2D materials as a diagnostic platform for the detection and sensing of the SARS-CoV-2 virus: a bird's-eye view

Engineered two-dimensional nanomaterials based diagnostics integrated with internet of medical things (IoMT) for COVID-19

More than four years have passed since an inimitable coronavirus disease (COVID-19) pandemic hit the globe in 2019 after an uncontrolled transmission of the severe acute respiratory syndrome (SARS-CoV-2) infection. The occurrence of this highly contagious respiratory infectious disease led to chaos and mortality all over the world. The peak paradigm shift of the researchers was inclined towards the accurate and rapid detection of diseases. Since 2019, there has been a boost in the diagnostics of COVID-19 via numerous conventional diagnostic tools like RT-PCR, ELISA, etc., and advanced biosensing kits like LFIA, etc. For the same reason, the use of nanotechnology and two-dimensional nanomaterials (2DNMs) has aided in the fabrication of efficient diagnostic tools to combat COVID-19. This article discusses the engineering techniques utilized for fabricating chemically active E2DNMs that are exceptionally thin and irregular. The techniques encompass the introduction of heteroatoms, intercalation of ions, and the design of strain and defects. E2DNMs possess unique characteristics, including a substantial surface area and controllable electrical, optical, and bioactive properties. These characteristics enable the development of sophisticated diagnostic platforms for real-time biosensors with exceptional sensitivity in detecting SARS-CoV-2. Integrating the Internet of Medical Things (IoMT) with these E2DNMs-based advanced diagnostics has led to the development of portable, real-time, scalable, more accurate, and cost-effective SARS-CoV-2 diagnostic platforms. These diagnostic platforms have the potential to revolutionize SARS-CoV-2 diagnosis by making it faster, easier, and more accessible to people worldwide, thus making them ideal for resource-limited settings. These advanced IoMT diagnostic platforms may help with combating SARS-CoV-2 as well as tracking and predicting the spread of future pandemics, ultimately saving lives and mitigating their impact on global health systems.

Recent Advances in Two-Dimensional Nanomaterials for Healthcare Monitoring

The development of advanced technologies for the fabrication of functional nanomaterials, nanostructures, and devices has facilitated the development of biosensors for analyses. Two-dimensional (2D) nanomaterials, with unique hierarchical structures, a high surface area, and the ability to be functionalized for target detection at the surface, exhibit high potential for biosensing applications. The electronic properties, mechanical flexibility, and optical, electrochemical, and physical properties of 2D nanomaterials can be easily modulated, enabling the construction of biosensing platforms for the detection of various analytes with targeted recognition, sensitivity, and selectivity. This review provides an overview of the recent advances in 2D nanomaterials and nanostructures used for biosensor and wearable-sensor development for healthcare and health-monitoring applications. Finally, the advantages of 2D-nanomaterial-based devices and several challenges in their optimal operation have been discussed to facilitate the development of smart high-performance biosensors in the future.

Liquid-phase catalyst pre-seeding for controlled growth of layered MoS2 films over a large area via chemical vapor deposition

We introduce an innovative method that facilitates precise control of high-quality molybdenum disulfide (MoS2) growth, extending up to three layers, on a large scale. This scalable growth is realized by employing solution-based catalysts and precursors in conjunction with chemical vapor deposition (CVD). The catalyst not only diminishes the precursor's activation energy and melting temperature but also augments the overall reaction rate. By regulating the concentration ratio, we directly manipulate the precursor concentrations, thereby promoting clean growth. This unique control mechanism, as delineated in this study, is unprecedented. Our findings confirm that the catalyst introduction does not compromise the quality of the resulting samples. Field effect transistors (FETs) fabricated from the synthesized MoS2 display superior electrical properties; they exhibit a high carrier mobility of 32.1 cm2 V-1 s-1 and an on/off current ratio of 108, signifying their promising electrical performance. Accordingly, our findings suggest that the solution-based CVD strategy presented herein can be potentially utilized for the integration of FETs into a multitude of practical applications.

