Combining electrochemical sensors with miniaturized sample preparation for rapid detection in clinical samples

Flexible Stacked Perovskite Photodetectors for High-Efficiency Multicolor Fluorescence Detection

A flexible, multicolor detector based on stacked perovskite layers with graded band gaps was presented. Different perovskite layers generate a series of photocurrents corresponding to light intensities at different wavelengths. Experimentally, the flexible detector demonstrated acceptable long-term stability and temperature stability in the bending state. To demonstrate the advantages of the flexible multicolor detector in biological applications, a tubular-shaped multicolor fluorescence detector that embraces the sample cell was constructed. As a result, the detection limits of three kinds of CdTe quantum dots (QDs) with central wavelengths of 545, 625, and 730 nm were 0.52, 0.85, and 0.43 nM, respectively, which was significantly improved by more than 10 times compared to those of planar detectors. Additionally, the detector was able to detect three kinds of QDs simultaneously in a mixed solution, and the relative deviation was smaller than 10% compared to the preset concentration. These results demonstrate that the flexible stacked perovskite detector and the tubular-shaped detection configuration hold promise for the simultaneous fluorescent detection of multiple biomolecules.

Pneumatically Driven Microfluidic Platform and Fully Automated Particle Concentration System for the Capture and Enrichment of Pathogens

In this study, we developed a pneumatically driven microfluidic platform (PDMFP) operated by a fully automated particle concentration system (FAPCS) for the pretreatment of micro- and nano-sized materials. The proposed PDMFP comprises a 3D network with a curved fluidic chamber and channel, five on/off pneumatic valves for blocking fluid flow, and a sieve valve for sequential trapping of microbeads and target particles. Using this setup, concentrated targets are automatically released into an outlet port. The FAPCS mainly comprises solenoid valves, glass reservoirs, a regulator, pressure sensor, main printed circuit board, and liquid crystal display touch panel. All pneumatic valves in the microfluidic platform as well as the working fluids in the glass reservoirs are controlled using FAPCS. The flow rate of the working fluids is measured to demonstrate the sequential programed operation of the proposed pretreatment process using FAPCS. In our study, we successfully achieved rapid and efficient enrichment using PDMFP-FAPCS with fluorescence-labeled Escherichia coli. With pretreatment-10 min for the microbead concentration and 25 min for target binding-almost all the target bacteria could be captured. A total of 526 Gram-negative bacteria were attached to 82 beads, whereas Gram-positive bacteria were attached to only 2 of the 100 beads. Finally, we evaluated the PDMFP-FAPCS for SARS-CoV-2 receptor-binding domain (RBD)-based outer membrane vesicles (OMVs) (RBD-OMVs). Specific probes involved in PDMFP-FAPCS successfully isolated RBD-OMVs. Thus, PDMFP-FAPCS exhibits excellent enrichment of particles, including microbes and nanovesicles, and is an effective pretreatment platform for disease diagnosis and investigation.

Synthesis, surface modifications, and biomedical applications of carbon nanofibers: Electrospun vs vapor-grown carbon nanofibers

Engineered nanostructures are materials with promising properties, enabled by precise design and fabrication, as well as size-dependent effects. Biomedical applications of nanomaterials in disease-specific prevention, diagnosis, treatment, and recovery monitoring require precise, specific, and sophisticated approaches to yield effective and long-lasting favorable outcomes for patients. In this regard, carbon nanofibers (CNFs) have been indentified due to their interesting properties, such as good mechanical strength, high electrical conductivity, and desirable morphological features. Broadly speaking, CNFs can be categorized as vapor-grown carbon nanofibers (VGCNFs) and carbonized CNFs (e.g., electrospun CNFs), which have distinct microstructure, morphologies, and physicochemical properties. In addition to their physicochemical properties, VGCNFs and electrospun CNFs have distinct performances in biomedicine and have their own pros and cons. Indeed, several review papers in the literature have summarized and discussed the different types of CNFs and their performances in the industrial, energy, and composites areas. Crucially however, there is room for a comprehensive review paper dealing with CNFs from a biomedical point of view. The present work therefore, explored various types of CNFs, their fabrication and surface modification methods, and their applications in the different branches of biomedical engineering.

