key: cord-1039623-yz4bsi2z
authors: Alphandéry, Edouard
title: The Potential of Various Nanotechnologies for Coronavirus Diagnosis/Treatment Highlighted through a Literature Analysis
date: 2020-07-08
journal: Bioconjug Chem
DOI: 10.1021/acs.bioconjchem.0c00287
sha: f872b3d3bcbda7c537a5ac560d3eb401f5f67ee0
doc_id: 1039623
cord_uid: yz4bsi2z

[Image: see text] With the current COVID-19 outbreak, it has become essential to develop efficient methods for the treatment and detection of this virus. Among the new approaches that could be tested, that relying on nanotechnology finds one of its main grounds in the similarity between nanoparticle (NP) and coronavirus (COV) sizes, which promotes NP–COV interactions. Since COVID-19 is very recent, most studies in this field have focused on other types of coronavirus than COVID-19, such as those involved in MERS or SARS diseases. Although their number is limited, they have led to promising results on various COV using a wide range of different types of nanosystems, e.g., nanoparticles, quantum dos, or nanoassemblies of polymers/proteins. Additional efforts deserve to be spent in this field to consolidate these findings. Here, I first summarize the different nanotechnology-based methods used for COV detection, i.e., optical, electrical, or PCR ones, whose sensitivity was improved by the presence of nanoparticles. Furthermore, I present vaccination methods, which comprise nanoparticles used either as adjuvants or as active principles. They often yield a better-controlled immune response, possibly due to an improved antigen presentation/processing than in non-nanoformulated vaccines. Certain antiviral approaches also took advantage of nanoparticle uses, leading to specific mechanisms such as the blocking of virus replication at the cellular level or the reduction of a COV induced apoptotic cellular death.

With the spread of the COVID-19 epidemic and the disorders that it has caused, i.e., an increased mortality rate, a saturation of the hospital infrastructures, and a sudden major slow-down of the world economy, it appears essential to better understand the behaviors of coronaviruses (COV) and to develop efficient methods for their detection and destruction. To this end, an enormous research effort has been implemented worldwide, which mainly relies on drug repositioning, i.e., testing as COV treatments drugs such as chloroquine and remdesivir or their derivatives, which have shown their efficacy against other diseases than COV, i.e., malaria and HIV. 1 Such an effort could be complemented by other approaches, e.g., in the field related to nanotechnologies for COV treatment. Indeed, the sizes of these viruses are similar to those of nanoparticles, hence promoting NP-COV interactions and potentially resulting in similar behaviors between NP and COV. 2 Thus, it has been suggested that certain drawbacks of standard attenuated/ inactivated vaccines, such as their pathogenic virulence or weak immune responses, could be overcome by using nanoformulations (NF). This is due to sizes, shapes, functionalities, and antigen presentation/processing that could be favorably adjusted in NF, potentially yielding a more efficient and better-controlled immune system response for nanoformulated than non-nanoformulated drugs. 3, 4 Here, methods using various types of nanotechnologies that have been tested for diagnosis and treatment of COV are reviewed. The different fields in which nanotechnologies could help to bring a solution linked to the COVID-19 crisis are (i) the development of a cheap and rapid test for diagnosing COVID 19 that could be deployed worldwide over the entire population, 1 (ii) the prevention of virus replication and viral RNA synthesis, for example, by using nanoparticles that block the interaction between COVID 19 and the cellular receptor ACE-2, 5 (iii) the development of new nanoparticle-based-vaccine, 3 and (iv) the restoration of innate immunity among infected patients. 3 Nanomaterial safety is a prerequisite for their administration to humans. To ensure this, regulatory agencies have set up specific regulations with dedicated biocompatibility tests. 6 Although it is difficult to consider nanomaterial safety in general terms due to the huge diversity of these materials, certain nanoparticles such as those composed of iron oxide have been granted authorization for human injection, 7 and could therefore potentially be tested clinically against COVID 19. Due to the recent outbreak of COVID-19, the majority of studies relates to other types of coronaviruses than COVID-19, i.e., human COV such as those associated with Middle East Respiratory Syndrome (MERS) and Severe Acute Respiratory Syndrome (SARS) diseases, and animal COV such as Feline Coronavirus (FCOV), Porcine Epidemic Diarrhea Viruses (PEDV), and Infectious Bronchitis Virus (IBV). The use of similar treatment strategies for COVID-19 than for these other COV may be foreseen, but even so, such therapies remain exploratory, and no effective MERS/SARS vaccine has yet been put in place to the author's knowledge. . It was suggested that some coronavirus could be transferred from one species to another. For example, it was reported that SARS and MERS could originate from bats or camels, which seems to be based on viral ARN similitudes observed between these different species. 11, 12 Following an incubation period, coronaviruses affect specific parts of the organism such as tract or gastrointestinal system, potentially resulting in severe diseases such as pneumonia. 13 Coronavirus detection is usually carried out through ELISA, immunofluorescence, PCR, and/or chest X-rays. 14 While coronavirus infection can be avoided through vaccination for PEDV, 15 vaccines have not yet been developed for SARS and MERS. 16 

