Immuno-impedimetric Biosensor for Onsite Monitoring of Ascospores and Forecasting of Sclerotinia Stem Rot of Canola

Spectroscopic detection of bioaerosols with the wibs-4+: Anthropogenic and meteorological impacts

This research builds upon a previous study that explored the potential of the modified WIBS-4+ to selectively differentiate and detect different bioaerosol classes. The current work evaluates the influence of meteorological and air quality parameters on bioaerosol concentrations, specifically pollen and fungal spore dynamics. Temperature was found to be the most influential parameter in terms of pollen production and release, showing a strong positive correlation. Wind data analysis provided insights into the potential geographic origins of pollen and fungal spore concentrations. Fungal spores were primarily shown to originate from a westerly direction, corresponding to agricultural land use, whereas pollen largely originated from a North-easterly direction, corresponding to several forests. The influence of air quality was also analysed to understand its potential impact on the WIBS fluorescent parameters investigated. Most parameters had a negative association with fungal spore concentrations, whereas several anthropogenic influences showed notable positive correlations with daily pollen concentrations. This is attributed to similar driving forces (meteorological parameters) and geographical origins. In addition, the WIBS showed a significant correlation with anthropogenic pollutants originating from combustion sources, suggesting the potential for such modified spectroscopic instruments to be utilized as air quality monitors. By combining all meteorological and pollution data along with WIBS-4+ channel data, a set of Multiple Linear Regression (MLR) analyses were completed. Successful results with R2 values ranging from 0.6 to 0.8 were recorded. The inclusion of meteorological parameters was dependent on the spore or pollen type being examined.

Label-free impedimetric immunosensor for point-of-care detection of COVID-19 antibodies

The COVID-19 pandemic has posed enormous challenges for existing diagnostic tools to detect and monitor pathogens. Therefore, there is a need to develop point-of-care (POC) devices to perform fast, accurate, and accessible diagnostic methods to detect infections and monitor immune responses. Devices most amenable to miniaturization and suitable for POC applications are biosensors based on electrochemical detection. We have developed an impedimetric immunosensor based on an interdigitated microelectrode array (IMA) to detect and monitor SARS-CoV-2 antibodies in human serum. Conjugation chemistry was applied to functionalize and covalently immobilize the spike protein (S-protein) of SARS-CoV-2 on the surface of the IMA to serve as the recognition layer and specifically bind anti-spike antibodies. Antibodies bound to the S-proteins in the recognition layer result in an increase in capacitance and a consequent change in the impedance of the system. The impedimetric immunosensor is label-free and uses non-Faradaic impedance with low nonperturbing AC voltage for detection. The sensitivity of a capacitive immunosensor can be enhanced by simply tuning the ionic strength of the sample solution. The device exhibits an LOD of 0.4 BAU/ml, as determined from the standard curve using WHO IS for anti-SARS-CoV-2 immunoglobulins; this LOD is similar to the corresponding LODs reported for all validated and established commercial assays, which range from 0.41 to 4.81 BAU/ml. The proof-of-concept biosensor has been demonstrated to detect anti-spike antibodies in sera from patients infected with COVID-19 within 1 h. Photolithographically microfabricated interdigitated microelectrode array sensor chips & label-free impedimetric detection of COVID-19 antibody.

An impedimetric biosensor for COVID-19 serology test and modification of sensor performance via dielectrophoresis force

Coronavirus disease 2019 (COVID-19) has caused significant global morbidity and mortality. The serology test that detects antibodies against the disease causative agent, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has often neglected value in supporting immunization policies and therapeutic decision-making. The ELISA-based antibody test is time-consuming and bulky. This work described a gold micro-interdigitated electrodes (IDE) biosensor for COVID antibody detection based on Electrochemical Impedance Spectroscopy (EIS) responses. The IDE architecture allows easy surface modification with the viral structure protein, Spike (S) protein, in the gap of the electrode digits to selectively capture anti-S antibodies in buffer solutions or human sera. Two strategies were employed to resolve the low sensitivity issue of non-faradic impedimetric sensors and the sensor fouling phenomenon when using the serum. One uses secondary antibody-gold nanoparticle (AuNP) conjugates to further distinguish anti-S antibodies from the non-specific binding and obtain a more significant impedance change. The second strategy consists of increasing the concentration of target antibodies in the gap of IDEs by inducing an AC electrokinetic effect such as dielectrophoresis (DEP). AuNP and DEP methods reached a limit of detection of 200 ng/mL and 2 μg/mL, respectively using purified antibodies in buffer, while the DEP method achieved a faster testing time of only 30 min. Both strategies could qualitatively distinguish COVID-19 antibody-positive and -negative sera. Our work, especially the impedimetric detection of COVID-19 antibodies under the assistance of the DEP force presents a promising path toward rapid, point-of-care solutions for COVID-19 serology tests.