Emerging Biosensing Technologies for the Diagnostics of Viral Infectious Diseases

Several viral infectious diseases appear limitless since the beginning of the 21^st century, expanding into pandemic lengths. Thus, there are extensive efforts to provide more efficient means of diagnosis, a better understanding of acquired immunity, and improved monitoring of inflammatory biomarkers, as these are all crucial for controlling the spread of infection while aiding in vaccine development and improving patient outcomes. In this regard, various biosensors have been developed recently to streamline pathogen and immune response detection by addressing the limitations of traditional methods, including isothermal amplification-based systems and lateral flow assays. This review explores state-of-the-art biosensors for detecting viral pathogens, serological assays, and inflammatory biomarkers from the material perspective, by discussing their advantages, limitations, and further potential regarding their analytical performance, clinical utility, and point-of-care adaptability. Additionally, next-generation biosensing technologies that offer better sensitivity and selectivity, and easy handling for end-users are highlighted. An emerging example of these next-generation biosensors are those powered by novel synthetic biology tools, such as clustered regularly interspaced short palindromic repeats (CRISPR) with CRISPR-associated proteins (Cas), in combination with integrated point-of-care devices. Lastly, the current challenges are discussed and a roadmap for furthering these advanced biosensing technologies to manage future pandemics is provided.

A novel miniaturized electroanalytical device integrated with gas extraction for the voltammetric determination of sulfite in beverages

Voltammetry and amperometry are inexpensive and high-performance analytical techniques. However, their lack of selectivity limits their use in complex matrices such as biological, environmental, and food samples. Therefore, voltammetric and amperometric analyses of these samples usually require time-consuming and laborious sample pretreatments. In this study, we present a simple and cost-effective approach to fabricate a miniaturized electrochemical cell that can be easily coupled to a head space-like gas extraction procedure in such a way the sample pretreatment and voltammetric detection are performed in a single step. As a proof of concept, we have used the proposed system to quantify sulfite in beverage samples after its conversion to SO_2(g). Despite the simplicity and low cost of the proposed system, it provided good analytical performance and a limit of detection of 4.0 μmol L^-1 was achieved after only 10 min of extraction. The proposed system is quite versatile since it can be applied to quantify any volatile electroactive species. Also, the proposed system provides a unique way to assess real-time extraction curves, which are essential to study and optimize new gas extraction procedures. Therefore, the approach described in this study could contribute to both applied and fundamental Analytical Chemistry.

Design of bioluminescent biosensors for assessing contamination of complex matrices

The presence of potentially toxic xenobiotics in complex matrices has become rather the rule than the exception. Therefore, there is a need for highly sensitive inexpensive techniques for analyzing environmental and food matrices for toxicants. Enzymes are selectively sensitive to various toxic compounds, and, thus, they can be used as the basis for detection of contaminants in complex matrices. There are, however, a number of difficulties associated with the analysis of complex matrices using enzyme assays, including the necessity to take into account properties and effects of the natural components of the test media for accurate interpretation of results. The present study describes the six-stage procedure for designing new enzyme sensors intended for assessing the quality of complex matrices. This procedure should be followed both to achieve the highest possible sensitivity of the biosensor to potentially toxic substances and to minimize the effect of the uncontaminated components of complex mixtures on the activity of the biosensor. The proposed strategy has been tested in designing a bioluminescent biosensor for integrated rapid assessment of the safety of fruits and vegetables. The biosensor is based on the coupled enzyme system NAD(P)H:FMN-oxidoreductase and luciferase as the biorecognition element. The study describes methods and techniques for attaining the desired result in each stage. The proposed six-stage procedure for designing bioluminescent enzyme biosensors can be used to design the enzymatic biosensors based on other enzymes.

Disposable Voltammetric Sensor Modified with Block Copolymer-Dispersed Graphene for Simultaneous Determination of Dopamine and Ascorbic Acid in Ex Vivo Mouse Brain Tissue

Dopamine (DA) and ascorbic acid (AA) are two important biomarkers with similar oxidation potentials. To facilitate their simultaneous electrochemical detection, a new voltammetric sensor was developed by modifying a screen-printed carbon electrode (SPCE) with a newly synthesized block copolymer (poly(DMAEMA-b-styrene), PDbS) as a dispersant for reduced graphene oxide (rGO). The prepared PDbS–rGO and the modified SPCE were characterized using a range of physical and electrochemical techniques including Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and linear sweep voltammetry. Compared to the bare SPCE, the PDbS–rGO-modified SPCE (PDbS–rGO/SPCE) showed better sensitivity and peak-to-peak separation for DA and AA in mixed solutions. Under the optimum conditions, the dynamic linear ranges for DA and AA were 0.1–300 and 10–1100 µM, and the detection limits were 0.134 and 0.88 µM (S/N = 3), respectively. Furthermore, PDbS–rGO/SPCE exhibited considerably enhanced anti-interference capability, high reproducibility, and storage stability for four weeks. The practical potential of the PDbS–rGO/SPCE sensor for measuring DA and AA was demonstrated using ex vivo brain tissues from a Parkinson’s disease mouse model and the control.

