Progress of Hollow Materials in Diagnosis of Covid-19

Hussain A; Shabbir S; Faizan M

Review Article

Austin J Pharmacol Ther. 2022; 10(2).1163.

Progress of Hollow Materials in Diagnosis of Covid-19

Hussain A^1,2, Shabbir S^1,2 and Faizan M^1,2*

¹Beijing Key Laboratory of Ionic Liquids Clean Process, State Key Laboratory of Multiphase Complex System, Institute of Process Engineering Chinese Academy of Sciences, PR China

²University of Chinese Academy of Sciences, PR China

*Corresponding author: Muhammad Faizan, Beijing Key Laboratory of Ionic Liquids Clean Process, State Key Laboratory of Multiphase Complex System, Institute of Process Engineering Chinese Academy of Sciences, PR China

Received: August 08, 2022; Accepted: September 09, 2022; Published: September 16, 2022

Abstract

Since the outbreak of COVID-19 in Wuhan, China, it has dramatically changed the global geopolitics, economics, and even society standard norms. The present world scenario is changed regarding business, traveling, and education. Rapid global dissemination and the high mortality rate of coronaviruses are the greatest challenges for drug developers. It will be moving forward toward the identification and treatment of emerging coronaviruses with the aid of nanotechnology. The COVID-19 pandemic raised the question of researchers’ capability to manage this dilemma in a short period. In the present review, we described how hallow material could be developed as a pro-drug that shows an excellent therapeutic effect. Hollow nanoparticles that exploration of antiviral or diagnostic agents against emerging coronaviruses. Hollow nanomaterials in vaccine development are essential because hollow nanocomposites are suitable for mimicking viral structures and antigen delivery. A biosensor that generates a signal from a transducer for comparing and analyzing biological conjugates such as cell receptors, antibodies, RNA, DNA, and nucleic acids. Different biosensors, such as graphene-based biosensors, nanoplasmonic sensor chips, nanomaterial biosensors, electrochemical biosensors, dual modality biosensors, and optical biosensors, have several advantages, characteristics, and a wide range of applications, most remarkably in medical treatment and are used for monitoring and diagnosis. This review focuses on modern experimental studies to identify intelligent and innovative bio/nanomaterials and matrices for developing targeted and controlled drug release systems, nanosensors and nanovaccines to combat pathogenic viruses.

Keywords: COVID-19; Nanoparticles; Hollow materials; Diagnostic agents; Nano/bio-sensors; Pathogenic viruses

Introduction

Since the 1918 influenza pandemic, coronavirus has emerged as a severe threat to human life. To solve the current pandemic situation, the planet needs both viral diagnostics and an antiviral vaccine [1]. However, the ongoing research and development period required for them is very lengthy, and they must pass multiple stages before being approved for human use. It is critical to develop a comprehensive and long-term strategy for combating infections, especially respiratory viruses. Material science and nanotechnology have revolutionized the biomedical industry, bringing numerous benefits to diagnostic and therapeutic applications [2]. Hollow nanomaterials play an excellent role in a vital role in diagnostics and drug delivery. Hollow nanomaterial-based delivery systems have recently attracted researchers to address drug treatment challenges and viral infection treatment. Alternatively, hollow nanomaterials have a charge with a small surface area that can be transformed into effective antiviral agents [3]. This is the most effective method for scientific investigation and biomedical use. Using hollow nanosystems exacerbates the low bioavailability and dose limit of drugs. Recently, hollow nanomaterials have been used with different mechanisms for promising antiviral activities. Hollow nanomaterial properties, such as surface charges [4], surface area, and size, make them an excellent tool for viral diagnostics and treatment [5].

The length of hollow nanomaterials can be adjusted to the delivery site, maximizing the drug's efficacy. Large molecules and drug payloads could be accommodated on the surface area. The biological system forges a strong link with nanoscience by incorporating hollow nanomaterials with nanomedicine to detect and treat diseases. Furthermore, the role of hollow nanomaterials is essential in drug delivery management [6,7]. Researchers have already faced several pandemics and viral outbreaks in the past; for example, the swine flu pandemic in 2009 infected many more people than the Ebola virus Zika outbreaks [8]. The current antiviral treatment is not as effective due to some hurdles. Hollow nanomaterials have shown great antiviral activity [9]. The drug and food organizations and other administrations approved so many nanobased platforms for an antiviral vaccine. For instance, an intramuscular vaccine such as epaxial is used for hepatitis A virus [10]. Such vaccines have liposome vehicles of 150 nm size. Epaxial possesses intrinsic adjuvant properties and helps reduce toxicity. Furthermore, a virosome vaccine has been developing as Influvac Plus, another approved virosome vaccine that is used to prevent certain types of influenza. Nanomaterial-based techniques such as polysaccharide particles, liposomes, dendrimers, and cationic nanoemulsions have been utilized to improve the distribution and stability of mRNA-based vaccines [11]. Therefore, the development of such vaccines with the administration of nanotechnology for COVID-19 is highly favorable. Hollow nanomaterials in vaccine development are essential because hollow nanocomposites are suitable for mimicking viral structures and antigen delivery [12]. In comparison to traditional vaccine design, this approach has many advantages. The ongoing threat of outbreaks of acute respiratory infections, for example, Middle East respiratory syndrome coronavirus (MERS-CoV), is to develop a potent and safe vaccine strategy based on novel vaccine technology that is useful in preventive measures. A hollow nanoscale vaccine was developed for the delivery of STING agonists and viral antigen subunits in a virus-type configuration [13]. Herein, STING agonists show multiple advantages, such as local immune potentiation and pH-responsive release profiles, after being encapsulated into hollow nanomaterials. Following antigen conjugation, the nanoparticles resemble native virions morphologically [14]. The nanoparticles morphologically resemble native virions, making it easier to deliver STING agonists and antigens to draining immune cells and lymph nodes for immune system potentiation. The effectiveness of nanocomposite vaccinations can be immunized with MERS-CoV nanoparticles in mice and has been encouraged with the derivation of effective neutralization of antigen-specific and antibody T cell interactions [15,16]. A transgenic MERS-CoV mouse model showed that immunized mice that accumulated hollow nanoparticles of the MERS-CoV vaccine were cured from a fatal MERS-CoV problem in the absence of unwanted eosinophilic immunopathology [17]. Biocompatible hollow nanoparticles were described here, with significant therapeutic potential for the creation of novel adjuvants and subunit vaccine candidates, enabling the quick synthesis of safe, efficient, and effective vaccinations against novel viral infections [15].

