Various sensitivity-enhancing strategies have been overviewed for GFET biosensors, from the perspective of optimizing graphene synthesis and transfer methods, refinement of surface functionalization strategies for the channel layer and gate electrode, design of biorecognition elements and reduction of nonspecific adsorption. Further, this review extensively explores GFET biosensors functionalized with antibodies, aptamers, and enzymes. It delves into sensitivity-enhancing strategies employed in the detection of biomarkers for various diseases (such as cancer, cardiovascular diseases, neurodegenerative disorders, infectious viruses, etc.) along with their application in integrated microfluidic systems. Finally, the issues and challenges in strategies for the modulation of biosensing interfaces are faced by GFET biosensors in detecting biomarkers.

Enzymatic Precipitation of Highly Electroactive and Ion-Transporting Prussian Blue for a Sensitive Electrochemical Immunosensor

Sensitive and/or multiplex electrochemical biosensors often require efficient (bio)catalytic conversion of substrates into insoluble electroactive products. The enzymatic formation and precipitation of coordination polymers under mild conditions offers a promising solution for this purpose. Herein, we report the enzymatic precipitation of Prussian blue (PB), a highly electroactive and ion-transporting coordination polymer, on an immunosensing electrode for application in a sensitive electrochemical immunosensor for detecting thyroid-stimulating hormone (TSH). Five pairs of redox enzymes and their specific reductants were examined to achieve rapid PB precipitation and electrochemical oxidation. Among these pairs, O2-insensitive flavin adenine dinucleotide-dependent glucose dehydrogenase (FAD-GDH) paired with glucose yielded the highest electrochemical signal-to-background (S/B) ratio. FAD-GDH catalyzed the conversion of Fe(CN)63- to Fe(CN)64-, which coordinated with Fe3+, leading to PB formation and subsequent precipitation through repeated conversions. The resulting PB precipitate, with its close proximity to the electrode, facilitated rapid electrochemical oxidation and generated a strong electrochemical signal. Notably, the precipitation and electrochemical oxidation of PB were more effective than those of its analogues. When applied to a sandwich-type immunosensor for TSH detection, the enzymatic PB precipitation achieved a calculated detection limit of approximately 2 pg/mL in artificial serum, covering the clinically relevant range. These findings indicate the potential widespread utility of PB precipitation and electrochemical oxidation for sensitive multiplex biomarker detection.

Interface-Engineered Field-Effect Transistor Electronic Devices for Biosensing

Promising advances in molecular medicine have promoted the urgent requirement for reliable and sensitive diagnostic tools. Electronic biosensing devices based on field-effect transistors (FETs) exhibit a wide range of benefits, including rapid and label-free detection, high sensitivity, easy operation, and capability of integration, possessing significant potential for application in disease screening and health monitoring. In this perspective, the tremendous efforts and achievements in the development of high-performance FET biosensors in the past decade are summarized, with emphasis on the interface engineering of FET-based electrical platforms for biomolecule identification. First, an overview of engineering strategies for interface modulation and recognition element design is discussed in detail. For a further step, the applications of FET-based electrical devices for in vitro detection and real-time monitoring in biological systems are comprehensively reviewed. Finally, the key opportunities and challenges of FET-based electronic devices in biosensing are discussed. It is anticipated that a comprehensive understanding of interface engineering strategies in FET biosensors will inspire additional techniques for developing highly sensitive, specific, and stable FET biosensors as well as emerging designs for next-generation biosensing electronics.

Quartz Crystal Microbalance as a Predictive Tool for Drug-Material of Construction Interactions in Intravenous Protein Drug Administration

As a growing number of protein drug products are developed, formulation characterization is becoming important. An IgG drug product is tested at concentrations from 0.0001-0.1 mg/mL for adsorption behavior to polymer surfaces polyvinyl chloride (PVC) and polypropylene (PP) upon dilution in normal saline (NS) using quartz crystal microbalance with dissipation (QCM-D). The studies mimicked IgG antibody interaction during IV administration with polymeric surfaces within syringes, lines, and bags. Drug product was characterized with excipients, with focus on surfactant. Drug solutions were run over polymer-coated sensors to measure the adsorption behavior of the formulation with emphasis on the behavior of each of the formulation's components. Over 60 sensorgram data sets were correlated with assayed protein solution concentrations in mock NS-diluted infusions of drug product in the equivalent concentrations to QCM experiments to build a preliminary predictive model for determining fraction of drug and surfactant adsorbed and lost at the hydrophobic surface during administration. These results create a method for reliably and predictively estimating drug product adsorption behavior and protein drug dose loss on polymers at different protein drug concentrations.

Bridging the Gap between Zeolites and Dense Silica Polymorphs: Formation of All-Silica Zeolite with High Framework Density from Natural Layered Silicate Magadiite

A silica zeolite (RWZ-1) with a very high framework density (FD) was synthesized from highly crystalline natural layered silicate magadiite, bridging the gap between the two research areas of zeolites and dense silica polymorphs. Magadiite was topotactically converted into a 3D framework through two-step heat treatment. The resulting structure had a 1D micropore system of channel-like cavities with an FD of 22.1 Si atoms/1000 Å3 . This value is higher than those of all other silica zeolites reported so far, approaching those of silica polymorphs (tridymite (22.6) and α-quartz (26.5)). RWZ-1 is a slight negative thermal expansion material with thermal properties approaching those of dense silica polymorphs. It contributes to the creation of a new field on microporous high-density silica/silicates. Synergistic interactions are expected between the micropores with molecular sieving properties and the dense layer-like building units with different topologies which provide thermal and mechanical stabilities.

