Introduction

Severe Acute Respiratory Syndrome-Coronavirus-2 is a novel virus with a correlated illness called COVID-19. It is spreading worldwide since late 2019, and a few months later, the World Health Organization (WHO) announced it as an epidemic (Schrank et al., 2020).

Coronaviruses are an enveloped and extensive family of viruses, transmitting between humans and animals and commonly provoke upper-respiratory-tract diseases ranging from typical cold to severe infection (Howley et al., 2020). SARS coronavirus (2002) and MERS Coronavirus (2012) are two severe and lethal members of this large family (Rai et al., 2020). SARS-CoV-2 viruses are positive-sense, single-stranded RNA viruses having a genome length of 26–32 kb (Rai et al., 2020) In comparison, SARS-CoV-2 is of special concern due to challenging control, higher reproduction numbers, longer incubation times, latent infections, and delayed symptoms (Almasi & Mohammadipanah, 2020; Schrank et al., 2020).

Since one of the most conventional interventions to inhibit the spread of this virus is adequate surface disinfection, there is an urgent requirement for disinfectants with lower toxicity (Rai et al., 2020; Saadatpour & Mohammadipanah, 2020). As the effectiveness of disinfectants depends on multiple factors, efforts to enhance their impact are inevitable in the current situation of the pandemic. Therefore, the advancement of authentic, innocuous, and eco-friendly disinfection methods is of utmost importance for the widespread continuation of their applications. Enhancement of antimicrobial effect using the natural additive to disinfectant formulation is generally regarded as safe while the emerging usage of new nanomaterial in antiseptic formulations is of health and ecological associated concern (Saadatpour & Mohammadipanah, 2021). In the first section of this review, we will focus on nanomaterials with antiviral activity. The second section will highlight several instances of their antiviral mechanisms. The third section will ultimately present the toxic impacts of nanomaterials on eukaryotic cells and the environment by their worldwide radically increased usage.

Nanoparticles and Nanomaterials

Nanomaterials (NMs) are materials constructed with a top-down or bottom-up nanotechnological approach. They are characterized by, at minimum, a single dimension fewer than 100 nm with a great surface area (Baroli, 2010). Depending on the composition, NMs are organized into four different groups: Based on metal, carbon, composites, and dendrimers (Kabir et al., 2018).

NMs based on carbon are concrete elements, which have been found in the form of nanoparticles (NPs), ellipsoids, sheets, and tubes that have specific and unusual physicochemical, optical, mechanical, and thermal qualities (Kabir et al., 2018). Quantum dots, silver NMs, gold NMs, and nano metallic oxides like titanium or zinc dioxide are the main metal NMs (Kabir et al., 2018). The dendrimers are symmetrical particles comprised tree-like branches in a monodispersed construction. The superficial layer may encounter variations in measure, form, and adjustability to other components (Abbasi et al., 2014). Nanocomposites have some features that could be created by referring to the requisition, selection of matrix, curing stage, and arrangement (Kabir et al., 2018).

Depending on how many dimensions fall below the 100 nm limit, NMs can also be sorted into four large families: Core–shell (zero dimension), surface films (one dimension), strands or fibers (two dimensions), and particles (three dimensions) (Baroli, 2010).

The NMs might have various shapes (e.g., spheres, rods, cups, ellipsoids, cubes) and might be coated with inorganic or organic materials to stabilize them against aggregation (Baroli, 2010). Applications of NMs include drug delivery, biosensor, reaction rate enhancement agent, magnetic separation and detection, and last but not least, as the antimicrobial agent (Li et al., 2011).

Nanomaterials with Antiviral Activity

Depending on the dimension, form, and surface charge, NMs can possess various formations and antiviral characteristics (Abd Elkodous et al., 2020). New NMs are being developed to improve their performance in treating respiratory diseases through various mechanisms (Sivasankarapillai et al., 2020).

The primary NMs reported for their inactivation effect on respiratory viruses can be subdivided into the following groups.

Polymeric NMs Their impressive qualities include adjustable features, available combinatorial protocols, and excellent biocompatibility (Sivasankarapillai et al., 2020).

Self-assembling proteins NMs They are produced by the oligomerization of monomeric proteins.

Inorganic NMs This type of NMs often has records of antiviral activities (Sivasankarapillai et al., 2020). Some of the most critical inorganic NMs include copper, silver, zinc, Titanium Dioxide (TiO2).

Copper Since copper NMs (CuNPs) contain a smaller size and high surface-to-volume rate, they are extensively realized antimicrobial, antifungal, and antiviral metals for use on surfaces (Imani et al., 2020; Ingle et al., 2014; Vincent et al., 2017).