In Wuhan china many COVID-19 cases were associated with the Huanan Seafood Market [18]. It considered an obvious candidate for the location of the initial zoonotic (that is, cross-species transmission) event. However, none of the animals from the market (including rabbits, snakes, stray cats, badgers and bamboo rats) tested positive for SARS-CoV-2 [19]. In addition, some of the early cases of COVID-19 in Wuhan were not epidemiologically linked to the market [20]. From the initial genomic judgements, it was clear that SARS-CoV-2 had a genomic group similar to SARS-CoV. The three three-dimensional structures of spike proteins of both viruses have similar same cell surface receptor in human Angiotensin-Converting Enzyme 2(ACE2) [18] that was very soon confirmed in vitro and using structural biology [21]. SARS-CoV-2 differs from SARS-CoV because, six amino acid positions in the Receptor-Binding Domain (RBD) of the spike protein that mediate the attachment of the SARSCoV and SARS-CoV-2 spike proteins to the human ACE2 receptor [22]. However, amino acids at five of the six positions differed between SARS-CoV and SARS-CoV-2, such differences caused SARS-CoV-2 to have a higher binding avidity to the human ACE2 receptor11, and may have contributed to the higher transmissibility of SARS-CoV-2 compared with SARS-CoV [23].

The comparison of alpha- and beta coronaviruses identifies two remarkable genomic features of SARS-CoV-2. First feature are, it can appears to beoptimized for binding to the human receptor ACE2, that can show on the basis of biochemical experiments [24,25] and structural studies [26-28]. Second feature are, the spike protein of SARSCoV-2 has a functional polybasic (furin) cleavage site at the S1–S2 boundary through the insertion of 12 nucleotides, which additionally led to the predicted acquisition of three O-linked glycans around the site [27].

The goal of this discussion is to review recent research on hollow nanoparticles in the search for antiviral or diagnostic medicines to combat developing coronaviruses. In this context, we also discussed the potential of hollow nanomaterial-based biosensors and vaccines. Furthermore, we explained the utilization of nanoparticles for the identification and treatment of coronaviruses because of their antiviral potential. Rapid global dissemination and the high mortality rate of coronaviruses are the greatest challenges for drug developers. It will be moving forward toward the identification and treatment of emerging coronaviruses with the aid of nanotechnology. We ascribed the three different aspects for the utilization of hallow nanoparticles as diagnosis the coronavirus via biosensors, combating the coronavirus, employing as nano drug and performed antiviral activity.

Mechanism of Actions SARS-CoV-2

1. Acter et al. described the stage of coronavirus infections, and its transcription/replication mode will be as follows:

2. As an intermediate host, people come in contact with environments that have SARS-CoV-2 virus germs.

3. In the initial phase, alveolar cells are affected due to the interaction of coronavirus cells with the lungs via the ACE2 enzyme with a spike (an exclusive glycoprotein surface is involved). Later, in the second stage, it makes its way to the host cell. In addition, the virus was detached. Consequently, the RNA genome intercalates with cytoplasmic cells and then connects to ribosomes (host cells). Eventually, it makes it to the host cell [29].

4. In regard to RNA transcription and replication, proteins that are not structurally rearranged and RdRp RdRp stand for as RNA-polymerase-RdRp Replicas the Transcriptase Complex (RTC) of multiple proteins, and RdRp produces genomic RNA (positivesense) descending viruses via subgenomics and transcripts of replication [30].

5. Figure 1 depicts the Human Coronaviruses (HCoVs), which are derived from genomic groups.


    

    

    Figure 1: SARS-CoV-2 schematic structure and possible diagnostic targets: Reprint and permission from ref [31]. Copyright 2020 King Abdulaziz City for Science

and Technology.


    

    

    Figure 2: Co-functional TiO₂ nanotube (Co-TNT)-based sensing platform for the detection of SARS-CoV-2. Reproduce with permission from ref [44]. Copyright

2020 MDPI.


    

    

    Figure 3: An electrochemical transducer biosensor. Reproduce with permission from ref [95]. Copyright 2010 The Royal Society of Chemistry.

Virus Detection Techniques

SARS-CoV-2 identification using real-time Reverse Transcription–Polymerase Chain Reaction (RT–PCR) is a vital step in COVID-19 management. Asymptomatic infected individuals whose biological shedding accidentally distributes the disease to the mature and comorbidities are tested to avoid infectious propagation across people and communities [32]. The first step in limiting the COVID-19 epidemic is accurate virus detection [33]. Serological testing is recommended for detecting viruses and determining prior infection that can be used for medicinal research. The identification of antibodies can be achieved from Enzyme-Linked Immunosorbent Assay (ELISA) [26], which is a qualitative approach for detecting Immunoglobulin M (IgM) or Immunoglobulin G(IgG) antibodies [34]. These studies detect an protected response to the spike protein(Sprotein) and could be useful in determining to protect against future pathological exposure as well as for contact outlining [35]. Such tests are crucial, and they cannot be exaggerated. It could be applied to epidemiological assessments as well as wide global therapeutic requirements [36]. In upcoming modern research, diagnostic tests might be developed to improve immunoassay specificity and sensitivity [35]. Such analysis will eventually demonstrate viral protection when infections occur [37]. Immunity induction against SARS-CoV-2 is the next step in COVID-19 control [37,38]. Instead of RT–PCR, hollow nanomaterial-based techniques provide speedy and effective viral detection.

