Silver Nanoparticles: A Comprehensive Review on Mechanism, Synthesis and Biomedical Applications

 

Pragati A. Bachhav1, Rajavi M. Shroff1, Atul A. Shirkhedkar2*

1Department of Quality Assurance, R. C. Patel Institute of Pharmaceutical Education and Research,

Karwand Naka, Shirpur, Dist: Dhule (MS.) India 425405.

2Central Instruments Facility (CIF), Department of Pharmaceutical Chemistry, R. C. Patel Institute of Pharmaceutical Education and Research, Shirpur, MS, India 425405.

*Corresponding Author E-mail: pragatibachhav01@gmail.com, rajavishroff1996@gmail.com, shirkhedkar@gmail.com

 

ABSTRACT:

Silver nanoparticles (AgNPs) are used in medicine as antimicrobial agents. AgNPs are the subjects of research because of their inimitable properties like size and shape depending on optical, catalytical, antimicrobial, and electrical properties. Even though the perfect mode of action of AgNPs is not exactly known but an antimicrobial mode of action by free radical, dephosphorylation and by inhibiting the replication of DNA by attaching to their soft acids and bases is considered. A variety of physical methods, chemical methods, and biological techniques are applied for the synthesis of AgNPs. In these, the biological method is mostly useful and has a wide scope in the future due to its easy availability. Silver particles even synthesized of different shapes like cubic, pyramidal, nanorods, nanowires, etc. AgNPshave diverse applications in the medical field; it is also recognized as a cytotoxic agent and anti-cancer agent. This review article prefers to highlight on the mode of action, synthesis of AgNPs with different methods and types of AgNP’s with different shapes and applications of them.

 

KEYWORDS: Silver nanoparticles, Mechanisms, Synthesis, Pharmaceuticals, Applications.

 

 

 

1.    INTRODUCTION:

Nanotechnology is an essential part of novel research related to design, synthesis of particle structures ranges from approximately 1- 100nm and it’s been a crucial component of pharmaceutical research nowadays [1]. The type of these units is identified by the word that follows. It is widely stated in the study of nanoscience and nanotechnologies, units should only those of dimensions, rather than any other scientific measurement. It is usually conventional that nanoparticles are aggregate of atoms in size of range 1- 100nm [2].

 

After learning theantibacterial action of silver ions and AgNPs; it displayed that this property is related to morphological and structural changes in the bacterial cell. Research has known with the size, morphological properties and stability characteristics of metal nanoparticles. Which are affected very powerfully due to experimental conditions, adsorption processes of stabilizing agents andthe kinetics of the reaction of metalswithreducing agents for metal nanoparticles [2]. Generally, control on size, shape, size of distribution of produced nanoparticles is received by changing processes of synthesis, reducing factors and stabilizing factors [3].

 

Biosynthesis of these nanoparticles based on yeast, bacteria, actinomycetes, fungi and plant extractsis performed now a days. Currently several partssuch as fruits, leaves, flowers, etc also enzymes have been used for preparation [4]. Currently, there is more need for the development of an eco-friendly process, which not involves the use of toxic chemicals in the synthesis. The use of mixed-valence polyoxometalates, poly-saccharides, tollens, biological and irradiation process is done; which have more advantages over traditional methods including chemical agents linked with environmental toxicity [5]. Acceptance of solvent medium and selection of eco-friendly non-toxic reducing and stabilizing agents are so important part which must be taken for consideration in green synthesis of NPs [6]. The use of plants for the preparation of nanoparticles can be more beneficial over other biological processes by subtracting the elaborate process of maintaining cell cultures. It is also suitable for the pilot-scale synthesis of nanoparticles [7]. Salts of silver are used to prohibit the growth of bacteria in humans, used in catheters, cuts, burns, and wounds to protect them from infection [8]. Silver NPs prepared from silk sericin (SS) which is a polar protein obtained from silkworms at pH 11only, which also contains water-soluble proteins with highly polar groups such as hydroxyl, carboxyl, and amino functional groups [9].

 

Nanoparticles are compound molecules made of three layers i.e. (a) the surface layer, that may be functionalized with a variety of small molecules, metal ions, surfactants, and polymers. (b) The shell layer is chemically distinct material from the medulla in all angles, and (c) the core/ medulla thatis basically the central part of NP and usually shows NP itself [10]. Another widely use applications are medical devices and implants prepared with silver-impregnated polymers [10]. Silver NPs may contain some supplementary antimicrobial properties that not exercised by ionic silver, because of its small size and its large surface to volume ratios, which again happened to mutually physical and chemical differences in their characteristics compared with their bulk counterparts [11].

 

This review article presents an overview of silver nanoparticle antimicrobial activity, preparation by physical, chemical and biological synthesis approaches and also their applications.

 

2.    MECHANISM OF ACTION FOR AGNPS:

The fix mechanism for AgNPs applicable to cause antimicrobial effect is truly notidentified and is a topic of debate. There are different theories proposedon the mechanism of action of AgNPs for bacteria to cause the bactericidaleffect. Figure 1 shows the possible mode of action of AgNPs on bacterial cell by three mechanisms one is free radical which allows penetration into cell membrane and causes cell death. Second is by dephosphorylation of Tyrosine which lead to inhibition of signal transduction and causes death of cell. And third mechanism is cell died due to interaction of silver with sulfur and phosphorous like soft bass which causes inhibition of DNA replication.

 

Figure 1: Showing possible mode of action of Silver nanoparticles on bacterial cell.

(A)Free radical mechanism, (B) cell death due to dephosphorylation of Tyrosine and inhibition of signal transduction, (C) cell death due to interaction of AgNP’s with sulphur and Phosphor like soft bases.

 

A.      Mechanism of Silver:

The mode of action of silver is associated to its interaction with the thiol functional group substrate that occurred in respiratory enzymes of a bacterial cell. Silver inhibits the growth of the cell by inhibiting the respiratory process by binding the cell wall of bacteria [12].

 

B.    Mechanism of silver ions/AgNo3:

Silver ions have the ability to attach the bacterial cell wall and then penetrate it, and then causing morphological changes in the cell membrane like the permeability in the cell membrane and death of the cell and death of microbe [13]. There is the formation of 'pits' on the surface of the cell, and hence there is an aggregation of the nanoparticles on the cell surface [14]. The free radicals are prepared by the AgNPs may also be considered to be one of the other modes of action by which the death of cells occurs [15].

 

C.      Mechanism of Free radicals of AgNPs:

There was ESR (Electron Spin Resonance) spectroscopy research explains that there is a formation of free radicals [16]. When AgNPs are attached to the bacteria, and these radicals make damage to thecell membrane [17]. Also, these radicals make it permeable and able to penetrate which then causes the death of cells [18].