Silver They have unusual physicochemical and biological features that lead to having many applications for antiviral purposes in the shape of ions, NPs (AgNPs), and hybrid coats (Gurunathan et al., 2020).

Zinc Zinc oxides are n-type semiconductor metal oxides having remarkable antiviral qualities. It has many advantages like low production costs, readiness preparation, distinctive UV filtering qualities, high catalytic and photochemical activity (Jayaseelan et al., 2012; Nisar et al., 2019).

TiO2 TiO2 has many technical purposes such as water treatment, air disinfection, UV absorber, food, semiconductor, and agricultural industry (Hossain et al., 2014).

Other Inorganic Antiviral Matters Other inorganic matters and NPs like gold, magnesium, transition metals, and silica have significant antiviral activities (Imani et al., 2020) (Table 1).

Table 1 Main inorganic and metal nanomaterial with antiviral activity
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Peptide-based NMs Earlier research has shown that the applications of peptide restrainer and modifications of amino acids may probably act against infections, especially the ones associated with SARS-CoV (Sivasankarapillai et al., 2020). Some of the most significant NMs that have shown activity against several respiratory viruses are summarized in Table 2.

Table 2 Effective nanomaterial (NMs) on facing respiratory viruses
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Antiviral Mechanisms of Nanomaterials

In recent years, several NMs have been suggested as an alternative material for advanced diagnostic and therapeutic uses and carriers for antiviral agents. The mechanisms of action are limited to the specific type of NMs or viruses. Some of the main mechanisms are discussed below. The antiviral activity of NMs in any form depends on the dose and the target virus (Castro-Mayorga et al., 2017; Sportelli et al., 2020).

Silver The interaction with the envelope, genome, surface proteins, replication factors, preventing cellular pathways, and viral penetration into cells are the main mechanisms (Rai et al., 2016). Silver as an antiviral interacts directly with sulfur and phosphate groups to interrupt the cell membrane. Besides, silver ions generate ROS (Reactive Oxygen Species) inside the cells, providing significant antiviral activity (Imani et al., 2020).

Zinc The antiviral mechanisms of zinc are based on interference with the replication of the virus, such as inactivation of the free virus, suppression of viral uncoating, transcription of the viral genome, translation of viral proteins, and the process of the polyprotein (Scott A Imani et al., 2020; Read, 2019).

Copper In general, viruses are more susceptible than fungi and bacteria to copper by the lack of repair mechanisms (Borkow, 2012). The viral genome is targeted by copper, especially a gene encoding VPg (viral-genome-protein-linked, a viral protein essential for viral infectivity) leading to a gene copy number reduction (Vincent et al., 2017). Moreover, ROS formation contributes to the death of the cell via interaction with viral envelope or capsid (Imani et al., 2020).

TiO2. The antiviral mechanism of TiO2 is based on electron/hole generation, absorption of light, and the oxidation of organic matter via ROS, which disrupts the lipid membrane and genetic materials, eventually leading to viral inactivation (Imani et al., 2020).

Since the initiation of the COVID-19 epidemic, new disinfectants and antiseptics formulations are being developed to limit disease transmission. As aforesaid, one of these changes is the use of NMs in their formulations (Abd Elkodous et al., 2020).

The action mechanism of NMs against the COVID-19 virus could be classified in distinct stages, before and after the viral entry inside the host cell (Fig. 1). Various kinds of NMs, like polymeric or virus-like NMs (Abd Elkodous et al., 2020), can inhibit the entrance of the virus inside the host cell by preventing it from attaching to the angiotensin-converting enzyme 2 (ACE2), which is the host cell receptor or the spike protein of the virus, through which the virus penetrates via the clathrin-mediated endosomal pathway (Almasi & Mohammadipanah, 2020). The spike protein NMs of virus can inhibit the viral entry or provoke the immune system to produce antibodies against it. Moreover, liposomes and nanoemulsions could break down the lipid bilayer envelope, which destroys its structure. Inorganic NMs could also produce extracellular ROS to kill viruses. Once the virus enters the host cell, Nanomaterials could provoke ROS, improve the propagation of lymphocytes, cytokines overexpression (IL-1B), and the generation of neutralizing (IL-4, IL-5, and IL-13) or opsonizing (C4b, IgE, C3b, and IgG) antibodies via Th1 or Th2 immune reactions, respectively (Abd Elkodous et al., 2020).