Hollow nanoparticles can be used to extract viral RNA via coprecipitation and polyamine ester attached with 3-aminopropyl (triethoxysilane) to perform almost 50000 diagnosis tests [29]. A colorimetric test consisting of thiol modified with antisense oligonucleotides linked to gold nanoparticles was developed to identify the N-gene RNA found in SARS-CoV-2. This technique is used for rapid diagnosis and can be completed in less than ten minutes. The detection limit for RNA particles is 0.18+ngl1 [39]. A binding of S-receptor domain linked with fluorescent Quantum dot QDs was designed by quenching with ACE2-attached gold nanoperticles (AuNPs). As the ACE2 receptor is linked with the S-protein, the fluorescence probe is quenched with adjacent gold nanoparticles, allowing for the observation of binding events present in solution. Through cell-based tests, QD probes will also help in the validation and discovery of ACE2 receptor binding and SARS-CoV-2 S-protein inhibitors [30]. QDs serve as probes for the investigation of additional viral receptors [40]. This system can be used to distinguish recombinant proteins and neutralizing antibodies against virus diagnosis, such as SARS-CoV-2, and many others that recognize and enter cells through the S-receptor. Similarly, TB biomarkers have been detected from co-functional TiO₂ _Nanotubes Tunneling Nanotubes (Ni-TNTs) with a greater surface to volume ratio [41]. A sensing mechanism is based on the creation of a complex between the biomarker and Co owing to Co ion reduction and biomarker oxidation. Simultaneously, they predicted that by coupling the Sprike Receptor Binding Domain (S-RBD) protein with functional nanoparticles, they might identify SARS-CoV-2 or S-RBD. Table 1 describe the comparison between different methods based on nanomaterials.

Table 1: Advantages and Cons of Common Virus Detection Method.








  

    Detection Method

    Technique

    Detection


      Base

    advantages

    Disadvantages

    Ref

  

  

    Serological detection

    immunoblotting assay, neutralization assay,

    viral protein

    easy; low-cost

    poor sensitivity; necessity for fresh reagents

     

  

  

    Nanobased detection

    nanobiosensors

    viral protein/nucleic acid

    very high selectivity and sensitivity; high    stability; fast response; portable system

    pH and temperature influence theselectivity and    sensitivity of biosensor

     

  

  

    basic detection

    cell culture

    infection test

    broad spectrum; low-cost

    difficulty in maintaining cell cultures;lengthy    test

    [42] 

  

  

    Molecular detection

    polymerase chain reaction, reverse transcription    polymerase chain reaction,

    viral nucleic acid

    high sensitivity; easy to set up

    extremely liable contamination noteasy to    quantitate results; high-skill operator required

    [43]






Table 1: Advantages and Cons of Common Virus Detection Method.

The current study evaluated whether cobalt Tunneling nanotubes Co-TNTs have the ability to electrochemically diagnose the S-RBD protein of SARS-CoV-2 [44]. Anodization electrochemical technique was used to make TNTs because it is easy and cost-effective. To accomplish Co functionalization, an incipient wetting approach was applied [45]. They presented that cobalt-functional TNTs can detect the SARS-CoV-2 S-RBD protein in just 30 seconds using an amperometry electrochemical method [45].

Numerous biosensors have been created to detect viruses, e.g. influenza, human immunodeficiency virus, and other viral illnesses [46]. Graphene-based biosensors have a wide variety of applications; they are made up of hexagonal carbon ordered in a 2D layer. Graphene biosensors are particularly sensitive due to their high electrical conductivity, large surface area and high carrier mobility. To construct a graphene based biosensor for SARS-CoV-2 diagnosis, the coronavirus S antibody was immobilized at the graphene surface from 1-pyrene-butyric acid with ester linkage of N-hydroxysuccinimide [47]. Toroidal plasmonic metal sensors were designed to detect viral S-protein concentrations as low as femtomolar. Monoclonal antibodies conjugated to functionalize AuNPs were detected at a concentration of 4.2FM, according to the researchers (lower limit of detection). A polarized light beam at the terahertz frequency might conceivably modify the transmission spectra of a metal sensor. In Point-Of-Care (POC) testing circumstances requiring a quick and fast assay, metasensors can be useful [48]. A one-step optical S-protein specific nanoplasmonic resonance sensor that needs little sample preparation and delivers direct and rapid viral detection has been developed as a consequence of a recent study. The detection limit for this assay is 30 virus particles and completed in just 15 minutes. Such an assay is capable of quantifying the virus at concentrations lower than those found in regular nasopharyngeal swabs and viral saliva [49]. It was discovered that nanoplasmonic sensor chips had a very high specificity (>1,000:1) for detecting SARS-CoV-2 after determining the sensor's specificity to bind SARS-CoV-2 with SARSCoV, MERS-CoV, and vesicular stomatitis pseudoviruses [50]. With sensitive viral detection, an affordable and portable device such as smartphone application may identify SARS-CoV-2 in a single phase within 15 minutes [51]. The virus may be measured linearly between 0 and 107 viral particles per milliliter, making it helpful in hospitals, houses, and highway screening stations, where the detection limit is 370. Thirty-eight gold nanoparticle-based sensors paired with artificial intelligence can identify volatile organic chemicals linked to SARS-CoV-2 in exhaled breaths [52]. The test can identify viruses based on changes in the resistivity of the nanomaterial biosensor layer. Collectively, biosensors and other hollow nanomaterial-based detection approaches can be used to perform quick and portable SARS-CoV-2 tests. Nths by using a variety of nanomaterials and undertaking a more thorough cohort study [53]. AuNP-based sensors paired with artificial intelligence can identify volatile organic chemicals linked to SARS-CoV-2 in exhaled breaths. The test identifies viruses based on changes in the nanomaterial biosensor layer resistance. The employment of additional nanomaterials and a greater sample size characterize the Nths [54]. A clinical diagnostic sensor with a dual-function plasmonic photothermal effect and transduction via localized Surface Plasmon Resonance (SPR) has been created. On 2-D gold nanoislands, several experiments are carried out. Gold nanoislands include complementary DNA receptors, which further hybridize with SARS-CoV-2 nucleic acids [53] and the device may be stimulated at two different wavelengths. F1ab-COVID, RdRp-COVID, and SARS-CoV-2 Envelope (E) genes may all be detected using this biosensor. The 0.22 pg/mL detection limit of the dual-purpose localized SPR biosensor allows for the exact identification of SARS-CoV-2 sequences in a multigene mixture. The development of antibody detection assays is underway, although progress is modest [55]. Numerous studies have had small differences, yet considering the remarkable regularity with which scientific information is communicated, few have published conclusions that should be questioned. One of the biggest current concerns with immunodiagnostic procedures have deficiency of accuracy, which may be give incorrect positive antigen readings. They are extensively conserved among CoV species and have a role in autoimmune disorders by interacting with auto antibodies. Immunodiagnostic approaches work best 7–11 days after exposure, rendering them ineffective for identifying acute infections [56].

