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The Importance of Essential-Oils in the Green Synthesis of Silver Nanoparticles

  • Received : 2022.03.21
  • Accepted : 2022.05.16
  • Published : 2022.08.20
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Abstract

The antibacterial activity of metallic nanoparticles (NPs), especially silver (Ag), has been investigated during the course of time in various chemical reactions for antibiotics free agents. Green synthesis of metallic NPs using either microorganisms or plant-extracts has appeared as a simple and replacement to chemical and physical methods. The synthesizing of these NPs through ecofriendly methods signifies an exceedingly applicable approach for offering economical, preferring scalability and possessing negligible ecological influences. Essential-oils are among the subordinate metabolites of plants and their antibacterial anti-inflammatory characteristics have been investigated widely and are commonly attained from the aromatic plants. The usage of essential-oils as reducing agents in biosynthesizing of Ag NPs bring together the interaction of a vital antibacterial agent that simplify the nucleation and growth process within the NPs formation. This review article is offering a progressive process of Ag NPs synthesis using essential oils along with proposing the most applicable formation mechanisms and their antibacterial activities.

Keywords

INTRODUCTION

Metallic nanoparticles (MNPs) have received increasing attention in the literatures due to their predicted chemical and physical properties,1 which cover antibacterial,2 catalytic,3 optical,4 electronic5 and magnetic activities.6 Nanoparticles are particles their size are between 1 and 100 nanometers, they have unique characteristics such as; local density of states,7 quantum confinement8 and excitation of surface Plasmon.9 They have promising properties which make them suitable candidate in various applications.10 The efficiency of MNPs for usage in applications such as those mentioned above is favored by the larger surface area, which gives the possibility of functionalization of active surface sites, stability and good adsorption capacity.11 Different MNPs have been synthesized and utilized in diverse areas. For instance, gold, silver, zinc, palladium and platinum, have been used in many sectors such as energy,12 medicine,13 agriculture,14 environment15 and biotechnology.16 MNPs can be prepared by three different methods namely; chemical, physical and biological or green methods.17 The chemical synthesis can be conducted in alcoholic medium, Microemulsion, via thermal disintegration of metallic salts and electro-synthesis. Also, the chemical method involves the usage of chemical agents, most of them in general, are toxic and harmful to the environment and the human being.18,19 While the physical method through utilizing evaporation-condensation, amorphous crystallization, pyrolysis and milling needs high energy and sophisticated equipment to produce NPs.20 In fact, the physical fragmentation and other processes comprising attractive force between the particles at the nanoscale,21 which involve different treatments can be considered a limiting factor, given the high techniques cost.22 In contrast the biological method, involves the reduction of metallic ions through the reaction of plant extracts, explicitly essential-oils, and microorganisms, including bacteria, fungi, yeasts and algae.23 This method is known as green or biological synthesis and has been used for reducing environmental impacts during the production process of NPs.24 This is owing to the reduction process needs sufficient amount of chemical agents which are responsible to generating of toxic by-products, or the processes need highly sophisticated and overpriced equipment.25 In continuation of our recent works26−37 regarding green synthesis nanomaterials, In this study, the author is highlighting the significance of essential-oils in the biosynthesizing process of Ag NPs. Among the metallic NPs, Ag NPs display excessive potential in the scientific community owing to their wide range of applications.38 In this review, the author is focusing on Ag NPs owing to its sole and progressively applications in different fields, comprising medical, food, health care, customer, and industrialized resolves, owing to their exclusive physical and chemical characteristics. These, also, comprise optical, electrical, thermal, and biological features. In addition, the superiority of Ag NPs is as a result of their nature, dimension, crystallinity, configuration and construction compared to the bulk analogues.39,40 These innovations have been employed in a large scope of possible applications for example biomedical tools, medicine, renewable energies, makeups, ecological remediation, food, user, and industrialized resolves.41

Thus, the main aim was to conduct a qualified review analysis on the green synthesis routes of Ag NPs. To realize this aim, a study plan was settled comprising the synthesis of Ag NPs through diverse bottom up approach, classifications, and analysis of antibacterial activity. The current study emphases more on the biological synthesis route of Ag NPs using essential-oils originating from different plant extracts.

GREEN OR BIOLOGICAL SYNTHESIS OF NANOPARTICLES

Biosynthesis, phytosynthesis or green synthesis of NPs has the advantages of reducing the energy consumption.23 This synthesizing method is isolated from using hazardous/toxic chemical elements, sophisticated and overpriced laboratories for NPs preparation.42 In plant extracts (Fig. 1) based green synthesis it is possible to produce Ag NPs through the reaction of the available secondary metabolites in these extracts, such as flavonoids, terpenes, alkaloids, phenols, saccharides and many others.43 These biomolecules are able to reduce Ag+ ions into metallic zero valent Ag0.44 These plant extracts function as reducing, capping and stabilizing agents.45 Yousaf et al.46 described the biosynthesis of Ag NPs utilizing the aqueous of Achillea millefolium L. extract. They showed that Ag NPs possess an average diameter of 20.77, 18.53 and 14.27 nm for spherical, rectangular and cubical shapes, produced from aqueous, ethanol and methanol extract correspondingly.