Fig. 1
figure 1

Molecular targets of SARS-CoV-2 which could be inactivated by NMs. Mechanism of action outside the host cell includes (I) inhibiting the viral entry inside the cell, (II) solvation of the lipid bilayer envelope of it, and (III) production of ROS via inorganic NMs. Mechanisms of action inside of the cell are overexpression of cytokines, polyprotein processing, transcription of the viral genome, blockage of viral uncoating, translation of the viral protein, and the most common mechanisms are activation of transcription agents through receptor signaling as a response of viral RNA, and the production of (IL-1B), and activation of the Th2 route, which leads to the production of neutralizing antibodies, or Th1 route, leading to the production of opsonizing antibodies, which are shown above (Abd Elkodous et al., 2020)

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Approved Nanomaterial-Based Disinfectants

The antimicrobial activity of NMs depends on numerous factors, including (i) size of the NMs, since there is an optimum size that results in optimum antimicrobial activity because of the quantum size effect (Morones et al., 2005). The size difference between the NMs (10–9 m) and microorganisms (10–6 m) favors the antimicrobial action because some NMs can penetrate through the cell membrane. (ii) the shape of the NMs, since the more faceted the particle, the greater its antimicrobial efficiency due to more outstanding adhesion and contact with microorganisms (Cacciatore et al., 2020; Pal et al., 2007). (iii) surface charge, since the electrostatic interactions are favored when the NM has positive zeta potential as microorganisms present negatively charged bacterial wall. (iv) microbial sensitivity to NMs, since the organisms have different sensitivity due to their morphology (Cacciatore et al., 2020). Some of the approved disinfectants containing NMs as the main component are shown in Table 3.

Table 3 The commercial NM-based products approved for surface or skin disinfection (https://statnano.com/)
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Nanomaterials with Antiviral Activity Against SARS-CoV-2

As mentioned in previous sections, the main NMs with anti-coronavirus features are Quantum dots, synthetic virus-like particles, nanostructured lipid carriers, polymeric nanocapsules, carbon nanotubes, carbon dots, metal nanoparticles, nanostars, and magnetic nanoparticles (Table 4). The effect of Lipid Nanoparticles (LNP) and Virus-Like Particles (VLP) on SARS-CoV-2 have often been investigated in cell line and animal models including HEK 293 T, HeLa, Vero E6, and Freestyle CHO-S cells and animal models like transgenic hACE2 mice, C57BL/6 mice, BALB/C mice, Rhesus macaques, and Syrian golden hamsters (Geng et al., 2021; Ma et al., 2020) (Table 4).

Table 4 Nanomaterials with anti-coronavirus activity (Carvalho & Conte‐Junior, 2021)
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Toxic Effects of Nanomaterials on Health

Nanotoxicity concerns are primarily raised by tiny dimensions of nanotechnological NMs and are secondly correlated to type and duration of exposure, NM penetration depth, preferential localization, and local delivery and/or systemic translocation (Baroli, 2010). Studies have shown that NMs may provoke the fragmentation of chromosomes, DNA strand breakage, point mutations, and modifications in gene expression (Singh et al., 2009). The toxicological studies of NMs so far have shown that the entry of NMs through inhalation, ingestion, and skin is of utmost importance, respectively (Laux et al., 2018). Repeated application of antiseptics can bring along the penetration of NMs through inhalation and skin. The entrance of NMs into the cells are demonstrated in Fig. 2.

Fig. 2
figure 2

NMs enter into the cells through endocytosis and endocytosis-free pathway. The endocytosis pathway can provoke intensive harm to the cell in contrast with the other one. The acidic environment of the lysosome leads to the burst discharge of NMs that interact with the proteins of cytosol and other molecules producing ROS, which mediate oxidative stress into the mitochondria, so cytochrome c is discharged. Discharged cytochrome c connects to Apaf-1, which stimulates the caspase cascade reaching to caspase-dependent apoptosis, leading to cell death and DNA fragmentation (Zielińska et al., 2020)

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Before any toxicological trial, a comprehensive and precise characterization of the contents of the nano-based antiseptics/disinfectants is essential. Duke et al. has proposed a three-stage solution for determining the properties of NMs, which includes (I) appearance properties of the composition like size, morphology, and surface area (II) dispersion properties including aggregation or agglomeration, and (III) interface of nano-bio (Laux et al., 2018).

Skin Adsorption

The skin is the most extensive (~ 10%) body part, which has a pivotal protective function (Crosera et al., 2009). The epidermis has a complicated structure consisting of composite physical and chemical systems and barriers at the nano- and micro-scale that, all together, form what is generally referred to as the defensive barrier.

