A review on green synthesis of silver nanoparticle and zinc oxide nanoparticle from different plants extract and their antibacterial activity against multi-drug resistant bacteria

Sumon Das¹, Tamalika Chakraborty¹

Introduction

In current days microbial infection became a Global concern and significant cause of morbidity and mortality because of the development of resistant strains of a virus, bacteria, pathogenic fungi, protozoa and they can survive the clinical treatment with the antibiotic, antifungal, antiviral, antiprotozoal drugs [1]. Highly potent antibiotics like fluoroquinolones and aminoglycosides can generate various effects, and they are retained only for critical infectious diseases. In present days, the growth of antibacterial resistant organisms results in the creation of newly developed methods for combating antibacterial drug resistance [2].

Nanotechnology is a conception of handling and the usage of resources having a size range of 1-100 nm, and they are known as Nanoparticle. In recent years, scientists concentrated their focus on nanoparticles due to their different magnetic, optoelectronic and physicochemical properties that are regulated by their size and shape distribution [3].

In present days as an antibacterial agent Nanoparticles are used, and they are highly effective and acquire huge attention as they satisfy the requirements where antibiotics fail to prevent the development of Multi-Drug Resistant (MDR) mutants [4-5]. Nanoparticles are used in different applications like catalysts, chemical sensors, electronic components, imaging for medical diagnostic and medical diagnostic protocols, pharmaceutical products, drug delivery (various nanoparticle platforms especially liposomes, polymeric nanoparticles, inorganic nanoparticles and dendrimers have acquired significant attention) because of their novel properties like physical, chemical and optoelectronic properties [6].

Antibacterial nanoparticles, i.e. metal and its oxide, and organic nanoparticles have several modes of action. In general, nanoparticles act in four lethal pathways, and these pathways are linked to each other, and in many situations, they coincide.

I. Disrupt the integrity and membrane potential.

II. Formation of reactive O² species and induction of Nitrogen reactive species.

III. Inhibition of several specific enzymes.

In this paper, the green synthesis of Ag and ZnO nanoparticle from a different plant extract and their antibacterial properties against the Multi-Drug Resistant bacteria are reviewed.

Nanotechnology is a branch of technology that deals with tremendously fine particles and having a length between 1-100 nm (sometimes higher than 100 nm) and having a three-dimensional structure. Nanotechnology, a different area of study field with a vast scale of application in cancer therapy, targeted drug delivery, electronics, cosmetic industry and biosensors [7]. At the end of 1970s Silver nanoparticles were used to treat the infectious diseases caused by pathogenic microorganisms during the diagnosis of orthopaedic disorders, resulting in quicker bone recovery. Several noble metallic nanoparticles are available for their exclusive properties like favourable chemical stability, catalytic activity, electrical conductivity, and antimicrobial activity such as antibacterial, antiviral, antifungal [8].

Furthermore, anti-inflammatory activities are combined into composite cryogenic superconducting materials, cosmetic product, food industry, electronic components have attracted distinct attention [9]. Due to antibacterial properties, the pernicious nature of Ag-np against several microorganisms (pathogenic bacteria) has been well known. Ag nanoparticle used in dental resin composites, coating for medical equipment and ion exchange [10-11]. Ag nanoparticle also applied in biomedical applications like wound dressing, topical medicines, antiseptic sprays, and fabrics. As antiseptic, silver nanoparticles disrupt the unicellular membrane of the microorganism and deactivate their cellular enzyme. Green synthesis of Ag nanoparticles was established by using plants, microbes and other biopolymers [9]. ZnO nanoparticles belong to the commercially applied inorganic materials because of their unique properties like electronic, structural, thermal, semiconducting, optical, piezoelectric properties. In case of stability, organic reagents are more unstable than ZnO nanoparticles. ZnO based nanomaterials have been studied for a vast diversity of applications such as catalysts, sensors, opto-electron, highly functional and effective photoelectron devices. ZnO nanoparticle has the vast surface area with an excessive catalytic activity which is a considerable advantage to use it in medical and pharmaceutical applications [12].

