Diagnostics is a critical weapon in the fight against this pandemic, as it is pivotal to isolate infected individuals as early as possible, preventing dissemination17. Several nanotechnology-based approaches for SARS-CoV-2 tagging and detection are being developed (Fig. 2).
Generally, testing kits operate based on detection of antibodies (by enzyme-linked immunosorbent assay, or enzyme-linked immunosorbent assay (ELISA)) or RNA (by polymerase chain reaction, or PCR) associated with the virus (from nasopharyngeal swabs taken from individuals’ noses and throats). This relies on their surface interactions with a complementary detection ligand or strand in the kit18. However, these testing kits are generally associated with problems such as false-negative results, long response times and poor analytical sensitivity19. To this end, due to their extremely large surface-to-volume ratios, nanosized materials can instigate highly efficient surface interactions between the sensor and the analyte, allowing faster and more reliable detection of the virus20. Accordingly, a group of researchers have developed a colloidal gold-based test kit that enables easy conjugation of gold nanoparticles to IgM/IgG antibodies in human serum, plasma and whole blood samples21. However, the targeted IgM/IgG antibodies in this kit were not specific to COVID-19, and as a result in some cases produced false results associated with patients who were suffering from irrelevant infections. Consequently, researchers from the University of Maryland, USA, developed a colorimetric assay based on gold nanoparticles capped with suitably designed thiol-modified DNA antisense oligonucleotides specific for N-gene (nucleocapsid phosphoprotein) of SARS-CoV-2, which were used for diagnosing positive COVID-19 cases within 10 min from the isolated RNA samples22. Such testing kits could potentially produce promising results, however their performance would still be affected by quantity of the viral load. To address this shortcoming, researchers from ETH, Switzerland, have recently reported a unique dual-functional plasmonic biosensor combining the plasmonic photothermal effect and localized surface plasmon resonance (LSPR) sensing transduction to provide an alternative and promising solution for clinical COVID-19 diagnosis23. The two-dimensional gold nano-islands functionalized with complementary DNA receptors provide highly sensitive detection of the selected sequences from SARS-CoV-2 through nucleic acid hybridization. For better sensing performance, thermoplasmonic heat is generated on the same gold nano-islands chip when illuminated at their plasmonic resonance frequency. Remarkably, this dual-functional LSPR biosensor exhibited high selectivity towards the SARS-CoV-2 sequences with a detection limit as low as 0.22 pM. In other work, to achieve rapid and accurate detection of SARS-CoV-2 in clinical samples, researchers from the Korea Basic Science Institute developed an ultra-sensitive field-effect transistor (FET)-based biosensing device24. The sensor was produced by coating graphene sheets of the FET with a specific antibody against SARS-CoV-2 spike protein. The FET device could detect the SARS-CoV-2 spike protein at concentrations of 1.31×10–5 pM in phosphate-buffered saline and 1.31×10–3 pM in clinical transport medium. Remarkably, the device exhibited no measurable cross-reactivity with Middle East respiratory syndrome coronavirus (MERS-CoV) antigen, indicating the extraordinary capability of this sensor to distinguish the SARS-CoV-2 antigen protein from those of MERS-CoV.
Another approach that can be used for SARS-CoV-2 and that was successfully used with MERS-CoV, Mycobacterium tuberculosis and human papillomavirus consists of a paper-based colorimetric sensor for DNA detection based on pyrrolidinyl peptide nucleic acid (acpcPNA)-induced silver nanoparticle aggregation25. Briefly, in the absence of complementary DNA, silver nanoparticles aggregate due their electrostatic interactions with the acpcPNA probe. However, in the presence of target DNA, a DNA–acpcPNA duplex starts to form which leads to dispersion of the silver nanoparticles as a result of electrostatic repulsion, giving rise to a detectable colour change25. The use of aptamers and molecular beacons instead of PNA can also represent a potential alternative.
Other avenue where nanomaterials can contribute to detection of SARS-CoV-2 is the extraction and purification of targeted molecules from biological fluids (blood and nasal/throat samples). Thus, nanomaterials with magnetic properties can be decorated with specific receptors of the virus, leading to attachment of virus molecules to the nanoparticles that will allow their magnetic extraction using an external magnetic field.
In this way nanomaterial-based detection can facilitate faster and more accurate detection of the virus even at early stages of the infection, in large due to versatility of surface modification of nanoparticles.
A shapeshifting material based on inorganic matter
Nanoscopic barcodes set a new science limit
Freeze like a star! Web exhibition explores the mysteries of the quantum world
|Nov 29, 2020|
|(Nanowerk News) Colder than in outer space, higher pressure than 30 sperm whales on a stamp, and super magnets that could hold two Eiffel Towers: The search for new quantum materials – the materials of the day after tomorrow – is taking place today under extreme conditions.|
|Yet it is often difficult to understand what the researchers actually do in their high-performance laboratories.|
|The Würzburg-Dresden Cluster of Excellence ct.qmat–Complexity and Topology in Quantum Matter has now taken a big step towards popular science communication.|
|The web exhibition SHOWCASE–Insight into our Research provides information about the goals, current activities, and research achievements of over 250 international cluster researchers – with easy-to-understand texts, catchy illustrations and entertaining videos.|
|“No less than three exhibitions were opened this year, all explaining our research themes. The positive response inspired us to prepare these topics in a multimedia format and make them accessible on our website. Now you can navigate through our mysterious quantum world from the comfort of your sofa anywhere in the world. This is an enormous advantage, not the least during the coronavirus pandemic,” emphasizes Prof. Matthias Vojta, spokesperson of the Dresden branch of the Cluster of Excellence.|
|Available in German and English, the web exhibition explains in an easily understandable way the extreme conditions that prevail in the high-performance laboratories, why researchers design quantum materials atom by atom, and what topological quantum physics has to do with hairy donuts.|
|An outlook on future applications leads from “cold chips” to “QuBits” and quantum computers. For those who want to know more, there are links to background information.|
|“In Germany we are leaders in the field of topological quantum materials and we play in the top league of our research field worldwide. But we also want to communicate to the general public outside our scientific community how exciting our experiments are, what groundbreaking results we have achieved and what this means for the society as a whole. This is particularly important to us, because we are convinced that quantum technologies will decisively shape the high-tech of the 21st century and lead to new applications,” explains Prof. Ralph Claessen, spokesperson of the Würzburg branch of the Cluster.|
|Source: Technische Universität Dresden|
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