On the utility of microfluidic systems to study protein interactions: advantages, challenges, and applications

Within the complex milieu of a cell, which comprises a large number of different biomolecules, interactions are critical for function. In this post-reductionist era of biochemical research, the 'holy grail' for studying biomolecular interactions is to be able to characterize them in native environments. While there are a limited number of in situ experimental techniques currently available, there is a continuing need to develop new methods for the analysis of biomolecular complexes that can cope with the additional complexities introduced by native-like solutions. We think approaches that use microfluidics allow researchers to access native-like environments for studying biological problems. This review begins with a brief overview of the importance of studying biomolecular interactions and currently available methods for doing so. Basic principles of diffusion and microfluidics are introduced and this is followed by a review of previous studies that have used microfluidics to measure molecular diffusion and a discussion of the advantages and challenges of this technique.

Internet-of-medical-things integrated point-of-care biosensing devices for infectious diseases: Toward better preparedness for futuristic pandemics

Microbial pathogens have threatened the world due to their pathogenicity and ability to spread in communities. The conventional laboratory-based diagnostics of microbes such as bacteria and viruses need bulky expensive experimental instruments and skilled personnel which limits their usage in resource-limited settings. The biosensors-based point-of-care (POC) diagnostics have shown huge potential to detect microbial pathogens in a faster, cost-effective, and user-friendly manner. The use of various transducers such as electrochemical and optical along with microfluidic integrated biosensors further enhances the sensitivity and selectivity of detection. Additionally, microfluidic-based biosensors offer the advantages of multiplexed detection of analyte and the ability to deal with nanoliters volume of fluid in an integrated portable platform. In the present review, we discussed the design and fabrication of POCT devices for the detection of microbial pathogens which include bacteria, viruses, fungi, and parasites. The electrochemical techniques and current advances in this field in terms of integrated electrochemical platforms that include mainly microfluidic- based approaches and smartphone and Internet-of-things (IoT) and Internet-of-Medical-Things (IoMT) integrated systems have been highlighted. Further, the availability of commercial biosensors for the detection of microbial pathogens will be briefed. In the end, the challenges while fabrication of POC biosensors and expected future advances in the field of biosensing have been discussed. The integrated biosensor-based platforms with the IoT/IoMT usually collect the data to track the community spread of infectious diseases which would be beneficial in terms of better preparedness for current and futuristic pandemics and is expected to prevent social and economic losses.

A quartz crystal microbalance biosensor based on polyethylenimine-modified gold electrode to detect hepatitis B biomarker

Biomarkers-based QCM-biosensors are suitable tools for the label-free detection of infectious diseases. In the current study, a QCM-biosensor was developed for the detection of HBsAg. Briefly, anti-HBsAg antibodies were covalently bound to the primary amines after PEI and thiolated-PEI surface modifications of gold-electrode. After RSM optimization, the statistical analysis revealed no significant difference between the immobilization yields of modified layers. Therefore, the PEI-modified QCM-biosensor was selected for further analysis. The PEI-surface was evaluated by FESEM, AFM, ATR-FTIR, and CA measurement. The surface hydrophilicity and its roughness were increased after PEI-coating. Also, FTIR confirmed the PEI-layering on the gold-surface. RSM optimization increased the antibody immobilization yield up to 80%. The QCM-biosensor showed noteworthy results with a wide dynamic range of 1-1 × 10³ ng/mL, LOD of 3.14 ng/mL, LOQ of 9.52 ng/mL, and detection capability in human-sera, which were comparable with the ELISA. The mean accuracy of the QCM-biosensor was obtained at 91% when measured by the spike recovery test using human-sera. The biosensor was completely regenerated using 50 mM NaOH and 1% SDS. The benefits provided by the developed biosensor such as broad dynamic range, sensitivity, selectivity, stability, regenerate ability, and low cost suggest its potential application for the non-invasive and timely monitoring of HBV-biomarker.

Laminar flow-based microfluidic systems for molecular interaction analysis-Part 1: Chip development, system operation and measurement setup

The recent advent of laminar flow-based microfluidic systems for molecular interaction analysis has enabled transformative new profiling of proteins in regards to their structure, disordering, complex formation and interactions in general. Based on the diffusive transport of molecules perpendicular to the direction of laminar flow in a microfluidic channel, systems of this type promise continuous-flow, high-throughput screening of complex, multi-molecule interactions, while remaining tolerant to heterogeneous mixtures. Using common microfluidic device processing, the technology provides unique opportunities, as well as device design and experimental challenges, for integrative sample handling approaches that can investigate biomolecular interaction events in complex samples with readily available laboratory equipment. In this first chapter of a two-part series, we introduce system design and experimental setup requirements for a typical laminar flow-based microfluidic system for molecular interaction analysis in the form of what we call the 'LaMInA system' (Laminar flow-based Molecular Interaction Analysis system). We provide microfluidic device development advice on choice of device material, device design, including impact of channel geometry on the signal acquisition, and on design limitations and possible post-fabrication treatments to redress these. Finally. we cover aspects of fluidic actuation, such as selecting, measuring and controlling the flow rate appropriately, and provide a guide to possible fluorescent labels for proteins, as well as options for the fluorescence detection hardware, all in the context of assisting the reader in developing their own laminar flow-based experimental setup for biomolecular interaction analysis.