 

D.    Mechanism of AgNPs:

The cells are maximum made of sulfur and phosphorus like soft bases. The effect of these AgNPs on the cell leads to the interaction and then causes cell death. Also, the DNA has sulfur and phosphorus in major quantity; the nanoparticles can act on these soft bases and destroy the DNA which would surely lead to cell death [19]. The interaction of the AgNPs with the DNA, sulphur, and phosphorus may lead to the problem of DNA replication in bacterial cells and microbes. It has also been known that the nanoparticles may also manage the control of the signal transduction in bacteria. It is a well-known fact that the phosphorylation of protein substrates in bacteria induces the bacterial signal transduction. Dephosphorylating is reported only in the tyrosine residues of gram-negative bacteria. The phosphotyrosine nature of bacterial peptides is modified by the nanoparticles. It was known that the nanoparticles dephosphorylate the peptide substrates on tyrosine residues, which stop the signal transduction and thus the inhibit growth of microbes. It is however, essential to understand that further research is required on the topic to deeply establish the claims [20]. When AgNPs penetrate in a cell of Bacteria they form a low molecular weight region in centre of bacteria on which the bacteria accumulate to prevent DNA from the silver ion. Mainly NPs attacked respiratory chain, cell division then it comes to the death of cells [21].

 

3.    METHODS FOR SYNTHESIS OF AgNPs:

There are three different methods for the preparation of AgNPs which are Physical, chemical and Biological which are showed diagrammatically in figure 2. The physical methods like Condensation, evaporation and Laser ablation are used. The chemical methods like chemical reduction, microwave assisted synthesis, photo induced reduction and microemulsion techniques are used for the AgNPs preparation. The Biological methods involves the use of plant parts, bacteria, algae and fungi for the synthesis of AgNPs.

 

Figure 2: Flow chart of Methods for Synthesis of AgNPs

 

A.    Physical method:

The condensation, evaporation, and laser ablation are very influential physical methods. When the solvent is not present, contamination in the synthesized thin films and homogeneity of NPs distribution are the positive points of physical methods in comparison with chemical processes. Physical synthesis of AgNPs using tube furnace at atmosphere pressure has some negative points, for example, tube furnace occupies a large space, consumes more energy while growing the atmospheric temperature around the source material, and need much of time to reach thermal stability [22]. A conventional tube furnace needs the power consumption of more than several kilowatts and a time for preheating of several minutes to achieve the stable and unchangeable operating temperature [23]. It is familiar that the silver NPs’preheating is produced by the small ceramic heater with a local heating area. The small ceramic heater was always being used to evaporate the source materials. The evaporated vapor can cold at a suitable rapid rate, because the temperature gradient in the proximity of the heater surface is very extra in contrast with that of tube furnace [24].

 

This makes possible for the development of small silver NPs in much more quantity. The formation of nanoparticles is very much stable, because of the temperature of the heater surface not changes with time. This physical process of synthesis may be convenient as a nanoparticle’s generator or nanoparticle formation for the long term of experiments of inhalation toxicity experiments, and also as calibration devices for thenanoparticlemeasurement equipment [24]. The result of observation showsthat the standard deviation of AgNPs and the total number ofconcentrations of silver NPs increases with the increasingtemperature of the heater surface. The spherical shape of NPs was observed without clusters, even at a high concentration with high heater surface temperature. The mean diameter (geometric) of AgNPs and the standard deviation (geometric) of silver NPs were ranges of 6.2-21.5 nm and 1.23-1.88 nm [25].

 

Silver NPs can be developed by the laser ablation method of metallic bulk materials in the solution [26]. The ablation efficiency of AgNPs and the properties of formed Nanosilver particles affected by the parameters such as the wavelength of laser impinging the metallic target, the time duration of the laser pulses, the laser fluency, the ablation time duration and the liquid medium, with or without in the existence of surfactants [27]. The most helpful advantage point of laser ablation technique forthe preparation of metal colloids is that thechemical reagents are not present in solutions [28]. Since, pure and not mix with contamination type of metal colloids for onward applications can be made by this technique [29]. The Nano spheroids were produced by laser ablation technique in water with femtosecond laser of pilses at 800 nm of wavelength [29]. In the results, it was found that, the formation proficiency for femtosecond pulses was decreased than that for nanosecond pulses. Ahead, it was found that the ablation efficiency for femtosecond ablation in water was fewer than that in air, while in the case of nanosecond pulses, the ablation efficiency was the same in both air as well as water [29].

 

In short, the summary of the physical synthesis of AgNPstypically uses the physical energy to synthesize AgNPs with approximately narrow size distribution. The physical property can allow producing a large amount of AgNPs in only one process. Also, thefirst costs for an investment of equipment should be well-thought-out [30].

 

The investigators Tien and his co-worker’s complete synthesis by fabricate theAgNPs suspension using the arc discharge method in deionized water with no involvement of surfactants. In this type of preparation method, silver wires of 1 mm in diameter were deep in deionized water and they used as an electrode [31]. This method of preparation of AgNPs, involves the physical deposition of a metal ion into propane-1, 2, 3-triol, provides an option to time-consuming, based on wet chemical synthesis techniques. Silver NPs havegot a round shape with a diameter of averagely 3.5 nm with an SD of 2.4nm. It was stated that there is no change in the size distribution of NPs and even particle dispersion for the diluted water-soluble solutions up to the ratio of glycerol-to-water is 1:20 [32].

 

B.    Chemical methods:

In general, the method of chemical synthesis for AgNPs use to employ three main components includes Precursorsof metals; Reducing agents (glucose, NaBH4); Stabilizing agents. The colloidal solutions are made by the reduction of silver salts which is of two stepslike nucleation and further growth. It was detected that the size and shape of produced AgNPs are based on those stages [33]. Equally, for the production of monodisperse AgNPs with the same size, all nuclei are appeared to form simultaneously. In that case, all nuclei have a similar size, and then they will have further same growth. The nucleation and the further growth of starting nuclei can also maintain by adjusting the parameters of reaction like temperature, pH, precursors, reducing and stabilizing agents [34].

 

1.     Chemical reduction:

The chemical reduction is the most studied method of synthesis for theAgNPs. This method of nanoparticle synthesis involves the use of organic and inorganic reducing agents like sodium citrate, ascorbate, NaBH4, hydrogen, polyol process, tollens reagent, N, N-dimethylformamide are used for the reduction of silver ions (Ag+) in aqueous as well as non-aqueous solutions. These type of reducing agents reduce Ag- and tends to form a metallic silver (Ag0), which then is followed by formation into oligomeric clusters. These agglomerations by time lead to form a metallic colloidal silver particle. It isutmostimperative to use protective to stabilize dispersive NPs in the course of the process of metal nanoparticle synthesis, and also protect the NPs which can be bind onto surfaces and avoids their agglomeration to form clusters. The use of surfactants leads to comprise the interactions with particle surface and also stabilizes the growth of particles, and also protect those particles from the settling down (sedimentation), the formation of clusters, and losing their surface properties.