Antibacterial agents like antiseptics, antidandruff shampoos, baby powder, calamine powder contain ZnO nanoparticle. Few mechanisms of ZnO nanoparticle were identified:

I. ZnO nanoparticle generates hydrogen peroxide, this can penetrate through the cell membrane, and it injured the cell and prevented the development of the cells [13].

II. The antibacterial property of the ZnO nanoparticles based on the affinity between the ZnO and bacterial cells [14].

Bacterial enzymes like dehydrogenase and specific protective enzymes like glutathione reductase and thiol peroxidase are inhibited by the ZnO nanoparticles [15]. ZnO nanoparticles interact with the membranes of microorganisms (bacteria) and act as a potential antibacterial agent because of their excellent reactivity. Antibacterial property of the ZnO nanoparticles based on the concentration, size and healing temperature. ZnO nanoparticles is an ideal potential antibacterial reagent to replace some antibiotic due to selective toxicity and are generally considered as a safe reagent to human and animals [16, 17].

Green synthesis of the Ag nanoparticle using plant extract

Usage of the plant for the nanoparticle synthesis does not require the maintenance of cell culture, and it supports the large-scale production of nanoparticle which is a valuable benefit in this field. Production of extracellular nanoparticle depends on the usage of plant leaf rather than the entire plant [18]. Plant extract holds various active biomolecules like alkaloids, phenolic acids, sugars, proteins, polyphenol and terpenoids. These active biomolecules have a crucial part in this biological reduction; first, it reduces and stabilizes the metallic ions [19-20]. Size and morphology of the produced nanoparticles based on several factors like the plant extract concentration, metal salt concentration, reaction time, temperature and pH of the reaction mixture [21-22]. Synthesis of the Ag nanoparticle by the usage of plant extract has several benefits due to its eco-friendly, rapid, economical, non-pathogenic protocol. A huge number of plants are used to synthesize the Ag nanoparticles and are stated in table 1 [23-24]. Plants parts should be taken, like the leaf of the plant, and then washed thoroughly by normal water followed by distilled water to eliminate the debris. Then these fresh leaves must be placed in the shaded region for 10-15 days for drying and then it should be powdered with the help of a domestic blender. Plant extract should be organized by adding around 10 gm of dried powder into 100ml of deionized distilled water. The synthesized infusion placed for the filtration carefully until no insoluble substance appeared in the broth. Then standard AgNO³ solution must be prepared followed by adding the few ml of desired plant extract, and it will be converted to desired Ag nanoparticle, and the reaction mixture was subjected to UV-visible spectra at a regular interval to check the production of Ag nanoparticle [24].

Table 1. Green synthesis of silver nanoparticles using different plant extracts [ 9-11, 23-24, 27-30].

Plants Plant parts

Averrhoa carambola Leaf Rhizome

Acorus calamus

Aristolochia indica Leaf Aloe vera Leaf gel Annona muricata Leaf Abutilon indicum Leaf Aerva lanata Leaf Alstonia scholaris Bark Azadirachta indica leaf Artocarpus heterophyllus Seed Alternanthera dentate Leaves Argyreia nervosa Seeds Leaf

Acalypha indica

Allium sativum Leaf Aloe vera Leaf Boerhaavia diffusa Whole plant Brassica rapa Leaf Clerodendrum serratum leaf Carica papaya Leaf Petals

Cucurbita maxima

Calotropis gigantea Latex Crataegus douglasii Fruit Cocos nucifera Coir Cymbopogan citratus Leaf Calastropis procera Plant Centella asiatica Leaf Leaf

Coccinia indica

Citrus sinensis Peel Datura metel Leaf Euphorbia helioscopia Leaf Enteromorpha flexuosa Seaweed Eucalyptus chapmaniana Leaf Eclipta prostrate Leaf Eucalyptus hybrid Peel Ficus carica Leaf Grewia flaviscences Leaf Garcinia mangostana Leaf Leaf