The combination of metagenomics detection and nucleic acid amplification techniques can provide clinicians and epidemiologists with new insights [57]. In the future, immunodiagnostic platforms based on S and N can be used in conjunction with nucleic acid amplification tests to significantly improve COVID-19 detection sensitivity at a low cost [58]. Future research into the creation of novel diagnostic platforms could be useful based on the tests' precision, specificity, and ease of use, as well as their ability to deliver results quickly and at a low cost. The benefits and disadvantages of continuous testing methods and their singular performance values are that outcomes should be close. In both clinical and nonclinical settings, data are analyzed before making decisions [59]. Additionally, it is important to consider alternative methods for forecasting potential outbreaks, such as low-budget mass pooling and metagenomics profiling. Efforts to improve coronavirus detection have been made to date, and a number of improved or novel methods have been developed. In practice, multiple strategies are typically combined to minimize the disadvantages of a single technique. In summary, we expect that with the rapid advancement of new technology and techniques, additional excellent and effective detection methods will be built in the future, providing scientists and clinicians with more options. Simultaneously, only by weighing the benefits and drawbacks of different detection assays for particular applications can we arrive at the most cost-effective and optimal solution [60].

Hollow Nanoparticles for Diagnostics

COVID-19 is clinically diagnosed using a combination of CT and RT–PCR results [59]. Apart from clinical settings, RT–PCR research accounts for the lion's share of testing for surveillance carried out on the job or classrooms. Since RT–PCR testing is so prevalent. By finding the flaws in research stage, potential detection methods can be improved [61]. Due to improper specimen collection timing, poor specimen consistency, and other factors, nucleic acid amplification tests can be difficult. The demands for qualified laboratory technicians is increasing, as well as lengthy wait times for results. RT–qPCR (quantitative PCR), considered the gold standard, takes 4–6 hours to complete without counting the time it takes to obtain the samples in the lab [62].

Additionally, the RT–PCR results are highly dependent on the type of sample used. Oropharyngeal swabs (32to 48 percent), nasopharyngeal swabs (63 percent), Broncho alveolar lavage fluid (79 to 93 percent), sputum (72–76 percent), and stool (72–76 percent) have significantly different rates of good sampling (29 percent) [62]. There may be a shortage of primers and other reagents necessary to conduct the experiments [63]. New platforms are being aggressively pursued in response to RT–PCR testing limitations. Due to its high selectivity and simplicity, RT–PCR is the most frequently used RNA detection tool. RT–PCR is commonly used in COVID-19 detection. However, this approach has several drawbacks, including low extraction performance, a lengthy procedure, and false positives due to contamination. Hollow nanomaterials have been employed to build viral detection technologies due to their huge surface area and ultrasmall size. Numerous hollow nanomaterials have been studied for their potential use in virus diagnosis, such as Quantum Dots (QDs), metal nanoparticles, silica nanoparticles, polymeric nanoparticles, and carbon nanotubes. The majority of these techniques are calorimetric, electrochemical, fluorescence, or optical in nature.

Qi et al. studied the applications and properties of hollow nano/ microstructures and described that the efficiency of additional shells was increased due to the involvement of more sites [64]. Hollow nanostructures have many benefits for sensor applications, such as shorter electron transfer paths, low densities, increased active sites, high permeability, and large communication areas between electrolytes and electrodes [65,66]. Hollow structures resist nanoparticle agglomeration due to their internal voids, enabling better volume adjustments to be accommodated in subsequent electrochemical measurements. Numerous previous studies have demonstrated the excellent catalytic activity of hollow nanomaterials in alkaline solutions for glucose detection [67-69]. Other nanomaterials can be used to adapt hollow nanomaterials with superior properties, such as wide surface area and strong electrical properties, to improved sensing properties—a necessary step in the battle against a viral pandemic. The first prerequisite is to detect the virus. The exploration of rapid and accurate testing techniques enables touch isolation and tracing of infected individuals, thus containing the virus's propagation. Specifically, SARS-CoV-2 is quickly transmitted via asymptomatic carriers [70].

A wide range of nanomaterials has been proposed for virus detection. These nanomaterials include metal, silica, polymeric nanoparticles, Quantum Dots (QDs), and carbon nanotubes (Table 2).

Table 2: Summary of Representative Engineered Nanomaterials Employed As Biosensors for Virus Detection.








  

    Nanoparticles    (NPs)

    Characteristics 

    Target viruses 

    biosensor type 

    Ref

  

  

    Graphene    oxide (GO)

    size    controllability of GO Nano sheets and changes in their oxidation level to    detect specific viruse.

    HIV, RotavirusHIV-1, HBV

    Potentiometric/    optical/ electrochemical

    [71.72]

  

  

    Carbon    nanotubes (CNTs)

    It    possess high selectivity and sensitivity due to their high surface area

    HPV,    HBV

    electrochemical/    FET

    [73,74]

  

  

    zinc    oxide (ZnO)

    Plays    a main role in special sensors known as mechano-chemicals

    HIV

    Electrochemical/    piezoelectric

    [75]

  

  

    quantum    dots (QDs)

    It    have unique optical and electrical properties, having are powerful tools for providing rapid and    sensitive virus detection and treatment of viral disease.