 

The size of Silver NPs is 17±2nm and was obtained at the rate of an injection 2.5ml/s, and a temperature of 100oC. The injection of the forerunner solution into a warm solution is an effective point to initiate fast nucleation in a little time, assuring that theproduction of silver NPs with a shorter size and a small size of the distribution. The reported processes of the formation of these NPs might be split into three stages: one growth, second incubation, and third is Ostwald ripening. The BP of 300oC of paraffin is higher which affords a widespreadrange of reaction temperature and made it possible to maintain the size of AgNPs at various heating temperature specifically without any modification in the ripening time, but again also by maintaining the ratio of oleyl amine and the silver precursor [35-42].

 

2.     Micro-emulsion techniques:

AgNPs of controllable and in form size can be formed by using these microemulsion techniques. The NPs synthesis in two-phase organic systems depends on the preliminary spatial resolution of metal precursors and reducing agents in two immiscible phases. The boundary between the two liquid and the powerof inter-phase transportationamong two phases; controlled by a quaternary alkyl-ammonium effect has occurredon the interaction rate in both the precursors of metals and reducing agents. The metal agglomerates producedat the interface are stabilized, because of their surface being covered with stabilizer molecules in the inorganic aqueous medium, and transferred to the polar medium by the transporter of inter-phase [43].

 

The positive points can also get in the applications of metal NPs as a catalyst to catalyse more organic (polar/ aqueous) reactions, which have been conducted in non-polar (inorganic/non-aqueous) solvents. It is imperative to change the metal NPs to the different physiochemical atmosphere in possible applications [44].

 

3.     UV-initiated photoreduction:

Themost simple and effective method of producing AgNPs has been reported was the UV–initiated photoreduction which is in the occurrence of citrate, polyvinyl pyrrolidine, poly (acrylic acid), and collagen [45]. The researchers synthesize AgNPs by photoreduction of silver nitrate in some few-layered non-polar laponite clay suspensions which are known as a stabilizing agent for a time of UV irradiation. The size distribution of two modes and then large silver NPs were received when irradiated under UV-radiation for 3h. Subsequent irradiation disintegrates the silver NPs into narrower sizes with an only one-time distribution were obtained. AgNPs have been synthesized by the UV irradiation photoreduction method at room temperature byusing polyvinyl alcohol as agents of stabilization and protection. Concentration (quantity) of both poly and silver nitrate performed an importantpart in the development of the silver nanorods and dendrites. [46]. The technique of Sono electricity uses the ultrasonic power first to manipulate the material mechanically. The synthetic method of Pulsed Son electro-Chemicals involves the changing sonic and electric pulses, and electrolyte composition performed a significant role in the formation of uniform shape. It was known that the silver Nanospheres might be synthesized by the sono-electrochemical reduction technique with a complexing agent, to avoid aggregations such as nitrilo triacetate [47].

 

4.     Photo induced reduction (photocatalytic):

Socol and his co-workers studied that Photo induced or reduction methods can produce Silver NPs. Photochemical synthesis is a process that has high spatial separation, better to use and great versatility. However, photochemical synthesis allows one to fabricate the NPs in different mediums involving cells, emulsion, films of polymer, surfactant micelles and glasses [48]. Silver particles of small size with an about size of 8 nm was produced by this technique using poly (styrene sulfonate)/ poly (alkylamine hydrochloride) polyelectrolyte capsules as microreactors. It was shown by the experiment that the photo-induced method might be used for transforming silver Nanospheres into triangular silver Nanocrystals (Nano prisms) with required lengths of edges in 30-120nm [49]. By the use of sodium citrate, the direct photo-reduction process of AgNO3 was performed with various light sources like ultra-violet light, blue light, green light and also orange at room temperature for the reaction [50]. The scientist Sato-Berrú and their co-workers found that the synthesis of silver NPs in an alkaline polar solution of AgNO3/carboxymethylated chitosan using Ultra-Violet light irradiation. The diameter of prepared silver NPs ranged from 2–8 nm, and they can be dispersed and formed a stable solution in the alkaline CMCTS for approximately more than 6months [51].

 

5.     Microwave-assisted synthesis:

Ghosh and other researchers stated thatMicrowave-assisted synthesis is one effective method for producing silver NPs. Heating using microwave is easy than a traditional oil bath when it relates to consistently obtaining small structures with smaller sizes, narrower size distributions, and a high degree of crystallization [52]. The known research contains that silver NPs might be preparedby microwave-assisted synthesis techniques employing carboxymethyl cellulose sodium (CMCNa) as a reducing agent and stabilizing agent. The size was based on the amount of sodium carboxymethyl cellulose and silver nitrate. The formed NPs were similar in size and stable at conditions, and also stable at room temperature for 2 months with no visible variations [53].

 

The team of Yin and co-workers [54] noted that the large-scale and size-controlled silver NPs might be rapidly prepared under microwave irradiation technique from a polar solution of silver nitrate and trisodium citrate with reducing agent formaldehyde. The size of NPs and size distribution of formed silver NPs are based on the silver cations state in the starting reaction solution. Various shapes of silver NPs can be equipped by microwave irradiation of silver nitrate ethylene- glycol-H2 [PtCl6] - PVP solution in 3 min [55]. The technique of the radiolysis method of silver ions in ethylene glycol is also known previously for synthesizing silver NPs [56]. Also, monodisperse silver NPs can be prepared in large amounts from the microwave-assisted chemistry technique in a polar system. In this case, amino acids acted as reducing agents and starch acts as a protecting agent. Silver as well as silver doped lanthanum chromite’s can also be produced with microwave power [57].

 

Both microwave energy and thermal reduction can be used by combining to synthesize silver NPs which can be dropped on electrodes of oxidized carbon paper. The silver NPs which are produced through this technique control a similar size in the particles and are well-dispersed over the carbon paper substrate. The microwave-assisted synthesis of silver NPs is made probable by depositing the silver catalysts on carbon paper electrodes. This technique can hypothetically be used in alkaline fuel cells the reason is the synthesis occurs very fast, also high activity, and a very simpleprocess [58]. It was detected that the power of the microwave had more impact on the particle size than the time length of the treatment.