Hypnea musciformis

Hemidesmus indicus Leaf Helicteres isora Root Hydrastis canadensis Whole plant Justicia adhatoda Leaf Lansium domesticum Fruit Lycopersicon esculentum Fruit Leaf

Moringa oleifera

Momordica cymbalaria Fruit Mukia maderaspatana Leaf Myrmecodia pendan Whole plant Leaf

Musa balbisiana

Morinda citrifolia Root Melia dubia Leaf Musa paradisiacal Peel Memecylon edule Leaf Nelumbo nucifera Root Onosma dichroantha Root Leaf

Ocimum tenuiflorum

Size Shape

30-55 Spherical Or Cubical 5-50 Octahedron 106 Crystalline 20 Triangular 10.78 Spherical And Irregular 50-80 Spherical And Triangular 19 Crystalline 2-32 Circular 35-60 Triangles, Pentagons, Hexagons 50-90 Pherical 21 Crystalline 30-40 Crystalline 11 Rectangle 20-50 Triangular, Circular, Hexagonal 16.7 Spherical, Triangular 50 Cuboidal Plukenetia volubilis Leaf Prosopis farcta Leaf Piper longum Fruit Potentilla fulgens Root Whole plant

Phytolacca decandra

Pistacia atlantica Seeds Premna herbacea Leaf Psoralea corylifolia Seeds Leaf

Portulaca oleracea

Pogostemon benghalensis Leaf Quercus brantii Leaf Rosmarinus officinalis Leaf Skimmia laureola Leaf Saraca indica Leaf Sinapis arvensis Seed Leaf

Swietenia mahogani

Tephrosia tinctoria Stem Tribulus terrestris Fruit Thevetia peruviana Latex Trachyspermum ammi Seeds Vitex negundo Leaf Vitis vinifera Fruit Leaf

Ziziphus jujuba

Ziziphora tenuior Leaf

Green synthesis of Ag nanoparticles along with the factors affecting the synthesis

Effects of pH

Synthesis of the Ag nanoparticle depends on the pH of the reaction medium, which plays a crucial role during synthesis [25]. Synthesis of the Ag nanoparticle occurs promptly between the basic to neutral pH range. Development of the Ag nanoparticles is delayed by acidic conditions or an acidic pH, and it is enhanced by the basic pH or in basic condition. Lower pH or the acidic pH results in larger nanoparticle whereas small shaped spherical nanoparticle formed in the basic pH [26]. For example, Cinnamon zeylanicum bark extract was used to synthesize the Ag nanoparticles, a higher concentration of the bark extract with pH 5 and above, forms the higher amount of spherically shaped nanoparticle and having a size range of 8-20 nm [27].

Effects of reactant concentration

During synthesis, the biomolecule concentration of the plant extract regulates the shape or structure of the nanoparticles. For example: Octahedron shaped Ag nanoparticle was formed from the leaf extract of Aloe vera, whereas hexagonal and spherical shaped Ag nanoparticle was formed from the seed extract of Mangifera indica, here the leaf gel extract of Aloe vera contains flavanones terpenoids, and Gallo tannins, tannins and phenolic compounds, are present in the seed extract of Mangifera indica [28].

4-25 Optical 46 Hexagonal 87, 99.8 Spherical 20 Cubic 20-30 Crystalline

Reaction time and temperature

A recent study discovered that the temperature and reaction time influence the size and shape of the nanoparticle. For example, a mixture of leaf extract of Azardirachta indica and Ag(NO)³ when combined, it forms larger nanoparticle with increasing reaction time. The time of the reaction was set between 30 min and 4hr to develop a variation in the size of the practice in between 10 to 35 nm [29]. Ag nanoparticle synthesized from the Citrus sinensis peel extract having an average size of approximately 35 nm, at the reaction temperature of 25°c and the size of the particle decreased to 10 nm when the reaction temperature increased to 60°c [30].

