Silver Nanoparticles: Synthesis, Characterization, Application, Future Outlook
 
Sonali P. Mahaparale*, Reshma S. Kore
Dr. D. Y. Patil College of Pharmacy, Akurdi, Pune, Maharashtra India

*Corresponding Author E-mail: korereshma@gmail.com

 

ABSTRACT:

Silver nanoparticles has received tremendous attention in recent years, owing to its wide range of application in various field. In this review article covers the different preparation methods and synthesis methods such as physical, chemical and biological. Moreover, an outlook is also providing different properties of AgNPs like antimicrobial, anti-inflammatory etc with also focus on anticancer effect of AgNPs. In this review article we focused on applications, toxicity and future outlook of AgNPs.

 

KEYWORDS: Silver nanoparticles, Surface plasmon resonance.

 

 


INTRODUCTION:

“Nano” is Greek word meaning small or dwarf. Nanoparticles can be defined as, the particle ranging in size from 1 to 100 nm or can be consider as ranging up to several 100 nm. Various terminologies are used for silver nanoparticles such as colloidal silver, Nano silver, silver nanostructure and silver nanoparticles[4]. Medicinal and preservative properties of silver have been known for over 2000 years. Throughout the most recent decades silver has been designed into nanoparticles. Silver vessels used to keep water potable[1]. Currently silver nanoparticles are widely used as antibacterial/antifungal agent in diverse range of consumer product, air sanitizer sprays, socks, pillows, sleepers, coating refrigerator, cellular phones etc. Recently AgNPs have been shown much interest because of their therapeutic application in cancer as anticancer agent in diagnosis and in probing[1,8].

 

In modern society, topically used silver sulfadiazine cream is the standard antibacterial treatment for serious burn wounds and is still widely used burn unit today. Due to recent advance in nanotechnology, it is now possible to produce silver at nanoscale. In addition to their potential electronic and transparent conductor applications, the emergence of nanosilver material in antimicrobial consumer goods and medical product is driving the growth of the nanosilver market[3]. The biological activity of AgNPs depends on factor including surface chemistry, size, shape, particle morphology, particle composition, coating/capping, dissolution rate, efficacy of iron release, particle reactivity in solution[8].

 

Silver's method of activity is ventured to be rely upon Ag+particles, while firmly restrain bacterial development through concealment of respiratory catalysts and electron transport segments and through impedance with DNA work. Therefore, the antibacterial, antifungal and antiviral properties of silver ions and silver compounds have been extensively studied[11,16]. It is well known that silver ions and silver-based compounds are highly toxic to micro-organisms[14]. Silver is nontoxic, safe inorganic antibacterial agent used for centuries and is capable killing about type disease causing micro-organisms[18]. Silver nanoparticles destabilize plasma membrane potential and depletion of levels of intracellular adenosine triphosphate (ATP) by targeting bacterial membrane resulting in bacterial cell death[19]. Actually 430 consumer products are currently reported to be o the market worldwide[20]. Silver-based nanomaterials play a major role in the field of nanomedicines and nanotechnology[21].

 

It has been reported that AgNPs can exhibit good conductivity when they are sintered at approximately 200-300°C[22]. AgNPs have been considered by most specialist with incredible medicinal and it’s as founding properties such as catalytic properties, biologic effects, as well as high surface to volume ratio[24]. Currently the silver nanoparticles are the single most manufacturer – identified material used in all of nanotechnology products[26]. Silver binds the bacterial DNA and RNA by denaturation and inhibits bacterial replication. The all AgNPs with bactericidal activity can be which may be applied to different fields i.e. medical instruments and devices, water treatment and food processing[30]. Silver nanoparticles exhibit strong antibacterial activity owning to their large surface to volume ratios and crystallographic surface structure[41].

 

Metal nanoparticles like silver and gold show different color due to their Surface Plasmon Resonance phenomenon (SPR)[55]. Different methods have been used to synthesized NPs including chemical reduction, photochemical, electrochemical physical methods such as physical vapor condensation[40].

 

Fig: Silver nanoparticle

 

Preparation Methods for AgNPs:

1.    Preparation of AgNPs by using Aloe vera extract:

AgNPs were prepared by chemical reduction of an aqueous solution, 12mM AgNO3. 50 ml of this solution is added into 30 ml of aqueous on ethanolic aloe vera extract. The whole reaction was carried out in presence of air and constant and natural pH. The mixer was vigorously stirred at temp. of 57°C during 3 hours and then heated 2°C/min to reach 80°C holding for 2 hours until obtaining a translucent solution with small suspended particles that could be removed by simple filtration (0.45 µm) [9].