 

This method can decrease the medicinal costs and time for hospitalization [59]. Silver composites based on polymer were formed using microwave energy on the course of interfacial polymerization. An interface of water and chloroform was used under microwave irradiation without oxidizing agents [60].

 

Transmission electron microscopy (TEM) images showed that the size of particles occurred was in the range of 5−10nm. The silver and polypyrene thick film, which could detect ammonia, hydrogen sulfide, and carbon dioxide at 100, 250, and 350°C [61]. The formed silver NPs were evaluated through freeze-etching replication TEM which shows the diameter and distribution of NPs. The gained silver NPs (30nm) are of sphere-shaped [62].

 

Diverse types of nanosilver colloids were prepared by this Microwave-assisted synthesis Silver nitrate and sodium citrate were added into each other and then divided into 5 groups. At different temperatures, every group was heated for different durations of time temperatures. Nanosilver colloids possess a negatively charged surface due to heating more period and a positively charged surface due to heating for a less period [63]. Further, the initiators such as Ag2O or AgNO3 with silica or alumina can also be used to produce silver NPs. The size of particles was observed in small was 3 nm and in large was 50 nm. The particles were well spread and not get oxidized [64].

 

C.      Bio-based methods:

As per the reports available in literatureindicate that synthesis of nanoparticles by chemical methods are un- ecofriendly and expensive. So, there is a rising need to develop environmentally and economically friendly processes, which not involve the usage of toxic chemicals in the synthesis protocols. This gives an idea to researchers to turn for organisms. Examples of nanoparticle synthesis including bacteria are like gold, silver, cadmium, zinc, magnetite, and iron NPs; also using yeasts for silver, by use of lead and cadmium NPs; by using fungi for gold, silver and cadmium NPs; by using algae also silver and gold NPs were synthesized; plants for silver, gold, palladium, zinc oxide, platinum, and magnetite NPs [65].

 

The particles sizes and physical assets of NPs may be controlled by changing some crucial conditions, by taking in consideration substrate concentration, pH, light, and temperature, buffer strength, electron donor e.g., glucose or fructose, biomass and concentration, mixing the speed of mixing, and time of exposure. The different species from the sources like plant, bacteria, fungi and algae are used for AgNPs synthesis; some examples are given in table 1 [66].

 

 

Table 1: Biological synthesis of AgNPs [66]

Bacteria

Plants

Fungi

Algae

Aeromonassp. SH10

(Bacterium)

Aloe veraleaf extract (Plant)

Nitrate reductases

(from Fusariumoxysporum)

Spirulinaplatensis

(Alga)

Klebsiella pneumonia (Bacterium)

Azadirachtaindica (Plant)

Phaeneroechaete

Chrysosporium (Fungus)

Oscillatoriawillei

(Alga)

Lactobacillus strains (Bacteria)

Cinnamomumcamphora (Plant)

Verticilliumsp. (Fungi)

Gelidiellaacerosa

(Alga)

Pseudomonas stutzeriAG259 (Bacterium)

EmblicaOfficinalis (Plant)

Aspergillusflavus (Fungus)

 

Corynebacteriumsp. SH09 (Bacterium)

Pelargonium graveolens leaves (Geranium) (Plant)

Aspergillusfumigatus (Fungus)

 

Enterobacter cloacae (Enterobacteriacae)

(Bacterium)

Pelargonium graveolens leaves (Geranium) (Plant)

Fusariumoxysporium (Fungus)

 

 

Pinuseldarica (Plant)

Fusariumsemitectum (Fungus)

 

 

 

 

4.    TYPES OF AGNPS DEPENDING UPON DIFFERENT SHAPES:

A.    Types:

The optical, electrical, magnetic and catalytic properties of nanoparticles depend on their shape, size and chemical atmosphere [67]. The shapes of NPs according to their interaction with surfactants and the inductors around them and also their method of preparation [67].

 

It is also notorious that the reaction rate is affected by the shape of prepared AgNPs. Xu et al. studied the oxidation of styrene over three shapes (nanocube, semi-round, and triangular nanoplate) of AgNPs for this determination. The results revealed that the reaction rate in cubic nanoparticles is 14 times more than triangular Nanoplates and 4 times higher than the semi-spherical nanoparticles [68]. The different shapes like cubic, nanorods, nanowires, pyramidal, nano prisms and spherical are synthesize by different methods like physical, chemical and biological and also, they are prepared using different reducing agents and stabilizers which leads to formation of various size of AgNPs which are elaborated in table no 2 by Khodashenas and Ghorbani.

 

 

Table 2: Synthesis of Ag nanoparticles with different shapes through chemical, physical and biological methods. [3, 69]

Sr. No

Shape

Particle size (nm)

Reducing agent

Stabilizer

Methods

1

Cubic

30-50 nm

2-8 nm

10-50 nm

Ethylene Glycol

Carboxymethylated Chitosan

Leaf extract from Eucalyptus macrocarpa

PVP

Carboxymethylated Chitosan

Leafextract Eucalyptus macrocarpa

Chemical Methods

Photochemical Method

Biological Synthesis

2

Silver nanorods

4±2 nm

Na borohydride presence of Na citrate

-

Wet chemical Method

3

Silver nanowires

30-40 nm

 

Ethylene glycol

 

-

 

Soft (solution-phase) Chemical Method

4

Silver Nanobars

-

Ethylene glycol

PVP

Chemical Method

5

Pyramidal

(Triangular)

50-200 nm

Hydrazine hydrate

PVP

Chemical reduction

Method

6

Nano prism

-

Ethylene glycol

PVP

Microwave assisted

Synthesis

7

 

 

Spherical

50-60 nm

11 nm

Trisodium citrate

Electrolysis cathode

Trisodium citrate

PVP

Chemical Method

Electrochemical (Polyol) Process

 

 

B.    Effective factors on the shape of produced AgNPs:

The different shapes of AgNPs are formed which are scanned under the SEM and TEM of different sizes like nanorods, triangular etc. which are showed in table 3. The shape and size of produced NPs are based upon the experimental conditions includes as temperature, amount of silver precursor, pH, the molar ratio between the capping agent and silver precursor, chemical interaction between PVP or capping agent and several crystallographic planes of silver [70, 71]. The researcher Dong, performed the development of silver NPs with the citrate reduction of silver nitrate between the pH of 5.7 to 11.1. They report that the pH of the solution affects the size or shape of the synthesized AgNPs. It was observed that in high pH, a product found of two shapes spherical and rod-like AgNPs that is a result of a rapid rate of reduction the precursor, also under low pH, the product was triangular or may be polygon because of a slow reduction rate of the initial product [72].

 

 

Table 3: SEM and TEM images different shapes of AgNPs [73]

Sr no.