Transmission of COVID 19 occurs through droplets containing the virus that are emitted by an infected person through coughing, sneezing, or talking. These droplets are either directly transmitted to another person in proximity or are evaporated to end up as dried nuclei located at the surface of an object such as a knob, a button, a table, or a door. From a general standpoint, virus transmission can be prevented by isolating the infected person, by cleaning contaminated objects, by frequently washing hands, or by wearing personal protection equipment. 17, 18 This latter aspect, notably the necessity (or not) to wear masks, has been the topic of contradictory recommendations from the authorities. This is essentially due the lack of knowledge on the efficacy of existing masks to filter COVID 19 virus. With the size of COVID 19 being nanometric, nanotechnological tools can help to clarify this issue. To this aim, a study has been led to compare the filtering efficacy of common masks made of cotton, silk, chiffon, flannel, and their combination. 19 It concluded that a mask made of a single fabric or containing holes was not optimal for filtering COVID 19, while that comprising a combination of cotton and silk, cotton and chiffon, or cotton and flannel could filter 80−90% of the virus, where such enhanced efficacy was attributed to a mechanism relying on a combination of mechanical and electrostatic interactions between the virus and the fabrics that could only be reached by combining materials. Another group used electrostatically charged PVDF nanofiber filters to capture the deadly airborne coronavirus. 20,21 A third approach consisted of depositing nanostructured graphene at the surface of surgical masks. Such masks became superhydrophobic with a temperature that could reach 80°C under sunlight illumination, making them sterilizable and reusable, an important aspect given the necessity to be able to easily decontaminate masks to avoid virus spreading through mask misuses. 22

To avoid false positive/negative that can occur in standard detection methods of COV such as PCR, ultrasensitive nanodetection methods have been developed. Nanotechnology-based COV detection methods are summarized in Figure 1 . They first rely on highly sensitive optical mechanisms. The latter can be a measurement of fluorescence at 412 nm of a complex made of Zr QDs bound to anti-COV antibodies linked to COV, following magnetic isolation. 23 It can also be fluorescence detection of green fluorescent protein (GFP) comprising a complex formed by SARS virus proteins attached to Au NP whose fluorescence is different from that of free GFP. 24 It can be based on several calorimetric assays enabling COV detection by using Au associated with various entities such as doublestranded DNA that specifically bind to COV, 25 antibodies acting against IBV spike proteins, 26 or monoclonal antibodies (mAbs) activated against PEDV, 27 or by using Ag NP attached to acpcPNA, which remain dispersed in the presence of complementary COV derived DNA, giving rise to a detectable color change. 28 Au nanoislands were also functionalized with specific DNA strands that bind to SARS-COV-2 nucleic acids under heating produced by laser illumination followed by Au NP plasmon absorption, enabling COVID-19 detection at virus concentration as low as 0.22 pM. 29 Another type of COV detection method relies on the use of nanotraps that capture COV, improving their stability and enabling their detection over a long period of time. 30 It was also reported that COV could be detected with a biosensor made of carbon electrodes that comprise Au NP associated with viral spike proteins, whose response, i.e., peak current position/intensity, depends on the presence (or not) of MERS-COV. 31 In another approach, a field-effect transistor (FET) coated with graphene sheets attached to antibodies that specifically recognize COVID 19 spike proteins enabled the detection of these proteins in different media (phosphate-buffered saline, culture medium, clinical samples) down to COVID 19 concentrations of 1 fg/ mL. 32 Finally, the efficacy of PCR, which is the most widespread method of COV detection, can be improved by using nanoparticles, either through the simultaneous (duplex) detection of two virus types such as DNA and RNA viruses, e.g., using nanoparticles conjugated to specific probes of these viruses, 33, 34 or by making the polymerase chain reaction more efficient in the presence than absence of nanoparticles. 35 Bioconjugate Chemistry pubs.acs.org/bc Review general, compared to standard PCR, nano-PCR presents the advantages of requiring a simplified operating mode, i.e., DNA/ RNA extraction, RNA purification, and reverse transcription may not be needed, of resulting in a better sensitivity, and of avoiding cross-contamination with other viruses.