    EBV,    HIV, HBV, CoVs

    optical/    electrochemical

    [76]

  

  

    copper    NPs

    Due    to small size and high surface-to-volume ratio of copper NPs are easy to    enable for detection of viruses.

    IAV,    HBV

    electrochemical

    [77,78]

  

  

    silica    NPs

    Silica    NP provided a platform important for bioanalytical studiessuch as    antigen-antibodies, peptides and DNA

    HBV,    HPV

    optical

    [79,80]

  

  

    Aluminum(AINPs)

    AINPs    is the most prominent and attractive feature for designing biosensors due to    Nano porous morphology.

    DENV,    Ebola

    electrochemical

    [81,82]

  

  

    Magnetic    (MNPS)

    MNPs    are widely used in reusable biosensor platforms

    CoVs,    IAV, HBV

    piezoelectric/    electrochemical

    [83]

  

  

    Gold(AuNPs)

    AuNPs    have been used widely for very sensitive detection of viral diseases due to    theirunique optical and electrical properties

    DENV,    RVFV, KSHV, CoVs

    optical/    electrochemical

    [84,85]

  

  

    Silver    (AgNPs)

    fluorescent    properties of AgNPs introduce high sensitivity to optical-based biosensors

    KSHV,    CoVs, WNVinfluenza

    optical/    electrochemica

    [86]






Table 2: Summary of Representative Engineered Nanomaterials Employed As Biosensors for Virus Detection.

Biosensors

A biosensor is a system that generates a signal from a transducer for comparing and analyzing biological conjugates such as cell receptors, antibodies, RNA, DNA, and nucleic acids. The biosensor device was made up of four important components: a bioreceptor, a transducer, a biosensor, and a digitally controlled detector [87]. The second element is the transducer or detector; it operates by detecting the signal associated with a physicochemical shift induced by the interaction of the analyte and bioreceptor. It converts the signal to an evaluable and quantifiable form. A biosensor's final component is the reader system. It entails a display that is produced by software and hardware [88]. The development of a new class of diagnostic biosensors known as nanobiosensors was enabled by electrodes fabricated at the microscopic nanoscale and scale sensors. The biosensor characteristics were affected by continuous-material dimension reductions from large to small scales up to 100 nm [89]. However, it greatly expands the scope of their implications.

Because of the interaction of the sensor surface with the analyte, biosensors with a high surface-to-volume ratio are very effective in nanosized devices. With the help of natural elements, hollownanomaterial transducers have been improved to develop commonly used biosensors for disease diagnostics and biomolecule detection.

Such instruments can assess a patient's physiological status quickly and accurately. Conduct pesticide and water contamination analyses on food and environmental samples [90]. Patients' physiological status can be quickly assessed with such instruments. The interaction of analytes with surface sensors will become very effective due to the large surface volume ratio of nanosized devices [91]. Biosensors can be used to detect bacteria and viruses in food and water, which are potential disease sources. Depending on the type of biosensor, biologically sensitive components recognize and interact with the analyte [92]. Zhao et al. designed and built a compact microfluidic device at a cheaper rate. For in situ fast diagnosis of E. coli, a biosensor is developed with the support of a graphene monolayervia streptavid in antibody and AuNPs. The surface of the biosensor is used to collect the bacteria, and identification is carried out electronically [93]. These devices incorporate bioreceptor sensing elements that mimic in vivo molecular recognition phenomena [94].

The combination of biosensor characteristics and nanotechnologies is now seen as a candidate that could be considered to accelerate the production of rapid, susceptible and precise devices for real bacterial and viral detection. Nanobiosensors, therefore, use magnetic, optical, electrical, and chemical characteristics of pathogens and biomolecules to detect the materials [96,97]. Research into hollow nanomaterials and nanostructures (e.g., nanogels, polymer nanocomposites, plasmonic nanomaterials, metal nanoclusters, metal oxide NPs, and carbon nanotubes) has made a significant contribution to the production of biosensors [98,99]. They have been used to adjust electrode surfaces and increase critical characteristics, including sensitivity, selectivity, and reproductiveness, due to their high adsorption capability, compatibility of structures, and biocompatibility.

Nanomaterials are candidates that are important for the use of biosensing. Nanotechnological advances have encouraged the production of medical diagnostic tests and quicker, cheaper, more sensitive, and more precise devices. Hollow nanomaterial biosensors put together diverse fields, such as chemistry, molecular biology, material science, and biotechnology. They give extreme sensitivity so that some biosensors can now detect as low as a parasite per microliter of blood [100].

Electrochemical Biosensor

Electrochemical studies provide essential benefits, such as design simplicity, higher selectivity and sensitivity, lower power demand, low-price equipment, and ready incorporation into instruments for microfluidics compared to techniques used in the past. Interestingly, the investigation of electrochemical gadgets has exhibited excellent performance in medical apparatuses [101]. In the last few decades, the world has been facing serious virus outbreak diseases such as SARS-CoV-2, SARS-CoV-1, MERS-CoV, and Ebola. It will be demanding a fast test kit to help and prevent more pandemics within the congested population. From a care diagnostic perspective, a new platform with specialized instruments for cases such as COVID-19 is a future obstacle [102].

Working electrodes can be made from semi conductive ingredients ranging from metals to nonmetals, such as materials and carbon of different sizes, ranging from main part materials to hollow nanostructures. Materials, fabrication methods, and design methods are all factors to consider, and the selectivity of the electrode and detection limit output are influenced by the electrode's characteristics and structures. As biosensors, a variety of gold- and platinumbased electrodes are used [103-105]. Cutting or conventional micromanufacturing techniques were used to create a large metal area or thin-film metal electrode using screen printing techniques and physical vapor deposition [106,107]. Polymer electrodes (which offer longevity, biocompatibility, and adjustable electric conductivity) and ceramic electrodes (made of indium tin oxide, polysilicon, and titanium dioxide) have also been utilized to produce electrodes [108]. However, selecting materials for electrochemical sensors, especially those used to detect pathogens, requires expert knowledge. Critical aspects of electrochemical sensors, including coupling chemistry, double-layer capacitance and heterogeneous electron transfer rate bioreceptors, may be normed, and they require immobilization. Hollow nanoparticle expendability and malleability have attracted interest in biological sectors, with several reaching commercialization, particularly for viral detection [109].