Image

Shape

Size (nm)

Scanned in

 

 

1

 

 

 

 

Nanorods

 

 

50 nm

 

 

SEM

 

 

2

 

 

 

 

Nanowires

 

 

500 nm

 

 

TEM

 

3

 

 

 

Nanobars

 

100 nm

 

TEM

 

4

 

 

 

Nanoprism

 

200 nm

 

TEM

 

5

 

 

 

Flower like

 

200 nm

 

SEM

 

6

 

 

 

Pyramid

 

100 nm

 

SEM

 

 

Yellow colour for spherical silver particles was also informed by Jin et al [73]. They obtained spherical silver particles by injection of NaBH4 solution to an aqueous solution of AgNO3 in the presence of trisodium citrate followed by the dropping of BSPP as particles stabilizing agent. After 70 h irradiation of silver particles, they detected a decrease in intensity of the characteristic surface plasmon band in the UV-vis spectroscopy for the sphere-shaped particles at גmax = 400 nm with associated growth of threenew bands of גmax = 335 (weak), 470 (medium) and 670nm (strong). Transmission electron microscopy shows that the initialsphere-shaped silver particles (8.0 + 1.7 nm) were transformed to prismatic structures [74].

C.    Particle size distribution:

Obtained AgNPs had a diameter of range from 5 to 100 nm. It was detected that the size of AgNPs gained in aqueous solutions using PVA as stabilizer not depend on the concentration of silver range from 250-1000 ppm. The particle size of colloids found in the aqueous solution using PVP as the protecting agent improved with the increasing of silver concentration from 36 nm to 82 nm for preliminary Ag concentration equalled 250 ppm and 1000 ppm, respectively. These particle size distribution by the usage of reducing agents like ascorbic acid and hydrazine, the protecting agents like PVP and PVA and colour formed given in table no 4 [75].

 

 

Table 4: Characteristics of silver particles obtained in from silver citrate [72]

Silver amount (mg/dm3)

Reducing agent

Protecting agent

Average particle size (nm)

pH

Relative abundance [%]

Colour of solution

<10

(nm)

10-50

(nm)

50-100

(nm)

>100

(nm)

250

Ascorbic acid

PVP

36

5.3

5

62

22

11

Green

500

Ascorbic acid

PVP

58

5.3

2

44

30

24

Light brown

1000

Ascorbic acid

PVP

82

5.6

1

27

40

32

Light brown

250

Ascorbic acid

PVA

44

5.6

3

53

27

17

Green

500

Ascorbic acid

PVA

45

5.8

3

53

27

17

Light brown

1000

Ascorbic acid

PVA

44

5.7

3

53

32

11

Brown

500

Hydrazine

PVP

67

7.1

1

45

37

17

Green

500

Hydrazine

PVA

48

7.6

3

51

30

16

Green

250

Sodium borohydrate

None

140

9.1

0

12

28

60

Yellow

 

 

 

5.    APPLICATIONS OF AGNPS:

The AgNPs have the wide applications in medical field. AgNPs are applied in cancer therapy, glucose biosensor, food industries, cytogenotoxic properties and such more applications are diagrammatically presented in figure 3.

 

Figure 3: Diagrammatic presentation illustrating applications of AgNPs

 

1.     AgNPs have been used broadly as anti-bacterial agents in the health industry, food storage, textile coatings and several environmental applications. Furthermore, the electrochemical characteristics of AgNPs merged them in nanoscale sensors that can proposed quicker response times and lower detection limits. The optical assets of a metallic nanoparticle depend mainly on its surface plasmon resonance, where the plasmon states to the collective oscillation of the free electrons within the metallic nanoparticle. It is well recognized that the plasmon resonant peaks and line widths are sensitive to the size and shape of the nanoparticle, the metallic species, and the surrounding medium. For example, nanoclusters composed of 2–8 silver atoms could be the root for a new type of optical data storage. Besides, fluorescent emissions from the clusters could possibly also be used in biological markers and electroluminescent exhibitions [76].

 

2.     AgNPs as an Anti-cancer agent

AgNPs are made wholly or least of metallic silver, exist in various shapes, and they range from 1-100 nm in diameter. The small size and ability of AgNPs of leading to the death of cells through multiple mechanisms made them an outstanding candidate for anti-cancer therapies.

 

3.     Drug Delivery using AgNPs

Nanoparticles make an outstanding platform for drug delivery hence they can release a one or many - type payload of small molecule chemotherapeutics in the proximity or inner side of a cancer cell.

 

AgNPs also coated with another material to decrease their cytotoxicity, increase biological retention time, or may approve selective targeting of a tissue or cancer cell.

 

Biomolecules like antibodies, proteins, enzymes, and others are regularly used as target ligands, which ensures the accumulation of nanoparticles within the tumour due to the increasing ability of permeation and effect of retention time in targeted tissue or cell [77].

 

4.     Also, AgNPs used in treatments in different types of wounds, burns [78].

 

5.     AgNPs also used in different infections [79].

 

6.     In food protection, disinfection and decontamination of different products AgNPs are applied [80].

 

7.     Again, in water purification by filtration, the AgNPs are used [80].

 

6.    LIMITATIONS AND FUTURE CHALLENGES:

One of the most significant limitations of AgNPs is their stability. Nevertheless, the stability can be boosted by controlling the environmental factors, temperature. Toxicological studies and regulations are requiredto entirelydescribe the biocompatibility in humans. In maximumcase, in vitro studies give selective results. And these results unluckily often isolated reality in vivo. In end, economic respect has to be taken into consideration to commercialize a new pharmaceutical drug delivery system, not only for patients but also for the pharmaceutical manufacturing. Scaling up is another vital limitation for the commercialization of NPs due to experimental factors like dialysis, ultracentrifugation, etc [83]. In future AgNPs have wide scope due to its unique and different chemical and physical characteristics. They are also applicable in the wound or burn to heal; also used for medical devices, applicable in textile fabrics because of their ability to release silver ion continue and it maintains its anti-microbial properties.Also, there are many questions necessity to be addressed, like fix mechanism of interaction of AgNPs with bacterial cells, the surface area of nanoparticles affects their killing property, use of animal models and clinical studies to get an efficient understanding of the antimicrobial property of silver dressings, the toxicity if any of the silver dressing, etc.

 

7.    CONCLUSIONS:

In summary, it can be determined that AgNPs are evolving as a next-generation application in various fields and subfields of nanotechnology and nanomedicines. Important benefits of the use of AgNPs as a choice of nanomaterial in the medical field and industrial areas have been known broadly. The pervasive review on AgNPs has been involved in this paper to know the methods of synthesis, mechanisms, and applications of AgNPs. In all the synthesis methods explained over here, the biological green synthesis method noticed as a promising option of choice because of its safety using natural agents and without toxic chemicals. Another application of AgNPs as plasmonic nanoantenna and biomedical and optoelectronic probes were also explained in the application.