A series of nanoformulated anticoronavirus vaccines, which are presented in Figure 2 , were developed. They often resulted in a better efficacy than their non-nanoformulated counterparts. Such vaccines contain a backbone made of gold nanoparticles, polymers such as PLGA, chitosan, and PEI, or protein assemblies. This backbone is conjugated or associated with an active principle consisting of COV antigen, inactivated or destroyed COV, DNA expressing certain COV proteins, or specific COV proteins such as spike ones (Table 1) . Although a nanoparticulate formulation usually refers to a material whose size is between 1 and 100 nm, 6 the sizes of these vaccines could exceed this upper limit, ranging from 12 to 600 nm (Table 1) .

Other specific properties of these vaccines include their charge, which is positive when it is measured apparently corresponding to the charge of their coating material, and their shape, which is most often reported as spherical (Table 1) . When animals such as mice and chicken were immunized with vaccines, it led to a production of cytokines, i.e., essentially γ-IFN, IL-1β, IL-2, and IL-6, as well as an activity of certain immune cells such as macrophages, lymphocytes, and B cells, which were more important using formulated than non-nanoformulated vaccines.

To the author'sknowledge, it was not reported whether the immune reaction was dominated by a humoral or cell mediated response. In fact, both types of responses seem to occur, resulting in some cases in the restoration of respiratory body activity and protection of specific body parts such as the trachea. Whereas in most cases, a specific antigen originating from COV was inserted in the nanoformulation to trigger a reaction against the virus, an interesting study presented a nanoformulated system, i.e., a protein cage nanoparticle (PCN), which was devoid of such antigens. Following its injection to mice, it resulted in the production of antiviral antibodies, and led to an increase in mouse survival. Beyond the explanation provided, i.e., the development of inducible bronchus-associated lymphoid tissue (iBALT) in the lung that triggered T and B cell responses, the most interesting aspect of this study seems to lie in the fact that a specific antigen may not be absolutely necessary for a nanoformulated COV vaccine to be efficient. 37 Very recently, a clinical trial was launched to study the efficacy of a vaccine against COVID 19 containing m-RNA lipid nanoparticles. 38 Its outcome is pending.

Even so, nanoformulated vaccines aimed at triggering an immune response against COV, while antiviral nanoformulations should prevent certain interactions between virus and cells or their consequences, these two types of mechanisms, whose details are provided in Figure 3 , can coexist together. The study of the response of the immune system was carried out in vivo to be able to monitor the production of specific antibodies acting against COV, whereas antiviral behaviors were examined in vitro to decipher the mechanisms of virus interactions with cells. As presented in Figure 2 and Bioconjugate Chemistry pubs.acs.org/bc Review were reported to be of essentially four types: (i) the antiviral agent diphyllin encapsulated in PEG−PLGA copolymers of 40 nm, 39, 40 (ii) Ag nanoparticles of 7.5 nm bound to graphene nanosheets, 41 (iii) Ag 2 S nanoclusters of 3.2 nm, 42 and (iv) several Ag based nanomaterials including Ag nanoparticles of 20 nm and Ag nanowires of 60 and 400 nm diameters. 43 The antiviral activity of these nanoformulations against COV was first achieved by blocking cellular endosomal acidification, which seems to be an essential step in COV replication, using an ATPase blocker, diphyllin, which is nanoformulated to yield a good solubility and be released in a sustainable manner. It resulted in efficient COV replication blockage in fcwf-4 cells. 39, 40 Second, inhibition of the synthesis of viral RNA was reached by using the various types of Ag nanomaterials mentioned above. 41−43 Third, antiviral activity could be associated with a certain level of cellular immune response, as highlighted by the expression of pro-inflammation cytokines following cellular exposure to Ag NP. 42 Fourth, it could correspond to a reduction of COV-induced apoptotic cellular death in the presence of Ag nanomaterials. 43 Finally, for the treatment of COVID 19, it has 