Validation of Selective Capture of Fimbriated Uropathogenic Escherichia coli by a Label-free Engineering Detection System Using Mannosylated Surfaces

Label-free detection of pathogens is of major concern to the microbiologist community. Most procedures require several steps and amplification techniques. Carbohydrates are well-established receptors for host-pathogen interactions, which can be amplified using glycodendritic architectures on the basis of multivalent binding interactions. Given that uropathogenic Escherichia coli bacterial FimH is based on such mannopyranoside-binding interactions, we demonstrate herein that synthetic monomeric and trimeric thiolated α-d-mannosides can be effectively bound to gold substrate-functionalized self-assembled monolayers (SAMs) preactivated with maleimide functionalities. Mannosides grafted onto SAMs were followed using Quartz Crystal Microbalance with Dissipation (QCM-D). Binding recognition efficiency was first evaluated using the plant lectin from Canavalia ensiformis (ConA) also using QCM-D. We showed a direct correlation between the amount of mannoside bound and the lectin attachment. Even though there was less trimer bound (nM/cm²) to the surface, we observed a 7-fold higher amount of lectin anchoring, thus further demonstrating the value of the multivalent interactions. We next examined the relative fimbriated E. coli selective adhesion/capture to either the monomeric or the trimeric mannoside bound to the surface. Our results established the successful engineering of the surfaces to show E. coli adhesion via specific mannopyranoside binding but unexpectedly, the monomeric derivative was more efficient than the trimeric analog, which could be explained by steric hindrance. This approach strongly suggests that it could be broadly applicable to other Gram-negative bacteria sharing analogous carbohydrate-dependent binding interactions.

Uricase Crowding via Polyelectrolyte Layers Coacervation for Carbon Fiber-Based Electrochemical Detection of Uric Acid

Urate oxidase (UOx) surrounded by synthetic macromolecules, such as polyethyleneimine (PEI), poly(allylamine hydrochloride) (PAH), and poly(sodium 4-styrenesulfonate) (PSS) is a convenient model of redox-active biomacromolecules in a crowded environment and could display high enzymatic activity towards uric acid, an important marker of COVID-19 patients. In this work, the carbon fiber electrode was modified with Prussian blue (PB) redox mediator, UOx layer, and a layer-by-layer assembled polyelectrolyte film, which forms a complex coacervate consisting of a weakly charged polyelectrolyte (PEI or PAH) and a highly charged one (PSS). The film deposition process was controlled by cyclic voltammetry and scanning electron microscopy coupled with energy-dispersive X-ray analysis (at the stage of PB deposition) and through quartz crystal microbalance technique (at latter stages) revealed uniform distribution of the polyelectrolyte layers. Variation of the polyelectrolyte film composition derived the following statements. (1) There is a linear correlation between electrochemical signal and concentration of uric acid in the range of 10-4-10-6 M. (2) An increase in the number of polyelectrolyte layers provides more reproducible values for uric acid concentration in real urine samples of SARS-CoV-2 patients measured by electrochemical enzyme assay, which are comparable to those of spectrophotometric assay. (3) The PAH/UOx/PSS/(PAH/PSS)2-coated carbon fiber electrode displays the highest sensitivity towards uric acid. (4) There is a high enzyme activity of UOx immobilized into the hydrogel nanolayer (values of the Michaelis-Menten constant are up to 2 μM) and, consequently, high affinity to uric acid.

Biochemical Interactions through Microscopic Techniques: Structural and Molecular Characterization

Many researchers and scientists have contributed significantly to provide structural and molecular characterizations of biochemical interactions using microscopic techniques in the recent decade, as these biochemical interactions play a crucial role in the production of diverse biomaterials and the organization of biological systems. The properties, activities, and functionalities of the biomaterials and biological systems need to be identified and modified for different purposes in both the material and life sciences. The present study aimed to review the advantages and disadvantages of three main branches of microscopy techniques (optical microscopy, electron microscopy, and scanning probe microscopy) developed for the characterization of these interactions. First, we explain the basic concepts of microscopy and then the breadth of their applicability to different fields of research. This work could be useful for future research works on biochemical self-assembly, biochemical aggregation and localization, biological functionalities, cell viability, live-cell imaging, material stability, and membrane permeability, among others. This understanding is of high importance in rapid, inexpensive, and accurate analysis of biochemical interactions.