 

8. ACKNOWLEDGEMENT:

The authors are thankful to Dr. S. J. Surana, Principal; R. C. Patel Institute of Pharmaceutical Education and Research, Shirpur (M.S.), India for providing the required facilities to carry out this review paper.

 

9. ABBREVIATIONS:

AgNPs - Silver Nanoparticles

AgNO3- Silver Nitrate

Ag2O - Silver Oxide

BSPP- bis-p-(sulfonatophenyl)phenyl phosphine

CMCNa-Carboxymethyl Cellulose Sodium

CMCTS - Carboxymethylated Chitosan

DNA - Deoxyribonucleic acid

ESR - Electron Spin Resonance

NaBH4-Sodium Borohydrate

NPs - Nanoparticles

TEM - Transmission Electron Microscopy

PVA - Polyvinyl Alcohol

 

10. REFERENCES:

1.     Iravani S, Korbekandi H, Mirmohammadi SV, Zolfaghari B. Synthesis of silver nanoparticles: chemical, physical and biological methods. Research in Pharmaceutical Sciences. 2014 Nov;9(6):385.

2.     El-Nour KM, Eftaiha AA, Al-Warthan A, Ammar RA. Synthesis and applications of silver nanoparticles. Arabian Journal of Chemistry. 2010 Jul 1;3(3):135-40.

3.     Khodashenas B, Ghorbani HR. Synthesis of silver nanoparticles with different shapes. Arabian Journal of Chemistry. 2019 Dec 1;12(8):1823-38.

4.     Siddiqi KS, Husen A, Rao RA. A review on biosynthesis of silver nanoparticles and their biocidal properties. Journal of Nanobiotechnology. 2018 Dec;16(1):14.

5.     Shahverdi AR, Minaeian S, Shahverdi HR, Jamalifar H, Nohi AA. Rapid synthesis of silver nanoparticles using culture supernatants of Enterobacteria: a novel Biological approach. Process Biochemistry. 2007 May 1;42(5):919-23.

6.     S. Senapati, Biosynthesis and immobilization of nanoparticles and their applications. India: University of Pune; 2005. Ph D. Thesis, 1-57.

7.     Klaus-Joerger T, Joerger R, Olsson E, Granqvist CG. Bacteria as workers in the living factory: metal-accumulating bacteria and their potential for materials science. Trends in Biotechnology. 2001 Jan 1;19(1):15-20.

8.     Shankar SS, Rai A, Ahmad A, Sastry M. Rapid synthesis of Au, Ag, and bimetallic Au core–Ag shell nanoparticles using Neem (Azadirachtaindica) leaf broth. Journal of Colloid and Interface Science. 2004 Jul 15;275(2):496-502.

9.     Catauro M, Raucci MG, De Gaetano F, Marotta A. Antibacterial and bioactive silver-containing Na 2 O· CaO· 2SiO 2 glass prepared by sol–gel method. Journal of Materials Science: Materials in Medicine. 2004 Jul 1;15(7):831-7.

10.  Crabtree JH, Burchette RJ, Siddiqi RA, Huen IT, Hadnott LL, Fishman A. The efficacy of silver-ion implanted catheters in reducing peritoneal dialysis-related infections. Peritoneal Dialysis International. 2003 Jan 1;23(4):368-74.

11.  Shin WK, Cho J, Kannan AG, Lee YS, Kim DW. Cross-linked composite gel polymer electrolyte using mesoporous methacrylate-functionalized SiO 2 nanoparticles for lithium-ion polymer batteries. Scientific Reports. 2016 May 18; 6:26332.

12.  Klasen HJ. Historical review of the use of silver in the treatment of burns. I. Early uses. Burns. 2000;26(2):117-30.

13.  Liau SY, Read DC, Pugh WJ, Furr JR, Russell AD. Interaction of silver nitrate with readily identifiable groups: relationship to the antibacterialaction of silver ions. Letters in Applied Microbiology. 1997 Sep;25(4):279-83.

14.  Prabhu S, Poulose EK. Silver nanoparticles: mechanism of antimicrobial action, synthesis, medical applications, and toxicity effects. International Nano Letters. 2012 Dec 1;2(1):32.

15.  Sondi I, Salopek-Sondi B. Silver nanoparticles as antimicrobial agent: a case study on E. coli as a model for Gram-negative bacteria. Journal of Colloid and Interface Science. 2004 Jul 1;275(1):177-82.

16.  Danilczuk M, Lund A, Sadlo J, Yamada H, Michalik J. Conduction electron spin resonance of small silver particles. SpectrochimicaActa Part A: Molecular and Biomolecular Spectroscopy. 2006 Jan 1;63(1):189-91.

17.  Kim JS, Kuk E, Yu KN, Kim JH, Park SJ, Lee HJ, Kim SH, Park YK, Park YH, Hwang CY, Kim YK. Antimicrobial effects of silver nanoparticles. Nanomedicine: Nanotechnology, Biology and Medicine. 2007 Mar 1;3(1):95-101.

18.  Zielińska A, Skwarek E, Zaleska A, Gazda M, Hupka J. Preparation of silver nanoparticles with controlled particle size. Procedia Chemistry. 2009 Nov 1;1(2):1560-6.

19.  Hatchett DW, White HS. Electrochemistry of sulfuradlayers on the low-index faces of silver. The Journal of Physical Chemistry. 1996 Jun 6;100(23):9854-9.

20.  Shrivastava S, Bera T, Roy A, Singh G, Ramachandrarao P, Dash D. Characterization of enhanced antibacterial effects of novel silver nanoparticles. Nanotechnology. 2007 May 4;18(22):225103.

21.  Feng QL, Wu J, Chen GQ, Cui FZ, Kim TN, Kim JO. A mechanistic study of the antibacterial effect of silver ions on Escherichia coli and Staphylococcus aureus. Journal of Biomedical Materials Research. 2000 Dec 15;52(4):662-8.

22.  Shenashen MA, El‐Safty SA, Elshehy EA. Synthesis, morphological control, and properties of silver nanoparticles in potential applications. Particle and Particle Systems Characterization. 2014 Mar;31(3):293-316.

23.  Kruis FE, Fissan H, Rellinghaus B. Sintering and evaporation characteristics of gas-phase synthesis of size-selected PbS nanoparticles. Materials Science and Engineering: B. 2000 Jan 14; 69:329-34.