In addition to methods of direct virus destruction presented above, the bases of other therapeutic approaches have been introduced, whose mechanisms of action rely on the correction of certain dysfunctions of the organism due to the virus. For example, the modification of the microbiote induced by COVID 19, which is suspected through several signs among infected patients such as diarrhea, a relatively long incubation time of 2− 5 days of the virus, the transmission of the virus through fecal route, but is not formally demonstrated, could be examined. On one hand, nanomaterials could be used for the detection of compounds or inflammatory proteins originating from a disturbed microbiota, which could indirectly reveal the presence of COVID 19. On the other hand, nanomaterials could serve to improve the local delivery of drugs in the gut, which would fight against COVID 19 by restoring healthy activity of the microbiome. 44 

In this topical review, I have highlighted the potential of certain nanotechnologies for improving the detection and destruction of coronavirus. Concerning COV detection using nanomaterials, it either allows specific COV binding at NP surface or improves PCR efficacy, generally leading to better sensitivity compared with other detection methods. Compared with their non-nanoformulated counterparts, nanodrugs display a series of advantages in the fight against COVID 19 such as an improved drug safety and solubility, 45 better virus inhibition, 5 and more efficient immune response and organ targeting, 3,4 as summarized in Figure 4 . In addition, when they are included in vaccines, they can replace standard adjuvants. The appealing properties of these nanomaterials have been highlighted not only through their use in new vaccination methods but also in the context of specific antiviral treatments, where nanoformulated antiviral drugs could block virus replication, trigger an anti-COV immune response, or prevent COV-induced apoptotic cellular death. In order to develop nanotechnology based treatments for COVID 19, certain additional aspects that have not been mentioned in the literature should be examined. They notably concern the interactions between nanomaterials and cells or cell receptors that should not only prevent virus replication but also yield minimal cellular toxicity. These two aspects should probably be studied in parallel to evaluate the benefit/risk ratio of nanomaterial-based treatment against COVID 19. Furthermore, the efficacy of nanotechnology-based vaccines or antiviral drugs against COVID 19 should be tested on suitable animal models such as hACE2 transgenic mice, 46 a task that has not been undertaken to the author's knowledge. The fact that we urgently need a treatment against COVID 19 should not make us skip some essential steps in drug development. It appears insufficient to start a human clinical trial based only on the observation of cellular drug efficacy. Drug assessment on animals is essential to examine the conditions under which a drug is efficient, notably to determine preclinically the dose or administration route of anti-COV 19 nanoformulated drugs that could potentially result in treatment efficacy on humans. The author declares the following competing financial interest(s): The author has been working in the start-up Nanobacterie (http://www.nanobacterie.fr).

■ ACKNOWLEDGMENTS

Paris Reǵion Entreprise, France"), the French Research Tax Credit program ("credit d'impot recherche"), the incubator Paris Biotech Sante

We also would like to thank the Nomis Foundation and Markus Reinhard for their support

ACE-2, Angiotensin-converting enzyme 2; COV, Coronavirus

Coronavirus disease; COVID 19, Coronavirus disease appearing in 2019.; ELISA, Enzyme linked immune-sorbent assays

Human immunodeficiency virus

IBV, infectious bronchitis virus

East Respiratory Syndrome; NM, Nanomaterial; NF, Nanoformulation

Polymerase chain reaction

Porcine epidemic diarrhea virus; PEG

Severe Acute Respiratory Syndrome; SEP, Self-assembled proteins

Potential Rapid Diagnostics, Vaccine and Therapeutics for 2019 Novel Coronavirus

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Nanoparticle-Based Vaccines Against Respiratory Viruses

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Coronaviruses: An Overview of Their Replication and Pathogenesis

MERS Coronavirus in Dromedary Camel Herd, Saudi Arabia

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Origin and evolution of pathogenic coronaviruses