2.    Preparation of AgNPs:

For the preparation of AgNPs, AgNO3 solution (0.01 mol dm-3) and CTAB (0.01 mol dm-3) were used respectively, as a metal salt precursor and stabilizing agent. Aniline solution (0.01 mol dm-3) was also used as reducing agent. The transparent colorless reaction mixture containing AgNO3 + CTAB was converted to the characteristics pale yellow color after addition of a required solution od aniline. The appearance of color was indicated the formation of AgNPs[3].

 

3.    Preparation of AgNPs:

The silver hydrosols were prepared by adding under agitation, 10cm3 of aq. 1 mol dm-3 ascorbic acid solution at a flow rate of 3 cm3 min-1 into 90 cm3 of an aq. Solution containing 5 wt % of daxad 19 and 0.33 mol dm-3 AgNO3. The reacting solution were agitated with a stirrer at 900 rpm at room temp. To remove the surfactant and excess silver ions, the resulting participated was washed 5 times with deionized water. Finally, nanosized silver was obtained as dried powder by freeze drying and kept for future experiments[14].

 

4.    Preparation of Ag Nanoparticles: -

100ml aq. Solution of 1.0 x 10-3M silver nitrate was mixed with a 300 ml aq. Solution 1.0 x 10-3 M sodium borohydride. Triply distilled water was used for solutions and both solutions were chilled to ice temp. before mixing. By mixing both solutions, Ag ions were reduced and clustered together to form monodispersed nanoparticles as a transparent solution in aq. medium. The Ag solution was yellow because of absorption at ̴̴ 390 nm. The solution was stirred repeatedly whenever some dark color appeared for approximately an hr until it became stabilized. At this point this solution od AgNPs was so stable that it did not change color for as long as several months without any stabilizing agent. Since the molecule centralization of the arrangement is just 3.3 nm, it was concentrated multiple times utilizing a revolving vacuum evaporator. Then, by diluting this solution each sample of different concentration was used to investigate the concentration dependence of the antifungal effect of AgNPs[15].

 

5.    Preparation of AgNPs using heparin:

An aq. solution of AgNO3 (1ml of variable concentration) was added to a 2ml aliquot of an aq. solution of heparin with magnetic stirring in a 70° C water bath. The depend upon the concentration of heparin and AgNO3, although 8 hours reaction time is sufficient[17].

 

6.    Preparation of AgNPs:

AgNO3 and the multi amino compounds (RSD-NH2) were dissolve in deionized water, separately. The AgNO3 aq. arrangement was included dropwise into the RSD-NH2 arrangement under enthusiastic blending. The initial concentration of the reaction components was 0.017, 0.085, 0.17 and 0.255 g/l for AgNO3 2 g/l for RSD-NH2. The reacting mixer of kept in stirring at room temp. until reduction of Ag+ to Ag was completed and brown silver NPs appeared[19].

 

7.    Preparation of AgNPs:

AgNPs (70.37% w/w Ag) stabilized with casein were obtained Argenol Laboratories. The nanoparticles are proposed to bind the casein polymer surface via complexation with carbohydrate or amino group of casein. A fresh AgNP stock solution of 4 mM was prepared immediately before testing using deionized water and respective electrolytes. Silver nitrate was used to compare the antimicrobial activity between AgNP and Ag+ ions. Silver ions released in each batch test concentration were measured after 20 hrs by passing a sample through an 10,000 nominal molecular weight cut-off (NMWCO) ultrafiltration membrane using a stirred ultrafiltration cell concentration of Ag were analyzed using ICP-MS[36].

 

SYNTHESIS OF AgNPs:

Generally, the synthesis of nanoparticles has been carried out using three different approaches, including physical, chemical, and biological methods[8].

 

1.    Physical method:

In physical techniques, nanoparticles are set up by dissipation buildup utilizing a cylinder heater at barometrical weight. Ordinary physical strategies including sparkle releasing and pyrolysis were utilized for the amalgamation of AgNPs. The advantages of physical methods are speed, radiation used as reducing agents, and no hazardous chemicals involved, but the downsides are low yield and high energy consumption, solvent contamination, and lack of uniform distribution [8]. AgNPs have been orchestrated with laser removal of metallic mass materials in arrangement. The attributes of the metal particles shaped and the removal efficiency firmly rely on numerous parameters, for example, the wavelength of the laser impinging the metallic focus on, the span of the laser beats (in the femto-, pico-and nanosecond routine), the laser fluence, the removal time length and the successful fluid medium, with or without the nearness of surfactants[25].