These discoveries have opened up incredible prospects for nanotechnology to detect and diagnose viral infections. As these materials exhibit a definite characteristic that compared to their bulk counterparts and have dramatically increased the ratio of surface-volume nanomaterials, to create robust materials for COVID detection [110], these materials have dramatically increased the aforementioned properties to create robust materials for COVID detection. Signals have been magnified from two aptamers. Zhao et al. produced a reliable electrochemical technique for detecting Hepatitis B Virus (HBV) based on nanoparticles of Cu₃ (PO₄)²-AuNP [111]. The constructed sensor had excellent binding sites, a flexible shape, and biocompatibility. Lee et al. devised a label-free avian influenza viral detection approach using electrochemistry and a multifunctional DNA structure on a porous (p) AuNP-modified electrode [112-114].

DNA sequence that has been proposed as a three-way intersection/p AuNP-based detection method can be used for the detection of a number of targets as a useful biosensor for the detection of pathogen subtypes on a single platform or single target detection with a high degree of reliability using the dual detection method [115]. The existing diagnostic procedures for SARS-CoV-2 are both timeconsuming and expensive. However, some excellent and low-cost techniques are available for immediate use, such as the synthesis of a low-cost but sensitive electrochemical sensor such as Co-TNTs for rapid SARS-CoV-2 diagnosis via spike detection (Receptor-Binding Domain, RBD) available on the virus's surface [44].

A potentiost at was used to cobalt-functionalize the TNT platform connected for data collection, after which a cheaper, onestep electrochemical technique was used to prepare TNTs. This sensor can detect the S-RBD protein of SARS-CoV-2 even at low concentrations (14–1400 nM). Furthermore, this sensor exhibits a linear relationship with viral protein diagnosis over a broad concentration range. In approximately 30 seconds, the Co-TNT sensor can sense SARS-CoV-2 S-RBD protein in nasal secretions and saliva samples, which might be exploited to establish quick point-ofcare diagnostics for SARS-CoV-2 detection in nasal secretions and saliva samples [44]. Because of their great sensitivity, precision, and accuracy in identifying biomarkers, electrochemical biosensors are crucial for detecting biomolecules [116]. Electrochemical biosensors have been used to successfully detect viruses such as MERS-CoV. Lahyquah et al. discovered MERS-CoV using a carbon electrode array to enhance its capability with gold nanoparticles. A biosensor for detecting SARS-CoV-2 has been described [117], which uses AuNP-decorated Fluorine Tin Oxide (FTO) glass impregnated with nCovid-19 monoclonal antibody.

By integrating hollow nanomaterials with the electrode, the efficiency of electrochemical biosensors can be improved. As the electrode surface area-volume ratio grows, the electrochemical reaction rate improves, resulting in a larger electrode surface area to analyte fluid volume. Tuberculosis biomarkers have also been detected using Ni-TNTs with a greater surface-volume ratio [118,119].

The suggested sensing method is based on the creation of a complex between the biomarker and Co due to Co ion reduction and biomarker oxidation at a certain bias voltage. As biosensors, several metal-based electrodes consisting of platinum and gold are utilized [103,104,120]. Cutting or traditional microfabrication techniques such as physical vapor deposition and screen printing, for example, were used to fabricate a thin film electrode or a thick surface based on metal. Additionally, polymer electrodes and ceramic electrodes composed of indium tin oxide, polysilicon, and titanium dioxide have the advantages of durability and flexibility. The fabrication of electrodes has been based on biocompatibility and tunable electric conductivity [108,121]. However, selecting materials for electrochemical sensors, especially those used to detect pathogens, requires expert knowledge.

The most frequent carbon materials used in conventional carbon sensors are glassy carbon, carbon fibers, and pyrolytic graphite, with pyrolytic graphite, carbon fibers, and glassy carbon being the most common carbon materials used in traditional carbon sensors [122,123]. The majority of carbon-based hollow nanomaterials exhibit several advantageous properties, including increased electrocatalytic activity, adsorption biocompatibility, and a high electron transfer rate [124].

Sensor applications have been investigated using carbon nanotubes and graphene. Simple drop casting, substrate growth, code position with metal nanoparticles, and field-effect transistors can all be used to directly integrate these into biological sensors [125]. Using the electrochemical impedimetric technique, researchers recently suggested the aid of gold hollow nanotubes for label-free detection of Human Papilloma Virus (HPV) [126]. An external electric field was used to force the negatively charged DNA oligonucleotide into the desired orientation in this study. By regulating immobilization and hybridization of the sequence onto gold nanotube surfaces, the sensing responsiveness may be improved. Silver nanoparticles (Ag- NP) are simple to make and have strong biomolecular attraction. As a result, they are perfect for making electrochemical biosensors [127]. Further investigation allowed researchers to explore an electrochemical immunoassay to detect antibodies against Tick- Borne Encephalitis Virus (TBEV) [128].

Before covalently immobilizing the antigen onto the electrode surface, the gold and carbon composite electrode was thiolated and gluttonized. Because of graphene's excellent chemical, mechanical, thermal, and electrical capabilities, hollow nanostructures are useful. They are the most often employed biosensors for DNA detection, because they have higher affinity for single-stranded DNA due to p-p stacking and hydrophobic interactions [129]. To improve biocompatibility, selectivity and solubility, graphene can be employed to interact with a variety of biomolecules and tissues. Wang et al. devised a sandwich-type electrochemical immunoassay by using apoferritin-embedded Cu nanoparticles with graphene QDs [23]. To determine the amount of Cu emitted from the apoferritin cavity assembly, differential plus voltammetry was used. Due to vast surface area of graphene quantum points, the electric signals increased, effectively accommodating considerable antibody loading [130]. Cu-apoferritin nanoparticles here have improved the charge of an electro active sample to further enhance the signals. The approach could identify avian leuck with a detection limit of 115 TCID50/mL and the range of 102.08 to 104.50 TCID50/mL.