A Mini-Review on Detection Methods of Microcystins

Cyanobacterial harmful algal blooms (CyanoHABs) produce microcystins (MCs) which are associated with animal and human hepatotoxicity. Over 270 variants of MC exist. MCs have been continually studied due of their toxic consequences. Monitoring water quality to assess the presence of MCs is of utmost importance although it is often difficult because CyanoHABs may generate multiple MC variants, and their low concentration in water. To effectively manage and control these toxins and prevent their health risks, sensitive, fast, and reliable methods capable of detecting MCs are required. This paper aims to review the three main analytical methods used to detect MCs ranging from biological (mouse bioassay), biochemical (protein phosphatase inhibition assay and enzyme linked immunosorbent assay), and chemical (high performance liquid chromatography, liquid chromatography-mass spectrometry, high performance capillary electrophoresis, and gas chromatography), as well as the newly emerging biosensor methods. In addition, the current state of these methods regarding their novel development and usage, as well as merits and limitations are presented. Finally, this paper also provides recommendations and future research directions towards method application and improvement.

Electrochemical biosensors for pathogen detection

Recent advances in electrochemical biosensors for pathogen detection are reviewed. Electrochemical biosensors for pathogen detection are broadly reviewed in terms of transduction elements, biorecognition elements, electrochemical techniques, and biosensor performance. Transduction elements are discussed in terms of electrode material and form factor. Biorecognition elements for pathogen detection, including antibodies, aptamers, and imprinted polymers, are discussed in terms of availability, production, and immobilization approach. Emerging areas of electrochemical biosensor design are reviewed, including electrode modification and transducer integration. Measurement formats for pathogen detection are classified in terms of sample preparation and secondary binding steps. Applications of electrochemical biosensors for the detection of pathogens in food and water safety, medical diagnostics, environmental monitoring, and bio-threat applications are highlighted. Future directions and challenges of electrochemical biosensors for pathogen detection are discussed, including wearable and conformal biosensors, detection of plant pathogens, multiplexed detection, reusable biosensors for process monitoring applications, and low-cost, disposable biosensors.

Optimization of Saliva Collection and Immunochromatographic Detection of Salivary Pepsin for Point-of-Care Testing of Laryngopharyngeal Reflux

Salivary pepsin is a promising marker for the non-invasive diagnosis of laryngopharyngeal reflux (LPR). For reliable results regarding pepsin in saliva, it is critical to standardize the collection, storage, and pre-processing methods. In this study, we optimized the saliva collection protocols, including storage conditions, i.e., solution, temperature, and time, and the pre-processing filter for pepsin. Moreover, we prepared a simple immunochromatographic strip for the rapid detection of pepsin and evaluated its sensing performance. As a result, we selected a polypropylene (PP) filter as the pre-processing filter for salivary pepsin in low resource settings, such as those where point of care testing (POCT) is conducted. This filter showed a similar efficiency to the centrifuge (standard method). Finally, we detected the pepsin using gold nanoparticles conjugated with monoclonal pepsin antibody. Under optimized conditions, the lower limit of detection for pepsin test strips was determined as 0.01 μg/mL. Furthermore, we successfully detected the salivary pepsin in real saliva samples of LPR patients, which were pre-processed by the PP filter. Therefore, we expect that our saliva collection protocol and pepsin immunochromatographic strip can be utilized as useful tools for a non-invasive diagnosis/screening of LPR in POCT.