 

2.    Chemical Method:

Concoction strategies use water or natural solvents to set up the silver nanoparticles. This procedure more often than not utilizes three fundamental segments, for example, metal forerunners, lessening specialists, and balancing out/topping operators. Basically, the reduction of silver salts involves two (1) nucleation: and (2) subsequent growth. When all is said in done, silver nanomaterials can be acquired by two techniques, classified as "top-down" and "base up". The “top-down” method is the mechanical grinding of bulk metals with subsequent stabilization using colloidal protecting agents. The "base up" strategies incorporate substance decrease, electrochemical techniques, and sono-disintegration. The major advantage of chemical methods is high yield, contrary to physical methods, which have low yield[8].

 

Method: 0.0849 gr AgNO3 was dissolved in 500 ml distilled water, then 5 gr of Trisodium Citrate solution was added to the 100 ml boiling AgNO3.The solution was placed at 90°C for 2 hours. Finally, the solution's color changed to red[23].

 

3.    Biological Method:

When Ag-NPs are produced by chemical synthesis, three main components are needed: a silver salt (usually AgNO3), a reducing agent (i.e. ethylene glycol) and a stabilizer or aping agent (i.e. PVP) to control the growth of the NPs and prevent them from aggregating. In case of the biological synthesis of Ag-NPs, the reducing agent and the stabilizer are replaced by molecules produced by living organisms. These reducing and/or stabilizing compounds can be utilized from bacteria, fungi, yeasts, algae or plants[25].

 

Method: About 50 mM aqueous solution of Ag nitrate (AgNO3) was arranged and utilized for the synthesis of AgNPs. 10 ml of PO extract was included into 90 ml of 50 mM solution of AgNO3 for conversion of Ag+ to PO-AgNPs[24].

 

CHARECTERIZATION:

Characterization of nanoparticles is important to understand and control nanoparticle synthesis and applications. Characterization is performed using variety of different techniques. These techniques are used for determination of different parameters such as particle size, shape, crystallinity, fractal dimensions, pore size and surface area. Moreover, orientation, intercalation and dispersion of nanoparticles and nanotube in nanocomposite materials could be determine by these techniques [8,25,31].

 

1.    Transmission Electron Microscopy:

TEM is a valuable, frequently used, and important technique for the characterization of nanomaterials, used to obtain quantitative measures of particle and/or grain size, size distribution, and morphology. The magnification of TEM is mainly determined by the ratio of the distance between the objective lens and the specimen and the distance between objective lens and its image plane[8]. TEM sample was prepared by drop-casting a dispersion of AgNPs on carbon-coated copper grids, which were allowed to dry at room temperature [31]. TEM has two advantages over SEM: it can provide better spatial resolution and the capability for additional analytical measurements. The disadvantages include a required high vacuum, thin sample section, and the vital aspect of TEM is that sample preparation is time consuming. Therefore, sample preparation is extremely important in order to obtain the highest-quality images possible[8,31].

 

2.    Scanning Electron Microscopy:

Electron microscopy systems, SEM is a surface imaging technique, completely fit for settling distinctive molecule sizes, measure circulations, nanomaterial shapes, and the surface morphology of the integrated particles at the small scale and Nano scales. Using SEM, we can probe the morphology of particles and derive a histogram from the images by either by measuring and counting the particles manually, or by using specific software. The combination of SEM with energy-dispersive X-ray spectroscopy (EDX) can be used to examine silver powder morphology and also conduct chemical composition analysis. The limitation of SEM is that it is not able to resolve the internal structure, but it can provide valuable information regarding the purity and the degree of particle aggregation. The modern high-resolution SEM is able to identify the morphology of nanoparticles below the level of 10 nm[8].