Micro- and nanoplastics in soil: Linking sources to damage on soil ecosystem services in life cycle assessment

Soil ecosystems are crucial for providing vital ecosystem services (ES), and are increasingly pressured by the intensification and expansion of human activities, leading to potentially harmful consequences for their related ES provision. Micro- and nanoplastics (MNPs), associated with releases from various human activities, have become prevalent in various soil ecosystems and pose a global threat. Life Cycle Assessment (LCA), a tool for evaluating environmental performance of product and technology life cycles, has yet to adequately include MNPs-related damage to soil ES, owing to factors like uncertainties in MNPs environmental fate and ecotoxicological effects, and characterizing related damage on soil species loss, functional diversity, and ES. This study aims to address this gap by providing as a first step an overview of the current understanding of MNPs in soil ecosystems and proposing a conceptual approach to link MNPs impacts to soil ES damage. We find that MNPs pervade soil ecosystems worldwide, introduced through various pathways, including wastewater discharge, urban runoff, atmospheric deposition, and degradation of larger plastic debris. MNPs can inflict a range of ecotoxicity effects on soil species, including physical harm, chemical toxicity, and pollutants bioaccumulation. Methods to translate these impacts into damage on ES are under development and typically focus on discrete, yet not fully integrated aspects along the impact-to-damage pathway. We propose a conceptual framework for linking different MNPs effects on soil organisms to damage on soil species loss, functional diversity loss and loss of ES, and elaborate on each link. Proposed underlying approaches include the Threshold Indicator Taxa Analysis (TITAN) for translating ecotoxicological effects associated with MNPs into quantitative measures of soil species diversity damage; trait-based approaches for linking soil species loss to functional diversity loss; and ecological networks and Bayesian Belief Networks for linking functional diversity loss to soil ES damage. With the proposed conceptual framework, our study constitutes a starting point for including the characterization of MNPs-related damage on soil ES in LCA.

Rapid and simultaneous multiple detection of a tripledemic using a dual-gate oxide semiconductor thin-film transistor-based immunosensor

The simultaneous infection with a tripledemic-simultaneous infection with influenza A pH1N1 virus (Flu), severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and respiratory syncytial virus (RSV)-necessitates the development of accurate and fast multiplex diagnostic tests. The coronavirus disease 2019 (COVID-19) pandemic has emphasized the importance of virus detection. Field-effect transistor (FET)-based immuno-biosensors have a short detection time and do not require labeling or polymerase chain reaction. This study demonstrates the rapid, sensitive detection of influenza A pH1N1, SARS-CoV-2, and RSV using a multiplex immunosensor based on a dual-gate oxide semiconductor thin-film transistor (TFT), a type of FET. The dual-gate oxide TFT was modified by adjusting both top and bottom gate insulators to improve capacitive coupling to approximately 120-fold amplification, exhibiting a high pH sensitivity of about 10 V/pH. The dual-gate oxide TFT-based immunosensor detected the target proteins (hemagglutinin (HA) protein of Flu, spike 1 (S1) protein of SARS-CoV-2, and fusion protein of RSV) of each virus, with a limit of detection of approximately 1 fg/mL. Cultured viruses in phosphate-buffered saline or artificial saliva and clinical nasopharynx samples were detected in 1-μL sample volumes within 60 s. This promising diagnosis could be potentially as point-of-care tests to facilitate a prompt response to future pandemics with high sensitivity and multiplexed detection without pretreatment.

Two-Dimensional (2D) materials in the detection of SARS-CoV-2

The SARS-CoV-2 pandemic has resulted in a devastating effect on human health in the last three years. While tremendous effort has been devoted to the development of effective treatment and vaccines against SARS-CoV-2 and controlling the spread of it, collective health challenges have been encountered along with the concurrent serious economic impacts. Since the beginning of the pandemic, various detection methods like PCR-based methods, isothermal nucleic acid amplification-based (INAA) methods, serological methods or antibody tests, and evaluation of X-ray chest results have been exploited to diagnose SARS-CoV-2. PCR-based detection methods in these are considered gold standards in the current stage despite their drawbacks, including being high-cost and time-consuming procedures. Furthermore, the results obtained from the PCR tests are susceptible to sample collection methods and time. When the sample is not collected properly, obtaining a false result may be likely. The use of specialized lab equipment and the need for trained people for the experiments pose additional challenges in PCR-based testing methods. Also, similar problems are observed in other molecular and serological methods. Therefore, biosensor technologies are becoming advantageous with their quick response, high specificity and precision, and low-cost characteristics for SARS-CoV-2 detection. In this paper, we critically review the advances in the development of sensors for the detection of SARS-CoV-2 using two-dimensional (2D) materials. Since 2D materials including graphene and graphene-related materials, transition metal carbides, carbonitrides, and nitrides (MXenes), and transition metal dichalcogenides (TMDs) play key roles in the development of novel and high-performance electrochemical (bio)sensors, this review pushes the sensor technologies against SARS-CoV-2 detection forward and highlights the current trends. First, the basics of SARS-CoV-2 detection are described. Then the structure and the physicochemical properties of the 2D materials are explained, which is followed by the development of SARS-CoV-2 sensors by exploiting the exceptional properties of the 2D materials. This critical review covers most of the published papers in detail from the beginning of the outbreak.