The electrode material used in electrochemical sensors is important because it may alter the sensor output in a variety of ways. The capacitance of the double layer (which affects S/N), the heterogeneous electron transfer rate (which affects sensitivity and reaction time), the presence of the coordination chemistry used to immobilize the receptors, and the proclivity of electrochemicalluminescent sensors for nonspecific binding and quenching are all factors to consider. Carbon is a popular electrode material that is used as a platform for sensor growth Fluorine-Doped Tin Oxide (FDTO) and silicon (oxide) [131-133].

Because the faradic electrode is now dependent on the active site of the electrode until the background current grows in proportion, increasing the active electrode region will improve the detection sensitivity. To increase the area, hollow nanomaterials form other receptors that can be immobilized to give a more possibly increasing sensitivity and dynamic range, e.g., nucleic acid capture rings or antibodies [134]. Serious respiratory diseases in humans, including MERS and SARS, that cause contemporary problems were detected by viruses. In particular, however, the COVID-19 virus SARS-CoV-2 [135]. To identify the coronavirus type virus MERS-CoV, an immune sensor using voltammetry detection was established.

An electrochemical sensor was developed using folding paper techniques by Crooks and coworkers [136] that detects a 30-base nucleotide associated with HBV DNA and has a limit of detection of 85 pM. Micrometer-scale particles are accommodated in a hollow tube, and an extremely advanced slip sheet enables the separate incubation phases to be conveniently staged in time [137]. By using silver nanoparticle labels, an overall amplification factor of 250,000 was achieved using two stages of amplification. Simultaneously, magnetic microbeads equipped with detention investigations can be pre concentrated at a detection electrode to approximately 25-fold amplify the signal [138]. Notably, the assay is carried out without the use of enzymes or antibodies, which increases its stability, speed, toughness, shelf life and temperature tolerance. Only one incubation step is required prior to detection.

Biosensors based on Field Effect Transistors (FETs) have several advantages and characteristics when used with various analyte concentrations. Biosensors based on FETs have a wide range of applications, most notably in medical treatment, monitoring, and diagnosis at the point of care [139-141]. Graphene is a new nanomaterial made up of 2-D carbon atom layers. This material is an ideal candidate for active sensing surfaces because of its high carrier mobility, superior electrical conductivity, wide surface area and ease of surface functionalization [142]. As a result, graphene base materials are regarded as the best material for improving the sensitivity of FET biosensors and are a prerequisite for preventing an influenza pandemic. A field-effect transistor based on a graphene (G-FET) configuration was used to detect biological substances. The high sensitivity and stability of biological objectives, including the bio-FET process and the virus gene of H5N1 influenza, allowed for rapid detection, which is used for a flow-through strategy and provides an admirable platform for label-free detection. Chan et al. improved its efficiency by employing reduced graphene oxide films on Si/SiO2 substrates. However, the Limit Of Detection (LOD) of influenza viruses was in the picomolar range, requiring the usage of a single-layer hexagonal carbon network [143,144]. Using a film of graphene-based material, Seo et al. produced an FET detector for the COVID-19 active virus that has antibodies functional with SARSCoV- 2 spike antibody (Figure 4) [47].

Figure 4: SARS-CoV-2 (spheres) attaches to antibodies (Y-shapes) in this schematic representation of the graphene-based field-effect transistor (FET) biosensor mechanism and detection (a). COVID-19 FET reaction to SARS-CoV-2 spike protein in real time (b). MERS-CoV and SARS-CoV-2 are two distinct proteins that bionanosensors respond to differently (c). Reprinted with permission from ref [145]. Copyright 2020 the American Chemical Society.


    

    

    Figure 4: SARS-CoV-2 (spheres) attaches to antibodies (Y-shapes) in this schematic representation of the graphene-based field-effect transistor (FET) biosensor

mechanism and detection (a). COVID-19 FET reaction to SARS-CoV-2 spike protein in real time (b). MERS-CoV and SARS-CoV-2 are two distinct proteins that

bionanosensors respond to differently (c). Reprinted with permission from ref [145]. Copyright 2020 the American Chemical Society.

As a bioreceptor, the spike antibody SARS-CoV-2 was used. Moreover, it is an immunogenic transmembrane protein that selectively recognizes SARS-CoV-2. By incorporating a graphenebased FET biosensor into this biosensor, electrical characterization revealed an actual response to COVID-19 detection. S-protein, 1 fg/mL SARS-CoV-2 has good real-time detection. 4C Additionally, Figure 4 shows the biosensor's selectivity and sensitivity in distinguishing SARS-CoV-2 from other antigen proteins, such as MERS-CoV, and the ability of the surface to bind directly to the SARS-CoV-2 antigen of choice. The accuracy with which this biosensor identified the virus is impressive, and it could be used or updated to screen for other diseases in the future. A biosensor based on FET for the detection of SARS-CoV-2 in clinical samples [146]. Cultured virus, antigen protein, and COVID-19 patient nasopharyngeal swab specimens were used to calculate the sensor output. The S-protein SARS-CoV-2 may be detected at 1fg/mL in phosphate-buffered saline and 100 fg/ mL in clinical transported medium by using the FET device. The yield-effect transistor sensor successfully identified SARS-CoV-2 in culture media (LOD 1.6 101 pfu/mL [145].

Biosensing system-based FETs have several advantages over other currently available diagnostic techniques. This includes the capability to perform instantaneous and sensitive analyses with trace quantities of analytes [147,148]. Electrochemical biosensors are excellent for biomolecule sensing and can detect biomarkers with specificity high and sensitivity accuracy. Viruses have been successfully identified using electrochemical biosensors (such as MERS-CoV) [149]. Recently, gold nanoparticle-coated immobilized FTO glass was used to detect SARS-CoV-2 with a nCovid-19 monoclonal antibody [117]. The electrochemical biosensor functionality can be developed even further by hollow nanostructuring of the electrode, which increases the electrode surface area-volume ratio, resulting in a higher electrode surface area to analyte fluid volume ratio. Personalized medicine and digital health tracking have grown in popularity in recent years, and this great potential is now a reality thanks to considerable developments in skin-interfaced wearable sensors [150]. These sensors interact with the skin on multiple scales, from cellular to molecular, and can perform therapeutic and diagnostic activities with pinpoint accuracy, consistency, and speed. Electrochemical detection is potentially the most suitable technique for such sensor devices due to its low electric power consumption and ease of miniaturization [151].