24.  Magnusson MH, Deppert K, Malm JO, Bovin JO, Samuelson L. Gold nanoparticles: production, reshaping, and thermal charging. Journal of Nanoparticle Research. 1999 Jun 1;1(2):243-51.

25.  Magnusson MH, Deppert K, Malm JO, Bovin JO, Samuelson L. Gold nanoparticles: production, reshaping, and thermal charging. Journal of Nanoparticle Research. 1999 Jun 1;1(2):243-51.

26.  Kabashin AV, Meunier M. Synthesis of colloidal nanoparticles during femtosecond laser ablation of gold in water. Journal of Applied Physics. 2003 Dec 15;94(12):7941-3.

27.  Dolgaev SI, Simakin AV, Voronov VV, Shafeev GA, Bozon FV, Nanoparticles produced by laser ablation of solids in a liquid environment, Applied Surf Sci. 2002; 186;546-551.

28.  Sylvestre JP, Kabashin AV, Sacher E, Meunier M, Luong JH. Stabilization and size control of gold nanoparticles during laser ablation in aqueous cyclodextrins. Journal of the American Chemical Society. 2004 Jun 16;126(23):7176-7.

29.  Kawasaki M, Nishimura N. 1064-nm laser fragmentation of thin Au and Ag flakes in acetone for highly productive pathway to stable metal nanoparticles. Applied Surface Science. 2006 Dec 15;253(4):2208-16.

30.  Natsuki J, Natsuki T, Hashimoto Y. A review of silver nanoparticles: synthesis methods, properties and applications. Int. J. Mater. Sci. Appl. 2015 Sep 29;4(5):325-32.

31.  Tsuji T, Iryo K, Watanabe N, Tsuji M. Preparation of silver nanoparticles by laser ablation in solution: influence of laser wavelength on particle size. Applied Surface Science. 2002 Dec 15;202(1-2):80-5.

32.  Tien DC, Tseng KH, Liao CY, Huang JC, Tsung TT. Discovery of ionic silver in silver nanoparticle suspension fabricated by arc discharge method. Journal of Alloys and Compounds. 2008 Sep 8;463(1-2):408-11.

33.  Siegel J, Kvítek O, Ulbrich P, Kolská Z, Slepička P, Švorčík V. Progressive approach for metal nanoparticle synthesis. Materials Letters. 2012 Dec 15; 89:47-50.

34.  Chen SF, Zhang H. Aggregation kinetics of nanosilver in different water conditions. Advances in Natural Sciences: Nanoscience and Nanotechnology. 2012 Jun 12;3(3):035006.

35.  Dang TM, Le TT, Fribourg-Blanc E, Dang MC. Influence of surfactant on the preparation of silver nanoparticles by polyol method. Advances in Natural Sciences: Nanoscience and Nanotechnology. 2012 Jun 12;3(3):035004.

36.  Wiley B, Sun Y, Mayers B, Xia Y. Shape‐controlled synthesis of metal nanostructures: the case of silver. Chemistry–A European Journal. 2005 Jan 7;11(2):454-63.

37.  Evanoff DD, Chumanov G. Size-controlled synthesis of nanoparticles. 2. Measurement of extinction, scattering, and absorption cross sections. The Journal of Physical Chemistry B. 2004 Sep 16;108(37):13957-62.

38.  Merga G, Wilson R, Lynn G, Milosalejevic B, Meisel D, Redox Catalysis on naked Silver nanoparticles, Journal of Phys Chem 2007; 111:122206.

39.  Oliveira MM, Ugarte D, Zanchet D, Zarbin AJ. Influence of synthetic parameters on the size, structure, and stability of dodecanethiol-stabilized silver nanoparticles. Journal of Colloid and Interface Science. 2005 Dec 15;292(2):429-35.

40.  Oliveira MM, Ugarte D, Zanchet D, Zarbin AJ. Influence of synthetic parameters on the size, structure, and stability of dodecanethiol-stabilized silver nanoparticles. Journal of Colloid and Interface Science. 2005 Dec 15;292(2):429-35.

41.  Kim D, Jeong S, Moon J. Synthesis of silver nanoparticles using the polyol process and the influence of precursor injection. Nanotechnology. 2006 Jul 14;17(16):4019.

42.  Zhang Y, Peng H, Huang W, Zhou Y, Yan D. Facile preparation and characterization of highly antimicrobial colloid Ag or Au nanoparticles. Journal of Colloid and Interface Science. 2008 Sep 15;325(2):371-6.

43.  Krutyakov YA, Olenin AY, Kudrinskii AA, Dzhurik PS, Lisichkin GV. Aggregative stability and polydispersity of silver nanoparticles prepared using two-phase aqueous organic systems. Nanotechnologies in Russia. 2008 Jun 1;3(5-6):303-10.

44.  Zhang W, Qiao X, Chen J. Synthesis of nanosilver colloidal particles in water/oil microemulsion. Colloids and Surfaces A: Physicochemical and Engineering Aspects. 2007 May 15;299(1-3):22-8.

45.  Cozzoli PD, Comparelli R, Fanizza E, Curri ML, Agostiano A, Laub D. Photocatalytic synthesis of silver nanoparticles stabilized by TiO2 nanorods: A semiconductor/metal nanocomposite in homogeneous nonpolar solution. Journal of the American Chemical Society. 2004 Mar 31;126(12):3868-79.

46.  Huang H, Yang Y. Preparation of silver nanoparticles in inorganic clay suspensions. Composites Science and Technology. 2008 Nov 1;68(14):2948-53.

47.  Zhou Y, Yu SH, Wang CY, Li XG, Zhu YR, Chen ZY. A novel ultraviolet irradiation photoreduction technique for the preparation of single‐crystal Ag nanorods and Ag dendrites. Advanced Materials. 1999 Jul;11(10):850-2.

48.  Socol Y, Abramson O, Gedanken A, Meshorer Y, Berenstein L, Zaban A. Suspensive electrode formation in pulsed sonoelectrochemical synthesis of silver nanoparticles. Langmuir. 2002 Jun 11;18(12):4736-40.

49.  Jin R, Cao YC, Hao E, Métraux GS, Schatz GC, Mirkin CA. Controlling anisotropic nanoparticle growth through plasmon excitation. Nature. 2003 Oct;425(6957):487-90.

50.  Malval JP, Jin M, Balan L, Schneider R, Versace DL, Chaumeil H, Defoin A, Soppera O. Photoinduced size-controlled generation of silver nanoparticles coated with carboxylate-derivatized thioxanthones. The Journal of Physical Chemistry C. 2010 Jun 17;114(23):10396-402.