 

3.    Atomic force microscopy:

AFM is utilized to research the scattering and total of nanomaterials, notwithstanding their size, shape, sorption, and structure; three distinctive checking modes are accessible, including contact mode, non-contact mode, and discontinuous example contact mode. AFM can likewise be utilized to describe the communication of nanomaterials with upheld lipid bilayers progressively, which isn't attainable with current electron microscopy (EM) procedures. In addition, AFM does not require oxide-free, electrically conductive surfaces for measurement, does not cause appreciable damage to many types of native surfaces, and it can measure up to the sub-nanometer scale in aqueous fluids[8].

 

4.    X- Ray photoelectron spectroscopy:

XPS is a quantitative spectroscopic surface compound examination procedure used to assess experimental formulae. XPS is otherwise called electron spectroscopy for substance investigation (ESCA). XPS assumes a novel job in offering access to subjective, quantitative/semi-quantitative, and speciation data concerning the sensor surface. XPS is performed under high vacuum conditions. X-beam light of the nanomaterial prompts the discharge of electrons, and the estimation of the active vitality and the quantity of electrons getting away from the outside of the nanomaterials gives XPS spectra[8].

 

 

 

5.    UV-Visible:

UV-vis spectroscopy is an exceptionally helpful and solid method for the essential portrayal of integrated nanoparticles which is likewise used to screen the union and soundness of AgNPs. AgNPs have one of a kind optical property which make them firmly connect with specific wavelengths of light. Also, UV-vis spectroscopy is quick, simple, basic, touchy, particular for various sorts of NPs, needs just a brief period time for estimation, and finally an adjustment isn't required for molecule portrayal of colloidal suspensions. In AgNPs, the conduction band and valence band lie very close to each other in which electrons move freely. These free electrons offer ascent to a surface plasmon reverberation (SPR) retention band, happening because of the aggregate swaying of electrons of silver nano particles in reverberation with the light wave. The assimilation of AgNPs relies upon the molecule estimate, dielectric medium, and synthetic environment[8,27].

 

6.    Dynamic light scattering:

The size distribution and average size of the synthesized AgNPs were determined by dynamic light scattering (DLS). DLS (Malvern, UK) measurements were carried out for size ranges from 0.1 nm to 10 mm[31].

 

7.    Fourier transform infrared spectroscopy:

The characterization of functional groups on the surface of AgNPs was performed by Fourier-transform infrared spectroscopy (FTIR 6100, Perkin-Elmer, Germany), and the spectra were scanned in the 400–4000 cm−1 range at a resolution of 4 cm[31].

 

BIOLOGICAL PROPERTIES:

1.    Antibacterial property:

Antibiotics are standard antimicrobials used in medicine that bind to specific chemical targets of bacteria not present in humans[3]. It is assumed that AgNPs may undergo redox reaction leading to the generation of free radicals (ROS, reactive nitrogen species) which triggers cytotoxicity in bacterial cells. The AgNPs first adhere to the bacterial cell wall leading to destabilization of cell membrane potential and low level of ATPs in the cell followed by cell death[4]. Antibacterial activity of AgNP is not only size but also shape dependent. Effect of AgNP against E. Coli the results showed that when compare to AgNPs, hydrogel- silver nanocomposite showed excellent antibacterial activity against E. Coli.[8].

 Nanosilver is an effective killing agent against abroad spectrum of gram -ve and gram +ve bacteria[25]. Small concentration of AgNP is harmless for human cell but deadly for majority of viruses and bacteria. AgNPs reduce toxicity of cell without affecting antibacterial efficacy. Nano particles shoe high antibacterial activity because finely honed surface and they are small enough to penetrate through membrane of cell to disturb the intracellular process[54].

2.    Antifungal Properties:

Long term repetitive administration of standard antifungal drugs leads to increased fungal resistance, especially by candida species. An ongoing report found that an AgNP–covered switch assimilation layer, which is utilized in water refinement framework, showed great antifungal exercises against contagious strain, for example, candida albicans[3]. The naturally incorporated AgNPs displayed solid antifungal action against Bipolaris sorokiniana by the restraint of conidial germination. AgNPs not only inhibit human and plant pathogenic fungi, but also indoor fungal species such as penicillium brevicompactum[8]. Silver nanoparticles exhibiting very strong bactericidal activity against both gram+ve and gram -ve bacteria including multi resistant strains. AgNPs kill bacteria at low concentration which do not reveals acute toxic effect on human cells [25]. AgNPs (diameter 13.5 ± 2.6 nm) are effective against yeast isolated form bovine mastitis[26].