Preparation of a quartz microbalance sensor based on molecularly imprinted polymers and its application in formaldehyde detection

Quartz crystal microbalances (QCMs) have been widely used in the food industry, environmental monitoring, and biomedicine. Here, a molecularly imprinted QCM sensor was prepared and used for formaldehyde detection. Using polyvinyl chloride as the embedding material and tetrahydrofuran as the solvent, a QCM electrode was modified with HCHO molecularly imprinted polymers (HCHO-MIPs). The detection conditions of the sensor were optimized, and its selectivity was investigated. The theoretical calculation results revealed that the acrylamide and pentaerythritol triacrylate were potential candidate functional monomer and cross-linking agent, respectively, in the preparation of HCHO-MIPs with high adsorbability, superselectivity, and stability. According to the calculated results, a sensor had been prepared. When the pH was 7, the added mass of the HCHO-MIPs (or NIPs) was 20 mg, and the amount of PVC coating was 20 μL, the sensor exhibited good adsorption, selectivity, repeatability, high sensitivity, high accuracy, and a short response time. The lowest detection limit was 10.72 ng mL-1. The sensor exhibited higher selectivity for HCHO than for propionaldehyde and benzaldehyde. The HCHO contents in fresh shrimp samples were detected using the sensor for four cycles, and the detection rates were in the range of 97.56-98.60%. This study provided a theoretical and experimental basis for the rapid detection of HCHO.

Interaction between organic matter and tetracycline in river sediments in cold regions

In this study, the interaction between river sediments collected from cold regions and typical antibiotics was investigated. The results show that tetracycline addition to the sediment can promote the fluorescence quenching of protein-like, marine humic acid, and humic acid-like substances. The degree of quenching increased with the increase of tetracycline concentration (0-80 μM). The fluorescence quenching degree of protein-like, marine humic acid, and humic acid-like substances is as high as 94.76%, 70.19%, and 77.80%, respectively. In addition, the process belongs to static quenching, and a ground-state complex is formed during the quenching reaction. The number of binding sites of tetracycline and protein-like, marine humic acid, and humic acid-like substances is 1.30, 1.51, and 1.34, respectively. The order of the strength of the formed complex is marine-like humic acid, protein-like, and humic acid-like substrates. The secondary structure of protein-like substrate in the sediment organic matter includes three types: aggregated strands, β-Sheet, and α-helix; and the content ratios are 10.23%, 8.33%, and 81.44%, respectively. When the concentration of tetracycline increased to 80 μM, the content of β-sheet increased significantly, while the content of α-helix decreased significantly. 2D-COS analysis showed that the reaction sequence of organic functional groups and tetracycline in the sediment was phenolic hydroxyl group, fatty group of amino acid structure, nonfluorescent polysaccharide, and protein-like α-helix substrates. After tetracycline interacts with water-extractable organic matters (WEOM), the structure of WEOM becomes compact, and its adsorption capacity on the surface of minerals is significantly reduced, resulting in an increase in the fluidity of tetracycline in the water environment.

Real-time changes of the adsorption process and conformation of marine dissolved organic matters on the solid-liquid interface

In this study, the adsorption characteristics of marine dissolved organic matters (MDOMs) on the solid-liquid interface in the coastal waters was investigated. The results showed that the organic macromolecules with adsorption ability in MDOMs are not rigid molecules. However, the macromolecules have viscoelasticity properties. At different dilution ratios, the MDOMs adsorption process includes rapid (0-200 s) and slow adsorption (200 s later) periods. MDOMs adsorption in the solid-liquid interface is a dynamic process in which adsorption and hydration occur simultaneously. MDOMs concentration is an important driving force for adsorption. The three macromolecules of acid polysaccharides, protein-like, and polycarboxylate-type humic acids in MDOMs are rich in functional groups and they have the ability to absorb to solid surface. Acidic polysaccharides exhibit a sustained adsorption ability, while the adsorption of other macromolecules occurred only in the initial rapid adsorption period. In addition, the acid polysaccharides show weak thixotropy during the adsorption process. It would cause the stretching of macromolecular structure of the adsorption layer, enhancing the hydration of the adsorption layer. The study shows the adsorption process of MDOMs at the solid-liquid interface and the structural characteristics of the adsorption layer. It can provide helpful information for the inhibition and removal of MDOMs pollution during the actual development of marine resources.

A novel near-infrared viscosity probe based on synergistic effect of AIE property and molecular rotors for mitophagy imaging during liver injury

Mitophagy, a specialized form of autophagy, holds the key to cellular metabolism and physiology. Viscosity is a significant marker for visualization of the mitophagy process in real-time. Hence, development of well-performing viscosity probe is beneficial to study mitophagy-related dynamic physiological and pathological processes. Here, a new strategy was proposed by combination of AIE property and molecular rotors to design novel viscosity probe. The probe named TPA-Py was obtained by Knoevenagel condensation reaction of AIE unit and pyridine salt, which giving the probe excellent near-infrared emission, good water-solubility and mitochondrial targeting ability. Most importantly, TPA-Py owns two rotatable parts of triphenylamine and double bond, enabling the probe to equip with AIE property and sensitive recognition units for viscosity. With the environmental viscosity increasing, the rotation of the molecular rotor and the AIE unit is restricted effectively, the probe displayed strong fluorescence. Then, TPA-Py was successfully employed for monitoring the mitophagy process in A549 cells by imaging viscosity alterations. As mitophagy constitutes an important consideration in the pathogenesis of drug-induced liver injury, TPA-Py was also applied to explore the variation of viscosity in production and remediation pathways of APAP-induced liver injury. These results demonstrated that TPA-Py was a highly sensitive viscosity probe which holds great potential of biological applications.