Middle East Respiratory Syndrome Infection Control and Prevention Guideline for Healthcare Facilities

COVID-19: A Call for Physical Scientists and Engineers

Electrostatic Charged Nanofiber Filter for Filtering Airborne Novel Coronavirus (COVID-19) and Nano-aerosols

Charged PVDF multilayer nanofiber filter in filtering simulated airborne novel coronavirus (COVID-19) using ambient nano-aerosols

Reusable and Recyclable Graphene Masks with Outstanding Superhydrophobic and Photothermal Performances

Chiral zirconium quantum dots: A new class of nanocrystals for optical detection of coronavirus

Development of Label-Free Colorimetric Assay for MERS-CoV Using Gold Nanoparticles

A Novel Immunochromatographic Strip for Antigen Detection of Avian Infectious Bronchitis Virus

A new immunochromatographic assay for on-site detection of porcine epidemic diarrhea virus based on monoclonal antibodies prepared by using cell surface fluorescence immunosorbent assay

Dual-Functional Plamonic Photothermal Biosensors for highly Accurate Severe Acute Respiratory Syndrome Coronavirus 2 Detection

Magnetic Nanotrap Particles Preserve the Stability of Venezuelan Equine Encephalitis Virus in Blood for Laboratory Detection

An electrochemical immunosensor for the corona virus associated with the Middle East respiratory syndrome using an array of gold nanoparticle-modified carbon electrodes

Rapid Detection of COVID-19 Causative Virus (SARS-CoV-2) in Human Nasopharyngeal Swab Specimens Using Field-Effect Transistor-Based Biosensor

Ultrasensitive Detection of RNA and DNA Viruses Simultaneously Using Duplex UNDP-PCR Assay

A sensitive duplex nanoparticle-assisted PCR assay for identifying porcine epidemic diarrhea virus and porcine transmissible gastroenteritis virus from clinical specimens

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Inducible Bronchus-Associated Lymphoid Tissue Elicited by a Protein Cage Nanoparticle Enhances Protection in Mice against Diverse Respiratory Viruses

Nanoparticulate vacuolar ATPase blocker exhibits potent hosttargeted antiviral activity against feline coronavirus

Antiviral efficacy of nanoparticulate vacuolar ATPase inhibitors against influenza virus infection

Antiviral Activity of Graphene−Silver Nanocomposites against Non-Enveloped and Enveloped Viruses

Glutathione-Capped Ag 2 S Nanoclusters Inhibit Coronavirus Proliferation through Blockage of Viral RNA Synthesis and Budding

Inhibitory effect of silver nanomaterials on transmissible virusinduced host cell infections

Considering the Effects of Microbiome and Diet on SARS-CoV-2 Infection: Nanotechnology Roles

Progress in Nanomedicine: Approved and Investigational Nanodrugs

The pathogenicity of SARS-CoV-2 in hACE2 transgenic mice

Prospects for the use of spherical gold nanoparticles in immunization

Inactivated infectious bronchitis virus vaccine encapsulated in chitosan nanoparticles induces mucosal immune responses and effective protection against challenge

Intranasal immunization with plasmid DNA encoding spike protein of SARS-coronavirus/polyethylenimine nanoparticles elicits antigenspecific humoral and cellular immune responses

Quaternized chitosan nanoparticles loaded with the combined attenuated live vaccine against Newcastle disease and infectious bronchitis elicit immune response in chicken after intranasal administration

Purified coronavirus spike protein nanoparticles induce coronavirusneutralizing antibodies in mice

MERS-CoV spike nanoparticles protect mice from MERS-CoV infection

Heterologous prime−boost vaccination with adenoviral vector and protein nanoparticles induces both Th1 and Th2 responses against Middle East respiratory syndrome coronavirus

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A self-adjuvanted nanoparticle based vaccine against infectious bronchitis virus

Human polyclonal immunoglobulin G from transchromosomic bovines inhibits MERS-CoV in vivo

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SARS Coronavirus Fusion Peptide-Derived Sequence Suppresses Collagen-Induced Arthritis in DBA/1J Mice

Inducible Bronchus-Associated Lymphoid Tissue Elicited by a Protein Cage Nanoparticle Enhances Protection in Mice against Diverse Respiratory Viruses