Dual Modality Biosensors

Magnetic hollow nanoparticles with numerous uses are a new type of material with much potential in terms of increased functionality. It is difficult to create new nanocomposites without compromising magnetic activity or adding useful characteristics. An optically active Quantum Dot (QD) (core) enclosed within iron oxide (hollow shell) is the first electrochemical/fluorescence dual-modality probe in this study [152]. The encapsulation of QDs on the hollow shell structure preserves fluorescence with negligible quenching effects and good magnetic characteristics, paving the way for future fluorescence modality readout applications. Various viruses (such as Hepatitis E Virus-Like Particles (HEV-LPs) and Norovirus (Nov), were detected using a dual-modality sensor with Quantum dot -encapsulated magnetic hollow sphere nanoparticles (QD@MHS NPS) with highly integrated multimodal sensing and magnetic separation capability. In addition, the sensitivity of feces from HEV-infected monkeys was comparable to that of a gold-standard real-time quantitative Reverse Transcription–Polymerase Chain Reaction (RT–qPCR). This welldefined QD@MHS NP-based nanoplatform intelligently integrates dual-modality sensing and magnetic bioseparation, paving the door for efficient virus diagnostic point-of-care testing [152].

Each method of sensing has its own set of drawbacks; combining them into multimodal sensing can provide additional data [153- 155]. Fabricating hollow nanomaterials with multiple functional constituents that act as bifunctional markers is fascinating. Hybrid nanomaterials with a variety of synergistic properties can be created by combining magnetic nanoparticles with other active components. High-fluorescence inorganic fluorescent QDs are an appealing component widely used in high-throughput detection [156]. Coen capsulation in inorganic materials such as silica, template-based syntheses utilizing physical appendage or chemical bonding, or attachment of individual nanoparticles is the most common way to make magneto-fluorescent materials. Magnetic nanoparticles (core) and fluorescent QDs (shell) were assembled in the presence of a thin layer of silica to create colloidal structures. These nanoassemblies are rich in fluorophores and have a high magnetic content [157].

Rather than developing traditional single-mode sensors, the researchers in this study used CdSeTeS-QD@Fe₂O₃ hollow sphere nanoparticles (QD@MHS NPs) to create a dual-mode biosensor. Although hollow nanoparticles with magnetic and fluorescence properties have been used in a variety of bioimaging and drug delivery applications, more research is needed [158-159]. To our knowledge, their use in virus detection has yet to be demonstrated. With the recent increase in demand for virus sensing, a viable embodiment of sensitive and accurate strategies, particularly for the early stages of infection, is required, capable of rapidly providing a reliable and precise signal. The authors described how they used the synthesized QD@MHS NPs to develop a dual-modality biosensor for virus detection that incorporated electrochemical and fluorescence modalities to minimize false movement and self-verification. Although the target virus is present in basic sample analysis, several interferences indicate that magnetic bioseparation is required [152- 160]. The most widely used method, fluorescence, is used to obtain rapid sensing signals, and QD@MHS NPs have both magnetic and fluorescence properties. These structures provide a novel platform for separating targets from a complex biological matrix while also amplifying significant and reliable signals for clinical diagnosis [161]. Anti-monoclonal antibodies against HEV (anti-HEV-IgG) and NoV (anti-NoV-IgG) were conjugated to the surface of QD@MHS NPs, conferring HEV and NoV specificity, respectively.

Antibody-functionalized QD@MHS NPs, as shown in Figure 5 (A), can be used to capture the target virus from complex virus samples, forming virus/QD@MHS complexes as a result of the specific antigen-antibody reaction. Without sample pretreatment by applied virus/QD@MHS complexes, excess QD@MHS NPs, or an external magnetic field, the magnetic response of QD@MHS NPs was quickly separated and enriched. Virus/QD@MHS complexes and free QD@MHS NPs were redispersed in the new buffer after magnetic separation, and the vial was filled with antibody-labeled reduced graphene oxide-modified gold electrodes. The virus/QD@ MHS complexes bind to antibodies on the electrode surface, forming sandwich structures that are used to read electrochemical modality signals using an impedimetric response. The supernatant was used to read the fluorescence modality signal using the back-calculation method [162]. The structural merits of the QD@MHS NPs allowed for high fluorescence efficiency, and optimizing situations for their sensing parameters and sensor formulation were thoroughly investigated. The immunological interactions between the target virus and antibody molecules on the surface of QD@MHS NPs are the basis for this dual-modality sensor. An electrochemical signal is generated when antibody-conjugated QD@MHS NPs capture the virus and then bind it to an antibody-conjugated electrode. The change in the fluorescence signal was measured using unbound QD@MHS NPs with a diameter of 20 nm. Both the electrochemical impedance and fluorescence signal from the same sensing sample will provide two distinct signals due to the specific antigen-antibody reactions that occur as the virus concentration changes. The unique structure of QD@MHS NPs allows sensitive and precise biomolecule detection, which has important implications in disease diagnosis [152]. with electrochemical impedance and fluorescence as dual modalities (c). RE, WE, and CE denote reference, working, and counter electrodes, respectively. Reprinted with permission from ref [152]. Copyright. 2020 Elsevier B.V.

Progress of Hollow Materials in Diagnosis of Covid-19

Abstract

Introduction

Mechanism of Actions SARS-CoV-2

Virus Detection Techniques

Hollow Nanoparticles for Diagnostics

Biosensors

Electrochemical Biosensor

Dual Modality Biosensors

Optical Biosensors

Conclusion and Future Prospects

Compliance with Ethics Requirement

Data Availability Statement

Conflicts of Interest

References