Highly Efficient Capture and Quantification of the Airborne Fungal Pathogen Sclerotinia sclerotiorum Employing a Nanoelectrode-Activated Microwell Array

In this study, we present a microdevice for the capture and quantification of Sclerotinia sclerotiorum spores, pathogenic agents of one of the most harmful infectious diseases of crops, Sclerotinia stem rot. The early prognosis of an outbreak is critical to avoid severe economic losses and can be achieved by the detection of a small number of airborne spores. However, the current lack of simple and effective methods to quantify fungal airborne pathogens has hindered the development of an accurate early warning system. We developed a device that remedies these limitations based on a microfluidic design that contains a nanothick aluminum electrode structure integrated with a picoliter well array for dielectrophoresis-driven capture of spores and on-chip quantitative detection employing impedimetric sensing. Based on experimental results, we demonstrated a highly efficient spore trapping rate of more than 90% with an effective impedimetric sensing method that allowed the spore quantification of each column in the array and achieved a sensitivity of 2%/spore at 5 kHz and 1.6%/spore at 20 kHz, enabling single spore detection. We envision that our device will contribute to the development of a low-cost microfluidic platform that could be integrated into an infectious plant disease forecasting tool for crop protection.

Biosensor Technologies for Early Detection and Quantification of Plant Pathogens

Plant pathogens are a major reason of reduced crop productivity and may lead to a shortage of food for both human and animal consumption. Although chemical control remains the main method to reduce foliar fungal disease incidence, frequent use can lead to loss of susceptibility in the fungal population. Furthermore, over-spraying can cause environmental contamination and poses a heavy financial burden on growers. To prevent or control disease epidemics, it is important for growers to be able to detect causal pathogen accurately, sensitively, and rapidly, so that the best practice disease management strategies can be chosen and enacted. To reach this goal, many culture-dependent, biochemical, and molecular methods have been developed for plant pathogen detection. However, these methods lack accuracy, specificity, reliability, and rapidity, and they are generally not suitable for in-situ analysis. Accordingly, there is strong interest in developing biosensing systems for early and accurate pathogen detection. There is also great scope to translate innovative nanoparticle-based biosensor approaches developed initially for human disease diagnostics for early detection of plant disease-causing pathogens. In this review, we compare conventional methods used in plant disease diagnostics with new sensing technologies in particular with deeper focus on electrochemical and optical biosensors that may be applied for plant pathogen detection and management. In addition, we discuss challenges facing biosensors and new capability the technology provides to informing disease management strategies.

Single ascospore detection for the forecasting of Sclerotinia stem rot of canola

Smart-agriculture technologies comprise a set of management systems designed to sustainably increase the efficiency and productivity of farming. In this paper, we present a lab-on-a-chip device that can be employed as a plant disease forecasting tool for canola crop. Our device can be employed as a platform to forecast potential outbreaks of one of the most devastating diseases of canola and other crops, Sclerotinia stem rot. The system consists of a microfluidic chip capable of detecting single airborne Sclerotinia sclerotiorum ascospores. Target ascospores are injected into the chip and selectively captured by dielectrophoresis, while other spores in the sample are flushed away. Afterward, captured ascospores are released into the flow stream of the channel and are detected employing electrochemical impedance spectroscopy and coplanar microelectrodes. Our device provides a design for a low-cost, miniaturized, and automated platform technology for airborne spore detection and disease prevention.

The B & B approach: Ball-milling conjugation of dextran with phenylboronic acid (PBA)-functionalized BODIPY

Mechanochemistry is an emerging and reliable alternative to conventional solution (batch) synthesis of complex molecules under green and solvent-free conditions. In this regard, we report here on the conjugation of a dextran polysaccharide with a fluorescent probe, a phenylboronic acid (PBA)-functionalized boron dipyrromethene (BODIPY) applying the ball milling approach. The ball milling formation of boron esters between PBA BODIPY and dextran proved to be more efficient in terms of reaction time, amount of reactants, and labelling degree compared to the corresponding solution-based synthetic route. PBA-BODIPY dextran assembles into nanoparticles of around 200 nm by hydrophobic interactions. The resulting PBA-BODIPY dextran nanoparticles retain an apolar interior as proved by pyrene fluorescence, suitable for the encapsulation of hydrophobic drugs with high biocompatibility while remaining fluorescent.