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Figure 1. Proposed mechanism of the biosynthesizing Ag NPs from plant extract.

Our group,30 utilized a rapid and easy method for biosynthesizing Ag/bentonite nanocomposite utilizing Euphorbia larica plant extract as a stabilizing and reducing agent. We found that the average size of green synthesized Ag NPs was assessed to be less than 32 nm. The catalytic activity of Ag/bentonite nanocomposite was examined in some organic dyes. Promising results obtained from this investigation showing that Ag/bentonite nanocomposite is a suitable candidate for degradation various organic dyes from wastewaters. In addition to utilizing plant extracts for synthesizing Ag NPs, it is possible to use microorganisms such as bacteria and fungi which are described as potential candidates for biosynthesizing of Ag NPs with different size and shapes.47 Kathiraven et al.48 synthesized Ag NPs using a marine algae, Caulerpa racemosa. They showed that the average size of Ag NPs was in the range of 5-25 nm. The biosynthesized Ag NPs showed the optimum antibacterial activity against human pathogens such as Staphylococcus aureus and Proteus mirabilis. Other groups such as; Quinteros et al.49 and Srivastava et al.50 individually synthesized Ag NPs, the average size was between 25-45 nm and 1-50 nm, from Pseudomonas aeruginosa and Fusarium oxysporum respectively. It can be stated that, this one-pot process is possible since fungi and bacteria of different species are able to excrete enzymes and other proteins that act as reducing agents.51 There is also possibility of utilizing the biomass of these microorganisms in the synthesis of NPs through distinct bioprocesses.52 However, synthesis of NPs using microorganisms is responsible for formation of cluster contamination, complexity of pro-procedures and less control over the size of NPs.53 On the other hand, different types of algae and microalgae can be used to produce different size and shape metallic NPs.54 Özturk et al.55 and Annamalai and Nallamuthu56 independently synthesized Ag NPs from Gelidium corneum and Chlorella vulgaris as reducing agents and the resultant size of Ag NPs were 20-50nm and 15-47 nm in that order. It is significant to emphasize that the particle size control of antibacterial agents, in particular, Ag NPs is the limiting factor for the toxicity of the final product.57 Kim et al.58 studied the size dependent cellular toxicity of Ag NPs by means of three different individual sizes, 10, 50, and 100 nm, against numerous cell lines. This is particularly important since it proposed that the size dependent Ag NPs can be utilized for biomedical usages.

Essential-Oil Mediated Biosynthesis Nanoparticles

In addition to the above described possibilities, recent studies have evaluated the efficiency of essential-oils (Fig. 2) from different plant extracts using green synthesis method, as these oils are complexes and responsible for bio reductive reaction.

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Figure 2. Photograph of some plants produce essential-oils.

Essential-oils are typically attained through vapor-distillation of aromatic plants, particularly those utilized as colognes and flavorings in the perfume and food manufacturing, correspondingly, and in recent times for herbal medicines and biosynthesis of metallic NPs. Chemical composition of some of the essential-oil elements are shown in Fig. 3 and several of them have strong biological activity and they are responsible for reducing, capping and stabilizing metallic NPs. These essential-oils are normally composed of multifaceted mixtures of monoterpenes, genetically related phenols, and sesquiterpenes. In fact, synthesized metallic NPs from plant essential-oils possess numerous significant advantages. Owing to their volatile-nature, there is a much lower level of danger to the surroundings than with present synthesizing methods.

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Figure 3. Chemical structures of essential oil constituents.59

Alfuraydi et al.60 showed that it is possible to synthesize Ag NPs through incubating AgNO3 with sesame essential-oil. This process can provide spherical NPs with diameters between 6.6-14.8 nm. Brindhadevi et al.61 studied the anti-microbial activity of wound fabrics treated with Ag NPs, sodium alginate and labdanum essential-oil.