Label-free characterization of an extracellular vesicle-based therapeutic

Interest in mesenchymal stem cell derived extracellular vesicles (MSC-EVs) as therapeutic agents has dramatically increased over the last decade. Current approaches to the characterization and quality control of EV-based therapeutics include particle tracking techniques, Western blotting, and advanced cytometry, but standardized methods are lacking. In this study, we established and verified quartz crystal microbalance (QCM) as highly sensitive label-free immunosensing technique for characterizing clinically approved umbilical cord MSC-EVs enriched by tangential flow filtration and ultracentrifugation. Using QCM in conjunction with common characterization methods, we were able to specifically detect EVs via EV (CD9, CD63, CD81) and MSC (CD44, CD49e, CD73) markers. Furthermore, analysis of QCM dissipation versus frequency allowed us to quantitatively determine the ratio of marker-specific EVs versus non-vesicular particles (NVPs) - a parameter that cannot be obtained by any other technique so far. Additionally, we characterized the topography and elasticity of these EVs by atomic force microscopy (AFM), enabling us to distinguish between EVs and NVPs in our EV preparations. This measurement modality makes it possible to identify EV sub-fractions, discriminate between EVs and NVPs, and to characterize EV surface proteins, all with minimal sample preparation and using label-free measurement devices with low barriers of entry for labs looking to widen their spectrum of characterization techniques. Our combination of QCM with impedance measurement (QCM-I) and AFM measurements provides a robust multi-marker approach to the characterization of clinically approved EV therapeutics and opens the door to improved quality control.

Label-Free Probing of Molecule Binding Kinetics Using Single-Particle Interferometric Imaging

Probing molecular interactions is critical for screening drugs, detecting pollutants, and understanding biological processes at the molecular level, but these interactions are difficult to detect, especially for small molecules. A label-free optical imaging technology that can detect molecule binding kinetics is presented, in which free-moving particles are driven into oscillations with an alternating electrical field and the interferometric scattering patterns of the particles are imaged via an optical imaging method. By tracking the charge-sensitive variations in the oscillation amplitude with sub-nanometer precision, the small molecules and metal ions binding to the surface as well as protein-protein binding kinetics were measured. The capability of the label-free measurement of molecular interactions can provide a promising platform for screening small-molecule drugs, probing conformational changes in proteins, and detecting environmental pollutants.

Recent advances in acoustic wave biosensors for the detection of disease-related biomarkers: A review

In the past several decades, acoustic wave biosensors, as an emerging kind of biosensors, have been developed and widely used for the detection of mass, viscosity, conductivity and density. Varieties of applications have been explored such as medical diagnosis, drug screening, environmental monitoring, food analysis and biochemical assay. Among them, the detection of disease-related biomarkers based on acoustic sensors has aroused great research interest all over the world. In this review, the classification and characteristics of acoustic wave biosensors are briefly introduced. Then, some classical studies and recent advances in disease-related biomarker detection utilizing these biosensors are summarized and detailed, respectively. Here, the disease-related biomarkers mainly include antigens, small molecular proteins, cancer cells, viruses and VOCs. Finally, challenges and future trends of these typical acoustic wave biosensors are discussed. Compared with other reviews of acoustic wave sensors, this review highlights the great potential of typical acoustic wave biosensors for early disease screening and diagnosis compared with widely-used medical imaging. Moreover, they are integrated with other technologies for the design of multi-analyte, multi-parameter and intelligent devices, collecting more comprehensive information from biomarkers. This review provides a new perspective on the applications and optimization of acoustic wave biosensors to develop more reliable platforms for disease-related biomarker detection and disease diagnosis.

Aggregation-induced Emission Based Fluorogens for Mitochondria-targeted Tumor Imaging and Theranostics

Occurrence and development of cancer are multifactorial and multistep processes which involve complicated cellular signaling pathways. Mitochondria, as the energy producer in cells, play key roles in tumor cell growth and division. Since mitochondria of tumor cells have a more negative membrane potential than those of normal cells, several fluorescent imaging probes have been developed for mitochondria-targeted imaging and photodynamic therapy. Conventional fluorescent dyes suffer from aggregation-caused quenching effect, while novel aggregation-induced emission (AIE) probes are ideal candidates for biomedical applications due to their large stokes shift, strong photo-bleaching resistance, and high quantum yield. This review aims to introduce the recent advances in the design and application of mitochondria-targeted AIE probes. The comprehensive review focuses on the structure-property relationship of these imaging probes, expecting to inspire the development of more practical and versatile AIE fluorogens (AIEgens) as tumor imaging and therapy agents for preclinical and clinical use.

Recent advances in aptasensors for mycotoxin detection: On the surface and in the colloid

Mycotoxins are a great potential threat to human health, and the progress in the development of mycotoxin detection methods is of an escalating importance with the increasing emphasis on food safety. Aptamer, performing the same function as antibody in specific binding with targets, exhibits profound potential in biosensing since its debut in 1990. Recent years have witnessed the rapid development of aptasensors for mycotoxin detection with the achievement of ultralow limit of detection and high sensitivity in the lab. However, there is still no officially approved aptasensing methods in mycotoxin detection application. In order to provide researchers with inspirations in the design and development of aptasensors for mycotoxin detection, we divide these aptasensors into two types, namely "on the surface" and "in the colloid", according to the location where the key sensing reaction occurs. We also systematically review aptasensors reported in the past 5 years under the abovementioned criterion of classification, and compare the advantages and disadvantages of each kind of aptasensors. Finally, we discuss prospective directions in the development of aptasensors for mycotoxin detection. This paper will offer insight and motivation to practitioners working on the research and practical application of aptasensors in the detection of mycotoxins and other substances.