 

3.    Antiviral Property:

Various viruses, such as influenza, hepatitis, HSV, and HIV can be life threatening. AgNPs act as a broad-spectrum agent against variety of viral stains and are not prone to developing resistance. AgNPs at nontoxic concentration was capable of inhibiting HSV-2 replication when administration prior to viral infection [3]. The potential of AgNPs was studied in both prokaryotic and eukaryotic organisms and it was reported that small size AgNPs of around 25 nm or less has outstanding potential in viral infection inhibition. Tannic acid modified AgNPs was used as antimicrobial agent in addition to cream or protective gel used for oral herps infection treatments[4]. AgNPs have unique interaction with bacteria and viruses based on size ranges and shapes. AgNPs have been demonstrated efficient inhibitory activities against HIV and hepatitis B virus[8].

 

AgNPs could inhibit production of HBV RNA and extracellular virions in vitro. AgNPs could bind to outer proteins of viral particles, resulting the inhibition of binding and replication of viral particles in cultured cells [25]. AgNPs (diameter 5-20 nm average diameter ̴ 10nm) inhibit HIV – 1 virus replication[26].

 

4.    Anti-inflammatory property:

Recently, there evidence that AgNPs are viable anti-inflammatory agents. At first, calming properties of AgNPs were researched by applying AgNP-covered, 0.5% silver nitrate (AgNO3), or saline injury dressings to a porcine model of contact dermatitis. AgNP-covered injury dressings beat other injury dressings as erythema, edema, and histological information demonstrated that AgNP-treated pigs had close ordinary skin following 72 hours, while other treatment gatherings stayed excited. Moreover, AgNP-covered injury dressings diminished dimensions of proinflammatory cytokines changing development factor-(TGF-) 𝛽 and tumor corruption factor-(TNF-) 𝛼 contrasted and other treatment gatherings[3].

 

5.    Anticancer property:

AgNPs have been prominent for their antibacterial and antifungal exercises. ecofriendly AgNPs were synthesized from the leaf extracts of Vitex negundo and Sesbania grandiflora, and their efficacy was tested against human colon cancer cell lines HCT15 and MCF-7, respectively. The results demonstrated that AgNPs obtained from V. negundo showed antiproliferative effects on cancer cell line, reduced DNA synthesis, and induced apoptosis[4]. The morphology analysis of cancer cell suggest that biologically synthesized AgNPs could death cell death very significantly. Instead giving of direct treatment of AgNPs into cells, some researchers develop chitosan as an carrier molecule for the delivery of silver to the cancer cell[8]. spherical-shaped (6.2±0.2 nm) silver- (protein lipid) nanoparticles (Ag-LP-NPs) were obtained using the seed extract of Sterculia foetida. These eco-friendly Ag-LP-NPs showed antiproliferative activity against HeLa cancer cell lines and also showed potential toxicity in a dose-dependent manner[55]. AgNPs with controlled shape are progressively successful against numerous kinds of malignant growth cell lines. They stabilized the shape of spherical silver nanoparticles by interaction with natural gum and then screened against cervical cancer cell lines (HeLa), lung cancer (A549), and mice macrophage or RAW 264.7 and found that the particles effectively killed these cell lines in a dose-dependent manner[56].

 

flexirubin (a bacterial pigment)-mediated silver nanoparticles for the first time that were highly cytotoxic (IC50 value of 36 μg/mL) against human breast cancer cell lines[57]. Plant extricate interceded union of AgNPs demonstrated increasingly articulated dangerous impact in human lung carcinoma cells (A549) than non-malignant growth cells like human lung cells, showing that AgNPs could target cell-specific poisonous quality, which could be the lower level of pH in the cancer cells [58].

 

6.    Antiprotozoal property:

According to the WHO, leishmaniasis is the sixth most infectious disease.302 Leishmaniasis is one of the most abandoned tropical infections around the globe, with occurrence in 88 countries and a predictable number of 500,000 cases of visceral form and 1.5 million cases of cutaneous leishmaniasis. biosynthesized nanosilver was four times more active as compared to chemically produced AgNPs in vitro, while the in vivo results showed it was even more effective[4].

 

 

 

7.    Optical properties of AgNPs:

Ag NPs has explicit solid association on electromagnetic radiation. The first application of Ag NPs is to prepare pigments for fabrication ceramics and glass. Optical properties of Ag NPs depend on individual particles shape, size, and composition, their environment and presence and structure of adsorption layers. The distinctive feature of spectrum of scattering and absorption of Ag NPs above 2 nm diameter is the appearance of a strong and wide-ranging band in the visible range or near -UV or -IR Ranges. Silver shows the highest surface plasmon resonance band intensity than any other metals like copper and gold[54].