It can be stated that, the essential-oils are utilized to reduce metal ions into NPs due to their complexity and diversity of the available reducing biomolecules.62 In addition, some functional groups of essential-oils may interact differently to neutralize ions as well as forming bonds that are necessitate in the nucleation process.63 de Melo et al.64 described the mechanism of biosynthesis of Ag NPs using essential-oil of thyme, Thymus vulgaris. This method is environmentally friendly method and it can be deliberated as a replacement approach to produce Ag NPs with optimum stability and extraordinary antibacterial activity. According to de Melo et al.,64 the reduction process from Ag+ to Ag0 occurred through the donation of H+ protons from borneol, a compound with higher concentration found in the essential-oil, with the simultaneous stabilization of borneol through the Na+ existing in the solution precursor. The reducing reaction of the essential-oil of thyme, Thymus vulgaris, was investigated throughout the Ag NPs formation, and its antibacterial activity against Escherichia coli and Staphylococcus aureus were evaluated.64 The nanoparticles had a spherical shape with an average size of 90 nm, and absorbance peak between 415 and 440 nm. Seventeen different compounds, by means of gas chromatography, were identified in the essential-oil. It is found that, most likely, barneol and α-terpineol are the major compounds, and perhaps they are responsible for formation of Ag NPs with potential anti-bacterial activity. Azizi et al.65 using essential-oil ginger, Zingiber zerumbet synthesized zinc oxide-silver, ZnO-Ag core-shell nanocomposite through utilizing the green method. In this study six gram-positive and gram-negative pathogens were utilized to study the antibacterial effect of these samples. It was found that, through the in vitro tests, Ag doping improves the bactericidal activity of ZnO NPs. This is, perhaps, due to that the essential-oil of ginger was efficient in the biosynthesis process and producing comparable nanocomposites to the conventional methods, which use hazardous and expensive chemical agents.65 Qaralleh et al.66 stated that Ag NPs can be synthesized by means of the culture supernatant of the fungal strain Tritirachium oryzae. Then the antibacterial activity of Ag NPs independently and in combination with some antibiotics and essential-oil of the Centaurea damascene plant extract were investigated. Ga’al et al.67 using essential-oil of Aquilaria sinensis extracts produced Ag NPs from green, quick and one-pot process. Ag NPs with average sizes ranging between 15 and 87 nm were obtained, and they exhibited significant antibacterial action. In addition, Ga’al et al.67 indicated that Ag NPs shows toxicity against the mosquito even at low doses. It is important to highlight the principle of the essential-oil reaction in reducing silver. Vilas68 and the coworkers utilized essential-oil present in plant parts as the bio-reducing agent for synthesizing Ag NPs. The chromatography analysis showed that the compounds in higher concentration were terpenes and terpene alcohols. At high temperatures terpene hydrocarbons are capable of cleaving double bonds, then perform the oxidation and dehydrogenation process. This mechanism leads to the formation of free radicals. These free radicals, in turn, are capable participate in reducing heavy metal ions such as Ag. In general, the silver reduction reaction involves balancing electron donation. The formation of Ag0 and its clustering sequence is known as the nucleation process. The combination of numerous Ag0 through the nucleation step forms a nanoparticle. The essential-oil biomolecules, in addition to participating in the bio-reduction of AgNO3, can link to the surface of the NPs making them more stable.64 Table 1 summarizes the main products obtained from the reducing action of essential-oils in metallic Ag NPs.

Table 1. Metallic Ag NPs biosynthesized from essential-oils from different plant extracts

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General Mechanisms of Formation Metallic NPs using Essential-Oils

Essential-oils are considered as suitable candidates in green synthesis metallic NPs.69 The possible mechanism of formation metallic NPs involve three possible complexation reactions as shown in Fig. 4. The first reaction occurs between the main components of essential-oils, such as: phenolic acids, flavonoids, terpenoids and anthocyanin; and the selected metal ions.1 The second possible reaction is occurring between the hydroxyl groups of anthocyanin, flavonoids and phenolic acids. Essential-oils, in turn, can directly cause the reduction of metallic ions. So the substances, the essential-oils, through their hydroxyl groups, combine with the metal ions resulting in formation of some compounds before producing the final metallic NPs through the reduction process.80 These transition compounds form NPs through electron transfer and the produced NPs will be coated with anthocyanin and phenolic acids. In the third stage of reaction, which is much slower, the other biomolecules present in the essential-oils, which do not possess reducing capacity in the solution, they diffuse continuously to the solid-liquid interfaces formed in the core of metallic NPs.81

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Figure 4. Complexation reaction as a possible mechanism for green synthesis of metallic NPs mediated by essential-oils.

The non-reducing surface coating derived from the essential-oils can be absorbed by the metallic NPs, contributing to greater stability in the synthesized NPs.77 Thus, as described in Fig. 5 the NPs formation process can be generalized by three main steps: the oxidation-reduction, nucleation and growth.82

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Figure 5. General steps of metallic NPs formation.

In the redox step, the functional groups of essential-oils, i.e. reducing agent, containing oxygen in the ligand they donate π electrons to the transition metal, i.e. oxidizing agent. In this process, the metal ions suffer from reduction as it oxidizes the chemical components of the essential-oils. In some cases, the thermal decomposition of the ionic complex of the precursor metal salts increasing the reaction rate.83 In the nucleation and growth stages, a series of metastable phases are actively promoted by the action of essential-oils, until the colloidal solution reaches a thermodynamically spatial stable stage.84 Within the thermodynamically stable stage, the atoms that experienced reduction in the reaction medium, give rise to groups that reaching a certain characteristic size form a stable particle. The smallest radius of stable nucleolar ions is characterized by its critical radius, whose properties are given by the capacitive ability of the essential-oil to maintain surface free-energy stability with respect to the surface area of the nucleation group.85 Thus, the greater the balance between these two factors, the greater the size of the critical core stable.86 Regarding the nucleation studies, there are two types of processes: homogeneous nucleation and heterogeneous nucleation.87 Homogeneous nucleation occurs in a single step, where the concentration reaches a critical supersaturating condition, and allows uniform diffusion growth of the reduced atoms to the formed core. In heterogeneous nucleation, the formation of nuclei occurs by the action of nucleating agents, these being the growth promoters of the particles.88 The next step after nucleation is called growth, a process in which the nuclei migrate to the surface of the solute. In this process, the transport of reactive species to the surface of the particles occurs, coalescence and aggregation that can compete with the growth process.89 At this point the stabilizing action of the essential-oil can balance the growth of the NPs by stabilizing them. The electrostatic potential of the electrical double layer on the surface of the NPs, i.e. Columbic repulsion, decreasing the NPs Polydispersity index.89