Hybrid reduced graphene oxide nanosheets with negative magnetoresistance for the diagnosis of hypoglycemia

Few glucometers are available to easily and quickly measure low blood glucose levels (≤4 mmol L^-1) from a small amount of blood samples. Here, a hybrid reduced graphene oxide (rGO)-based magnetoresistance (MR) sensor has been developed to monitor blood glucose levels to quickly detect hypoglycemia. Hybrid rGO nanosheets, incorporating Fe₅₀Co₅₀ nanoparticles onto rGO nanosheets, with an unusual large negative MR (-5.7%) at room temperature under a small magnetic field (9.5 kOe) have been successfully fabricated through a one-pot reaction. To quickly detect the low concentration of glucose in a small amount of blood (1 μL), a two-step process has been further developed by using the "sandwich" structural MR sensor. The results show that the higher the negative MR value of the sensor, the lower the concentration of glucose that can be detected. A linear relationship between the MR and the concentration of the spiked plasma glucose taken from streptozotocin-induced diabetic rats can be found when the concentration of glucose is in the range of 0-6 mmol L^-1. The limit of detection (LOD) of this MR glucose sensor is 0.867 mmol L^-1. The accuracy of the rGO-based MR sensor is improved in measuring low concentration of plasma glucose as compared to that of a commercialized glucometer. Furthermore, the selectivity of the rGO-based MR sensor has been studied. The results demonstrate that the rGO-based MR sensor is a flexible and sensitive detection platform and specifically suitable for monitoring low concentrations of plasma glucose to prevent from hypoglycemia.

Iron Oxide Nanoparticle-Based Ferro-Nanofluids for Advanced Technological Applications

Iron oxide nanoparticle (ION)-based ferro-nanofluids (FNs) have been used for different technological applications owing to their excellent magneto-rheological properties. A comprehensive overview of the current advancement of FNs based on IONs for various engineering applications is unquestionably necessary. Hence, in this review article, various important advanced technological applications of ION-based FNs concerning different engineering fields are critically summarized. The chemical engineering applications are mainly focused on mass transfer processes. Similarly, the electrical and electronics engineering applications are mainly focused on magnetic field sensors, FN-based temperature sensors and tilt sensors, microelectromechanical systems (MEMS) and on-chip components, actuators, and cooling for electronic devices and photovoltaic thermal systems. On the other hand, environmental engineering applications encompass water and air purification. Moreover, mechanical engineering or magneto-rheological applications include dampers and sealings. This review article provides up-to-date information related to the technological advancements and emerging trends in ION-based FN research concerning various engineering fields, as well as discusses the challenges and future perspectives.

Application of 2D Materials for Adsorptive Removal of Air Pollutants

Air pollution is on the priority list of global safety issues, with the concern of fatal environmental and public health deterioration. 2D materials are potential adsorbent materials for environmental decontamination, owing to their high surface area, manageable interlayer binding, large surface-to-volume ratio, specific binding capability, and chemical, thermal, and mechanistic stability. Specifically, graphene oxide and reduced graphene oxide have been attracting attention, taking advantage of their low cost synthesis, excessive oxygen containing surface functionalities, and intrinsic aqueous dispersibility, making them desirable for the development of cost-effective, high performance air filters. Many different material designs have been proposed to expand their filtration capability, including the functionalization and integration with other metals and metal oxides, which act not only as binding agents to the target pollutants but also as antimicrobial agents. This review highlights the advantages and drawbacks of 2D materials for air filtration and summarizes the interrelationships among various strategies and the resultant filtration performance in terms of structural engineering, morphology control, and material compositions. Finally, potential future directions are suggested toward the idealized designs of 2D material based air filters.