Antibacterial activity of silver nanoparticle

Today, Antibiotic-Resistant microbes are the growing global threat, certain MDR pathogens like gram-positive and gram-negative bacteria (table 2) are responsible for some infections which increase the death rate and treatment cost in undeveloped countries and today biomedical science need more advancement for the education and the creation of unique antibacterial agents which are more potent to encounter the MDR strains [26]. Metallic nanoparticles are governed to inhibit the development of the growth of the Multi-Drug Resistant organism because they can prevent their growth. Properties like physical, chemical, thermal, electrical and optical are the main factors in their selection. Certain gram-positive and gram-negative bacteria which belong to the MDR pathogen groups are responsible for certain infections which increase the death rate and treatment

Corynebacterium diphtheriae β-lactam antibiotics Chloramphenicol Tetracycline Trimethoprim Sulfamethoxazole Enterococcus faecium Vancomycin Gentomicin Listeria monocytogenes Erythromycin Gentomicin Kanamycin Rifampin Streptomycin Sulfamethoxazole Tetracycline Staphylococcus aureus Methicillin Vancomycin Streptococcus pneumonia Penicillin Erythromycin Streptococcus pyogenes Erythromycin macrolides

GRAM-NEGATIVE

Acinetobacter baumanii Carbapenems Imipenem Escherichia coli Ampicillin Cephalosporins Chloramphenicol Fluoroquinolones Nalidixic acid Rifampin Sulfamethoxazole Streptomycin Tetracycline Carbapenems

Klebsiella pneumonia

Imipenem Pseudomonas aeruginosa β-lactams Chloramphenicol Novobiocin Sulfonamides Tetracycline Trimethoprim Shigella flexneri Ciprofloxacin Nalidixic acid Vibrio cholera Fluoroquinolones Tetracycline In the entire world, the Ag nanoparticle has been applied popularly for various purposes. The antibacterial effectiveness of Ag nanoparticles is strongly determined by their shape, size, concentration and colloidal state. It was established by the scientist that the reduction of the size of Ag np increased the stability and biocompatibility of Ag np. Antibacterial effectiveness of Ag nanoparticles is strongly determined by their shape, size, concentration and colloidal state [33]. As a well-recognized antibacterial agent, silver is used against several types of microorganisms like bacteria, fungi, and viruses. Ag has been defined as a healing agent for several diseases in Ayurveda [34]. Commonly Ag is applied in their nitrate form as an active antibacterial agent, but when the Ag nanoparticle is applied as an antibacterial agent, it is more Fluoroquinolones Macrolides effective than Silver Nitrate because Silver nanoparticle has more surface area than Silver Nitrate (table 3) [35]. Silver nanoparticles are coupled with four distinct antibacterial actions [36]:

I. Attachment of the Ag nanoparticles on the surface of cell wall and membrane.

II. An incursion of the Ag nanoparticles within the cell results in the destruction of the structures within the cell-like mitochondria, vacuoles, ribosomes, and biomolecules like lipids, protein, and DNA.

III. Ag nanoparticles yield the reactive oxygen species (ROS) and free radicals which stimulate the oxidative stress and cellular toxicity.

IV. Regulate the signal transduction pathway.

Clostridium diphtheria 28.42 Rupture of cell wall;Structural loss of proteins Listeria monocytogenes - Penetration the bacterial cell 23±2 Functional deactivation of the electron transport chain; increasing level of Reactive Oxygen Species at the cell membrane Staphylococcus aureus - Adhesion to cell wall; separation of cell membrane from the cell wall; condensation of DNA; replication inhibition; proteins inactivation 5 Damage of the Cell membrane; outflow of reducing sugars 25 Interact with the cell membrane and S- and P-containing compounds; blockage of respiration