Factors Affecting the Biosynthesis of Metallic NPs

Different factors are involved in the synthesizing process of metallic NPs. The reaction and interference of chemical and physical parameters involved in reduction of metal ions has been studied intensively.90 As shown in Table 2, temperature, pH and reaction time are among the main factors that directly affect the size and morphologies of NPs. In green synthesis method, the concentration and amount of the bio-reducing agent are also among the factors that have impact on the size, shape and stability of NPs.62 The combination between pH and temperature begin to determine the size and shape of these nanostructures given the importance of the role of thermal agitation in the efficiency of the nucleation process and growth of nanostructures.91 In general, the created Ag NPs are stable under pH 9 and they start agglomeration at pH greater than 9.92 Accordingly, most of the pH values in Table 2 are below pH 9. As described before, an increase in temperature leads to an increase in both the plasmonic bands and the rate of formation of NPs. This feature is characteristic of the formation of nanostructures, which leads to decreasing their average size, given the contribution that temperature makes to the nucleation rate of nanostructures faster.93 These consequences specify that the influence of temperature not only impacts the reaction rate but also affects the morphologies of Ag NPs in the plasmonic mediated reaction.

Table 2. Parameters affecting the biosynthesis of Ag NPs using essential-oils from different plant extracts

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Another important point which brings to our attention from Table 2 is that the majority of the reaction temperature is less than 100℃. This can be directly related to producing the spherical shape of Ag NPs. This, in turn, might be explained utilizing the Gibbs free energy equation, ΔG = ΔH – TΔS, where ΔH is the enthalpy change and ΔS is the entropy change. The spherical Ag NPs possess a larger surface area to the volume ratio than the other shapes, therefore, it is more likely, to generate smaller entropy and smaller heat of formation. The precise reaction at a low temperature causes spherical NPs since at a lower temperature |ΔH| is greater than |TΔS|. Conversely, the precise reaction at a high temperature causes nonspherical shape formation since |TΔS| is greater than |ΔH| at a higher temperature.94

Vilas et al.68 reported that essential oil of Myristica fragrans can be used for synthesizing Ag NPs. This preparation method provides highly pure crystalline Ag NPs with average size between 12-26 nm. These biosynthesized Ag NPs possess excellent catalytic and bioactive activity due to their surface modification. Nishanthi96 and coworkers stated that Ag NP can be synthesized within a green and environmentally friendly method using the extract of the fruit of Garcinia mangostana. The formation of Ag NPs occurred at 80℃. This process took place through the reaction between increasing temperature and increasing the rate of reaction as well as the formation of nucleation center.91 The pH of the reaction medium also plays a key role in the formation of NPs. Just like the temperature, pH regulates the formation of nucleation centers. As the pH increases, the number of nucleation centers also increase.96 It is significant to high-light this point since the oxidation of phenolic groups is accompanied by the release of H+ ions, and therefore the nucleation of Ag NPs is expected to be preferred in an alkaline medium. This step, in turn, leads to the synthesis of smaller particles and also by the production of Ag2O, element according to the following reaction:

2Ag+ = 2OH− → Ag2O + H2O

Maciel et al.69 conducted a study on biosynthesizing Ag NPs using essential-oil of Syzygium aromaticum. They have evaluated the formation of Ag NPs under different pH conditions, i.e. 7, 8, 9 and 10. As anticipated, smaller diameter Ag NPs were formed with the increase of pH values and an increase in the polydispersity index is also observed. Zeta potential standards provide evidence about the surface charge around the NPs and stability of the synthesized Ag NPs.97 The zeta potential of the biosynthesized Ag NPs for pH ranging from 7 to 10 also increased in that order. Depending on the pH values Ag NPs possess sizes between 31 and 72 nm, and different shapes, namely triangular, square, hexagonal and mostly spheres. de Melo et al.64 carried out an investigation using thyme essential-oil for synthesizing Ag NPs. They evaluated the formation of the NPs under different pH conditions, i.e. pH 7, 8, 9, and 10, as shown in Table 3. However, the highest maximum absorbance from the UV-Vis spectrum obtained at pH 10, the maximum absorbance at 440 nm. Regarding the size of the Ag NPs, the pH of the solution interfered differently in the mean diameter of Ag NPs. For instance, at pH 7 the average diameter for Ag NPs was 40 nm, while at pH 10 the average diameter increased to 90 nm. According to our best knowledge a conceivable reason for this outcome is that once the pH value is increased, the reaction rate will be increased as well, with consequent crystallization into smaller particles, which involved the nucleation and growth procedures of smaller particles from Ag nuclei.98 In other words, pH value is critically affects the nucleation kinetics of Ag NPs formation. In another attempt Guimarães et al.99 using the extract of Ziziphus joazeiro produced Ag NPs with different sizes. In an alkaline environment, i.e. pH 11, the Ag NPs displayed high polydispersity index with different sizes NPs. However, in the neutral condition, i.e. pH 7, NPs with smaller size and reduced degree of agglomeration were obtained. Along with temperature and pH, reaction time is also described as one of the main factors that influence the morphology and size of NPs.100 This is more likely due to the fact that prolonged kinetic reaction can be conducted to a process of excessive agglomeration of the nuclei forming nanostructures making Ag aggregates on a microscopic scale. Besides, the variation in the conditions of the medium pH and the favored kinetic reaction that supplied to the system through the thermal energy is determine a characteristic time for the optimized reaction. This, in turn, producing materials with a low polydispersity index.101 In addition to these conditions, i.e. prolonged reaction time, the formation of large aggregates is induced, which affects the antibacterial property of the system. On the other hand, Veisi et al.73 biosynthesized Ag NPs utilizing essential-oil of orange peel. The prepared solutions were monitored at different time intervals, i.e. 0 h, 12 h, 14 h, 36 h and 48 h, at a fixed temperature, 70 ℃. The absorbance peaks of Ag NPs, recorded from UV-Vis spectrum, increased with increasing the interaction time of the silver nitrate with the essential-oil. The reaction time proved to be important factor in the reduction of the Ag+ ions in Ag0. The highest absorbance maximum peak found at 412 nm after 48 hours of reaction. Alfuraydi et al.60 using sesame essential-oil, Sesamum indicum, synthesized Ag NPs. In their study, the formation of Ag NPs at different time intervals, i.e. 96, 120, 146 and 170 h, was monitored. However, the color change of the solution from colorless to brown occurred after 48 h, confirming the formation of Ag NPs. From the UV-Vis spectrum, a characteristic Surface Plasmonic Resonance (RPS) band was obtained of Ag NPs. The absorbance peak increased with increasing the interaction time of between Ag NO3 solution and the utilized essential-oil.60