2D materials: increscent quantum flatland with immense potential for applications

Quantum flatland i.e., the family of two dimensional (2D) quantum materials has become increscent and has already encompassed elemental atomic sheets (Xenes), 2D transition metal dichalcogenides (TMDCs), 2D metal nitrides/carbides/carbonitrides (MXenes), 2D metal oxides, 2D metal phosphides, 2D metal halides, 2D mixed oxides, etc. and still new members are being explored. Owing to the occurrence of various structural phases of each 2D material and each exhibiting a unique electronic structure; bestows distinct physical and chemical properties. In the early years, world record electronic mobility and fractional quantum Hall effect of graphene attracted attention. Thanks to excellent electronic mobility, and extreme sensitivity of their electronic structures towards the adjacent environment, 2D materials have been employed as various ultrafast precision sensors such as gas/fire/light/strain sensors and in trace-level molecular detectors and disease diagnosis. 2D materials, their doped versions, and their hetero layers and hybrids have been successfully employed in electronic/photonic/optoelectronic/spintronic and straintronic chips. In recent times, quantum behavior such as the existence of a superconducting phase in moiré hetero layers, the feasibility of hyperbolic photonic metamaterials, mechanical metamaterials with negative Poisson ratio, and potential usage in second/third harmonic generation and electromagnetic shields, etc. have raised the expectations further. High surface area, excellent young's moduli, and anchoring/coupling capability bolster hopes for their usage as nanofillers in polymers, glass, and soft metals. Even though lab-scale demonstrations have been showcased, large-scale applications such as solar cells, LEDs, flat panel displays, hybrid energy storage, catalysis (including water splitting and CO₂ reduction), etc. will catch up. While new members of the flatland family will be invented, new methods of large-scale synthesis of defect-free crystals will be explored and novel applications will emerge, it is expected. Achieving a high level of in-plane doping in 2D materials without adding defects is a challenge to work on. Development of understanding of inter-layer coupling and its effects on electron injection/excited state electron transfer at the 2D-2D interfaces will lead to future generation heterolayer devices and sensors.

Salivary SARS-CoV-2 antibody detection using S1-RBD protein-immobilized 3D melt electrowritten poly(ε-caprolactone) scaffolds

Sensitive detection of immunoglobulin antibodies against SARS-CoV-2 during the COVID-19 pandemic is critical to monitor the adaptive immune response after BNT162b2 mRNA vaccination. Currently employed binding antibody detection tests using 2D microplate-based enzyme-linked immunosorbent assays (ELISA) are limited by the degree of sensitivity. In this study, a 3D antibody test was developed by immobilizing the receptor-binding domain on Spike subunit 1 (S1-RBD) of SARS-CoV-2 onto engineered melt electrowritten (MEW) poly(ε-caprolactone) (PCL) scaffolds (pore: 500 μm, fiber diameter: 17 μm) using carbodiimide crosslinker chemistry. Protein immobilization was confirmed using X-ray photoelectron spectroscopy (XPS) by the presence of peaks corresponding with nitrogen. Self-developed indirect ELISA was performed to assess the functionality of the 3D platform in comparison with a standard 2D tissue culture plate (TCP) system, using whole unstimulated saliva samples from 14 non-vaccinated and 20 vaccinated participants (1- and 3- weeks post-dose 1; 3 days, 1 week and 3 weeks post-dose 2) without prior SARS-CoV-2 infection. The three-dimensional S1-RBD PCL scaffolds, while demonstrating a kinetic trend comparable to 2D TCP, exhibited significantly higher sensitivity and detection levels for all three immunoglobulins assayed (IgG, IgM, and IgA). These novel findings highlight the potential of MEW PCL constructs in the development of improved low-cost, point-of-care, and self-assessing diagnostic platforms for the detection and monitoring of SARS-CoV-2 antibodies.

Our work developed a 3D SARS-CoV-2 antibody detection platform in non-invasive saliva samples using S1-RBD protein-immobilized 3D melt electrowritten poly(ε-caprolactone) scaffolds.