Electrochemical cardiovascular platforms: Current state of the art and beyond

Cardiovascular diseases (CVD) remain the leading cause of death within industrialized nations as well as an increasing cause of mortality and morbidity in many developing countries. Smoking, alcohol consumption and increased level of blood cholesterol are the main CVD risk factors. Other factors, such as the prevalence of overweight/obesity and diabetes, have increased considerably in recent decades and are indirect causes of CVD. Among CVDs, the acute coronary syndrome (ACS) represents the most common cause of emergency hospital admission. Since the prognosis of ACS is directly associated with timely initiation of revascularization, missed, misdiagnosis or late diagnosis have unfavorable medical implications. Early ACS diagnosis can reduce complications and risk of recurrence, finally decreasing the economic burden posed on the health care system as a whole. To decrease the risk of ACS and related CVDs and to reduce associated costs to healthcare systems, a fast management of patients with chest pain has become crucial and urgent. Despite great efforts, biochemical diagnostic approaches of CVDs remain difficult and controversial medical challenges as cardiac biomarkers should be rapidly released into the blood at the time of ischemia and persistent for a sufficient length of time to allow diagnostics, with tests that should be rapid, easy to perform and relatively inexpensive. Early biomarker assessments have involved testing for the total enzyme activity of aspartate aminotransferase (AST), lactate dehydrogenase (LDH) and creatine kinase (CK), which cardiac troponins being the main accepted biomarkers for diagnosing myocardial injury and acute myocardial infarction (AMI). To allow rapid diagnosis, it is necessary to replace the traditional biochemical assays by cardiac biosensor platforms. Among the numerous of possibilities existing today, electrochemical biosensors are important players as they have many of the required characteristics for point-of-care tests. Electrochemical based cardiac biosensors are highly adapted for monitoring the onset and progress of cardiovascular diseases in a fast and accurate manner, while being cheap and scalable devices. This review outlines the state of the art in the development of cardiac electrochemical sensors for the detection of different cardiac biomarkers ranging from troponin to BNP, N-terminal proBNP, and others.

Detecting Biothreat Agents: From Current Diagnostics to Developing Sensor Technologies

Although a fundamental understanding of the pathogenicity of most biothreat agents has been elucidated and available treatments have increased substantially over the past decades, they still represent a significant public health threat in this age of (bio)terrorism, indiscriminate warfare, pollution, climate change, unchecked population growth, and globalization. The key step to almost all prevention, protection, prophylaxis, post-exposure treatment, and mitigation of any bioagent is early detection. Here, we review available methods for detecting bioagents including pathogenic bacteria and viruses along with their toxins. An introduction placing this subject in the historical context of previous naturally occurring outbreaks and efforts to weaponize selected agents is first provided along with definitions and relevant considerations. An overview of the detection technologies that find use in this endeavor along with how they provide data or transduce signal within a sensing configuration follows. Current "gold" standards for biothreat detection/diagnostics along with a listing of relevant FDA approved in vitro diagnostic devices is then discussed to provide an overview of the current state of the art. Given the 2014 outbreak of Ebola virus in Western Africa and the recent 2016 spread of Zika virus in the Americas, discussion of what constitutes a public health emergency and how new in vitro diagnostic devices are authorized for emergency use in the U.S. are also included. The majority of the Review is then subdivided around the sensing of bacterial, viral, and toxin biothreats with each including an overview of the major agents in that class, a detailed cross-section of different sensing methods in development based on assay format or analytical technique, and some discussion of related microfluidic lab-on-a-chip/point-of-care devices. Finally, an outlook is given on how this field will develop from the perspective of the biosensing technology itself and the new emerging threats they may face.

Label-Free Detection of Salivary Pepsin Using Gold Nanoparticle/Polypyrrole Nanocoral Modified Screen-Printed Electrode

Detection of salivary pepsin has been given attention as a new diagnostic tool for laryngopharyngeal reflux (LPR) disease, because saliva collection is non-invasive and relatively comfortable. In this study, we prepared polypyrrole nanocorals (PPNCs) on a screen-printed carbon electrode (SPCE) by a soft template synthesis method, using β-naphthalenesulfonic acid (NSA) (for short, PPNCs/SPCE). Gold nanoparticles (GNPs) were then decorated on PPNCs/SPCE by electrodeposition (for short, GNP/PPNCs/SPCE). To construct the immunosensor, pepsin antibody was immobilized on GNP/PPNCs/SPCE. Next, citric acid was applied to prevent non-specific binding and change the electrode surface charge before pepsin incubation. Electrochemical stepwise characterization was performed using cyclic voltammetry, and immunosensor response toward different pepsin concentrations was measured by differential pulsed voltammetry. As a result, our electrochemical immunosensor showed a sensitive detection performance toward pepsin with a linear range from 6.25 to 100 ng/mL and high specificity toward pepsin, as well as a low limit of detection of 2.2 ng/mL. Finally, we quantified the pepsin levels in saliva samples of LPR patients (n = 2), showing that the results were concordant with those of a conventional ELISA method. Therefore, we expect that this electrochemical immunosensor could be helpful for preliminarily diagnosing LPR through the detection of pepsin in saliva.