Table 3. Antibacterial activity of Ag NPs biosynthesized from different essential-oils

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Size, Shape and of Ag NPs Biosynthesized from Essential-Oils

The size, shape, and surface area per unit volume of nanoparticles can significantly influence their applications. Therefore, this review articles aimed to highlight the common size and shape of the utilized Ag NPs using essential-oils. The corresponding size and shape of Ag NPs biosynthesized from essential-oils using the utilized references in Table 2 can be find in Table 4. It can be noticed, from Table 4, that the utilized essential-oils, in general, are able to produce spherical NPs. In terms of the size, it can be seen from Table 4 the size of the biosynthesized Ag NPs using different essential-oils are ranging between 6-92 nm. This a good indicator that the wide range Ag NPs size can be obtained by changing the type of the essential-oils.

Table 4. TEM, SEM images, size shape of the Ag NPs biosynthesized using essential-oils

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Antibacterial Activity of Ag NPs Biosynthesized from Essential-Oils

The biosynthesized NPs from essential-oils have been applied as alternative antibacterial agents to combat pathogenic bacteria.64,66,69,102−104 The selected results found in the literature are presented in Table 3, which show the anti-bacterial activity by the inhibition halo method where (-) results indicate non-sensitive result with diameter halo less than 8 mm, (+) sensitive with halo between 9-14 mm, (++) very sensitive with halo between 15-19 mm and (+++) extremely sensitive with a halo greater than 20 mm.

It is significant to note that, the measurement of the halo of inhibition, shown in Table 3, signifies a qualitative analysis of the antibacterial action of the compounds, characterizing the diffusion capacity of the species with high toxicity against bacteria. It can be seen that, there is no direct relationship between the essential-oil and the size of the halo of inhibition, since the antibacterial action of the biosynthesized NPs depends on multiple factors, such as interaction of NPs with cell walls that vary according to the nature of the bacterium, i.e. gram-positive or gram-negative, and its own characteristics of each organism.107 However, the most important aspect refers to the antibacterial activity of all synthesized NPs, demonstrating the potential of green synthesis of NPs towards the antibacterial activity.108 A practical challenge of the reported research works is to understand what is the actual mechanisms of NPs reaction against the utilized bacteria. Vilas et al.68 in their investigation showed that how the differences in cell wall of Gram-negative and Gram-positive bacteria interfered with the action of the utilized NPs synthesized from essential-oil of Coleus aromaticus. In fact, NPs were more efficient in controlling growth bacterial strain of E. coli (Gram-negative) than that of S. aureus (Gram-positive), which has a structure able to restrict the action and permeability of NPs in cells, called peptidoglycan. A similar result was found by Alfuraydi et al.60 in their research using biosynthesized Ag NPs prepared form the essential-oil of Sesamum indicum. Ag NPs inhibited the growth of Gram-negative bacteria, i.e. P. aeruginosa, K. pneumoniae and E. coli, however they were not efficient in combating Gram-positive bacteria, i.e. B. subtilis and S. aureus. This result can be associated with the ability of Ag NPs to bind with the surface of the cell membrane of Gram-negative bacteria, causing changes in respiration and cell permeability, in addition to the protective biological barrier found in Gram-positive bacteria, which hinders the reaction of NPs.60 In contrast, Manju and coworkers109 evaluated the reaction of the NPs biosynthesized from essential-oil of Nigella sativa, obtaining greater activity against the S. aureus bacteria, Gram-positive, with halos of inhibition 16 mm, than against Vibrio harveyi, Gram-negative, with 5 mm inhibition halos. The size and shape of metallic nanoparticles directly interfere with their antibacterial activity.110 The high surface/volume ratio of NPs increases their affinity with the bacterial cell membrane.111 Furthermore, the attraction between positive and negative charges of NPs and bacterial cell membrane, respectively, increases due to the presence of lipopolysaccharide or techoic acid.112 In a study conducted by de Melo et al.64 spherical shape Ag NPs with mean diameters of 40 nm and predominance were more efficient in controlling Gram-negative bacteria, E. coli, and Gram-positive, S. aureus than bigger Ag NPs, i.e. 90 nm, and they are mainly stem shaped. Maciel et al.69 discussed the influence of the shape and size of NPs with the ability to inhibit bacterial growth. Metallic NPs can impair exopolysaccharide synthesis, making the possibility of this reaction to be zero interactions between bacteria and host cells. With decreased exopolysaccharide synthesis, hydrophobicity of the cell surface is reduced, directly affecting biofilm production in different microorganisms.113 Investigations on metallic NPs against bacterial biofilm formation showed favorable results against different bacteria. Depending on the dose, the metallic NPs are able to disintegrate and inhibit the hydrophobicity of S. aureus and V. harveyi colonies, in 78% and 46%, respectively.109 This response, perhaps, associated with inhibition of exopolysaccharide synthesis confirming the efficiency of NPs as bacterial biofilm inhibitory agents.109 The production of metallic NPs as antibacterial agents is a very essential technology. mentioned in the literature, mainly with Ag and Au NPs. The influence of essential-oils on biosynthesized NPs process is a promising strategy both from the view point of morphology, i.e. how much of the antibacterial role for the resulting system.