GRAM-NEGATIVE

Escherichia coli 5±2 Interact with cell membrane and S- and P-containing molecules attach to cell wall; - separation of cell membrane from the cell wall; condensation of DNA; replication Inhibition; proteins inactivation 10 Interact with S- and P-containing molecules 5 damage of the cell membrane; outflow of the reducing sugars 1-10 Interact with the cell membrane results increasing permeability; inappropriate transport activity; outflow of 25 cellular elements 16 Interact with S- and P-containing molecules - Interact with the cell membrane; interact with S- and P- containing molecules 9.3 Disruption of ribosomes; inhibition of translation; preventing the ATP formation by inactivating the functional enzyme Interaction with the cell membrane Klebsiella pneumonia <50 Interaction with DNA; preventing the of cell division Pseudomonas aeruginosa 5±2 Interaction with the cell membrane and the S- and P- containing molecules 10 Penetrating the cell 28 Reduction of quorum sensing property of the bacteria Salmonella typii 5±2 Interact with the cell membrane and the S- and P-containing molecules 2-23 lysis of the cell wall 5±2 Interact with the cell membrane and the S- and P-containing

Vibrio cholera

molecules 90-100 Retardation of the metabolic pathways

population reduced up to 80% Microorganisms, when treated with Ag nanoparticles, results in binding of nanoparticles on the cell wall which leads to morphological changes like shrinkage of the cytoplasm and membrane separation which directs the busting of the cell wall [37]. The integrity of the lipid bilayer and the cell membrane permeability are destroyed by the Ag nanoparticles when it reacts with the sulfurcontaining enzymes which present within the cell wall and this interaction completely change the cell wall morphology [38]. Also, composition and width of the microbial cell wall also regulate the antibacterial property of Ag nanoparticles. The gram-positive bacterial cell wall is much thicker than the gram-negative bacterial cell wall, and the amount of peptidoglycan present in the grampositive bacterial cell wall is much higher than the gramnegative bacteria. Positively charged Ag nanoparticles when applied to the gram-positive bacteria, it deposited on their cell wall due to the presence of high negative charges [31].

Furthermore, Ag nanoparticles are more lethal against the gram-negative bacterial species due to the presence of a thinner cell wall and the presence of a small amount of peptidoglycan. Therefore, they are used for better antibacterial treatment against the gram-negative bacteria.

In addition, the cell membrane of gram-negative bacteria contains lipopolysaccharide layer, which contributes the negative changes on the cell membrane, and this LPS molecules boost the binding of the Ag nanoparticles and make bacteria more sensitive against Ag nanoparticlemediated antibacterial treatment (table 3). For example, 3.56μg/l the

Green synthesis of Zinc Oxide (ZnO) nanoparticle

Synthesis of the metallic nanoparticle by the using the green resources like plant extract is an eco-friendly, costeffective, biocompatible and safer technique. Being a member of metal oxide nanoparticle, Zinc Oxide (ZnO) nanoparticle has been applied in different field like S. aureus a gram-positive bacterium which is less prone to the Ag nanoparticle than E. coli, which is a gramnegative bacterium [32, 23].

Ag nanoparticle destructs the intracellular structures and biomolecules in various ways. Firstly, suppression of translation is done by Ag nanoparticles by the denaturing the translational machinery ribosome. Secondly, Ag+ denature the protein molecules by deactivating their functional groups. Furthermore, Ag nanoparticles and Ag+ also disrupt the disulphide bonds on the active site of an enzyme, which results in the cell death. Ionized form of the Ag nanoparticle also has the capability of forming a complex with nucleosides of nucleic acid rather than developing a complex with phosphate groups of the nucleic acid (table 4). Ag+ ions also act as an intercalating agent and denature the DNA molecule, which results in the cell death [39-41].

Ag nanoparticle act as an antibacterial, antifungal and antiviral agent, because it can produce the reactive oxygen species (ROS) like Hydrogen peroxide (H²O²), - Superoxide anion (O ), Hydroxyl radical (OH•), 2 Hypochlorous acid (HOCl) and Singlet oxygen (O ) and 2 generation of these radicals within the cell by Ag nanoparticle results in the cell death [42-43]. Phosphorylation of several proteins or enzyme molecules in a bacterium is an important process; this process is inhibited by Ag nanoparticles by dephosphorylating the protein or enzyme molecules which results in the cell death [44].