Based on physicochemical features and integrity of barrier, NMs can enter the skin in four ways, including intracellular, extracellular, and two transappendageal via follicles of hair and sweat glands (Crosera et al., 2009). Sometimes skin exposure to NMs is intentional, such as dispersion of a liquid or creamy fluid (sunscreens having titanium or zinc oxides) or textiles (antimicrobial gauzes containing AgNPs) (Baroli, 2010) even though, allergic reactions also occur due to this penetration. Studies with macroscopically non-compromised skin showed that nanotechnological NMs mainly accumulate in SC (stratum corneum) and HF (hair follicle) infundibulum (Table 5). Even small permeation of agents inside the superficial strata of SC may lead to fatal reactions (Baroli, 2010). Figure 3 has been shown that NMs could induce cytotoxicity, genotoxicity, endothelial activation, and impairment of NOS signaling.

Table 5 The skin absorption studies of NMs
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Fig. 3
figure 3

Schematic illustration of toxic effects of NMs on endothelial cells. NMs could provoke cytotoxicity (necrosis, apoptosis), genotoxicity (DNA destruction), the activation of endothelial (adhesion molecules, the adhesion of monocyte), and NOS dysfunction (over-production of ROS) in endothelial cells. LDH Lactate dehydrogenase, NOS Endothelial nitric oxide synthase (Zielińska et al., 2020)

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Epigenetic Effect

Inappropriate regulation of cellular epigenetic mechanisms can be deleterious to health making it a necessity to analyze the effect of NM exposure on epigenetic pathways. The mechanisms are methylation and hydroxymethylation of DNA, posttranslational adjustment of histones tails, remodeling of chromatin, methylation of RNA, and non-coding RNA. Epigenetic modifications, which can change in response to specific cellular and environmental status, could be permanent or even passed on to later generations (Table 6). Since these modifications play crucial roles in regulating various cellular activities like gene expression, DNA replication, and recombination, they could affect exposed people and their next generation (Sierra et al., 2016; Stoccoro et al., 2013) [52].

Table 6 Epigenetic effects of some NMs and their current applications
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Cell Accumulation

NMs are being used due to their novel features, while nanotoxicological studies are relatively neglected. NMs could enter the mucosal membrane by inhalation, and NMs lighter than 10 μm could rapidly penetrate the respiratory system. The extent of cellular destruction depends on the size of NMs, which means the smaller the NMs, the stronger their damage (Rai et al., 2020).

These NMs can accumulate in alveoli and cause inflammation in the lungs. Also, repeated exposure to them induces alveolar cell injuries, penetrates the blood vessels, and could be transmitted to other organs by systemic circulation (Rai et al., 2020).

Because there is no mechanism in the body to exclude the majority of NMs, NMs with low-solubility that have accumulated in the tissues and cells can remain for a longer duration. Metal NMs also reduce the viability of the cells and induce ROS, which leads to oxidative stress and cellular irreversible damages. The accumulated ROS inside the cell communicates with the cellular protein machinery and consequently can modify whole cellular processes, destroying mitochondria and nuclear DNA, leading to apoptosis (Cioffi & Rai, 2012; Rai, Ashok, et al., 2020; Rai, Bonde, et al., 2020).

Biological Accumulation

Detrimental effects of NMs on biology, particularly their toxic effects on plants, are among the most frequent study cases. NMs like carbon could even repress the plant nutrients absorption; others could restrain the content of plant protein, carotenoids, and chlorophyll. NMs can also be transferred from roots to leaves, entering the food chain. Generally, bioaccumulation factor (BAF) is a chemical mass per kg biomass in an organism to that in water (Hou, et al., 2013). As an example, Ag negatively affects the remediation process of the plant, ZnO, even at low concentration has a toxic effect on Hydrilla verticillata and Phragmites, and Ag, CeO2, Co, and Ni influence Ocimum basilicum L's fresh weight (Zhu et al., 2019).

Environmental Impact of the NM Containing Wastes

Despite the progress mentioned earlier in NM technology, data on the potential impacts of NMs on personal health is insufficient. The remediation process of NMs is essential because they are not detectable and may have long-term destructive effects on the environment by their persistent presence in the environment. Although some approaches such as green nanoscience have been introduced to decrease the detrimental outcomes of NMs on health and the ecosystem, their environmental discharge must be avoided (Iavicoli et al., 2014; Kabir et al., 2018).