CONCLUSIONS

This investigation was aimed to describe researches in which Ag NPs were biosynthesized utilizing essential-oils as reducing, capping and stabilizing agents. This study showed that the biosynthesized Ag NPs possessed a cap derived from essential-oils, conferring the NPs’ stability. The mechanisms of formation as well as the applications of Ag NPs using essential-oils are also discussed intensively. Although essential-oils have not yet awakened the attention of researchers about its use in the field of green synthesis of metallic NPs, but they are an excellent natural medium for synthesizing of Ag NPs with high antibacterial activity. This investigation showed that significant results have been obtained regarding the activity of Ag NPs against strains of pathogens. It has been shown that essential-oils, are effective, inexpensive and environmentally friendly routes for synthesizing controllable size and shape Ag NPs. Accordingly, there is a possibility of controlling the antibacterial activity, since smaller size and spherical shape NPs displays optimum results. Finally, there is another factor that requires important perspectives to investigate indicates the synergy between the synthesized NPs and the reaction medium. Thus, the usage of synergy between biosynthesized Ag NPs and biomolecule capping active against particular pathogens is expected to be developed in the nearest future.

Acknowledgments

The author would like to thank Dr Mukhtar Ahmed at SISAF, Ulster University, UK, for his valuable assistance throughout this investigation. He also wants to thank Dr. David M.W. Waswa at Tishk International University for his diligent proofreading of this manuscript. And the publication cost of this paper was supported by the Korean Chemical Society.