respectively added to membrane, Ag+ ions affect the agar surface and the DNA replication piezoelectric, optical, and magnetic gas sensing [45]. ZnO nanoparticle is an inorganic water-insoluble compound and seems like white powder. ZnO nanoparticle has great diversity with biomedical properties like antibacterial, and it used to disinfect wastewater and to disintegrate pesticides, herbicides [46]. It has been stated that the synthesis of ZnO nanoparticle has been done by various Table 5. A large number of plants are used to synthesize the ZnO nanoparticles are mentioned below [47-50]. plant extract, known as green synthesis (table 5). Plant extracts contain some phytochemicals that performed like reducing and stabilizing factor in the reaction system. Phytochemicals are produced by the plant parts like root, stem, leaf, fruit, and seed because they can produce phytochemicals they are applied in the reaction mixture during the synthesis of ZnO nanoparticles.

Plants are the most promising source for the nanoparticle production because they conduct a higher amount of nanoparticle formation, with stable, modified size and shape. Green synthesis of ZnO nanoparticle require the target plant part like a leaf, flower, stem then the desired plant part should be washed properly in running tap water then sterilized in double distilled water. Then the desired plant part is kept in dry place for 10-15 days to make it dry. Then with the help of the domestic blender, dried

Plants Plants part

Azadirachta indica Leaf Agathosma betulina Leaf Aloe vera Leaf Anisochilus carnosus Leaf Calatropis gigantea Leaf Cocus nucifera Coconut water Coptidis rhizoma Dried rhizome Eichhornia crassipes Leaf Moringa oleifera Leaf Nephelium lappaceum L Fruit peels Leaf

Ocimum basilicum

Parthenium hysterophorus Leaf Leaf

Phyllanthus niruri

Plectranthus amboinicus Leaf Pongamia pinnata Leaf Fruit extract

Rosa canina

Santalum album Leaf Leaf

Sphathodea campanulata

Trifolium pratense Flower Vitex negundo Leaf

Factors that are affecting the green synthesis of Zinc Oxide nanoparticle

Effect of pH

pH plays an important role in the unification of ZnO nanoparticle, the pH of the reaction mixture controls the size of the ZnO nanoparticle. For example, ZnO nanoparticle synthesized from Sargassum myriocystum extracts shows that the when the pH of the reaction mixture low (pH 5-7), accumulation of the ZnO nanoparticle occur to form larger particle, whereas in the high pH (pH 8) this accumulation does not occur, and it results in the complete reduction of Zinc Nitrate to Zinc plant part should be converted into powder. Then Milli-Q water should be added to the desired plant part and then boiled the mixture with continuous stirring by using a magnetic stirrer. Then the Whatman filter paper was used to purify the mixture and separate the desired solution which is needed for further experiments. The obtained extract should be mixed with Zinc Nitrate (Zn(NO³)²) or Zinc Sulphate (ZnSO⁴) with the addition of NaOH and boiled at 30°-35°c for 1-4 hour. Reaction mixture changes its colour to yellow within the incubation time which visually confirms the formation of ZnO nanoparticles. The reaction mixture should be centrifuged to get the pellet followed by measuring the absorption maxima using UV visible spectrophotometer to confirm the formation of ZnO nanoparticle [47].

Size(nm) Shape

15.8 Quasi-spherical agglomerates 8-20 Spherical, oval, hexagonal 56.14 Hexagonal wurtzite, quasi-spherical 30-35 Spherical shaped forming agglomerates 20-80 Spherical and predominantly hexagonal without any agglomeration 2.9-25.2 Spherical, rod shaped 32-36 Spherical without aggregation 24 Spherical and granular nanosized shape with a group of aggregates 50.95 Needle-shaped forming agglomerate 50 Hexagonal 22-35 Spherical, hexagonal 25.61 Hexagonal wurtzite, quasi-spherical 50-180 Rod shaped nanoparticle with agglomerates 26 Spherical, hexagonal, nanorod 100 Nanorods 30-50 Spherical shaped forming agglomerates