51.  Sato‐Berrú R, Redón R, Vázquez‐Olmos A, Saniger JM. Silver nanoparticles synthesized by direct photoreduction of metal salts. Application in surface‐enhanced Raman spectroscopy. Journal of Raman Spectroscopy: An International Journal for Original Work in all Aspects of Raman Spectroscopy, Including Higher Order Processes, and also Brillouin and Rayleigh Scattering. 2009 Apr;40(4):376-80.

52.  Nadagouda MN, Speth TF, Varma RS. Microwave-assisted green synthesis of silver nanostructures. Accounts of Chemical Research. 2011 Jul 19;44(7):469-78.

53.  Polshettiwar V, Nadagouda MN, Varma RS. Microwave-assisted chemistry: a rapid and sustainable route to synthesis of organics and nanomaterials. Australian Journal of Chemistry. 2009 Feb 10;62(1):16-26.

54.  Chen J, Wang J, Zhang X, Jin Y. Microwave-assisted green synthesis of silver nanoparticles by carboxymethyl cellulose sodium and silver nitrate. Materials Chemistry and Physics. 2008 Apr 15;108(2-3):421-4.

55.  Yin H, Yamamoto T, Wada Y, Yanagida S. Large-scale and size-controlled synthesis of silver nanoparticles under microwave irradiation. Materials Chemistry and Physics. 2004 Jan 15;83(1):66-70.

56.  Tsuji M, Matsumoto K, Jiang P, Matsuo R, Hikino S, Tang XL, Kamarudin KS. The role of adsorption species in the formation of Ag nanostructures by a microwave-polyol route. Bulletin of the Chemical Society of Japan. 2008 Mar 15;81(3):393-400.

57.  Soroushian B, Lampre I, Belloni J, Mostafavi M. Radiolysis of silver ion solutions in ethylene glycol: solvated electron and radical scavenging yields. Radiation Physics and Chemistry. 2005 Feb 1;72(2-3):111-8.

58.  Athawale AA, Desai PA. Silver doped lanthanum chromites by microwave combustion method. Ceramics International. 2011 Dec 1;37(8):3037-43.

59.  Hsieh CT, Pan C, Chen WY. Synthesis of silver nanoparticles on carbon papers for electrochemical catalysts. Journal of Power Sources. 2011 Aug 1;196(15):6055-61.

60.  Ipekoglu M, Altintas S. Silver substituted nanosized calcium deficient hydroxyapatite. Materials Technology. 2010 Nov 1;25(5):295-301.

61.  Kate KH, Singh K, Khanna PK. Microwave formation of Polypyrrole/Ag nano-composite based on interfacial polymerization by use of AgNO3. Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry. 2011 Feb 24;41(2):199-202.

62.  Kate KH, Damkale SR, Khanna PK, Jain GH. Nano-silver mediated polymerization of pyrrole: synthesis and gas sensing properties of polypyrrole (PPy)/Ag nano-composite. Journal of Nanoscience and Nanotechnology. 2011 Sep 1;11(9):7863-9.

63.  Ma SN, Ou ZW, Sun XF, Bai M, Liu ZH. In-situ synthesis of ultra-dispersion-stability nano-Ag in epoxy resin and toughening modification to resin. J Funct Mater. 2009; 40:1029-32.

64.  Si MZ, Fang Y, Dong G. Research on nano-silver colloids prepared by microwave synthesis method and its SERS activity. Acta Photon Sin. 2008; 37:1034-6.

65.  Tai CY, Wang YH, Liu HS. A green process for preparing silver nanoparticles using spinning disk reactor. AIChE Journal. 2008 Feb;54(2):445-52.

66.  Guozhong C. Nanostructures and nanomaterials: synthesis, properties and applications. World Scientific; 2004 Apr 8.

67.  Haruta M. Nanoparticulate Gold Catalysts for Low‐Temperature CO Oxidation. Chem Inform. 2004 Nov 30;35(48):no-.

68.  Xu R, Wang D, Zhang J, Li Y. Shape‐dependent catalytic activity of silver nanoparticles for the oxidation of styrene. Chemistry–An Asian Journal. 2006 Dec 18;1(6):888-93.

69.  Xu R, Wang D, Zhang J, Li Y. Shape‐dependent catalytic activity of silver nanoparticles for the oxidation of styrene. Chemistry–An Asian Journal. 2006 Dec 18;1(6):888-93.

70.  Jin R, Cao Y, Mirkin CA, Kelly KL, Schatz GC, Zheng JG. Photoinduced conversion of silver nanospheres to nanoprisms. Science. 2001 Nov 30;294(5548):1901-3.

71.  Dong X, Ji X, Wu H, Zhao L, Li J, Yang W. Shape control of silver nanoparticles by stepwise citrate reduction. The Journal of Physical Chemistry C. 2009 Apr 23;113(16):6573-6.

72.  Zielinska A, Skwarek E, Zaleska A, Gazda M, Hupka J. Preparation of silver nanoparticles with controlled particle size. Procedia Chem 1: 1560–1566.

73.  Aslan K, Leonenko Z, Lakowicz JR, Geddes CD. Fast and slow deposition of silver nanorods on planar surfaces: application to metal-enhanced fluorescence. The Journal of Physical Chemistry B. 2005 Mar 3;109(8):3157-62.

74.  Senapati S. Biosynthesis and immobilization of nanopaticles and their applications, 2005.

75.  Bhattacharya D, Gupta RK. Nanotechnology and potential of microorganisms. Critical Reviews in Biotechnology. 2005 Jan 1;25(4):199-204.

76.  El-Nour KM, Eftaiha AA, Al-Warthan A, Ammar RA. Synthesis and applications of silver nanoparticles. Arabian Journal of Chemistry. 2010 Jul 1;3(3):135-40.

77.  www.news.medical.com,Michael G., Dr. Surat P.

78.  Feng QL, Wu J, Chen GQ, Cui FZ, Kim TN, Kim JO. A mechanistic study of the antibacterial effect of silver ions on Escherichia coli and Staphylococcus aureus. Journal of Biomedical Materials Research. 2000 Dec 15;52(4):662-8.

79.  Rai M, Yadav A, Gade A. Silver nanoparticles as a new generation of antimicrobials. Biotechnology Advances. 2009 Jan 1;27(1):76-83.

80.  Naskar S, Sharma S, Kuotsu K. Chitosan-based nanoparticles: An overview of biomedical applications and its preparation. Journal of Drug Delivery Science and Technology. 2019 Feb 1; 49:66-81.

 

 

Received on 06.03.2020          Modified on 26.03.2020

Accepted on 28.04.2020   ©Asian Pharma Press All Right Reserved

Asian J. Pharm. Res. 2020; 10(3):202-212.

DOI: 10.5958/2231-5691.2020.00035.0