References

  1. Ovais, M., et al. International Journal of Molecular Sciences 2018, 19, 4100.
  2. Hamouda, H.; Abdel-Ghafar, H.; Mahmoud, M. Journal of Environmental Chemical Engineering 2021, 9, 105034.
  3. Lee, S. J., et al. Environmental Pollution 2021, 269, 116174.
  4. Brett, C. J., et al. ACS Applied Materials & Interfaces 2021, 13, 27696.
  5. Bouafia, A., et al. Nanomaterials 2021, 11, 2318.
  6. Guadagnini, A., et al. Journal of Colloid and Interface Science 2021, 585, 267.
  7. Vinod, M.; Biju, V.; Gopchandran, K. Superlattices and Microstructures 2016, 89, 369.
  8. Banerjee, S.; Maity, A.; Chakravorty, D. Journal of Applied Physics 2000, 87, 8541.
  9. Nolle, E.; Shchelev, M. Y. Technical Physics Letters 2004, 30, 304.
  10. Verma, P.; Maheshwari, S. K. International Journal of Nano Dimension 2019, 10, 18.
  11. Rafigh, S. M.; Heydarinasab, A. ACS Sustainable Chemistry & Engineering 2017, 5, 10379.
  12. Konur, O. "Biodiesel Fuels: A Scientometric Review of the Research", Biodiesel Fuels 2021, 225.
  13. Salamanca-Buentello, F.; Daar, A. S. Nature Nanotechnology 2021, 16, 358.
  14. Kalita, R., et al. Nanotechnology in Agriculture, In Nanobiotechnology; Springer: 2021; p 101.
  15. Taran, M., et al. Biointerface Research in Applied Chemistry 2021, 11, 7860.
  16. Wang, W.; Yuan, J.; Jiang, C. Plant Molecular Biology 2021, 105, 43.
  17. Ingale, A. G.; Chaudhari, A. J. Nanomed Nanotechol 2013, 4, 1.
  18. Lu, X., et al. Annual Review of Physical Chemistry 2009, 60, 167.
  19. Yaqoob, A. A.; Umar, K.; Ibrahim, M. N. M. Applied Nanoscience 2020, 10, 1369.
  20. Iravani, S., et al. Research in Pharmaceutical Sciences 2014, 9, 385.
  21. Polte, J. CrystEngComm 2015, 17, 6809.
  22. Abdelghany, T., et al. BioNanoScience 2018, 8, 5.
  23. Jadoun, S., et al. Environmental Chemistry Letters 2021, 19, 355.
  24. Salem, S. S.; Fouda, A. Biological Trace Element Research 2021, 199, 344.
  25. Irshad, M. A., et al. Ecotoxicology and Environmental Safety 2021, 212, 111978.
  26. Barzinjy, A. A., et al. Inorganic and Nano-Metal Chemistry 2020, 50, 620.
  27. Barzinjy, A. A.; Azeez, H. H. SN Applied Sciences 2020, 2, 1.
  28. Nasrollahzadeh, M., et al. Materials Research Bulletin 2018, 102, 24.
  29. Barzinjy, A. A., et al. Materials in Electronics 2020, 31, 11303.
  30. Sajadi, S. M., et al. Chemistry Select 2018, 3, 12274.
  31. Barzinjy, A. A., et al. Current Organic Synthesis 2020, 17, 558.
  32. Barzinjy, A. A., et al. Micro & Nano Letters 2020, 15, 415.
  33. Shnawa, B. H., et al. Emergent Materials 2021; p 1.
  34. Barzinjy, A. Eurasian Journal of Science & Engineering 2019, 4, 74.
  35. Azeez, H. H.; Barzinjya, A. A. Desalination Water Treat 2020, 190, 179.
  36. Jabbar, K. Q.; Barzinjy, A. A.; Hamad, S. M. Monitoring & Management 2022, p 100661.
  37. Mustafa, S. M., et al. International Nano Letters 2021 p 1.
  38. Islam, M. A.; Jacob, M. V.; Antunes, E. Journal of Environmental Management 2021, 281, 111918.
  39. Syafiuddin, A., et al. Journal of the Chinese Chemical Society 2017, 64, 732.
  40. Atwater, H. A.; Polman, A. Plasmonics for Improved Photovoltaic Devices; Materials for Sustainable Energy: a collection of peer-reviewed research and review articles from Nature Publishing Group: 2011; p 1.
  41. De, M.; Ghosh, P. S.; Rotello, V. M. Advanced Materials 2008, 20, 4225. https://doi.org/10.1002/adma.200703183
  42. Martinez-Cabanas, M., et al. Nanomaterials 2021, 11, 1679.
  43. Marslin, G., et al. Materials 2018, 11, 940.
  44. Behravan, M., et al. International Journal of Biological Macromolecules 2019, 124, 148.
  45. Basnet, P., et al. Journal of Photochemistry and Photobiology B: Biology 2018, 183, 201.
  46. Yousaf, H., et al. Materials Science and Engineering: C 2020, 112, 110901.
  47. Bahrulolum, H., et al. Journal of Nanobiotechnology 2021, 19, 1.
  48. Kathiraven, T., et al. Applied Nanoscience 2015, 5, 499.
  49. Quinteros, M. A., et al. International Journal of Biomaterials 2016, 2016.
  50. Srivastava, S., et al. Microbial Pathogenesis 2019, 129, 136. https://doi.org/10.1016/j.micpath.2019.02.013
  51. Janakiraman, V.; Govindarajan, K.; Magesh, C. BioNanoScience 2019, 9, 573.
  52. Thomas, R., et al. Brazilian Journal of Microbiology 2014, 45, 1221.
  53. Siddique, S.; Parveen, Z.; Mazhar, S. Arabian Journal of Chemistry 2020, 13, 67.
  54. Mohseniazar, M., et al. BioImpacts: BI 2011, 1, 149.
  55. Ozturk, B. Y.; Gursu, B. Y.; Dag, I. Process Biochemistry 2020, 89, 208. https://doi.org/10.1016/j.procbio.2019.10.027
  56. Annamalai, J.; Nallamuthu, T. Applied Nanoscience 2016, 6, 259.
  57. Levard, C., et al. Environmental Science & Technology 2012, 46, 6900.