Label-Free Bimetallic In Situ-Grown 3D Nickel-Foam-Supported NH2-MIL-88B(Fe2Co)-MOF-based Impedimetric Immunosensor for the Detection of Cardiac Troponin I

In this study, a simple and competent metal-organic framework (MOF)-based nickel foam (NF)-supported three-dimensional (3D) immunosensor (Ab-NH₂-MIL-88B(Fe₂Co)-MOF/NF) was constructed and utilized for the specific recognition of the biomarker cardiac troponin (I) (cTnI). In the present work, biosensor fabrication was progressed through the modification of the NF substrate with the MOF material (NH₂-MIL-88B(Fe₂Co)-MOF) to enable an amine-functionalized electrode. This amine-functionalized NF electrodes (NH₂-MIL-88B(Fe₂Co)-MOF/NF) were then biointerfaced with anti-cTnI antibodies, which ended up as Ab-NH₂-MIL-88B(Fe₂Co)-MOF/NF electrodes. Analytical executions of the constructed bioelectrode were investigated for the quantitative analysis of cTnI in both buffered and serum solutions. Then, the electrochemical studies were carried out using the electrochemical impedance spectroscopy (EIS) method by monitoring changes concerning the charge transfer resistance (R_ct) characteristics. The limit of detection (LOD) of the Ab-NH₂-MIL-88B(Fe₂Co)-MOF/NF immunosensor was achieved to be 13 fg/mL with great specificity. This kind of immunosensor imparts a new platform for the construction and application of MOF-hybrid 3D electrode materials with enhanced electrochemical behavior in cTnI sensing for the first time.

DNA aptamer-based non-faradaic impedance biosensor for detecting E. coli

Developing a real-time, portable, and inexpensive sensor for pathogenic bacteria is crucial since the conventional detection approaches such as enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR) assays are high cost, time-consuming, and require an expert operator. Here we present a portable, inexpensive, and convenient impedance-based biosensor using Interdigitated Electrode (IDE) arrays to detect Escherichia coli (E. coli) as a model to demonstrate the feasibility of an impedance-based biosensor. We manipulated the affinity of the IDE array towards E. coli (E. coli BL21 series) by functionalizing the IDEs' surface with an E. coli outer membrane protein (OMP) Ag1 Aptamer. To determine the dominant factors affecting the sensitivity and the performance of the biosensor in detecting E. coli, we investigated the roles of the substrate material used in the fabrication of the IDE, the concentration of the aptamer, and the composition of the carboxy aliphatic thiol mixture used in the pre-treatment of the IDE surface. In the sensing experiments we used an E. coli concentration range of 25-1000 cfu mL-1 and confirmed the binding of the OMP Ag1 Aptamer to the outer membrane protein of the E. coli by Field Emission Scanning Electron Microscopy (FESEM), Optical Microscopy, and Atomic Force Microscopy (AFM). By tuning the surface chemistry, the IDEs' substrate material, and the concentration of the OMP Ag1 Aptamer, our sensor could detect E. coli with the analytical sensitivity of approximately 1.8 Ohm/cfu and limit of detection of 9 cfu mL-1. We found that the molecular composition of the self-assembled monolayer (SAM) formed on the top of the IDEs before the attachment of the OMP Ag1 Aptamer significantly impacted the sensitivity of the sensor. Notably, with straightforward changes to the molecular recognition elements, this platform device can be used to detect a wide range of other microorganisms and chemicals relevant for environmental monitoring and public health.

Integrated Electrochemical Biosensors for Detection of Waterborne Pathogens in Low-Resource Settings

More than 783 million people worldwide are currently without access to clean and safe water. Approximately 1 in 5 cases of mortality due to waterborne diseases involve children, and over 1.5 million cases of waterborne disease occur every year. In the developing world, this makes waterborne diseases the second highest cause of mortality. Such cases of waterborne disease are thought to be caused by poor sanitation, water infrastructure, public knowledge, and lack of suitable water monitoring systems. Conventional laboratory-based techniques are inadequate for effective on-site water quality monitoring purposes. This is due to their need for excessive equipment, operational complexity, lack of affordability, and long sample collection to data analysis times. In this review, we discuss the conventional techniques used in modern-day water quality testing. We discuss the future challenges of water quality testing in the developing world and how conventional techniques fall short of these challenges. Finally, we discuss the development of electrochemical biosensors and current research on the integration of these devices with microfluidic components to develop truly integrated, portable, simple to use and cost-effective devices for use by local environmental agencies, NGOs, and local communities in low-resource settings.

Cardiac Troponin I: Ultrasensitive Detection Using Faradaic Electrochemical Impedance

An electrochemical biosensor for the detection of cardiac troponin I, cTnI, an important cardiac biomarker, is described. A combination of a novel monoclonal antibody, mAb20B3, and a novel Ir(III)-based metal complex was used for detection using faradaic electrochemical impedance spectroscopy. A limit of detection of 10 ag/mL was achieved, which is significantly lower than established assays. The ability to detect these ultralow concentrations enables rapid and early stage detection of cardiac events and opens up the possibility of developing a point-of-care device.