 

APPLICATIONS:

1.    Wound dressings:

Silver wound dressings have been used for over a decade to clinically treat various wounds, such as burns, chronic ulcers, toxic epidermal necrolysis, and pemphigus. Shockingly, contrasted with standard silver sulfadiazine and bandage dressings, AgNP wound dressings altogether diminished injury mending time by a normal of 3.35 days while at the same time expanding bacterial freedom from contaminated injuries with no unfriendly impacts[3]. AgNPs are widely used in antimicrobial wound dressings because of their recognized antibacterial activity. Wound dressings are manufactured by means of a bi-layer of silver-coated, high-density polyethylene mesh with a rayon adsorptive polyester core that delivers nanocrystalline silver that maintains an effective antimicrobial activity[46].

 

2.    Cardiovascular Implant:

So as to lessen the event of endocarditis, a prosthetic silicone heart valve was the main cardiovascular gadget covered with silver component. The utilization of silver was planned to forestall bacterial disease on the silicone valve in this way lessening the irritation reaction of the heart. In any case, clinical preliminaries testing the silver heart valve found that silver causes touchiness, restrains typical fibroblast capacity, and prompts paravalvular spillage in patients. Thus, efforts turned towards incorporating AgNPs into medical devices as a potential for providing a safe, nontoxic antibacterial coating [3].

 

3.    Catheters:

Catheters utilized in the emergency clinic setting have a high inclination for disease, which can prompt undesirable confusions. In this manner, AgNPs have been explored as a technique for lessening biofilm development on catheters. Various examinations have revealed that AgNP-covered catheters can viably decrease microbes for as long as 72 hours in creature models. Furthermore, a follow-up 10-day in vivo study in mice confirmed that the AgNP- coated catheter was nontoxic[3].

 

4.    Food Industry:

Nanotechnology, which uses little particles estimating one billionth of a meter, is as of now utilized for different applications in regions, for example, sustenance supplements, useful nourishment fixings and in nourishment bundling[26]. Materials whose surfaces are coated with Ag-NPs can be useful in preventing the preserved food from contamination (preventing contamination caused by microbes) due to slow release of Ag-NPs from the coated surface along with preventing growth of the microbes on the surface of the packaging material[29]. Silver nanoparticles are widely used in food industry due to antibacterial actions and free of preservative. Small concentration of Ag NPs is harmless for human cell but deadly for majority of viruses and bacteria. For this reason, it is extensively used in decontamination of food and water in day to day lifecycle and infection resistor in medicine. Ag NPs are widely used in consumer product namely soaps, food, plastics, pastes and textiles due to their anti-fungicidal and anti-bactericidal activities[54].

 

5.    Textiles:

Fabrication of functionalized fabrics with AgNPs has affair share in the functionalized fabricated materials. Blaser et al. proposed an exposure model in which fabrics functionalized with Ag-NPs and polyethene bags are considered to be the prime governing factors for presence of silver in the atmosphere. Garments such as socks, T-shirts, sports-wear are functionalized with Ag-NPs, but the most advantageous use of Ag-NPs is considered to be in medical field because of the high risks of contamination associated with surgical suits. Various techniques are used for fabric functionalized with AgNPs; blending AgNPs with the fabricated material and 2nd by surface immobilization of fabrics with AgNPs[29,54].

 

6.    Water Treatment: -

Stable AgNPs synthesized using Anacardium occidentale fresh leaf extract at 80C bud as a novel probe for sensing chromium ions [Cr (VI)] in tap water. The population of bacteria decreased when the concentration of silver nanoparticles prepared using Prosopis juliflora leaf extract (10mg) was treated with 100mL of sewage after 6h and increases as the time of incubation increases[55].

 

7.    Optical Activity:

Silver nano-particles also used in optical purposes. It is used in Solar cells, medical imaging, optical limiters, plasmonic devices etc.[54].