Far-Forward Diagnostics in Toxic Industrial Chemical and Material Exposure Scenarios and Biomarker Identification

: This study describes key technical solutions for detecting environmental toxicants and diagnosing adverse health effects in military operational settings as outlined at a symposium cosponsored by the Department of Defense and the Johns Hopkins University-Applied Physics Laboratory (October 27 to 28, 2015). Such technologies are urgently needed in order to provide critical decision-aid tools and prognostic assessment of potential clinical sequelae. This review summarizes the state-of-the-science on (1) prioritization of adverse health effects, (2) existing technologies and diagnostic tools available for use in theater, (3) challenges to advancing diagnostic tools far-forward, and (4) the potential utility of anchoring diagnostic tools to adverse outcome pathways. Emerging technologies are increasingly available for physiological, environmental, and individual exposure monitoring. Challenges to overcome in austere environments include cold chain requirements and determination of adequate sampling intervals.

Molecularly imprinted polymers for sample preparation and biosensing in food analysis: Progress and perspectives

Molecularly imprinted polymers (MIPs) are biomimetics which can selectively bind to analytes of interest. One of the most interesting areas where MIPs have shown the biggest potential is food analysis. MIPs have found use as sorbents in sample preparation attributed to the high selectivity and high loading capacity. MIPs have been intensively employed in classical solid-phase extraction and solid-phase microextraction. More recently, MIPs have been combined with magnetic bead extraction, which greatly simplifies sample handling procedures. Studies have consistently shown that MIPs can effectively minimize complex food matrix effects, and improve recoveries and detection limits. In addition to sample preparation, MIPs have also been viewed as promising alternatives to bio-receptors due to the inherent molecular recognition abilities and the high stability in harsh chemical and physical conditions. MIPs have been utilized as receptors in biosensing platforms such as electrochemical, optical and mass biosensors to detect various analytes in food. In this review, we will discuss the current state-of-the-art of MIP synthesis and applications in the context of food analysis. We will highlight the imprinting methods which are applicable for imprinting food templates, summarize the recent progress in using MIPs for preparing and analysing food samples, and discuss the current limitations in the commercialisation of MIPs technology. Finally, future perspectives will be given.

Rapid, Portable, Multiplexed Detection of Bacterial Pathogens Directly from Clinical Sample Matrices

Enteric and diarrheal diseases are a major cause of childhood illness and death in countries with developing economies. Each year, more than half of a million children under the age of five die from these diseases. We have developed a portable, microfluidic platform capable of simultaneous, multiplexed detection of several of the bacterial pathogens that cause these diseases. This platform can perform fast, sensitive immunoassays directly from relevant, complex clinical matrices such as stool without extensive sample cleanup or preparation. Using only 1 µL of sample per assay, we demonstrate simultaneous multiplexed detection of four bacterial pathogens implicated in diarrheal and enteric diseases in less than 20 min.

Development of a label-free SPR sensor for detection of matrixmetalloproteinase-9 by antibody immobilization on carboxymethyldextran chip

Surface plasmon resonance (SPR) immunosensor has been widely utilized for monitoring antigen-antibody interactions. The sensor measures changes of refractive index upon binding of analyte molecules to specific ligand immobilized on the sensor chip. This effort reports development of SPR immunosensor for real-time and label-free detection of recombinant human matrix metalloproteinases-9 (MMP-9), which has been associated with malignant tumor progression and metastasis by matrix degradation. MMP-9 was expressed in Escherichia coli BL21 and purified by Ni-NTA agarose column. CMD 50 D was activated by EDC/NHS for immobilization of monoclonal anti-MMP-9. Atomic force microscopy images showed uniform distribution of anti-MMP-9 over the sensor chip. Equilibrium constant (KD), maximum binding capacity (Rmax) and ∆Gb values for interaction of MMP-9 and anti-MMP-9 were 0.4nM, 680 µRIU and -53.51kJ/mol, respectively. Concentration of MMP-9 in saliva samples was determined, with linearity in the range of 10-200ng/mL. The limit of detection was found to be 8pg/mL, being lower than most of the previously reported techniques.