NMs with various shapes as free NMs, functionalized NMs, aggregates, or embedded in a matrix can be found in the ecosystem (Nowack & Bucheli, 2007). The fate of NMs in environmental conditions is related to their interactions with different contaminants and their physicochemical features (Kabir et al., 2018; Maiti et al., 2016). According to their type, they may be discharged into the air and persisted in aerosols and the soil, sediment, and surface water for a long time or absorbed by organic molecules or biological systems. Therefore, their accumulation can cause an ecotoxicological risk, biodegradation, or bioaccumulation in the food chain. In this part, we present the destiny of NMs in various environmental matrices.

Air There is not enough information concerning the environmental destiny of NMs, particularly after releasing into the atmosphere. In all phases of the life cycle of NMs (e.g. generation, transportation, storage, and usage), it might swift release into the ambient atmosphere (Kabir et al., 2018).

Soil Soil is a multilayer matrix and complicated interface among several materials and organisms. Since NMs have a large surface area, NMs can adhere to the particles of the soil. Moreover, large aggregates of NMs through precipitation and purification could be immobilized in small holes. Plants could absorb and transport NMs from the soil, thereby affecting the germination and plant growth (Hong et al., 2014; Khodakovskaya et al., 2009).

Water NMs could immediately enter the aquatic ecosystems through industrial discharge, dumping of wastewater, and surface runoff from soils (Batley et al., 2011; Kabir et al., 2018). Several factors such as aggregation, distribution, reactions among different elements, organic matter, and aerobic, anaerobic, and abiotic degradation may influence the concentration of NMs in aquatic ecosystems. Exposure of NMs to aquatic organisms poses many detrimental consequences, such as DNA fragmentation,, oxidative pressure, and growth reduction (Kabir et al., 2018).

Concluding Remarks

Numerous reports are available demonstrating remarkable bioactivities of NMs, including antiviral activity against RNA viruses, due to their unique physicochemical properties. Due to its potent antiviral nature, specific NMs have been used to prepare various nano-based disinfectants and antiseptics.

In this report, the latest advancement in studying NMs and disinfectants are discussed from three perspectives: positive impacts, toxicity, and their mechanisms of action. The type of nanomaterial that has been studied for augmentation of antiseptics and disinfectants included polymeric, self-assembling proteins, inorganic and peptide-based among which inorganic nanomaterial are more frequently studied and applied for these purposes.

Despite this remarkable antiviral effect at low concentration, there is a serious consequence in the long-term application of nanomaterial in the antiseptic formulation which has been underestimated. Although NMs have molecular targets and remarkable antiviral activity to inactivate several viral pathogens, these compounds have toxic effects on social health and the ecosystem due to the accumulation of their wastes in the environment and the inability to eliminate or detoxify them from the ecological cycles.

Some investigations have shown that these nanoparticles can produce critical impairment in respiratory sites and toxic effects on the skin, and even could weaken lung function. The oxidative stress, inflammation, fibrosis, and genotoxicity are among pathological consequences of the repeated exposure of human cell lines to nanomaterial (Imani et al., 2020).

As a result, the prevalent commercialization and usage of NM-based disinfectants during this pandemic can have long-lasting detrimental effects on human health and other animals, environmental microorganisms and plants in the ecosystem (Hossain et al., 2014; Imani et al., 2020; Zhu et al., 2019). According to multiple studies, these formations are influencing the environment by several mechanisms, e.g. (i) by raising the non-decomposable contamination level of air, soil, and water, (ii) through environmental accumulation, and (iii) via changing the life-cycle of living systems in the ecosystem (Kabir et al., 2018).

Future Perspective

The effect of NMs exposure is starting to be analyzed, and to reveal the full impact of such disclosure on human physiology, a great deal of effort needs to be made. However, precise prediction can calculate the toxicity potential of nanomaterial-based antivirals and decrease their long-term side effects. This prediction can be also achieved by a machine learning approach like the other lines of applications for control of SARS-CoV-2 (Sadeq et al., 2021).

Besides, the principal focus of later studies is to expand biocompatible and biodegradable NMs without any cytotoxicity, developing new techniques for nanotoxicology analysis, defining the level of exposure and level of discharge for different nanoparticles, understanding the biological effects of NMs in the environment.

Considering the ecological destiny and the possible consequence of NM on ecotoxicity, it appears essential to recognize the modifications of NMs during their diverse life cycle steps since they are capable of changing the toxic properties of substances in different conditions.

Moreover, NMs are extremely reactive constructions; they may interact with different contaminants and make more/less virulent forms. So investigations should also be included in the forthcoming analysis.