Common bacterial, viral, and parasitic diseases in pigeons (Columba livia): A review of diagnostic and treatment strategies

Pigeons (Columba livia) have been associated with humans for a long time now. They are raised for sport (pigeon race), exhibition (display of fancy breeds), food, and research. Most of the pigeons kept are Racing Homers, trained to compete in the pigeon race. Other breeds, such as Rollers, Nose Divers, Doneks are bred for their aerial abilities. Incorporation of a good preventive medicine program is one of the most critical factors in averting infectious diseases in pigeon flocks. This review summarizes the common bacterial, viral, and parasitic infections in pigeons. The different clinical signs, symptoms, diagnostic strategies, prevention, and treatments were described in this review. Current researches, molecular diagnostic assays, and treatment strategies such as vaccines and drug candidates were included. The information found in this review can provide insights for veterinarians and researchers studying pigeons to develop effective and efficient immunoprophylactic and diagnostic tools for pigeon diagnosis and therapeutics.

Protein Assays on Organic Electronics: Rational Device and Material Designs for Organic Transistor-Based Sensors

Artificial receptor-based protein assays have various attractive features such as a long-term stability, a low-cost production process, and the ease of tuning the target specificity. However, such protein sensors are still immature compared with conventional immunoassays. To enhance the application potential of synthetic sensing materials, organic field-effect transistors (OFETs) are some of the suitable platforms for protein assays because of their solution processability, durability, and compact integration. Importantly, OFETs enable the electrical readout of the protein recognition phenomena of artificial receptors on sensing electrodes. Thus, we believe that OFETs functionalized with artificial protein receptors will be a powerful tool for the on-site analyses of target proteins. In this Minireview, we summarize the recent progress of the OFET-based protein assays including the rational design strategies for devices and sensing materials.

“Vanishing mass” in the Sauerbrey world: quartz crystal microbalance study of self-assembled monolayers based on a tripod-branched structure with tuneable molecular flexibility

Complex loadings that appear on a surface with flexible spatial organisation can reveal anti-Sauerbrey behaviour due to their variable interfacial architecture even for an ultrathin monomolecular sensitive layer.

Diagnosis and potential treatments for acute hepatopancreatic necrosis disease (AHPND): a review

Acute hepatopancreatic necrosis disease (AHPND) or formerly known as early mortality syndrome (EMS) is an emerging disease that has caused significant economic losses to the aquaculture industry. The primary causative agent of AHPND is Vibrio parahaemolyticus, a Gram-negative rod-shaped bacterium that has gained plasmids encoding the fatal binary toxins Pir A/Pir B that cause rapid death of the infected shrimp. In this review, the current research studies and information about AHPND in shrimps have been presented. Molecular diagnostic tools and potential treatments regarding AHPND were also included. This review also includes relevant findings which may serve as guidelines that can help for further investigation and studies on AHPND or other shrimp diseases.

A guide to supramolecular polymerizations

Supramolecular polymers are non-covalent assemblies of unimeric building blocks connected by secondary interactions and hold great promises due to their dynamic nature.

A new amplification strategy for a quartz crystal microbalance miRNA sensor based on selective interactions between a metal–organic framework and miRNA

UiO-66 is used as an effective amplifier in a QCM miRNA sensor to detect Let-7a.

A lysosome-targeting viscosity-sensitive fluorescent probe based on a novel functionalised near-infrared xanthene-indolium dye and its application in living cells

The viscosity of lysosomes plays a significant role in modulating biological processes and reflects the status and function of this kind of organelle, e.g., locations, morphologies, and components.

The deposition and wet etching of Mg-doped ZnO films and their applications for solidly mounted resonators

In this report, a solidly mounted resonator (SMR), consisting of an Au electrode, Mg-doped ZnO (Mg_XZn_1−XO) piezoelectric film and Bragg acoustic reflector, was fabricated on a Si substrate by radio frequency (RF) magnetron sputtering. As a key processing step for the SMR, Mg_XZn_1−XO films with high c-axis orientation were fabricated and the crystalline structure, surface morphology and roughness of the films were investigated. The surface morphology, optical transmittance and shape control of Mg_XZn_1−XO films were investigated by the chemical wet-etching method with various etchants. The profiles and line patterns of Mg_XZn_1−XO films etched with FeCl₃·6H₂O solutions are satisfactory and fully meet the industrial requirements. The Bragg acoustic reflector, made entirely of metal, has small internal stress and good heat conduction. An SMR based on a Mg_XZn_1−XO piezoelectric film shows a resonant frequency of 2.402 GHz, and the k_eff², Q_S and Q_P of the SMR are 3.07%, 415 and 546, respectively.

In this report, a solidly mounted resonator (SMR), consisting of an Au electrode, Mg-doped ZnO (Mg_XZn_1−XO) piezoelectric film and Bragg acoustic reflector, was fabricated on a Si substrate by radio frequency (RF) magnetron sputtering.