  58. Kim, T. H., et al. Journal of Biomedical Materials Research Part A 2012, 100, 1033.
  59. Koul, O.; Walia, S.; Dhaliwal, G. Biopesticides International 2008, 4, 63.
  60. Alfuraydi, A. A., et al. Journal of Photochemistry and Photobiology B: Biology 2019, 192, 83.
  61. Brindhadevi, K., et al. Applied Nanoscience 2021, p. 1.
  62. Sana, S. S., et al. Journal of Molecular Liquids 2021, p. 115951.
  63. Gherasim, O., et al. Romanian Journal of Morphology and Embryology 2020, 61, 1099.
  64. de Melo, A. P. Z. et al. Materials Research Express 2020, 7, 015087.
  65. Azizi, S. et al. Applied Surface Science 2016, 384, 517.
  66. Qaralleh, H. et al. Advances in Natural Sciences: Nanoscience and Nanotechnology 2019, 10, 025016.
  67. Ga'al, H., et al. Artificial Cells, Nanomedicine, and Biotechnology 2018, 46, 1171.
  68. Vilas, V.; Philip, D.; Mathew, J. Materials Science and Engineering: C 2016, 61, 429.
  69. Maciel, M. V. d. O. B., et al. Biocatalysis and Agricultural Biotechnology 2020, 28, 101746.
  70. Jayaseelan, C., et al. Parasitology Research 2011, 109, 185.
  71. Sutthanont, N.; Attrapadung, S.; Nuchprayoon, S. Insects 2019, 10, 27.
  72. Vilas, V.; Philip, D.; Mathew, J. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 2014, 132, 743.
  73. Veisi, H., et al. Materials Science and Engineering: C, 2019, 105, 110031.
  74. Arassu, R. T.; Nambikkairaj, B.; Ramya, D. J. Pharm. Phytochem 2018, 7, 1778.
  75. Pauline, M. C., et al. Uttar Pradesh Journal of Zoology 2019, 40, 54.
  76. Liu, Z., et al. Archives of Medical Science, 2021.
  77. Erkoc, P. Journal of the Turkish Chemical Society Section A: Chemistry 2021, 8, 1.
  78. Dodevska, T., et al. Materials Chemistry and Physics 2019, 231, 335.
  79. Szweda, P., et al. Indian Journal of Microbiology 2015, 55, 175.
  80. Jin, X., et al. Journal of Cleaner Production 2018, 176, 929.
  81. Ahmad, T., et al. Colloids and Surfaces B: Biointerfaces 2013, 107, 227.
  82. Varghese, R. J.; Zikalala, N.; Oluwafemi, O. S. Green Synthesis Protocol on Metal Oxide Nanoparticles Using Plant Extracts, in Colloidal Metal Oxide Nanoparticles; 2020; Elsevier: p. 67-82.
  83. Biswal, A. K.; Misra, P. K. Materials Chemistry and Physics 2020, 250, 123014.
  84. Keat, C. L., et al. Bioresources and Bioprocessing 2015, 2, 1.
  85. Bilia, A. R., et al. Evidence-Based Complementary and Alternative Medicine 2014, 2014.
  86. El-Sayed, A. S.; Ali, D. Journal of Microbiology and Biotechnology 2018.
  87. Wette, P., et al. Journal of Physics: Condensed Matter 2009, 21, 464115.
  88. Abbasi, E., et al. Critical Reviews in Microbiology 2016, 42, 173. https://doi.org/10.3109/1040841X.2014.912200
  89. Edison, T. J. I.; Sethuraman, M. Process Biochemistry 2012, 47, 1351.
  90. Dzimitrowicz, A., et al. Arabian Journal of Chemistry 2019, 12, 4795.
  91. Zuorro, A., et al. Processes 2019, 7, 193.
  92. Ramnani, S.; Biswal, J.; Sabharwal, S. Radiation Physics and Chemistry 2007, 76, 1290.
  93. Amendola, V., et al. Journal of Physics: Condensed Matter 2017, 29, 203002.
  94. Lee, S.-W., et al. Materials 2014, 7, 7781. https://doi.org/10.3390/ma7127781
  95. Scandorieiro, S., et al. Frontiers in Microbiology 2016, 7, 760. https://doi.org/10.3389/fmicb.2016.00760
  96. Nishanthi, R.; Malathi, S.; Palani, P. Materials Science and Engineering: C 2019, 96, 693.
  97. Kamshad, M., et al., Journal of Biomolecular Structure and Dynamics 2019, 37, 2030.
  98. Anigol, L. B.; Charantimath, J. S. Gurubasavaraj, P. M. Org. Med. Chem. Int. J. 2017, 3, 1.
  99. Guimaraes, M. L., et al. Applied Nanoscience 2020, 10, 1073.
  100. Velmurugan, P., et al. Bioprocess and Biosystems Engineering 2014, 37, 1935.
  101. Nasiriboroumand, M.; Montazer, M.; Barani, H. Journal of Photochemistry and Photobiology B: Biology 2018, 179, 98.
  102. Cinteza, L. O., et al. Nanomaterials 2018, 8, 826.
  103. Abdel-Aziz, M. S., et al. Journal of Saudi Chemical Society 2014, 18, 356.
  104. Patra, J. K.; Baek, K.-H. Frontiers in Microbiology 2017, 8, 167.
  105. Bomma, M., et al. International Journal of Current Engineering and Technology 2020, 10, 518.
  106. Khlaifat, A. M., et al. Tropical Journal of Pharmaceutical Research 2019, 18, 2605.
  107. Letchamo, W., et al. Journal of Agricultural and Food Chemistry 2004, 52, 3915.
  108. Okafor, F., et al. International Journal of Environmental Research and Public Health 2013, 10, 5221.
  109. Manju, S., et al. Microbial Pathogenesis 2016, 91,
  110. Xiu, Z.-M., et al. Nano Letters 2012, 12, 4271.
  111. Singh, A., et al. Biotechnology Reports 2020, 25, e00427.
  112. Najafpoor, A., et al. Journal of Molecular Liquids 2020, 303, 112640.
  113. Dertli, E.; Mayer, M. J.; Narbad, A. BMC Microbiology 2015, 15, 1.