 

 

 

 

 

8.    Applications of AgNPs in pharmaceuticals, medicines and dentistry[53]

A)  Pharmaceutics and medicines:

     i.Treatment of dermatitis; inhibition of HIV-1 replication.

    ii.Treatment of ulcerative colitis and acne

  iii.Silver/dendrimer nanocomposite for cell labeling

   iv.Molecular imaging of cancer cells

    v.Enhanced Raman Scattering (SERS) spectroscopy

   vi.Detection of viral structures (SERS and Silver nanorods)

 vii.Coating of hospital textile (surgical gowns, face mask)

viii.Orthopedic stocking; Hydrogel for wound dressing

 

B)   Dentistry:

     i.Additive in polymerizable dental materials Patent

    ii.Silver-loaded SiO2 nanocomposite resin filler (Dental resin composite)

  iii.Polyethylene tubes filled with fibrin sponge embedded with AgNPs dispersion.

 

9.    Other Applications of AgNPs[3, 16, 25,26,28,33]:

1.    AgNPs are also available in many commercial products such as water filters and purification systems, deodorants, soaps, socks, food preservation, and room sprays, which contributes to the increasing market of AgNPs.

2.    The Fe3O4 attached Ag nanoparticles can be used for the treatment of water and easily removed using magnetic field to avoid contamination of the environment

3.    The nanocrystalline silver dressings, creams, gel effectively reduce bacterial infections in chronic wounds

4.    Silver impregnated medical devices like surgical masks and implantable devices show significant antimicrobial efficacy

5.    Silver zeolite is used in food preservation, disinfection and decontamination of products.

6.    The silver nanoparticles are reported to show better wound healing capacity, better cosmetic appearance and scar less healing when tested using an animal model.

7.    AgNPs widely used in medicines. Their applications can be broadly divided into diagnostic and therapeutic uses.

8.    The nanoparticles used in industry as catalyst for the high surface to volume ratio of AgNPs provides high surface energy, which promotes surface relatively such as adsorption and catalysts.

9.    AgNPs have been used extensively as electronic products in the industry, anti-bacterial agent in the health industry, food storage, textile coating and no. of environmental applications.

10. Inkjet technology has been used to produce flexible electronic circuits at low cost and many studies reading this application has been repeated in recent years.

 

 

 

TOXICITY:

Silver is considered as one of the most imperative metals which can be used in various fields. It has been reported that low amount of silver has excessive potential against microorganisms, while the AgNPs at high concentration (10 μM) are toxic to mammals as well as host   organisms [4]. AgNPs was found to be highly cytotoxic to mammalian cell based on the assessment of mitochondrial function, membrane leakage of lactate dehydrogenase, and abnormal cell morphologies[11]. With the use of AgNPs in many clinical conditions, potential toxicity remains concern. Indeed, hypersensitivity reaction have been reported in small proportion of burn patients who received ionic silver treatment[25].

 

There are many ways AgNPs may accidently enter human organism the most common of which are orally by inhalation and through the skin. When AgNPs reach specific cell microenvironment it is possible to certain % of NPs may be transformed into ionic form into under influence of certain chemical mediators[42]. AgNPs can cause destabilization of the external film causing the plasma layer potential to fall. It has been observed that expressions of several cell envelope proteins were stimulated after a short exposure of AgNPs[46].

 

FUTURE OUTLOOK:

The utilization of AgNPs is now settled for some business applications and certain medicinal applications, for example, wound dressings, while numerous new potential applications are by and large intensely explored. AgNPs possess great potential due to their antibacterial, antifungal, antiviral, and anti-inflammatory properties while our recent research has revealed novel osteo inductive properties as well[3]. Lack of toxicity in healthy individuals after oral administration of AgNPs indicate their bright future as a potential cancer theragnostic agent. Biocompatibility of green synthesized AgNPs towards normal cells and self- fluorescence may pave the way for beginning a new era in the treatment and diagnosis of cancer[12].

 

Colloidal AgNPs in concentrations present in today’s dietary supplements caused time dependent reduction of nuclear structural complexity in isolated buccal epithelial cells[42]. A major effort towards successful nanoparticle-based therapeutics will be to avoid extensive and non-specific immunostimulatory reaction to the nanomaterials once administered into the body[45]. Nanomaterials in drug delivery may have dual functions for diagnosis and therapeutics[48]. Present study concluding that the characterization is carried out only in-vitro. There is need to carryout the in-vivo studies [50].

 

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Received on 27.06.2019        Accepted on 15.07.2019

© Asian Pharma Press All Right Reserved

Asian J. Pharm. Res. 2019; 9(3):181-189.

DOI: 10.5958/2231-5691.2019.00029.7