Protective Face Masks: Current Status and Future Trends

Management of the COVID-19 pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has relied in part on the use of personal protective equipment (PPE). Face masks, as a representative example of PPE, have made a particularly significant contribution. However, most commonly used face masks are made of materials lacking inactivation properties against either SARS-CoV-2 or multidrug-resistant bacteria. Therefore, symptomatic and asymptomatic individuals wearing masks can still infect others due to viable microbial loads escaping from the masks. Moreover, microbial contact transmission can occur by touching the mask, and the discarded masks are an increasing source of contaminated biological waste and a serious environmental threat. For this reason, during the current pandemic, many researchers have worked to develop face masks made of advanced materials with intrinsic antimicrobial, self-cleaning, reusable, and/or biodegradable properties, thereby providing extra protection against pathogens in a sustainable manner. To overview this segment of the remarkable efforts against COVID-19, this review describes the different types of commercialized face masks, their main fabrication methods and treatments, and the progress achieved in face mask development.

Electronic and electrochemical viral detection for point-of-care use: A systematic review

Detecting viruses, which have significant impact on health and the economy, is essential for controlling and combating viral infections. In recent years there has been a focus towards simpler and faster detection methods, specifically through the use of electronic-based detection at the point-of-care. Point-of-care sensors play a particularly important role in the detection of viruses. Tests can be performed in the field or in resource limited regions in a simple manner and short time frame, allowing for rapid treatment. Electronic based detection allows for speed and quantitative detection not otherwise possible at the point-of-care. Such approaches are largely based upon voltammetry, electrochemical impedance spectroscopy, field effect transistors, and similar electrical techniques. Here, we systematically review electronic and electrochemical point-of-care sensors for the detection of human viral pathogens. Using the reported limits of detection and assay times we compare approaches both by detection method and by the target analyte of interest. Compared to recent scoping and narrative reviews, this systematic review which follows established best practice for evidence synthesis adds substantial new evidence on 1) performance and 2) limitations, needed for sensor uptake in the clinical arena. 104 relevant studies were identified by conducting a search of current literature using 7 databases, only including original research articles detecting human viruses and reporting a limit of detection. Detection units were converted to nanomolars where possible in order to compare performance across devices. This approach allows us to identify field effect transistors as having the fastest median response time, and as being the most sensitive, some achieving single-molecule detection. In general, we found that antigens are the quickest targets to detect. We also observe however, that reports are highly variable in their chosen metrics of interest. We suggest that this lack of systematisation across studies may be a major bottleneck in sensor development and translation. Where appropriate, we use the findings of the systematic review to give recommendations for best reporting practice.

Reusable and highly sensitive SERS immunoassay utilizing gold nanostars and a cellulose hydrogel-based platform

The development of robust and sensitive point-of-care testing platforms is necessary to improve patient care and outcomes. Surface-enhanced Raman scattering (SERS)-based immunosensors are especially suited for this purpose. Here, we present a highly sensitive and selective SERS immunoassay, demonstrating for example the detection of horseradish peroxidase (HRP), in a sandwich format. The strength of our biosensor lies in merging: (i) SERS-immunotags based on gold nanostars, allowing exceptional intense SERS from attached Raman probes, covalent attachment of anti-HRP antibodies by a simple chemical method providing exceptional antigen binding activity; (ii) the ease of preparation of the capture platform from a regenerated cellulose-based hydrogel, a transparent material, ideal for microfluidics applications, with low background fluorescence and Raman signal, particularly suited for preserving high activity of the covalently bound anti-HRP antibodies. The sandwich complexes formed were characterised by atomic force microscopy, and by scanning electron microscopy coupled with electron diffraction spectroscopy; and (iii) the robustness of the simple Classical Least Squares method for SERS data analysis, resulting in superior discrimination of SERS signals from the background and much better data fitting, compared to the commonly used peak integral method. Our SERS immunoassay greatly improves the detection limits of traditional enzyme-linked immunosorbent assay approaches, and its performance is better or comparable to those of existing SERS-based immunosensors. Our approach successfully overcomes the main challenges of application at point-of-care, including increasing reproducibility, sensitivity, and specificity, associated with an environmentally friendly and robust design. Also, the proposed design withstands several cycles of regeneration, a feature absent in paper-SERS immunoassays and this opens the way for sensitive multiplexing applications on a microfluidic platform.