Reaction-Based Amine and Alcohol Gases Detection with Triazine Ionic Liquid Materials

We demonstrated in this work the use of affinity ionic liquids, AIL 1 and AIL 2, for chemoselective detection of amine and alcohol gases on a quartz crystal microbalance (QCM). These detections of gaseous amines and alcohols were achieved by nucleophilic aromatic substitution reactions with the electrophilic 1,3,5-triazine-based AIL 1 thin-coated on quartz chips. Starting with inexpensive reagents, bicyclic imidazolium ionic liquids AIL 1 and AIL 2 were readily synthesized in six and four synthetic steps with high isolated yields: 51% and 63%, respectively. The QCM platform developed in this work is readily applicable and highly sensitive to low molecular weight amine gases: for isobutylamine gas (a bacterial volatile) at 10 Hz decrease in resonance frequency (i.e., ΔF = -10 Hz), the detectability using AIL 1 was 6.3 ppb. Our preliminary investigation on detection of the much less nucleophilic alcohol gas by AIL 1 was also promising. To our knowledge, no example to date of reports based on nucleophilic aromatic substitution reactions demonstrating sensitive gas detection in these triazine ionic liquids on a QCM has been reported.

Chemical Sensing Platforms Based on Organic Thin-Film Transistors Functionalized with Artificial Receptors

Organic thin-film transistors (OTFTs) have attracted intense attention as promising electronic devices owing to their various applications such as rollable active-matrix displays, flexible nonvolatile memories, and radiofrequency identification (RFID) tags. To further broaden the scope of the application of OTFTs, we focus on the host-guest chemistry combined with the electronic devices. Extended-gate types of OTFTs functionalized with artificial receptors were fabricated to achieve chemical sensing of targets in complete aqueous media. Organic and inorganic ions (cations and anions), neutral molecules, and proteins, which are regarded as target analytes in the field of host-guest chemistry, were electrically detected by artificial receptors. Molecular recognition phenomena on the extended-gate electrode were evaluated by several analytical methods such as photoemission yield spectroscopy in the air, contact angle goniometry, and X-ray photoelectron spectroscopy. Interestingly, the electrical responses of the OTFTs were highly sensitive to the chemical structures of the guests. Thus, the OTFTs will facilitate the selective sensing of target analytes and the understanding of chemical conversions in biological and environmental systems. Furthermore, such cross-reactive responses observed in our studies will provide some important insights into next-generation sensing systems such as OTFT arrays. We strongly believe that our approach will enable the development of new intriguing sensor platforms in the field of host-guest chemistry, analytical chemistry, and organic electronics.

Target-Triggered Polymerization of Branched DNA Enables Enzyme-free and Fast Discrimination of Single-Base Changes

Single-base changes lead to important biological and biomedical implications; however, the discrimination of single-base changes from normal DNA always remains a grand challenge. Herein we developed a DNA recognition and amplification system based on artificial branched DNA, namely, target-triggered polymerization (TTP), to realize enzyme-free and fast discrimination of single-base changes. Branched DNA as monomers rapidly polymerized into DNA nanospheres only with the trigger of specific DNA. Our TTP system worked reliably over a wide range of conditions. Remarkably, our TTP system was capable of discriminating base-changing DNA from normal DNA, including distinguishing 1-4 nucleotide changes and positions of single base, which was attributed to the significant amplification of small differences in hybridization thermodynamics and kinetics. We further proposed a theoretical method for calculating the hybridization probability of nucleic acids, which performed highly consistent with experimental results.

Solidly mounted resonator sensor for biomolecule detections

We report the fabrication of a solidly mounted resonator (SMR) that can also function as a sensor for biological molecules. The SMR, consisting of a Au electrode, aluminum nitride (AlN) piezoelectric thin film and Bragg acoustic reflector, was fabricated on a Si substrate by radio frequency (RF) magnetron sputtering. The Bragg acoustic reflector, made entirely of metal, has small internal stress and good heat conduction. Human immunoglobulin G (IgG) antibody was immobilized on the modified (by self-assembled monolayer method) Au electrode surface of the SMR and goat anti-human IgG antigen was captured through the specificity of bond between the antibody and antigen on the electrode surface. We found a linear relationship between the resonant frequency shift and the concentration of goat anti-human IgG antigen for concentrations smaller than 0.4 mg ml⁻¹ and a relatively constant frequency shift for concentrations greater than 0.5 mg ml⁻¹. A series of interference experiments can prove that the selectivity of the sensor is satisfactory. Our findings suggest that the SMR sensor is an attractive alternative for biomolecule detection.

We report the fabrication of a solidly mounted resonator (SMR) that can also function as a sensor for biological molecules.

Advances in biosensors for the detection of ochratoxin A: Bio-receptors, nanomaterials, and their applications

Ochratoxin A (OTA) is a class of mycotoxin mainly produced by the genera Aspergillus and Penicillium. OTA can cause various forms of kidney, liver and brain diseases in both humans and animals although trace amount of OTA is normally present in food. Therefore, development of fast and sensitive detection technique is essential for accurate diagnosis of OTA. Currently, the most commonly used detection methods are enzyme-linked immune sorbent assays (ELISA) and chromatographic techniques. These techniques are sensitive but time consuming, and require expensive equipment, highly trained operators, as well as extensive preparation steps. These drawbacks limit their wide application in OTA detection. On the contrary, biosensors hold a great potential for OTA detection at for both research and industry because they are less expensive, rapid, sensitive, specific, simple and portable. This paper aims to provide an extensive overview on biosensors for OTA detection by highlighting the main biosensing recognition elements for OTA, the most commonly used nanomaterials for fabricating the sensing interface, and their applications in different read-out types of biosensors. Current challenges and future perspectives are discussed as well.