Effect of temperature and time

Temperature plays a crucial role in the green synthesis of ZnO nanoparticle when we use the green synthesis technology the required temperature for the reaction must be less than 100°c. For example, leaves extract of Sargassum myriocystum when used to synthesize the ZnO nanoparticles, the optimum temperature for this synthesis process is 80°c, within this temperature the absorption peaks were detected at 376 nm. At this temperature Zinc Nitrate which is present in the solution converts into Zinc Oxide nanoparticle. But when this reaction was performed in other temperatures like 50°c,

376 nm [48]. Time plays a crucial role in the synthesis process. The incubation time of the reaction medium relies on the plant extract. For example, the incubation period for the green synthesis of ZnO nanoparticle from Parthenium hysterophorus leaves extract was 6 hours [49].

Influence of the reactant

Plant extract concentration in the reaction medium plays a crucial role in the formation of ZnO nanoparticles. For example, Azadirachta indica extract contains some functional group like ketone, alcohol, amine, a carboxylic acid which produces spherical shaped ZnO nanoparticles, whereas Agathosma betulina extract includes a hydroxyl group, which produces Quasi-spherical agglomerates [50, 51].

Antibacterial activity and other applications of Zinc Oxide nanoparticles

ZnO nanoparticle shows antibacterial activity by forming intercellular reaction oxygen species like Hydrogen peroxide (H O ), which is lethal to bacterial cells. H O 2 2 2 2 which is produced by the Zinc Oxide nanoparticle, penetrate the bacterial cell through its membrane and kill

Conclusion

The particle which belongs to the nanoscale dimension has a big surface area to volume ratio, which makes them more specific and available. Nanoparticles which are metallic can be synthesized by using plant extract, in other words by the help of green synthesis technology we can synthesize metallic nanoparticles. Nanoparticles synthesized by green technology is eco-friendly, cause no pollution and less expensive. A crucial role is played by the plant extract in this synthesis process, and act as stabilizing, capping or hydrolytic agents. Silver (Ag) and Zinc Oxide (ZnO) are two metallic nanoparticles, and these two nanoparticles can be synthesized with the help of plant extract. There are numerous diverse plants are present those may be utilized for the creation of these two nanoparticles. Nanoparticles like Ag and ZnO have the them (table 6) [52-54]. In the development of several kinds of medicinal products, ZnO nanoparticles are governed due to its disinfecting, antibacterial, and drying properties. In the past ZnO nanoparticles were applied for the treatment of epilepsy and diarrhoea and administered orally [55-56]. ZnO nanoparticle can absorb the radiation like UV A and UV B, and now it is applied in sunscreens [57]. It also applied in the development of dermatological products against inflammation and itching. It also applied as a dusting powder and used treat wound. ZnO nanoparticles are also applied in the nutritional products and diet supplements, and it also applied in the dental paste [53].

As a pollutant removal and disinfectant, ZnO nanoparticle has been applied extensively because of their high chemical stability and oxidation-reduction capability. ZnO nanoparticles also applied in bioimaging technique, used in the biosensor technique and gene therapy technology [59]. Thermal conductivity property of ZnO nanoparticle makes it useful by the rubber manufacturing industry to construct various product in which ZnO nanoparticle act as a cross-linking agent with rubber. In the textile industry ZnO nanoparticle used as UV protective and air permeable agent [60].

diseases, caused by Multi-Drug Resistant (MDR) bacteria. These two particles have excessive potential to inhibit MDR bacteria.The MIC value of Ag NPs against E. coli and S. aureus were 70% and 80%. The applied concentration of Ag NP against E. coli was 10 μg/ml and for S. aureus was 3.56 μg/ml. Additionally, the MIC value of ZnO against E. coli and S. aureus was 99% and 95%. The applied concentration of ZnO NP was 400 μg/ml for both bacteria, and this value was much higher than Ag NP. From the above information, we can conclude that Ag NP is a more active antibacterial agent because it has a lower MIC value with respect to MIC value of ZnO NP; hence, Ag NP is more potent antibacterial agent than ZnO NP. Along with antibacterial properties, ZnO np can also utilize in other fields like the cosmetic industry, water purification industry, rubber

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