A "Soft" and "Hard" Ionization Method for Comprehensive Studies of Molecules

Ambient mass spectrometry can be rapidly and directly effective for molecular studies, while there still seems to be a gap between two major groups of electrospray ionization (ESI)- and atmospheric pressure chemical ionization (APCI)-related techniques, for detection of moderately polar to polar and low polar to nonpolar molecules in a relatively low mass range, respectively. Here, an extensively applicable "soft" and "hard" ionization method, spray-dependent plasma mass spectrometry (SDP MS), was established for detecting various molecules with diverse polarities or molecular weights. By SDP MS, both fragment ions and intact molecular ions can be obtained. Significantly, cluster ions of aggregates in high mass range formed by weak molecular interactions can also be well recorded, much softer than traditional ESI MS. By filling the gap between ESI-based and APCI-based ionization techniques, SDP MS would enhance MS performance for comprehensive molecular studies and be extensively applicable in fields of organic synthesis, biological chemistry, medical chemistry, and clinical diagnosis.

A Label-free Resonance Rayleigh Scattering Sensor for Detection of Thrombin Based on Aptamer Recognizing

The interaction between thrombin binding aptamer (TBA) and thrombin (TB) was studied by resonance Rayleigh scattering (RRS). In neutral medium, TBA is present in a balanced form between a G-quadruplex structure and a random coil structure, and the TBA can be induced by metal ions to form a G-quadruplex structure. Upon addition of thrombin, the G-quadruplex selectively bound to TB, which resulted in enhanced resonance Rayleigh scattering. The scattering intensities increased proportionally with the concentration of TB from 10 to 50 nM. The method had very high sensitivity and good selectivity, and the detection limit (3δ/s) was 1 nM. In this work, the spectral characteristics of RRS, the optimum conditions of the reaction, and influencing factors for the RRS intensities were investigated. Furthermore, the structure of the TBA-TB complex and the sensing mechanism were explored. The TB sensor was applied to a diluted human serum sample with satisfactory results, indicating the potential of this method to be applied to biological samples. A selective and simple RRS sensor for the detection of trace amounts of TB is proposed based on conformational change of TBA.

Overcoming Interfacial Scaling Using Engineered Nanocelluloses: A QCM-D Study

Nucleation of sparingly soluble species, such as the inorganic salts of calcium, magnesium, and phosphorous, followed by their growth at solid-liquid interfaces has turned into a major concern in water-based industries. Increased resistance against heat, mass, and momentum transfer is the main drawback of the so-called scaling phenomenon. Although phosphorous-, nitrogen-, and sulfur-based antiscaling macromolecules offer adequate antiscaling performance, their potential negative environmental impacts render them less desirable. Despite recent efforts in developing green antiscalants, there has been no promising green solution based on biomass due to its chemical inertness. Here, we use quartz crystal microbalance with dissipation monitoring (QCM-D) to evaluate the real-time performance of an emerging family of nanoengineered anionic hairy cellulose crystals, bearing dicarboxylated amorphous cellulose chains, with a charge density of more than 5.5 mequiv per g, in preventing the nucleation and growth of calcium carbonate, the most common industrial scale. Remarkably, a CaCO₃ mass deposition rate ∼0 (complete scale inhibition) is obtained when less than 10 ppm of the hairy nanocellulose is added to an already scaled surface under a harsh supersaturated condition at 50 °C. Motivated by their threshold antiscaling effect, we show that coating planar silica surfaces with hairy nanocelluloses may result in scale-resistant interfaces. This research envisions how engineered hairy nanocelluloses may have practical implications for developing scale-resistant interfaces based on the most abundant biopolymer in the world.

On the Measurement of Energy Dissipation of Adhered Cells with the Quartz Microbalance with Dissipation Monitoring

We previously reported the finding of a linear correlation between the change of energy dissipation (Δ D) of adhered cells measured with the quartz crystal microbalance with dissipation monitoring (QCM-D) and the level of focal adhesions of the cells. To account for this correlation, we have developed a theoretical framework for assessing the Δ D-response of adhered cells. We rationalized that the mechanical energy of an oscillating QCM-D sensor coupled with a cell monolayer is dissipated through three main processes: the interfacial friction through the dynamic restructuring (formation and rupture) of cell-extracellular matrix (ECM) bonds, the interfacial viscous damping by the liquid trapped between the QCM-D sensor and the basal membrane of the cell layer, and the intracellular viscous damping through the viscous slip between the cytoplasm and stress fibers as well as among stress fibers themselves. Our modeling study shows that the interfacial viscous damping by the trapped liquid is the primary process for energy dissipation during the early stage of the cell adhesion, whereas the dynamic restructuring of cell-ECM bonds becomes more prevalent during the later stage of the cell adhesion. Our modeling study also establishes a positive linear correlation between the Δ D-response and the level of cell adhesion quantified with the number of cell-ECM bonds, which corroborates our previous experimental finding. This correlation with a wide well-defined linear dynamic range provides a much needed theoretical validation of the dissipation monitoring function of the QCM-D as a powerful quantitative analytical tool for cell study.